To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content ...To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content in coal)catalysts were prepared by the incipient wetness impregnation method,followed by acid washing to remove calcium-containing minerals.Comprehensive characterization and low-temperature denitrification tests revealed that calcite-induced structural modulation of coal-derived AC significantly enhances catalytic activity.Specifically,NO conversion increased from 88.3%of Mn-Ce/De-AC to 91.7%of Mn-Ce/De-AC-1CaCO_(3)(210℃).The improved SCR denitrification activity results from the enhancement of physicochemical properties including higher Mn^(4+)content and Ce^(4+)/Ce^(3+)ratio,an abundance of chemisorbed oxygen and acidic sites,which could strengthen the SCR reaction pathways(richer NH_(3)activated species and bidentate nitrate active species).Therefore,NO removal is enhanced.展开更多
The crystallinity has the potential to distinguish the primary and secondary calcite in Chinese loess, which then provides insights into illuviation depth and variations of the East Asian Summer Monsoon. However, this...The crystallinity has the potential to distinguish the primary and secondary calcite in Chinese loess, which then provides insights into illuviation depth and variations of the East Asian Summer Monsoon. However, this aspect has been rarely investigated. In this study, we defined the crystallinity of calcite as the height/area (H/A) ratio of the diffracted peak at crystal face (1 0 4). The H/A ratio inversely correlates with the average width of the diffracted peak, where a higher H/A ratio indicates higher crystallinity of calcite. Through the mixing and synthetic experiments, we found that the H/A ratio is minimally affected by factors such as calcite content, deposition temperature or rate but significantly influenced by the ionic impurity and the mixing proportion of different calcites. Subsequently, we examined desert samples of loess sources and loess carbonate nodules. Desert samples predominantly consist of primary calcite which inherits characteristics from cryptocrystalline limestone with high levels of ionic impurities resulting in low H/A ratio of 4.30 ± 0.51. In contrast, loess carbonate nodules contain abundant secondary calcite precipitated within soil interstices with low levels of ionic impurities leading to a significantly higher H/A ratio of 7.76 ± 0.82. Consequently, higher H/A ratios during interglacial periods compared to glacial periods are attributed to variations in relative proportions between primary and secondary calcite in loess sequences. The thickness, between the glacial-interglacial boundary and the depth where the H/A ratio starts to increase from the bottom to the top in the loess layer, can be used to indicate the illuviation depth of upper-soil carbonates and the intensity of the East Asian Summer Monsoon. This proxy can be further applied in long-term loess sequences to uncover the summer monsoon evolution.展开更多
Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to pre...Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to predict the biochemical reactions and hydraulic characteristics of MICP and EICP reactions was proposed and verified by physical experiments.Results showed that:This model could describe the variations of bacteria,calcium,calcite,permeability over time reasonably.It is necessary to consider the influence of the calculation domain scale when simulating the convection-diffusionreaction in the multi-process of MICP and EICP reactions.The numerical and experimental values of calcite content are 0.841 g/cm^(3) and 0.861 g/cm^(3) for MICP-reinforced sand,0.263 g/cm^(3) and 0.227 g/cm^(3) for EICP-reinforced sand after 192 h of reaction.The reaction rate k_(rea) is an important parameter to control the calcite content.Accordingly,the permeability coefficient of MICP and EICP reinforced calcareous sand decreases by 32%and 18%.Due to the influence of substance transportation and calcite precipitation,the calcite shows a trend of decreasing firstly and then increasing with the enhancing of the initial permeability coefficient in biochemical reactions.The optimal injecting ratio q11:q12 in this study is 100:300 mL/min.The process for the application of MICP and EICP coupled numerical model is also recommended,which provides reference for engineering projects in ground improvement.展开更多
This study investigated the effect of konjac glucomannan(KGM)on the flotation separation of calcite and scheelite.Micro-flotation tests showed that under the action of 50 mg/L KGM,the floatability of calcite notably d...This study investigated the effect of konjac glucomannan(KGM)on the flotation separation of calcite and scheelite.Micro-flotation tests showed that under the action of 50 mg/L KGM,the floatability of calcite notably decreased,while the impact on scheelite was negligible,resulting in a recovery difference of 82.53%.Fourier transform infrared(FTIR)spectroscopy and atomic force micro-scopy(AFM)analyses indicated the selective adsorption of KGM on the calcite surface.Test results of the zeta potential and UV-visible absorption spectroscopy revealed that KGM prevented the adsorption of sodium oleate on the calcite surface.X-ray photoelectron spec-troscopy(XPS)analysis further confirmed the chemical adsorption of KGM on the calcite surface and the formation of Ca(OH)_(2).The density functional theory(DFT)simulation results were consistent with the flotation tests,demonstrating the strong adsorption perform-ance of KGM on the calcite surface.This study offers a pathway for highly sustainable and cost-effective mineral processing by utilizing the unique properties of biopolymers such as KGM to separate valuable minerals from gangue minerals.展开更多
The efficiency and mechanism of hydrous iron oxide(HFO)and HFO/calcite mixture to inactivate the phosphorus in the overlying water(OW)/sediment system under the feed adding condition were explored,and the effect of HF...The efficiency and mechanism of hydrous iron oxide(HFO)and HFO/calcite mixture to inactivate the phosphorus in the overlying water(OW)/sediment system under the feed adding condition were explored,and the effect of HFO and HFO/calcite mixture addition on the diversity,composition and function of bacterial communities in the sediment was examined.HFO and HFO/calcite mixture direct addition can effectively lower the concentration of soluble reactive phosphorus(RSP)and diffusion gradient in thin film-unstable phosphorus(PD GT)in OW and inactivate the P DGTin the upper sediment.The elimination efficiencies of RSP by the direct HFO and HFO/calcite mixture addition were 48.9%-97.0%and 42.4%-95.4%,respectively.The alteration in the addition mode from the one-time to multiple direct addition was beneficial to the immobilization of RSP and PD GTin OW and P DGTin the upper sediment by HFO and HFO/calcite mixture under the feed input condition in the long run.Permeable fabric wrapping reduced the inactivation efficiency of RSP in OW by HFO and HFO/calcite mixture,but it made the recycling of these materials possible.Most of P immobilized by HFO and HFO/calcite mixture was relatively or very stable.After the HFO and HFO/calcite mixture addition,the composition of bacterial communities in the surface sediment changed.However,the bacterial communities in the amended sediments still can perform good ecological function.Our findings suggest that HFO and HFO/calcite mixture are promising phosphorus-immobilization materials for the inactivation of RSP and PD GTin OW and PD GTin the upper sediment under the feed inputting condition.展开更多
The effectiveness of Elodea nuttallii combined with a mixture of hydrous ferric oxide,zeolite and calcite(HZC)to reduce the internal loading of phosphorus(P)from sediment and its mechanism were studied,and the effect ...The effectiveness of Elodea nuttallii combined with a mixture of hydrous ferric oxide,zeolite and calcite(HZC)to reduce the internal loading of phosphorus(P)from sediment and its mechanism were studied,and the effect of Elodea nuttallii combined with HZC on the composition and function of the microbial communities in the surface sediment was also investigated.The results showed that the combination utilization of Elodea nuttallii and HZC can decrease the risk of phosphorus liberation from sediment to the overlying water,and the controlling efficiency of Elodea nuttallii combined with HZCwas higher than that of Elodea nuttallii or HZC alone.The passivation of labile P measured by diffusive gradient in thin film device and mobile P played a crucial role in the control of internal P loading from sediment by the combined Elodea nuttallii+HZC treatment.HZC capping had a promoting effect on the growth of Elodea nuttallii.This was beneficial to the absorption of phosphorus from sediment by Elodea nuttallii.The combined application of Elodea nuttallii and HZC not only had a certain negative effect on the diversity of bacteria in the surface sediment,but also changed themicrobial compositions of the surface sediment at the levels of phylum and genus.However,the microbial communities in the surface sediment still can perform good ecological function.The above results suggest that the combined application of Elodea nuttallii and HZC has a high potential in the management of internal P loading from sediment.展开更多
In this study,the effect of Cu^(2+)on the cassiterite and calcite flotation using octanohydroxamic acid(OHA)as collector was investigated through flotation tests,solution reaction tests and calculation,zeta potential ...In this study,the effect of Cu^(2+)on the cassiterite and calcite flotation using octanohydroxamic acid(OHA)as collector was investigated through flotation tests,solution reaction tests and calculation,zeta potential measurements,XPS analysis and residual reagent concentration measurements.Results indicated that Cu^(2+)played an activation role on cassiterite flotation but a depression role on calcite flotation.The copper cations were adsorbed on the cassiterite surface by forming a Cu—O bond,and the pre-adsorbed copper cations and the OHA-Cu complexes promoted the adsorption of OHA on the cassiterite surface.Thus,cassiterite flotation was activated.The dissolved HCO_(3)-in the calcite pulp underwent a double hydrolysis reaction with copper cations(Cu^(2+),CuOH^(+),Cu_(2)(OH)_(2)^(2+)and Cu_(3)(OH)_(4)^(2+))to form CuCO_(3).Some copper cations were adsorbed on the calcite surface as well,but some adsorbed Cu^(2+)on the calcite surface was desorbed by bonding with OHA,and most of OHA was consumed by Cu^(2+),basic copper carbonate and copper hydroxide.The residual OHA in the pulp was not sufficient for flotation,so calcite flotation was depressed.Finally,a model of the reaction mechanism of Cu^(2+)and OHA on the cassiterite and calcite surfaces was established.展开更多
Anisotropic surface broken bond densities of six different surfaces of calcite and three surfaces of fluorite were calculated. In terms of the calculated results, the commonly exposed surfaces of the two minerals were...Anisotropic surface broken bond densities of six different surfaces of calcite and three surfaces of fluorite were calculated. In terms of the calculated results, the commonly exposed surfaces of the two minerals were predicted and the relations between surface broken bonds densities and surface energies were analyzed. Then the anisotropic wettability of the commonly exposed surfaces was studied by means of contact angle measurement. The calculation results show that the （101^-4）, （213^-4）and （01 1^-8）surfaces for calcite and （111） for fluorite are the most commonly exposed surfaces and there is a good rectilinear relation between surface broken bond density and surface energy with correlation of determination （R^2） of 0.9613 and 0.9969, respectively. The anisotropic wettability of different surfaces after immersing in distilled water and sodium oleate solutions at different concentrations can be explained by anisotropic surface broken bond densities and active Ca sites densities, respectively.展开更多
Two geothermal fields with calcite scaling in some wells in Iceland were selected for the study of calcite scaling potential. An allowable supersaturation was found by comparing the degree ...Two geothermal fields with calcite scaling in some wells in Iceland were selected for the study of calcite scaling potential. An allowable supersaturation was found by comparing the degree of calcite supersaturation and actual scaling status in the selected wells.The saturation index,0.37～ 0.48, was the boundary between calcite scaling and no scaling. The information about changes in chloride concentration shows that mixing different waters is the main cause to form calcite scaling in the geothermal wells selected in this study.In this case, the content of chloride can be used as an index of scaling.展开更多
The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb＋Zn reserves of more than 5 million ton...The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb＋Zn reserves of more than 5 million tons at Pb＋Zn grade of higher than 25%and contains abundant associated metals,such as Ag,Ge,Cd,and Ga.The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield.Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types,namely lumpy,patch and vein calcites in accordance with their occurrence.There is not intercalated contact between calcite and ore minerals and among the three types of calcite,indicating that they are the same ore-forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element（REE） and C-O isotopic compositions of calcites in the Huize Pb-Zn deposits.From lumpy to patch to vein calcites,REE contents decrease as LREE/ HREE ratios increase.The chondrite-normalized REE patterns of the three types of calcites are characterized by LREE-rich shaped,in which the lumpy calcite shows（La）_N〈（Ce）_N〈（Pr）_N≈（Nd）_N with Eu/Eu~＊〈1,the patch calcite has（La）_N〈（Ce）_N〈（Pr）_N≈（Nd）_N with Eu/Eu~＊〉1,and the vein calcite displays（La）_N〉（Ce）_N〉（Pr）_N〉（Nd）_N with Eu/Eu~＊〉1.The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield.Theδ^（13） C_（PDb） andδ^（18）O_（Smow） values of the three types of calcites vary from-3.5‰to-2.1‰and 16.7‰to 18.6‰,respectively,falling within a small field between primary mantle and marine carbonate in theδ^（13）C_（PDb） vsδ^（18）O_（Smow） diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages.The ore-forming fluids of the deposits resulted from crustal -mantle mixing processes,in which the mantle-derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts,and the crustal fluid was mainly provided by carbonate strata in the orefield.The ore-forming fluids in the deposits were homogenized before mineralization,and the ore-forming environment varied from relatively reducing to oxidizing.展开更多
We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides （HFOs） using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents （denoted as HFO-201 and IOCCS...We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides （HFOs） using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents （denoted as HFO-201 and IOCCS） were employed for Sb（V） removal from water. Increasing solution pH from 3 to 9 apparently weakened Sb（V） removal by both composites, while increasing temperature from 293 to 313 K only improved Sb（V） uptake by IOCCS. HFO-201 exhibited much higher capacity for Sb（V） than for IOCCS in the absence of other anions in solution. Increasing ionic strength from 0.01 to 0.1 mol/L NaNO3 would result in a significant drop of the capacity of HFO-201 in the studied pH ranges; however, negligible effect was observed for 1OCCS under similar conditions. Similarly, the competing chloride and sulfate pose more negative effect on Sb（V） adsorption by HFO-201 than by IOCCS, and the presence of silicate greatly decreased their adsorption simultaneously, while calcium ions were found to promote the adsorption of both adsorbents. XPS analysis further demonstrated that preferable Sb（V） adsorption by both hybrids was attributed to the inner sphere complexation of Sb（V） and HFO, and Ca（II） induced adsorption enhancement possibly resulted from the formation of HFO-Ca-Sb complexes. Column adsorption runs proved that Sb（V） in the synthetic water could be effectively removed from 30 μg/L to below 5μg/L （the drinking water standard regulated by China）, and the effective treatable volume of IOCCS was around 6 times as that of HFO-201, implying that HFO coatings onto calcite might be a more effective approach than immobilization inside D201.展开更多
Polyaspartic acid(PASP)was used as a novel environmental-friendly depressant,and its inhibition effect on flotation performance of scheelite and calcite using sodium oleate(NaOL)as a collector was investigated by ways...Polyaspartic acid(PASP)was used as a novel environmental-friendly depressant,and its inhibition effect on flotation performance of scheelite and calcite using sodium oleate(NaOL)as a collector was investigated by ways of flotation experiments,zeta potential measurement,contact angle measurement and infrared spectroscopic analysis(IR).The results show that PASP exhibits stronger inhibition capability and selectivity than acidified water glass,and the flotation separation of scheelite from calcite can be realized in the presence of 6 mg/L PASP and 20 mg/L NaOL at pH>6.In the presence of PASP,the zeta potential of calcite surface almost keeps unchanged after adding NaOL,and the contact angle decreases sharply.Therefore,it is indicated that PASP significantly decreases the adsorption of NaOL on calcite surface.By contrast,it has no distinct effect on the adsorption of NaOL on the scheelite surface,which is further confirmed by IR results.展开更多
In this study, the innovative use of ethylenediamine tetramethylene phosphonic sodium(EDTMPS) as a calcite depressant in scheelite flotation was investigated by flotation experiments, and its selective depression mech...In this study, the innovative use of ethylenediamine tetramethylene phosphonic sodium(EDTMPS) as a calcite depressant in scheelite flotation was investigated by flotation experiments, and its selective depression mechanism was revealed by contact angle measurement, FTIR analysis, Zeta potential test and XPS analysis. The flotation experiment results showed that scheelite and calcite could be efficiently separated under the following conditions: pulp p H=9.5, Na OL concentration of 1.5×10^(-4)mol/L, EDTMPS concentration of 3.0×10^(-5)mol/L, a scheelite concentrate with WO3grade of 65.49%, recovery of 83.29%and separation efficiency of 65.29% could be obtained from the artificially mixed minerals. The analysis results of mineral surface properties demonstrated that EDTMPS was strongly adsorbed onto the calcite surface through the reaction between the phosphonate group and the calcium ions, which hindered Na OL adsorption and increased the hydrophilicity of calcite. However, EDTMPS had weak adsorption strength on the scheelite surface, which didn’t affect further adsorption of Na OL, hence, the scheelite remained hydrophobic. Consequently, the selective adsorption of EDTMPS on the two minerals’ surfaces increased a difference in wettability and thus enabling them to be separated by flotation. Finally, the mechanism model of this flotation separation process was established.展开更多
The flotation separation of magnesite from calcium-containing minerals has always been a difficult subject in minerals processing.This work studied the inhibition effects of carboxymethyl cellulose(CMC),sodium lignosu...The flotation separation of magnesite from calcium-containing minerals has always been a difficult subject in minerals processing.This work studied the inhibition effects of carboxymethyl cellulose(CMC),sodium lignosulphonate,polyaspartic acid(PASP)and sodium silicate on flotation behaviors of magnesite,dolomite and calcite,providing guidance for the development of reagents in magnesite flotation.The micro-flotation results showed that among these four depressants,sodium silicate presented the strongest selectivity due to the highest recovery difference,and the flotation separation of magnesite from dolomite and calcite could be achieved by using sodium silicate as the depressant.Contact angle measurement indicated that the addition of sodium silicate caused the largest differences in surface wettability of the three minerals,which was in line with micro-flotation tests.Furthermore,zeta potential test,the Fourier transform infrared(FT-IR)spectroscopy and atomic force microscope(AFM)imaging were used to reveal the inhibition mechanism of sodium silicate.The results indicated that the dominated component SiO(OH)3of sodium silicate could adsorb on minerals surfaces,and the adsorption of sodium silicate hardly affected the adsorption of NaOL on magnesite surface,but caused the reduction of NaOL adsorption on dolomite and calcite surfaces,thereby increasing the flotation selectivity.展开更多
Abundant burrows of Skolithos linearis, Palaeophycus tubularis, and Taenidium barretti are preserved in the Upper Devonian Donghe sandstone of Tarim basin, China. They are commonly highlighted in core by the color of ...Abundant burrows of Skolithos linearis, Palaeophycus tubularis, and Taenidium barretti are preserved in the Upper Devonian Donghe sandstone of Tarim basin, China. They are commonly highlighted in core by the color of the burrow fill in contrast to the surrounding matrix and have dif-ferent textures and fabrics from the matrix. There are three kinds of calcite cements in burrows, microcrystalline-crystalline calcite cement, mosaic calcite cement, and ferroan calcite cement. Microcrystalline-crystalline calcite cement is widely distributed in the lower part of the Donghe sand-stone, but it is rare in burrows filling. It displays a globule structure under burial cementation and sel-dom replaces the quartz grains in shallow burial depth stage. Mosaiccalcite cement is widespread in the Donghe sansdtone reservoir of North Tarim basin. It shows chrysoidine, orange and bright orange lu-minescence, and intensely replaces the quartz grains, forming in early diagenetic and shallow burial depth stage. Ferroan calcite is asymmetrically distributed in the Donghe sandstone reservoir of Central Tarim basin. It fills the remanent pores in the shape of mosaic and replaces the quartz grains, matrix, and early calcite cement, forming in late diagenetic and deep burial depth stage. The burrows filled with white calcite cements have low oil saturation or may be oil-stained. In contrast, there is high oil saturation in the sandstone reservoir where the bioturbation is sparse or not present. With increased bioturbation, the porosity, permeability, and oil saturation decrease; thus, bioturbation intensity and reservoir property appear to be negatively correlated.展开更多
The flotation separation of smithsonite from calcite and quartz using a alkyl diamine ether(GE-609)as the collector was investigated through micro-flotation experiments and the real ore flotation experiments.The resul...The flotation separation of smithsonite from calcite and quartz using a alkyl diamine ether(GE-609)as the collector was investigated through micro-flotation experiments and the real ore flotation experiments.The results show that GE-609exhibits good collecting capability to three minerals without selectivity.The presence of sodium sulfide enhances the flotation of smithsonite and calcite while inhibits quartz.Moreover,both sodium silicate and sodium hexametaphosphate exhibit good selective inhibition to calcite.The real ore test results show that a zinc concentrate containing23.51%Zn with the recovery of71.02%is obtained in the closed-circuit test.To understand the adsorption of GE-609on smithsonite surface,zeta potential measurement and FTIR analysis were carried out,and the results indicate that the collector GE-609can adsorb on smithsonite surface through both electrostatic adsorption and chemical adsorption,and the presence of sodium sulfide enhances the adsorption of GE-609.展开更多
Carbonate minerals and water （or geofluids） reactions are important for modeling of geochemical processes and have received considerable attention over the past decades. The calcite dissolution rates from 50℃ to 25...Carbonate minerals and water （or geofluids） reactions are important for modeling of geochemical processes and have received considerable attention over the past decades. The calcite dissolution rates from 50℃ to 250℃ at 10 MPa in deionized water with a flow rate varying from 0.2 to 5 mL/min were experimentally measured in a continuous flow column pressure vessel reactor. The dissolution began near the equilibrium with c/ceq 〉 0.3 and finally reached the equilibrium at 100℃-250℃, so the corresponding solubility was also determined as 1.87, 2.02, 2.02 and 1.88×10^-4.mol/L at 100℃, 150℃, 200℃ and 250℃ respectively, which was first increasing and then switching to decreasing with temperature and the maximum value might occur between 150℃ and 200℃. The experimental dissolution rate not only increased with temperature, but also had a rapid increase between 150℃ and 200℃ at a constant flow rate of 4 mL/min. The measured dissolution rates can be described using rate equations of R = k（1-c/ceq）n or R = kc-n. In these equations the reaction order n changed with temperature, which indicates that n was a variable rather than a constant, and the activation energy was 13.4 kJ/mol calculated with R = k（1-c/ceq）n or 18.0 kJ/mol with R = kc^-n, which is a little lower than the surface controlled values. The varied reaction order and lower activation energy indicates that calcite dissolution in this study is a complex interplay of diffusion controlled and surface controlled processes.展开更多
The surface properties of fluorite are often affected by dissolved gangue species(e.g.,calcite)during the flotation process.Microflotation testing with and without the addition of calcite supernatant was conducted usi...The surface properties of fluorite are often affected by dissolved gangue species(e.g.,calcite)during the flotation process.Microflotation testing with and without the addition of calcite supernatant was conducted using octanohydroxamic acid(OHA)as the collector.The results revealed that dissolved calcite species significantly affected the flotation behavior of fluorite.Fourier transform infrared spectra confirmed that the decrease in flotation recovery was linked to lower OHA adsorption.Solution chemistry analysis indicated that CaCO_(3) and Ca^(2+)from the calcite supernatant were the most favorably adsorbed species,and X-ray photoelectron spectroscopy analysis confirmed the surface adsorption of calcite species.Density functional theory simulations provided a detailed analysis of the multidentate adsorption configuration of OHA,which was the most favorable for adsorption on the fluorite surface.The adsorption energy calculation showed that the calcite dissolved species were more stably adsorbed on the fluorite surface than OHA.The pre-adsorption of calcite dissolved species hindered the adsorption of OHA due to electrostatic repulsion.展开更多
The calcite dissolution rates at 50-250 ℃ and 20 MPa in deionized water with flow rate varying from 0.2 to 5 mL/min were experimentally measured in a continuous flow column pressure vessel reactor. Equilibrium concen...The calcite dissolution rates at 50-250 ℃ and 20 MPa in deionized water with flow rate varying from 0.2 to 5 mL/min were experimentally measured in a continuous flow column pressure vessel reactor. Equilibrium concentration （Ceq） of calcite dissolution in deionized water at 20 MPa was determined using dissolution data according to the iterative method presented by Jeschke and Dreybrodt. The equilibrium concentrations at 50, 100, 150, 200 and 250 ℃ are 1.84×10^-4, 2.23×10^-4, 2.25×10^-4, 2.31×10^-4 and 2.24×10^-4 mol/L, respectively. The Ceq increases first and then decreases with temperature varying from 50 to 250 ℃ at 20 MPa, and the same variation trend occurs at 10 MPa with lower values. The maximum value （or extremum） of Ceq would increase with temperature at constant pressures. The dissolution reaction of calcite in this experiment is approaching the calcite equilibrium, and the reaction order doesn＇t keep a constant at different temperatures, which could imply that a change of the reac- tion mechanism was occurring. The Arrhenius equation shouldn＇t be used to calculate apparent activation energy using rate constant data at different temperatures when the reaction order or reaction mechanism changed.展开更多
Serpentinization and calcite precipitation of mantle peridotites exhumed along detachment faults at the slow-to ultraslow-spreading centers can provide important clues to the hydrothermal alteration processes.The Tian...Serpentinization and calcite precipitation of mantle peridotites exhumed along detachment faults at the slow-to ultraslow-spreading centers can provide important clues to the hydrothermal alteration processes.The Tianxiu hydrothermal field is a new-found active and ultramafichosted hydrothermal vent site along the Carlsberg Ridge,Northwest Indian Ocean.Two types of calcite veins are recognized in serpentinized harzburgite samples collected from the seafloor at the water depth of 3 500 m(3.67°N/63.83°E) and 400 m north of Tianxiu hydrothermal field.Calcite veins Ⅰ occur in the fractures that cut through mesh texture in the highly serpentinized harzburgite,while calcite veins Ⅱ precipitate within the mesh texture in the relatively weaker serpentinized harzburgite.Both veins show similar δ13CPDB(+0.54‰ and +0.58‰) but different δ18OPDB(-16.67‰ and +4.46‰) values,suggesting that they were derived from the same carbon source but precipitated at different temperatures.Taking the deep seawater temperature of 2℃as the precipitation temperature of the calcite veins I,the equilibrium δ18OV-SMOW of calcite-precipitating fluid was calculated to be 1.78‰,which is close to the average δ18OV-SMOW value(1.74‰) of vent fluid samples from the ultramafic-hosted hydrothermal systems worldwide.The formation temperature of calcite veins Ⅱ is inferred to be approximately 134℃,based on the calculated δ18OV-SMOW above.The temperature differences of calcite precipitation probably resulted from the fluid cooling conductively and mixing with seawater along the presumed fractures during slow upflow.The low-temperature calcite postdates the mesh texture,while the high-temperature calcite may precipitate under relatively low water/rock ratios,alkaline and reduced conditions among the mesh texture,which is revealed by the geochemical models.Therefore,it is suggested that they both have been influenced by hydrothermal fluids and the sampling site is near the discharge zone of hydrothermal circulation.展开更多
基金Supported by the Science and Technology Cooperation and Exchange special project of Cooperation of Shanxi Province(202404041101014)the Fundamental Research Program of Shanxi Province(202403021212333)+3 种基金the Joint Funds of the National Natural Science Foundation of China(U24A20555)the Lvliang Key R&D of University-Local Cooperation(2023XDHZ10)the Initiation Fund for Doctoral Research of Taiyuan University of Science and Technology(20242026)the Outstanding Doctor Funding Award of Shanxi Province(20242080).
文摘To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content in coal)catalysts were prepared by the incipient wetness impregnation method,followed by acid washing to remove calcium-containing minerals.Comprehensive characterization and low-temperature denitrification tests revealed that calcite-induced structural modulation of coal-derived AC significantly enhances catalytic activity.Specifically,NO conversion increased from 88.3%of Mn-Ce/De-AC to 91.7%of Mn-Ce/De-AC-1CaCO_(3)(210℃).The improved SCR denitrification activity results from the enhancement of physicochemical properties including higher Mn^(4+)content and Ce^(4+)/Ce^(3+)ratio,an abundance of chemisorbed oxygen and acidic sites,which could strengthen the SCR reaction pathways(richer NH_(3)activated species and bidentate nitrate active species).Therefore,NO removal is enhanced.
基金funded by the National Natural Science Foundation of China(Nos.42173061,42473068).
文摘The crystallinity has the potential to distinguish the primary and secondary calcite in Chinese loess, which then provides insights into illuviation depth and variations of the East Asian Summer Monsoon. However, this aspect has been rarely investigated. In this study, we defined the crystallinity of calcite as the height/area (H/A) ratio of the diffracted peak at crystal face (1 0 4). The H/A ratio inversely correlates with the average width of the diffracted peak, where a higher H/A ratio indicates higher crystallinity of calcite. Through the mixing and synthetic experiments, we found that the H/A ratio is minimally affected by factors such as calcite content, deposition temperature or rate but significantly influenced by the ionic impurity and the mixing proportion of different calcites. Subsequently, we examined desert samples of loess sources and loess carbonate nodules. Desert samples predominantly consist of primary calcite which inherits characteristics from cryptocrystalline limestone with high levels of ionic impurities resulting in low H/A ratio of 4.30 ± 0.51. In contrast, loess carbonate nodules contain abundant secondary calcite precipitated within soil interstices with low levels of ionic impurities leading to a significantly higher H/A ratio of 7.76 ± 0.82. Consequently, higher H/A ratios during interglacial periods compared to glacial periods are attributed to variations in relative proportions between primary and secondary calcite in loess sequences. The thickness, between the glacial-interglacial boundary and the depth where the H/A ratio starts to increase from the bottom to the top in the loess layer, can be used to indicate the illuviation depth of upper-soil carbonates and the intensity of the East Asian Summer Monsoon. This proxy can be further applied in long-term loess sequences to uncover the summer monsoon evolution.
基金supports from the National Key R&D Program of China(Grant No.2023YFB4203301)National Natural Science Foundation of China(Grant No.52238008)Postdoctoral Fellowship Program of CPSF(Grant No.GZC20241516).
文摘Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to predict the biochemical reactions and hydraulic characteristics of MICP and EICP reactions was proposed and verified by physical experiments.Results showed that:This model could describe the variations of bacteria,calcium,calcite,permeability over time reasonably.It is necessary to consider the influence of the calculation domain scale when simulating the convection-diffusionreaction in the multi-process of MICP and EICP reactions.The numerical and experimental values of calcite content are 0.841 g/cm^(3) and 0.861 g/cm^(3) for MICP-reinforced sand,0.263 g/cm^(3) and 0.227 g/cm^(3) for EICP-reinforced sand after 192 h of reaction.The reaction rate k_(rea) is an important parameter to control the calcite content.Accordingly,the permeability coefficient of MICP and EICP reinforced calcareous sand decreases by 32%and 18%.Due to the influence of substance transportation and calcite precipitation,the calcite shows a trend of decreasing firstly and then increasing with the enhancing of the initial permeability coefficient in biochemical reactions.The optimal injecting ratio q11:q12 in this study is 100:300 mL/min.The process for the application of MICP and EICP coupled numerical model is also recommended,which provides reference for engineering projects in ground improvement.
基金supported by the National Natural Science Foundation of China(No.52164022).
文摘This study investigated the effect of konjac glucomannan(KGM)on the flotation separation of calcite and scheelite.Micro-flotation tests showed that under the action of 50 mg/L KGM,the floatability of calcite notably decreased,while the impact on scheelite was negligible,resulting in a recovery difference of 82.53%.Fourier transform infrared(FTIR)spectroscopy and atomic force micro-scopy(AFM)analyses indicated the selective adsorption of KGM on the calcite surface.Test results of the zeta potential and UV-visible absorption spectroscopy revealed that KGM prevented the adsorption of sodium oleate on the calcite surface.X-ray photoelectron spec-troscopy(XPS)analysis further confirmed the chemical adsorption of KGM on the calcite surface and the formation of Ca(OH)_(2).The density functional theory(DFT)simulation results were consistent with the flotation tests,demonstrating the strong adsorption perform-ance of KGM on the calcite surface.This study offers a pathway for highly sustainable and cost-effective mineral processing by utilizing the unique properties of biopolymers such as KGM to separate valuable minerals from gangue minerals.
基金supported by the Capacity Building Project of Local University of Shanghai Municipal Science and Technology Commission(No.10230502900)the Program for Shanghai Collaborative Innovation Center for Cultivating Elite Breeds and Green-culture of Aquaculture animals(No.2021-KJ-02-12)the Innovation Project for Chongming Agriculture Industry from Chongming District Agriculture Commission of Shanghai(No.2022CNKC-01-05)。
文摘The efficiency and mechanism of hydrous iron oxide(HFO)and HFO/calcite mixture to inactivate the phosphorus in the overlying water(OW)/sediment system under the feed adding condition were explored,and the effect of HFO and HFO/calcite mixture addition on the diversity,composition and function of bacterial communities in the sediment was examined.HFO and HFO/calcite mixture direct addition can effectively lower the concentration of soluble reactive phosphorus(RSP)and diffusion gradient in thin film-unstable phosphorus(PD GT)in OW and inactivate the P DGTin the upper sediment.The elimination efficiencies of RSP by the direct HFO and HFO/calcite mixture addition were 48.9%-97.0%and 42.4%-95.4%,respectively.The alteration in the addition mode from the one-time to multiple direct addition was beneficial to the immobilization of RSP and PD GTin OW and P DGTin the upper sediment by HFO and HFO/calcite mixture under the feed input condition in the long run.Permeable fabric wrapping reduced the inactivation efficiency of RSP in OW by HFO and HFO/calcite mixture,but it made the recycling of these materials possible.Most of P immobilized by HFO and HFO/calcite mixture was relatively or very stable.After the HFO and HFO/calcite mixture addition,the composition of bacterial communities in the surface sediment changed.However,the bacterial communities in the amended sediments still can perform good ecological function.Our findings suggest that HFO and HFO/calcite mixture are promising phosphorus-immobilization materials for the inactivation of RSP and PD GTin OW and PD GTin the upper sediment under the feed inputting condition.
基金supported by the Capacity Building Project of Local University of Shanghai Municipal Science and Technology Commission(No.10230502900)the Program for Shanghai Collaborative Innovation Center for Cultivating Elite Breeds and Green-culture of Aquaculture animals(No.2021-KJ-02-12)the Innovation Project for Chongming Agriculture Industry from Chongming District Agriculture Commission of Shanghai(No.2022CNKC-01-05).
文摘The effectiveness of Elodea nuttallii combined with a mixture of hydrous ferric oxide,zeolite and calcite(HZC)to reduce the internal loading of phosphorus(P)from sediment and its mechanism were studied,and the effect of Elodea nuttallii combined with HZC on the composition and function of the microbial communities in the surface sediment was also investigated.The results showed that the combination utilization of Elodea nuttallii and HZC can decrease the risk of phosphorus liberation from sediment to the overlying water,and the controlling efficiency of Elodea nuttallii combined with HZCwas higher than that of Elodea nuttallii or HZC alone.The passivation of labile P measured by diffusive gradient in thin film device and mobile P played a crucial role in the control of internal P loading from sediment by the combined Elodea nuttallii+HZC treatment.HZC capping had a promoting effect on the growth of Elodea nuttallii.This was beneficial to the absorption of phosphorus from sediment by Elodea nuttallii.The combined application of Elodea nuttallii and HZC not only had a certain negative effect on the diversity of bacteria in the surface sediment,but also changed themicrobial compositions of the surface sediment at the levels of phylum and genus.However,the microbial communities in the surface sediment still can perform good ecological function.The above results suggest that the combined application of Elodea nuttallii and HZC has a high potential in the management of internal P loading from sediment.
基金Project(52074355)supported by the National Natural Science Foundation of ChinaProject(2023JJ10070)supported by the Outstanding Youth Scientist Foundation of Hunan Province,China。
文摘In this study,the effect of Cu^(2+)on the cassiterite and calcite flotation using octanohydroxamic acid(OHA)as collector was investigated through flotation tests,solution reaction tests and calculation,zeta potential measurements,XPS analysis and residual reagent concentration measurements.Results indicated that Cu^(2+)played an activation role on cassiterite flotation but a depression role on calcite flotation.The copper cations were adsorbed on the cassiterite surface by forming a Cu—O bond,and the pre-adsorbed copper cations and the OHA-Cu complexes promoted the adsorption of OHA on the cassiterite surface.Thus,cassiterite flotation was activated.The dissolved HCO_(3)-in the calcite pulp underwent a double hydrolysis reaction with copper cations(Cu^(2+),CuOH^(+),Cu_(2)(OH)_(2)^(2+)and Cu_(3)(OH)_(4)^(2+))to form CuCO_(3).Some copper cations were adsorbed on the calcite surface as well,but some adsorbed Cu^(2+)on the calcite surface was desorbed by bonding with OHA,and most of OHA was consumed by Cu^(2+),basic copper carbonate and copper hydroxide.The residual OHA in the pulp was not sufficient for flotation,so calcite flotation was depressed.Finally,a model of the reaction mechanism of Cu^(2+)and OHA on the cassiterite and calcite surfaces was established.
基金Project (50834006) supported by the National Natural Science Foundation of ChinaProject (CX2011B122) supported by Hunan Provincial Innovation Foundation for PostgraduateProject (2011ybjz045) supported by Graduate Degree Thesis Innovation Foundation of Central South University
文摘Anisotropic surface broken bond densities of six different surfaces of calcite and three surfaces of fluorite were calculated. In terms of the calculated results, the commonly exposed surfaces of the two minerals were predicted and the relations between surface broken bonds densities and surface energies were analyzed. Then the anisotropic wettability of the commonly exposed surfaces was studied by means of contact angle measurement. The calculation results show that the （101^-4）, （213^-4）and （01 1^-8）surfaces for calcite and （111） for fluorite are the most commonly exposed surfaces and there is a good rectilinear relation between surface broken bond density and surface energy with correlation of determination （R^2） of 0.9613 and 0.9969, respectively. The anisotropic wettability of different surfaces after immersing in distilled water and sodium oleate solutions at different concentrations can be explained by anisotropic surface broken bond densities and active Ca sites densities, respectively.
文摘Two geothermal fields with calcite scaling in some wells in Iceland were selected for the study of calcite scaling potential. An allowable supersaturation was found by comparing the degree of calcite supersaturation and actual scaling status in the selected wells.The saturation index,0.37～ 0.48, was the boundary between calcite scaling and no scaling. The information about changes in chloride concentration shows that mixing different waters is the main cause to form calcite scaling in the geothermal wells selected in this study.In this case, the content of chloride can be used as an index of scaling.
基金jointly by National Basic Research Program of China(973 Program) (2007CB411402)the Knowledge innovation project of Chinese Academy of Sciences(KZCX2-YW-Q04-05, KZCX2-YW-111-03)the National Natural Science Foundation of China(No.40573036).
文摘The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb＋Zn reserves of more than 5 million tons at Pb＋Zn grade of higher than 25%and contains abundant associated metals,such as Ag,Ge,Cd,and Ga.The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield.Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types,namely lumpy,patch and vein calcites in accordance with their occurrence.There is not intercalated contact between calcite and ore minerals and among the three types of calcite,indicating that they are the same ore-forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element（REE） and C-O isotopic compositions of calcites in the Huize Pb-Zn deposits.From lumpy to patch to vein calcites,REE contents decrease as LREE/ HREE ratios increase.The chondrite-normalized REE patterns of the three types of calcites are characterized by LREE-rich shaped,in which the lumpy calcite shows（La）_N〈（Ce）_N〈（Pr）_N≈（Nd）_N with Eu/Eu~＊〈1,the patch calcite has（La）_N〈（Ce）_N〈（Pr）_N≈（Nd）_N with Eu/Eu~＊〉1,and the vein calcite displays（La）_N〉（Ce）_N〉（Pr）_N〉（Nd）_N with Eu/Eu~＊〉1.The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield.Theδ^（13） C_（PDb） andδ^（18）O_（Smow） values of the three types of calcites vary from-3.5‰to-2.1‰and 16.7‰to 18.6‰,respectively,falling within a small field between primary mantle and marine carbonate in theδ^（13）C_（PDb） vsδ^（18）O_（Smow） diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages.The ore-forming fluids of the deposits resulted from crustal -mantle mixing processes,in which the mantle-derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts,and the crustal fluid was mainly provided by carbonate strata in the orefield.The ore-forming fluids in the deposits were homogenized before mineralization,and the ore-forming environment varied from relatively reducing to oxidizing.
基金supported by the National Natural Science Foundation of China(No.21177059)the Depart-ment of Science and Technology,Jiangsu Province(No.BK2012017/2011016,BE2012160)
文摘We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides （HFOs） using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents （denoted as HFO-201 and IOCCS） were employed for Sb（V） removal from water. Increasing solution pH from 3 to 9 apparently weakened Sb（V） removal by both composites, while increasing temperature from 293 to 313 K only improved Sb（V） uptake by IOCCS. HFO-201 exhibited much higher capacity for Sb（V） than for IOCCS in the absence of other anions in solution. Increasing ionic strength from 0.01 to 0.1 mol/L NaNO3 would result in a significant drop of the capacity of HFO-201 in the studied pH ranges; however, negligible effect was observed for 1OCCS under similar conditions. Similarly, the competing chloride and sulfate pose more negative effect on Sb（V） adsorption by HFO-201 than by IOCCS, and the presence of silicate greatly decreased their adsorption simultaneously, while calcium ions were found to promote the adsorption of both adsorbents. XPS analysis further demonstrated that preferable Sb（V） adsorption by both hybrids was attributed to the inner sphere complexation of Sb（V） and HFO, and Ca（II） induced adsorption enhancement possibly resulted from the formation of HFO-Ca-Sb complexes. Column adsorption runs proved that Sb（V） in the synthetic water could be effectively removed from 30 μg/L to below 5μg/L （the drinking water standard regulated by China）, and the effective treatable volume of IOCCS was around 6 times as that of HFO-201, implying that HFO coatings onto calcite might be a more effective approach than immobilization inside D201.
基金financial support from the Youth Science Foundation of China(No.52004333)。
文摘Polyaspartic acid(PASP)was used as a novel environmental-friendly depressant,and its inhibition effect on flotation performance of scheelite and calcite using sodium oleate(NaOL)as a collector was investigated by ways of flotation experiments,zeta potential measurement,contact angle measurement and infrared spectroscopic analysis(IR).The results show that PASP exhibits stronger inhibition capability and selectivity than acidified water glass,and the flotation separation of scheelite from calcite can be realized in the presence of 6 mg/L PASP and 20 mg/L NaOL at pH>6.In the presence of PASP,the zeta potential of calcite surface almost keeps unchanged after adding NaOL,and the contact angle decreases sharply.Therefore,it is indicated that PASP significantly decreases the adsorption of NaOL on calcite surface.By contrast,it has no distinct effect on the adsorption of NaOL on the scheelite surface,which is further confirmed by IR results.
基金the National Natural Science Foundation of China(Nos.51604302 and 51574282)the Key Laboratory of Hunan Province for Clean and Efficient Utilization of Strategic Calcium-containing Mineral Resources(No.2018TP1002).
文摘In this study, the innovative use of ethylenediamine tetramethylene phosphonic sodium(EDTMPS) as a calcite depressant in scheelite flotation was investigated by flotation experiments, and its selective depression mechanism was revealed by contact angle measurement, FTIR analysis, Zeta potential test and XPS analysis. The flotation experiment results showed that scheelite and calcite could be efficiently separated under the following conditions: pulp p H=9.5, Na OL concentration of 1.5×10^(-4)mol/L, EDTMPS concentration of 3.0×10^(-5)mol/L, a scheelite concentrate with WO3grade of 65.49%, recovery of 83.29%and separation efficiency of 65.29% could be obtained from the artificially mixed minerals. The analysis results of mineral surface properties demonstrated that EDTMPS was strongly adsorbed onto the calcite surface through the reaction between the phosphonate group and the calcium ions, which hindered Na OL adsorption and increased the hydrophilicity of calcite. However, EDTMPS had weak adsorption strength on the scheelite surface, which didn’t affect further adsorption of Na OL, hence, the scheelite remained hydrophobic. Consequently, the selective adsorption of EDTMPS on the two minerals’ surfaces increased a difference in wettability and thus enabling them to be separated by flotation. Finally, the mechanism model of this flotation separation process was established.
基金supported by the Youth Science Foundation of China(No.52004333)the Key Laboratory of Hunan Province for Clean and Efficiency Utilization of Strategic Calcium-containing Mineral Resources(No.2018TP1002).
文摘The flotation separation of magnesite from calcium-containing minerals has always been a difficult subject in minerals processing.This work studied the inhibition effects of carboxymethyl cellulose(CMC),sodium lignosulphonate,polyaspartic acid(PASP)and sodium silicate on flotation behaviors of magnesite,dolomite and calcite,providing guidance for the development of reagents in magnesite flotation.The micro-flotation results showed that among these four depressants,sodium silicate presented the strongest selectivity due to the highest recovery difference,and the flotation separation of magnesite from dolomite and calcite could be achieved by using sodium silicate as the depressant.Contact angle measurement indicated that the addition of sodium silicate caused the largest differences in surface wettability of the three minerals,which was in line with micro-flotation tests.Furthermore,zeta potential test,the Fourier transform infrared(FT-IR)spectroscopy and atomic force microscope(AFM)imaging were used to reveal the inhibition mechanism of sodium silicate.The results indicated that the dominated component SiO(OH)3of sodium silicate could adsorb on minerals surfaces,and the adsorption of sodium silicate hardly affected the adsorption of NaOL on magnesite surface,but caused the reduction of NaOL adsorption on dolomite and calcite surfaces,thereby increasing the flotation selectivity.
基金supported by the National Natural Science Foundation of China (No. 4072003)Fostering Foundation of Henan Polytechnic University for the Excellent PhD Dissertation (No. 2011011001)
文摘Abundant burrows of Skolithos linearis, Palaeophycus tubularis, and Taenidium barretti are preserved in the Upper Devonian Donghe sandstone of Tarim basin, China. They are commonly highlighted in core by the color of the burrow fill in contrast to the surrounding matrix and have dif-ferent textures and fabrics from the matrix. There are three kinds of calcite cements in burrows, microcrystalline-crystalline calcite cement, mosaic calcite cement, and ferroan calcite cement. Microcrystalline-crystalline calcite cement is widely distributed in the lower part of the Donghe sand-stone, but it is rare in burrows filling. It displays a globule structure under burial cementation and sel-dom replaces the quartz grains in shallow burial depth stage. Mosaiccalcite cement is widespread in the Donghe sansdtone reservoir of North Tarim basin. It shows chrysoidine, orange and bright orange lu-minescence, and intensely replaces the quartz grains, forming in early diagenetic and shallow burial depth stage. Ferroan calcite is asymmetrically distributed in the Donghe sandstone reservoir of Central Tarim basin. It fills the remanent pores in the shape of mosaic and replaces the quartz grains, matrix, and early calcite cement, forming in late diagenetic and deep burial depth stage. The burrows filled with white calcite cements have low oil saturation or may be oil-stained. In contrast, there is high oil saturation in the sandstone reservoir where the bioturbation is sparse or not present. With increased bioturbation, the porosity, permeability, and oil saturation decrease; thus, bioturbation intensity and reservoir property appear to be negatively correlated.
基金Project(2016RS2016) supported by Innovation Team of Interface Chemistry of Efficient and Clean Utilization of Complex Mineral Resources,China
文摘The flotation separation of smithsonite from calcite and quartz using a alkyl diamine ether(GE-609)as the collector was investigated through micro-flotation experiments and the real ore flotation experiments.The results show that GE-609exhibits good collecting capability to three minerals without selectivity.The presence of sodium sulfide enhances the flotation of smithsonite and calcite while inhibits quartz.Moreover,both sodium silicate and sodium hexametaphosphate exhibit good selective inhibition to calcite.The real ore test results show that a zinc concentrate containing23.51%Zn with the recovery of71.02%is obtained in the closed-circuit test.To understand the adsorption of GE-609on smithsonite surface,zeta potential measurement and FTIR analysis were carried out,and the results indicate that the collector GE-609can adsorb on smithsonite surface through both electrostatic adsorption and chemical adsorption,and the presence of sodium sulfide enhances the adsorption of GE-609.
文摘Carbonate minerals and water （or geofluids） reactions are important for modeling of geochemical processes and have received considerable attention over the past decades. The calcite dissolution rates from 50℃ to 250℃ at 10 MPa in deionized water with a flow rate varying from 0.2 to 5 mL/min were experimentally measured in a continuous flow column pressure vessel reactor. The dissolution began near the equilibrium with c/ceq 〉 0.3 and finally reached the equilibrium at 100℃-250℃, so the corresponding solubility was also determined as 1.87, 2.02, 2.02 and 1.88×10^-4.mol/L at 100℃, 150℃, 200℃ and 250℃ respectively, which was first increasing and then switching to decreasing with temperature and the maximum value might occur between 150℃ and 200℃. The experimental dissolution rate not only increased with temperature, but also had a rapid increase between 150℃ and 200℃ at a constant flow rate of 4 mL/min. The measured dissolution rates can be described using rate equations of R = k（1-c/ceq）n or R = kc-n. In these equations the reaction order n changed with temperature, which indicates that n was a variable rather than a constant, and the activation energy was 13.4 kJ/mol calculated with R = k（1-c/ceq）n or 18.0 kJ/mol with R = kc^-n, which is a little lower than the surface controlled values. The varied reaction order and lower activation energy indicates that calcite dissolution in this study is a complex interplay of diffusion controlled and surface controlled processes.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(Nos.51874247,51922091,51904249)Young Elite Scientists Sponsorship Program by CAST,China(No.2018QNRC001)+2 种基金Sichuan Science and Technology Program,China(Nos.2019YFS0453,2018JY0148)Open Research Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization,China(No.CNMRCUKF2001)Postgraduate Innovation Fund by Southwest University of Science and Technology,China(No.20ycx0027).
文摘The surface properties of fluorite are often affected by dissolved gangue species(e.g.,calcite)during the flotation process.Microflotation testing with and without the addition of calcite supernatant was conducted using octanohydroxamic acid(OHA)as the collector.The results revealed that dissolved calcite species significantly affected the flotation behavior of fluorite.Fourier transform infrared spectra confirmed that the decrease in flotation recovery was linked to lower OHA adsorption.Solution chemistry analysis indicated that CaCO_(3) and Ca^(2+)from the calcite supernatant were the most favorably adsorbed species,and X-ray photoelectron spectroscopy analysis confirmed the surface adsorption of calcite species.Density functional theory simulations provided a detailed analysis of the multidentate adsorption configuration of OHA,which was the most favorable for adsorption on the fluorite surface.The adsorption energy calculation showed that the calcite dissolved species were more stably adsorbed on the fluorite surface than OHA.The pre-adsorption of calcite dissolved species hindered the adsorption of OHA due to electrostatic repulsion.
基金supported by the National Basic Research Program of China (973 Program) (No. 2009CB421006)the State Key Laboratory of Geological Processes and Mineral Resources (No. GPMR200843)
文摘The calcite dissolution rates at 50-250 ℃ and 20 MPa in deionized water with flow rate varying from 0.2 to 5 mL/min were experimentally measured in a continuous flow column pressure vessel reactor. Equilibrium concentration （Ceq） of calcite dissolution in deionized water at 20 MPa was determined using dissolution data according to the iterative method presented by Jeschke and Dreybrodt. The equilibrium concentrations at 50, 100, 150, 200 and 250 ℃ are 1.84×10^-4, 2.23×10^-4, 2.25×10^-4, 2.31×10^-4 and 2.24×10^-4 mol/L, respectively. The Ceq increases first and then decreases with temperature varying from 50 to 250 ℃ at 20 MPa, and the same variation trend occurs at 10 MPa with lower values. The maximum value （or extremum） of Ceq would increase with temperature at constant pressures. The dissolution reaction of calcite in this experiment is approaching the calcite equilibrium, and the reaction order doesn＇t keep a constant at different temperatures, which could imply that a change of the reac- tion mechanism was occurring. The Arrhenius equation shouldn＇t be used to calculate apparent activation energy using rate constant data at different temperatures when the reaction order or reaction mechanism changed.
基金funded by the National Key Research and Development Program of China(No.2018YFC0309903)the Scientific Research Fund of the Second Institute of Oceanography,MNR(No.QNYC1701)+1 种基金the China Ocean Mineral Resources R&D Association Project(No.DY135-S2-1-02&05)the National Science Foundation of China(No.41976076)
文摘Serpentinization and calcite precipitation of mantle peridotites exhumed along detachment faults at the slow-to ultraslow-spreading centers can provide important clues to the hydrothermal alteration processes.The Tianxiu hydrothermal field is a new-found active and ultramafichosted hydrothermal vent site along the Carlsberg Ridge,Northwest Indian Ocean.Two types of calcite veins are recognized in serpentinized harzburgite samples collected from the seafloor at the water depth of 3 500 m(3.67°N/63.83°E) and 400 m north of Tianxiu hydrothermal field.Calcite veins Ⅰ occur in the fractures that cut through mesh texture in the highly serpentinized harzburgite,while calcite veins Ⅱ precipitate within the mesh texture in the relatively weaker serpentinized harzburgite.Both veins show similar δ13CPDB(+0.54‰ and +0.58‰) but different δ18OPDB(-16.67‰ and +4.46‰) values,suggesting that they were derived from the same carbon source but precipitated at different temperatures.Taking the deep seawater temperature of 2℃as the precipitation temperature of the calcite veins I,the equilibrium δ18OV-SMOW of calcite-precipitating fluid was calculated to be 1.78‰,which is close to the average δ18OV-SMOW value(1.74‰) of vent fluid samples from the ultramafic-hosted hydrothermal systems worldwide.The formation temperature of calcite veins Ⅱ is inferred to be approximately 134℃,based on the calculated δ18OV-SMOW above.The temperature differences of calcite precipitation probably resulted from the fluid cooling conductively and mixing with seawater along the presumed fractures during slow upflow.The low-temperature calcite postdates the mesh texture,while the high-temperature calcite may precipitate under relatively low water/rock ratios,alkaline and reduced conditions among the mesh texture,which is revealed by the geochemical models.Therefore,it is suggested that they both have been influenced by hydrothermal fluids and the sampling site is near the discharge zone of hydrothermal circulation.
