Objective This study aimed to study the effects of different crystalline states of Sheng Shigao(raw gypsum,RG)and its inorganic elements on the antipyretic efficacy of Baihu Decoction(BHT).Methods RG samples calcined ...Objective This study aimed to study the effects of different crystalline states of Sheng Shigao(raw gypsum,RG)and its inorganic elements on the antipyretic efficacy of Baihu Decoction(BHT).Methods RG samples calcined at different temperatures were prepared.The phase composition of RG and Duan Shigao(calcination of gypsum,CG)as well as the changes in phase composition before and after adding water to RG calcined at specific temperatures,were determined using X-ray diffraction(XRD).A fever model was established by subcutaneously injecting 20%yeast suspension(10 mL·kg~(-1))into the backs of rats.The effects of BHT containing RG in different crystalline states on rat body temperature were measured.Serum levels of IL-1β,IL-6,and hypothalamic prostaglandin E2(PGE_2)were detected using ELISA.Serum Ca~(2+)levels were measured using a microplate method.The content of trace elements in RG and CG and the corresponding freeze-dried BHT powder was determined using inductively coupled plasma mass spectrometry(ICP-MS).The complexation of representative inorganic elements with mangiferin,a major active component in BHT,was investigated using UV-Vis spectroscopy and fluorescence spectroscopy.A validation model was established using RAW264.7 mouse macrophages.Drug-containing serum of BHT with different inorganic elements was prepared,and the nitric oxide(NO)levels in the cell supernatant of different treatment groups were measured using the Griess method.The mRNA levels of IL-6,TNF-α,and PGE2in each group were detected using qPCR(real-time fluorescent quantitative PCR).Results After calcination,the phase composition of RG changed,and the content of inorganic elements in RG,CG170(RG calcined at 170°C),and CG350(RG calcined at 350°C)showed similar trends.Compared with RG,the content of Ca,Sr,Al,and Na in CG changed significantly.Compared with BHT,the content of Ca,Sr,Si,and Na in CG changed significantly when incorporated into the formula.Intermolecular interactions confirmed strong binding between mangiferin and Cu~(2+)and Al~(3+).Cu~(2+)and Fe~(3+)exhibited fluorescence quenching effects on mangiferin solution,while Al~(3+)and Zn~(2+)showed strong fluorescence enhancement,with fluorescence intensity increasing by 120-fold and 30-fold,respectively.In vitro evaluation of synergistic anti-inflammatory effects confirmed that Ca,Fe,Cr,Al,and Si exhibited synergistic anti-inflammatory effects.Conclusion The crystalline state of RG has little effect on its antipyretic properties,while Ca,Sr,Na,Fe,and Al are likely the key material bases influencing its efficacy.展开更多
Gypsum rocks are highly susceptible to mechanical deterioration under the coupled effects of wet-dry(W-D)cycles and flow rates,which significantly influence the stability of underground excavations.Despite extensive r...Gypsum rocks are highly susceptible to mechanical deterioration under the coupled effects of wet-dry(W-D)cycles and flow rates,which significantly influence the stability of underground excavations.Despite extensive research on the effects of W-D cycles,the coupling influence of flow rates and W-D cycles on gypsum rocks remains poorly understood.This study investigates the mechanical behavior and deterioration mechanisms of gypsum rocks subjected to varying W-D cycles and flow rate conditions.Axial compression tests,along with nuclear magnetic resonance(NMR)techniques,were employed to analyze the stress-strain response and microstructural changes.Based on the disturbed state concept(DSC)theory,a W-D deterioration model and a DSC-based constitutive model were developed to describe the degradation trends and mechanical responses of gypsum rocks under different conditions.The results demonstrate that key mechanical indices,elastic modulus,cohesion,uniaxial compressive strength(UCS),and internal friction angle,exhibit logarithmic declines with increasing W-D cycles,with higher flow rates accelerating the deterioration process.The theoretical models accurately capture the nonlinear compaction behavior,peak stress,and post-peak response of gypsum specimens.This study provides valuable insights for predicting the mechanical behavior of gypsum rocks and improving the stability assessments of underground structures under complex environmental conditions.展开更多
In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calc...In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calculations of the thermodynamic stability region show that 89.36%Zn,>99%Pb and>99%Cu of gypsum residue and zinc-containing fume can be sulfured to ZnS,PbS and Cu 2 S,under sufficient sulfur partial pressure,low oxygen partial pressure and 400-1000℃.Sulfidation roasting experiments show that the sulfidation rate of Cu,Pb and Zn reach 81.43%,88.25% and 92.31%,respectively,under the roasting conditions of material mass ratio of 30 g:10 g,carbon dosage of 3.75 g,roasting temperature of 800℃ for 3 h.E−pH plots show that ZnS,PbS and Cu_(2)S can be enriched in the leaching residue,under leaching conditions at 25℃,pH<4 and-0.4 V<φ(E)<0.04 V.The leaching experiments showed that the sulfide is retained in the leaching residue,while the leaching rates of Cu,Pb and Zn are 1.94%,2.05% and 1.51%,respectively,under the conditions of 25℃,C_(HCl) of 0.5 mol/L,L/S of 5 mL/g,stirring rate of 300 r/min,and stirring time of 30 min.This study provides a new approach for the synergistic disposal of gypsum residue and zinc containing fume.展开更多
Practical applications of desulfurization gypsum are limited owing to its brittleness and low strength.To overcome these challenges,researchers have developed engineered desulfurization gypsum composites(EDGCs)by inco...Practical applications of desulfurization gypsum are limited owing to its brittleness and low strength.To overcome these challenges,researchers have developed engineered desulfurization gypsum composites(EDGCs)by incorporating ultrahigh molecular weight polyethylene(UHMWPE)fiber and sulfoaluminate cement(SAC).The mix ratio was optimized using response surface methodology(RSM).Experimental testing of EDGC under compressive and tensile loads led to the creation of a regression model that investigates the influence of variables and their interactions on the material’s compressive and tensile strengths.Additionally,microscopic morphology and hydration product composition were analyzed to explore the influence mechanism.The results indicated that EDGC’s compressive strength increased by up to 38.4%owing to a decreased water-binder ratio and higher SAC content.Similarly,tensile strength increased by up to 38.6%owing to increased SAC and fiber content.Moreover,EDGC demonstrated excellent strain-hardening behavior and multiple cracking characteristics,achieving a maximum tensile strain of nearly 3%.The research findings provide valuable insights for optimizing the performance of desulfurization gypsum.展开更多
The massive accumulation of flue gas desulfurization(FGD)gypsum produced in the wet limestone-gypsum flue gas desulfurization process not only encroaches on lands but also causes serious environmental pollution.The pr...The massive accumulation of flue gas desulfurization(FGD)gypsum produced in the wet limestone-gypsum flue gas desulfurization process not only encroaches on lands but also causes serious environmental pollution.The preparation ofα-hemihydrate gypsum(α-HH)is an important way to achieve high-value utilization of FGD gypsum.Although the glycerol-water solution approach can be used to produceα-HH from FGD gypsum under mild conditions,the transition is kinetically unfavorable in the mixed solution.Here,an easy pretreatment was used to activate FGD gypsum by calcination and hydration to readily complete the transition.The pretreatment deteriorated the crystallinity of FGD gypsum and caused it to form small irregular flaky crystals,which dramatically increased the specific surface area.Additionally,most of the organics adsorbed onto FGD gypsum surfaces were removed after pretreatment.The poor crystallinity,increased specific surface area,and elimination of organics adsorbed onto crystal surfaces effectively improved the conversion activity of FGD gypsum,thereby promoting dihydrate gypsum(DH)dissolution andα-HH nucleation.Overall,the phase transition of FGD gypsum toα-HH is facilitated.展开更多
Lime pretreated phosphogypsum（PG） was calcined at 500 ℃ to produce anhydrate gypsum cement. Due to the slow hydration of anhydrate gypsum, additives, K2SO4 and hemihydrate gypsum were selected to accelerate the hyd...Lime pretreated phosphogypsum（PG） was calcined at 500 ℃ to produce anhydrate gypsum cement. Due to the slow hydration of anhydrate gypsum, additives, K2SO4 and hemihydrate gypsum were selected to accelerate the hydration of anhydrate. The hydration characteristics, the resistance to hydrodynamic water, and the mineralogical studies were investigated. The experimental results suggest that activated by K2SO4 and hemihydrate, anhydrate PG hydrates much more rapidly than that in the presence of only K2SO4 or in the absence of additives. The binder has proper setting time, good strength development, and relatively better resistance to water. The hardened binder has hydrated products of rod or stick like shaped dihydrate gypsum crystals.展开更多
Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at ...Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373-503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern,Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.展开更多
In order to more efficiently utilize gypsum to improve meadow alkali soil slightly salinized by soda and sulfate chloride, a total of 27 treatments were de- signed from the perspectives of field capacity, alkalinity, ...In order to more efficiently utilize gypsum to improve meadow alkali soil slightly salinized by soda and sulfate chloride, a total of 27 treatments were de- signed from the perspectives of field capacity, alkalinity, alkaline salt content, optimal irrigation, gypsum conversion, gypsum and soil treatment and improvement depth. The ions on the obtained filtrate were analyzed in terms of salts. The improving ef- ficiency of gypsum for meadow alkali soil was analyzed through comparing the con- tents of soluble salts in pre-improvement and post-improvement soil by reasoning and calculation. The results showed that, （1） the dissolved amount and conversion amount of gypsum were increased, and the soil alkalinity was decreased corre- spondingly with the increased irrigation amount. However, after reaching a certain extent, the linear relationships became unobvious gradually. Therefore, the irrigation amount should be arranged reasonably for different treatment. （2） Compared with those at low temperature, the dissolved amount of gypsum at high temperature was increased by 1.47-1.50 times, the release amount of exchangeable sodium was in- creased by 2.98-4.70 times, and the release amount of exchangeable magnesium was increased by 2.07-2.90 times. In overall, the improving efficiency of gypsum in summer was better. However, gypsum had two shortcomings in summer. First, a large amount of gypsum leaked away. Second, a large amount of exchangeable magnesium, along with exchangeable sodium, was substituted by gypsum. （3） Compared with the other two treatments, treatment B （mixing gypsum and top 20- cm soil） showed the best improving efficiency, and it was characterized by stepwise dealkalization from top to down. In addition, mixing gypsum and topsoil is more practical in the production.展开更多
In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG)on the environment and improve the workability of HPG,the effects of the content of quicklime and types of biopolymer(hydroxypropyl methy...In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG)on the environment and improve the workability of HPG,the effects of the content of quicklime and types of biopolymer(hydroxypropyl methylcellulose,xanthan gum,sodium polyacrylate(PAANa))on the compressive strength,softening coefficient and ultrasonic velocity of HPG were evaluated.When the content of quicklime was 1.5%and the content of PAA-Na was 0.2%,HPG had the best mechanical properties and workability,its water retention rate can be increased by 5.8%,and unconfined compressive strength of 3 days increased by 10.3%and 7 days increased by 13.1%.Through the analysis of scanning electron microscope and X-ray diffraction,it was found that the hydration reac-tion of HPG was more sufficient,the pores size and number decreased,the number of impurities on the crystal surface decreased obviously,and CaF2 and other substances were formed by the reaction after the addition of quicklime.After adding quicklime and PAANa,the indicators of gypsum self-leveling mortar prepared by HPG meet the requirements of the standard.展开更多
The excessive demand for phosphorus-based fertilizers is contributing to the undesired byproduct of phosphogypsum(PG),typically found in large quantities in phosphoric acid industry.Without proper management,this indu...The excessive demand for phosphorus-based fertilizers is contributing to the undesired byproduct of phosphogypsum(PG),typically found in large quantities in phosphoric acid industry.Without proper management,this industrial waste poses a significant environmental pollution risk.Current technologies are struggle to effectively handle the volume of PG produced,but one promising solution is its conversion into hemihydrate gypsum(CaSO_(4)·0.5 H_(2)O,HH).HH can exist in two phases,α-HH andβ-HH,withα-hemihydrate gypsum(α-HH)being preferred for its complete crystal structure and lower water requirement for hydration.The morphology ofα-HH gypsum is crucial for its material applications,and controlling crystal morphology is possible through the use of suitable crystal modifiers.This review explores various aspects of crystal modifiers and highlights their role in the preparation ofα-HH from PG.It suggests that leveraging the interfacial properties of PG could lead to innovative applications.Additionally,the review outlines future directions for PG development and identifies challenges to be addressed in the next steps.展开更多
A novel utilization way of the sludge from wet calcium-based flue gas desulfurization （FGD） processes has been developed in this paper. This study focused on the conversion of the FGD gypsum into α-hemihydrate calc...A novel utilization way of the sludge from wet calcium-based flue gas desulfurization （FGD） processes has been developed in this paper. This study focused on the conversion of the FGD gypsum into α-hemihydrate calcium sulfate by a hydrothermal salt solution method at atmospheric pressure. Experimental study has been carried out in a batch reactor. Qualitative and quantitative analyses were made by DSC/TG thermal analysis, SEM, XRD, metalloscope and chemical analysis. The experimental results showed that the modification of FGD gypsum was controlled by the dissolution and recrystallization mechanisms. With the introduction of FGD gypsum the salt solution was supersaturated, then crystal nucleus of α-hemihydrate calcium sulfate were produced in the solution. With the submicroscopic structure of FGD gypsum crystal changed, the crystal nucleus grew up into α-hemihydrate calcium sulfate crystals. Thus ,the modification of FGD gypsum was fulfilled.展开更多
Failure of rock mass that is subjected to compressive loads occurs from initiation, propagation, and linkage of new cracks from preexisting fissures. Our research investigates the cracking behaviour and coalescence pr...Failure of rock mass that is subjected to compressive loads occurs from initiation, propagation, and linkage of new cracks from preexisting fissures. Our research investigates the cracking behaviour and coalescence process in a brittle material with two non-parallel overlapping flaws using a high-speed camera. The coalescence tensile crack and tensile wing cracks were the first cracks to occur from the preexisting flaws. The initiation stresses of the primary cracks at the two tips of each flaw were simultaneous and decreased with reduced flaw inclination angle. The following types of coalescence cracks were identified between the flaws: primary tensile coalescence crack, tensile crack linkage, shear crack linkage, mixed tensile-shear crack, and indirect crack coalescence. Coalescence through tensile linkage occurred mostly at pre-peak stress. In contrast, coalescence through shear or mixed tensile-shear cracks occurred at higher stress. Overall, this study indicates that the geometry of preexisting flaws affect crack initiation and coalescence behaviour.展开更多
Previous studies have mainly focused on changes in soil physical and chemical properties to evaluate the reclamation of sodic soils using flue gas desulfurization(FGD)gypsum.However,information on the effects of this ...Previous studies have mainly focused on changes in soil physical and chemical properties to evaluate the reclamation of sodic soils using flue gas desulfurization(FGD)gypsum.However,information on the effects of this reclamation method on microbial-based indicators of soil quality is limited,particularly after many years of FGD gypsum application.This study aimed to investigate the long-term effects of FGD gypsum on soil organic carbon(SOC),nutrients,microbial biomass and enzyme activity.Data were collected from soils of three exchangeable sodium percentage(ESP)classes(i.e.,low-,middle-and hjgh-ESP classes of 6.1-20,20-30 and 30-78.4%,respectively)17 years after FGD gypsum treatment in Inner Mongolia,China.Averaged across the three ESP classes,FGD gypsum application increased the SOC contents at the 0-20 and 20-40-cm soil depths by 18 and 35%,respectively,and increased available potassium at the 0-20-cm soil depth by 51%compared with the no-gypsum controls.The microbial biomass carbon and microbial biomass nitrogen contents at the 20-40-cm soil depth increased by 69 and 194%,respectively,under FGD gypsum.Except in the high-ESP class,urease activities in the 0-40 cm soil profile were significantly higher in the FGD gypsum treatments than in the controls.A significant increase in alkaline phosphatase activity was concentrated in the 20-40 cm soil layer;few classes showed significant increases in catalase and invertase activities in the 0-20 cm soil layer.Pearson correlation analysis showed that increases in soil fertility and biological activity could be attributed to reductions in electrical conductivity,pH and ESP caused by FGD gypsum application.These results confirm that FGD gypsum application is a viable strategy for reclaiming sodic soils due to its positive effects on soil fertility and biochemistry and that it may contribute to soil ecosystem sustainability.展开更多
Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pres-sure was investigated.The effects of temperature,salt species,salt concentration,solids content,pH and modifier w...Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pres-sure was investigated.The effects of temperature,salt species,salt concentration,solids content,pH and modifier were examined.The crystals obtained under different conditions and solubility of calcium sulfate in contact with solid gypsum were also determined.α-Calcium sulfate hemihydrate crystals of stubby columnar shape and regular pentahedral sides were obtained under the following conditions：salt concentration 20%-30%,operation tempera-ture 95-100 °C,solids mass content in the slurry 10%-30% and neutral pH.Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium sulfate hemihydrate occurs because of the difference in solubilities between the two solid gypsum phases in this system.展开更多
The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxid...The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane（AOM） coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor（cmbsf） in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values（δ^34 S） of pyrite vary greatly（from –46.6‰ to –12.3‰ V-CDT） and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction（OSR） and is influenced by AOM with depth.The relative high abundance and δ^34 S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone（SMTZ）.The sulfur isotopic composition of gypsum（from–25‰ to –20.7‰） is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO2,iron（Ⅲ） and oxygen driven by the SMTZ location shift to great depths.The δ^34 S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.展开更多
The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization （FGD） units of coal- fired power plants. Studies have been carried out in confined greenhouses using FGD gypsu...The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization （FGD） units of coal- fired power plants. Studies have been carried out in confined greenhouses using FGD gypsum treated soils. Major research focus is uptakes of mercury by plants, and emission of mercury into the atmosphere under varying application rates of FGD gypsum, simulating rainfall irrigations, soils, and plants types. Higher FGD gypsum application rates generally led to higher mercury concentrations in the soils, the increased mercury emissions into the atmosphere, and the increased mercury contents in plants （especially in roots and leaves）. Soil properties and plant species can play important roles in mercury transports. Some plants, such as tall fescue, were able to prevent mercury from atmospheric emission and infiltration in the soil. Mercury concentration in the stem of plants was found to be increased and then leveled off upon increasing FGD gypsum application. However, mercury in roots and leaves was generally increased upon increasing FGD gypsum application rates. Some mercury was likely absorbed by leaves of plants from emitted mercury in the atmosphere.展开更多
The feasibility of flue gas desulphurization （FGD） as concrete admixture was studied. A combined concrete admixture of the thermally-treated FGD gypsum and slag powder was explored. The FGD gypsum was roasted at 200...The feasibility of flue gas desulphurization （FGD） as concrete admixture was studied. A combined concrete admixture of the thermally-treated FGD gypsum and slag powder was explored. The FGD gypsum was roasted at 200℃ for 60 min and then mixed with the slag powder to form FGD gypsum-slag powder combined admixture in which the SO3 content was 3.5wt%. Cement was partially and equivalently replaced by slag powder alone or FGD gypsum-slag powder, at concentration of 25wt%, 40wt%, and 50wt%, respectively. The setting times, hydration products, total porosity and pore size distributions of the paste were determined. The compressive strength and drying shrinkage of cement mortar and concrete were also tested. The experimental results show that, in the presence of FGD gypsum, the setting times are much slower than those of pastes in the absence of FGD gypsum. The combination of FGD gypsum and slag powder provides synergistic benefits above that of slag powder alone. The addition of FGD gypsum provides benefit by promoting ettringite formation and forms a compact microstructure, increasing the compressive strength and reduces the drying shrinkage of cement mortar and concrete.展开更多
The microstructure, phase composition, and thermal characteristics of various natural gypsums and the high-strength gypsum──the converted product of natural one are analysed.The formation mecbanism of high-strength ...The microstructure, phase composition, and thermal characteristics of various natural gypsums and the high-strength gypsum──the converted product of natural one are analysed.The formation mecbanism of high-strength gypsum is further discussed. It is found that the high-streugth gypsum is of hollow irregular hexagonal prism structure, which is almost free from tbe (010) and (100) cleavages and can form clustered fibrous crystals with high-strength.展开更多
In this paper,the solid waste desulfurization gypsum produced by coal-fired power plants was used as a raw material to prepare calcium sulfate whiskers with high application prospects.Calcium sulfate whiskers with uni...In this paper,the solid waste desulfurization gypsum produced by coal-fired power plants was used as a raw material to prepare calcium sulfate whiskers with high application prospects.Calcium sulfate whiskers with uniform morphology and high aspect ratio can be prepared by hydrothermal method in sulfuric acid solution.A new process of desulfurization gypsum activated by high-energy grinding to reduce the reaction temperature and sulfuric acid concentration was developed.Through the comparison of product morphology,the best grinding time was determined to be 3.5 h.The mechanism of desulfurization gypsum through physical–chemical coupling to reduce energy consumption was clarified.The activation of desulfurization gypsum by grinding and the acidic environment provided by the sulfuric acid solution made the calcium sulfate solution reached rapid saturation and accelerated the nucleation rate.By calculating the conversion and crystallization rate of calcium sulfate whiskers,it was found that there were obvious"autocatalytic"kinetic characteristics during the crystallization process.展开更多
Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was...Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was added into the CaCl2 solution by slow titration or in multiple stages over 2-8 h followed by 2 h equilibration.In order to regenerate KCl solution as concentrated as possible,K2SO4 solid was added into the given CaCl2 solution instead of K2SO4 solution,obtaining gypsum crystals with almost the same quality by multistage addition with[SO4 2-]/[Ca 2+]molar ratio no larger than 0.8.However,impurity of K2SO4·CaSO4·H2O was detected by XRD and was further confirmed by SEM-EDS in the produced crystals when the[SO4 2-]/[Ca 2+] ratio increased to 1.1.It is proved that appearance of the double sulfate is attributed to the relatively high concentration of K2SO4.So,it is essential to properly control the[SO4 2-]/[Ca 2+]ratio and make sure[Ca 2+ ]in excess to suppress the solubility of CaSO4 even at the expense of low calcium removal rate.展开更多
基金Joint Fund Project of the Henan Provincial Science and Technology Research and Development Plan(222301420060)。
文摘Objective This study aimed to study the effects of different crystalline states of Sheng Shigao(raw gypsum,RG)and its inorganic elements on the antipyretic efficacy of Baihu Decoction(BHT).Methods RG samples calcined at different temperatures were prepared.The phase composition of RG and Duan Shigao(calcination of gypsum,CG)as well as the changes in phase composition before and after adding water to RG calcined at specific temperatures,were determined using X-ray diffraction(XRD).A fever model was established by subcutaneously injecting 20%yeast suspension(10 mL·kg~(-1))into the backs of rats.The effects of BHT containing RG in different crystalline states on rat body temperature were measured.Serum levels of IL-1β,IL-6,and hypothalamic prostaglandin E2(PGE_2)were detected using ELISA.Serum Ca~(2+)levels were measured using a microplate method.The content of trace elements in RG and CG and the corresponding freeze-dried BHT powder was determined using inductively coupled plasma mass spectrometry(ICP-MS).The complexation of representative inorganic elements with mangiferin,a major active component in BHT,was investigated using UV-Vis spectroscopy and fluorescence spectroscopy.A validation model was established using RAW264.7 mouse macrophages.Drug-containing serum of BHT with different inorganic elements was prepared,and the nitric oxide(NO)levels in the cell supernatant of different treatment groups were measured using the Griess method.The mRNA levels of IL-6,TNF-α,and PGE2in each group were detected using qPCR(real-time fluorescent quantitative PCR).Results After calcination,the phase composition of RG changed,and the content of inorganic elements in RG,CG170(RG calcined at 170°C),and CG350(RG calcined at 350°C)showed similar trends.Compared with RG,the content of Ca,Sr,Al,and Na in CG changed significantly.Compared with BHT,the content of Ca,Sr,Si,and Na in CG changed significantly when incorporated into the formula.Intermolecular interactions confirmed strong binding between mangiferin and Cu~(2+)and Al~(3+).Cu~(2+)and Fe~(3+)exhibited fluorescence quenching effects on mangiferin solution,while Al~(3+)and Zn~(2+)showed strong fluorescence enhancement,with fluorescence intensity increasing by 120-fold and 30-fold,respectively.In vitro evaluation of synergistic anti-inflammatory effects confirmed that Ca,Fe,Cr,Al,and Si exhibited synergistic anti-inflammatory effects.Conclusion The crystalline state of RG has little effect on its antipyretic properties,while Ca,Sr,Na,Fe,and Al are likely the key material bases influencing its efficacy.
基金Projects(52378392,52478390)supported by the National Natural Science Foundation of ChinaProject(2024J08213)supported by the Natural Science Foundation of Fujian Province,China+1 种基金Project(00387088)supported by the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province,ChinaProject(GY-Z23072)supported by the Scientific Research Foundation of Fujian University of Technology,China。
文摘Gypsum rocks are highly susceptible to mechanical deterioration under the coupled effects of wet-dry(W-D)cycles and flow rates,which significantly influence the stability of underground excavations.Despite extensive research on the effects of W-D cycles,the coupling influence of flow rates and W-D cycles on gypsum rocks remains poorly understood.This study investigates the mechanical behavior and deterioration mechanisms of gypsum rocks subjected to varying W-D cycles and flow rate conditions.Axial compression tests,along with nuclear magnetic resonance(NMR)techniques,were employed to analyze the stress-strain response and microstructural changes.Based on the disturbed state concept(DSC)theory,a W-D deterioration model and a DSC-based constitutive model were developed to describe the degradation trends and mechanical responses of gypsum rocks under different conditions.The results demonstrate that key mechanical indices,elastic modulus,cohesion,uniaxial compressive strength(UCS),and internal friction angle,exhibit logarithmic declines with increasing W-D cycles,with higher flow rates accelerating the deterioration process.The theoretical models accurately capture the nonlinear compaction behavior,peak stress,and post-peak response of gypsum specimens.This study provides valuable insights for predicting the mechanical behavior of gypsum rocks and improving the stability assessments of underground structures under complex environmental conditions.
基金Projects(52174269,52374293)supported by the National Natural Science Foundation of ChinaProject(2022RC1123)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calculations of the thermodynamic stability region show that 89.36%Zn,>99%Pb and>99%Cu of gypsum residue and zinc-containing fume can be sulfured to ZnS,PbS and Cu 2 S,under sufficient sulfur partial pressure,low oxygen partial pressure and 400-1000℃.Sulfidation roasting experiments show that the sulfidation rate of Cu,Pb and Zn reach 81.43%,88.25% and 92.31%,respectively,under the roasting conditions of material mass ratio of 30 g:10 g,carbon dosage of 3.75 g,roasting temperature of 800℃ for 3 h.E−pH plots show that ZnS,PbS and Cu_(2)S can be enriched in the leaching residue,under leaching conditions at 25℃,pH<4 and-0.4 V<φ(E)<0.04 V.The leaching experiments showed that the sulfide is retained in the leaching residue,while the leaching rates of Cu,Pb and Zn are 1.94%,2.05% and 1.51%,respectively,under the conditions of 25℃,C_(HCl) of 0.5 mol/L,L/S of 5 mL/g,stirring rate of 300 r/min,and stirring time of 30 min.This study provides a new approach for the synergistic disposal of gypsum residue and zinc containing fume.
基金The National Natural Science Foundation of China(No.51978504).
文摘Practical applications of desulfurization gypsum are limited owing to its brittleness and low strength.To overcome these challenges,researchers have developed engineered desulfurization gypsum composites(EDGCs)by incorporating ultrahigh molecular weight polyethylene(UHMWPE)fiber and sulfoaluminate cement(SAC).The mix ratio was optimized using response surface methodology(RSM).Experimental testing of EDGC under compressive and tensile loads led to the creation of a regression model that investigates the influence of variables and their interactions on the material’s compressive and tensile strengths.Additionally,microscopic morphology and hydration product composition were analyzed to explore the influence mechanism.The results indicated that EDGC’s compressive strength increased by up to 38.4%owing to a decreased water-binder ratio and higher SAC content.Similarly,tensile strength increased by up to 38.6%owing to increased SAC and fiber content.Moreover,EDGC demonstrated excellent strain-hardening behavior and multiple cracking characteristics,achieving a maximum tensile strain of nearly 3%.The research findings provide valuable insights for optimizing the performance of desulfurization gypsum.
基金Projects(51904104,51974117,51804114)supported by the National Natural Science Foundation of ChinaProjects(2018YFC1901601,2018YFC1901602,2018YFC1901605)supported by the National Key Scientific Research Project of China+1 种基金Project(2015CX005)supported by the Innovation Driven Plan of Central South University,ChinaProject(18B226)supported by the Excellent Youth Project of Hunan Education Department,China
文摘The massive accumulation of flue gas desulfurization(FGD)gypsum produced in the wet limestone-gypsum flue gas desulfurization process not only encroaches on lands but also causes serious environmental pollution.The preparation ofα-hemihydrate gypsum(α-HH)is an important way to achieve high-value utilization of FGD gypsum.Although the glycerol-water solution approach can be used to produceα-HH from FGD gypsum under mild conditions,the transition is kinetically unfavorable in the mixed solution.Here,an easy pretreatment was used to activate FGD gypsum by calcination and hydration to readily complete the transition.The pretreatment deteriorated the crystallinity of FGD gypsum and caused it to form small irregular flaky crystals,which dramatically increased the specific surface area.Additionally,most of the organics adsorbed onto FGD gypsum surfaces were removed after pretreatment.The poor crystallinity,increased specific surface area,and elimination of organics adsorbed onto crystal surfaces effectively improved the conversion activity of FGD gypsum,thereby promoting dihydrate gypsum(DH)dissolution andα-HH nucleation.Overall,the phase transition of FGD gypsum toα-HH is facilitated.
基金Funded by the National Natural Science Foundation of China (No. 50802019)
文摘Lime pretreated phosphogypsum（PG） was calcined at 500 ℃ to produce anhydrate gypsum cement. Due to the slow hydration of anhydrate gypsum, additives, K2SO4 and hemihydrate gypsum were selected to accelerate the hydration of anhydrate. The hydration characteristics, the resistance to hydrodynamic water, and the mineralogical studies were investigated. The experimental results suggest that activated by K2SO4 and hemihydrate, anhydrate PG hydrates much more rapidly than that in the presence of only K2SO4 or in the absence of additives. The binder has proper setting time, good strength development, and relatively better resistance to water. The hardened binder has hydrated products of rod or stick like shaped dihydrate gypsum crystals.
基金Supported by the Turkish Republic Prime Ministry State Planning Organization (No. 98-DPT-07-01-02) and the Yildiz Technical University Research Foundation (No. 95-B-07-01-04).
文摘Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373-503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern,Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.
基金Supported by National Natural Science Foundation of China(41401559)Project of Hubei Provincial Science and Technology Department(2014CFB558)Project of Hubei Provincial Department of Education(D20141001)~~
文摘In order to more efficiently utilize gypsum to improve meadow alkali soil slightly salinized by soda and sulfate chloride, a total of 27 treatments were de- signed from the perspectives of field capacity, alkalinity, alkaline salt content, optimal irrigation, gypsum conversion, gypsum and soil treatment and improvement depth. The ions on the obtained filtrate were analyzed in terms of salts. The improving ef- ficiency of gypsum for meadow alkali soil was analyzed through comparing the con- tents of soluble salts in pre-improvement and post-improvement soil by reasoning and calculation. The results showed that, （1） the dissolved amount and conversion amount of gypsum were increased, and the soil alkalinity was decreased corre- spondingly with the increased irrigation amount. However, after reaching a certain extent, the linear relationships became unobvious gradually. Therefore, the irrigation amount should be arranged reasonably for different treatment. （2） Compared with those at low temperature, the dissolved amount of gypsum at high temperature was increased by 1.47-1.50 times, the release amount of exchangeable sodium was in- creased by 2.98-4.70 times, and the release amount of exchangeable magnesium was increased by 2.07-2.90 times. In overall, the improving efficiency of gypsum in summer was better. However, gypsum had two shortcomings in summer. First, a large amount of gypsum leaked away. Second, a large amount of exchangeable magnesium, along with exchangeable sodium, was substituted by gypsum. （3） Compared with the other two treatments, treatment B （mixing gypsum and top 20- cm soil） showed the best improving efficiency, and it was characterized by stepwise dealkalization from top to down. In addition, mixing gypsum and topsoil is more practical in the production.
基金This study was financially supported by National Natural Science Foundation of China(GrantNo.51834001)Fundamental Research Funds for the Central University(Grant No.FRF-BD-20-01B).
文摘In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG)on the environment and improve the workability of HPG,the effects of the content of quicklime and types of biopolymer(hydroxypropyl methylcellulose,xanthan gum,sodium polyacrylate(PAANa))on the compressive strength,softening coefficient and ultrasonic velocity of HPG were evaluated.When the content of quicklime was 1.5%and the content of PAA-Na was 0.2%,HPG had the best mechanical properties and workability,its water retention rate can be increased by 5.8%,and unconfined compressive strength of 3 days increased by 10.3%and 7 days increased by 13.1%.Through the analysis of scanning electron microscope and X-ray diffraction,it was found that the hydration reac-tion of HPG was more sufficient,the pores size and number decreased,the number of impurities on the crystal surface decreased obviously,and CaF2 and other substances were formed by the reaction after the addition of quicklime.After adding quicklime and PAANa,the indicators of gypsum self-leveling mortar prepared by HPG meet the requirements of the standard.
基金Project(2022YFC3902703)supported by the National Key R&D Program of ChinaProject(KF22028)supported by the Special Project for High Quality Development of the Ministry of Industry and Information Technology of China+1 种基金Project(62004143)supported by the National Natural Science Foundation of ChinaProject(2022BAA084)supported by the Key R&D Program of Hubei Province,China。
文摘The excessive demand for phosphorus-based fertilizers is contributing to the undesired byproduct of phosphogypsum(PG),typically found in large quantities in phosphoric acid industry.Without proper management,this industrial waste poses a significant environmental pollution risk.Current technologies are struggle to effectively handle the volume of PG produced,but one promising solution is its conversion into hemihydrate gypsum(CaSO_(4)·0.5 H_(2)O,HH).HH can exist in two phases,α-HH andβ-HH,withα-hemihydrate gypsum(α-HH)being preferred for its complete crystal structure and lower water requirement for hydration.The morphology ofα-HH gypsum is crucial for its material applications,and controlling crystal morphology is possible through the use of suitable crystal modifiers.This review explores various aspects of crystal modifiers and highlights their role in the preparation ofα-HH from PG.It suggests that leveraging the interfacial properties of PG could lead to innovative applications.Additionally,the review outlines future directions for PG development and identifies challenges to be addressed in the next steps.
文摘A novel utilization way of the sludge from wet calcium-based flue gas desulfurization （FGD） processes has been developed in this paper. This study focused on the conversion of the FGD gypsum into α-hemihydrate calcium sulfate by a hydrothermal salt solution method at atmospheric pressure. Experimental study has been carried out in a batch reactor. Qualitative and quantitative analyses were made by DSC/TG thermal analysis, SEM, XRD, metalloscope and chemical analysis. The experimental results showed that the modification of FGD gypsum was controlled by the dissolution and recrystallization mechanisms. With the introduction of FGD gypsum the salt solution was supersaturated, then crystal nucleus of α-hemihydrate calcium sulfate were produced in the solution. With the submicroscopic structure of FGD gypsum crystal changed, the crystal nucleus grew up into α-hemihydrate calcium sulfate crystals. Thus ,the modification of FGD gypsum was fulfilled.
基金supported by the National Natural Science Foundation of China (Grants 41572310, 41272351)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grants XDB10030301, XDB10030304)support provided by the CAS-TWAS Presidential Fellowship, University of Chinese Academy of Sciences, Beijing, China
文摘Failure of rock mass that is subjected to compressive loads occurs from initiation, propagation, and linkage of new cracks from preexisting fissures. Our research investigates the cracking behaviour and coalescence process in a brittle material with two non-parallel overlapping flaws using a high-speed camera. The coalescence tensile crack and tensile wing cracks were the first cracks to occur from the preexisting flaws. The initiation stresses of the primary cracks at the two tips of each flaw were simultaneous and decreased with reduced flaw inclination angle. The following types of coalescence cracks were identified between the flaws: primary tensile coalescence crack, tensile crack linkage, shear crack linkage, mixed tensile-shear crack, and indirect crack coalescence. Coalescence through tensile linkage occurred mostly at pre-peak stress. In contrast, coalescence through shear or mixed tensile-shear cracks occurred at higher stress. Overall, this study indicates that the geometry of preexisting flaws affect crack initiation and coalescence behaviour.
基金the National Key Research and Development Program of China(2018YFE0207202 and 2016YFC0501306).
文摘Previous studies have mainly focused on changes in soil physical and chemical properties to evaluate the reclamation of sodic soils using flue gas desulfurization(FGD)gypsum.However,information on the effects of this reclamation method on microbial-based indicators of soil quality is limited,particularly after many years of FGD gypsum application.This study aimed to investigate the long-term effects of FGD gypsum on soil organic carbon(SOC),nutrients,microbial biomass and enzyme activity.Data were collected from soils of three exchangeable sodium percentage(ESP)classes(i.e.,low-,middle-and hjgh-ESP classes of 6.1-20,20-30 and 30-78.4%,respectively)17 years after FGD gypsum treatment in Inner Mongolia,China.Averaged across the three ESP classes,FGD gypsum application increased the SOC contents at the 0-20 and 20-40-cm soil depths by 18 and 35%,respectively,and increased available potassium at the 0-20-cm soil depth by 51%compared with the no-gypsum controls.The microbial biomass carbon and microbial biomass nitrogen contents at the 20-40-cm soil depth increased by 69 and 194%,respectively,under FGD gypsum.Except in the high-ESP class,urease activities in the 0-40 cm soil profile were significantly higher in the FGD gypsum treatments than in the controls.A significant increase in alkaline phosphatase activity was concentrated in the 20-40 cm soil layer;few classes showed significant increases in catalase and invertase activities in the 0-20 cm soil layer.Pearson correlation analysis showed that increases in soil fertility and biological activity could be attributed to reductions in electrical conductivity,pH and ESP caused by FGD gypsum application.These results confirm that FGD gypsum application is a viable strategy for reclaiming sodic soils due to its positive effects on soil fertility and biochemistry and that it may contribute to soil ecosystem sustainability.
基金Supported by the National High Technology Research and Development Program of China（2006AA06Z385） the Science Foundation of Wuhan University of Science and Technology（2008RC06）
文摘Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pres-sure was investigated.The effects of temperature,salt species,salt concentration,solids content,pH and modifier were examined.The crystals obtained under different conditions and solubility of calcium sulfate in contact with solid gypsum were also determined.α-Calcium sulfate hemihydrate crystals of stubby columnar shape and regular pentahedral sides were obtained under the following conditions：salt concentration 20%-30%,operation tempera-ture 95-100 °C,solids mass content in the slurry 10%-30% and neutral pH.Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium sulfate hemihydrate occurs because of the difference in solubilities between the two solid gypsum phases in this system.
基金The Qingdao National Laboratory for Marine Science and Technology under contract No.QNLM2016ORP0210the National Natural Science Foundation of China under contract Nos 41306061,41473080 and 41376076the Scientific Cooperative Project by China National Petroleum Corporation and Chinese Academic of Sciences under contract No.2015A-4813
文摘The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane（AOM） coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor（cmbsf） in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values（δ^34 S） of pyrite vary greatly（from –46.6‰ to –12.3‰ V-CDT） and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction（OSR） and is influenced by AOM with depth.The relative high abundance and δ^34 S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone（SMTZ）.The sulfur isotopic composition of gypsum（from–25‰ to –20.7‰） is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO2,iron（Ⅲ） and oxygen driven by the SMTZ location shift to great depths.The δ^34 S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.
基金Financial support for this project was provided by the U.S.Department of Agriculture (No. 6445-12630-003-00D)
文摘The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization （FGD） units of coal- fired power plants. Studies have been carried out in confined greenhouses using FGD gypsum treated soils. Major research focus is uptakes of mercury by plants, and emission of mercury into the atmosphere under varying application rates of FGD gypsum, simulating rainfall irrigations, soils, and plants types. Higher FGD gypsum application rates generally led to higher mercury concentrations in the soils, the increased mercury emissions into the atmosphere, and the increased mercury contents in plants （especially in roots and leaves）. Soil properties and plant species can play important roles in mercury transports. Some plants, such as tall fescue, were able to prevent mercury from atmospheric emission and infiltration in the soil. Mercury concentration in the stem of plants was found to be increased and then leveled off upon increasing FGD gypsum application. However, mercury in roots and leaves was generally increased upon increasing FGD gypsum application rates. Some mercury was likely absorbed by leaves of plants from emitted mercury in the atmosphere.
基金Funded by the National Natural Science Foundation of China(Nos.51208370,51172164)the Doctoral Program of Higher Education of China(No.20110072120046)+1 种基金the Fundamental Research Funds for the Central Universities(No.0500219170)the Opening Measuring Fund of LargeApparatus of Tongji University(No.0002012011)
文摘The feasibility of flue gas desulphurization （FGD） as concrete admixture was studied. A combined concrete admixture of the thermally-treated FGD gypsum and slag powder was explored. The FGD gypsum was roasted at 200℃ for 60 min and then mixed with the slag powder to form FGD gypsum-slag powder combined admixture in which the SO3 content was 3.5wt%. Cement was partially and equivalently replaced by slag powder alone or FGD gypsum-slag powder, at concentration of 25wt%, 40wt%, and 50wt%, respectively. The setting times, hydration products, total porosity and pore size distributions of the paste were determined. The compressive strength and drying shrinkage of cement mortar and concrete were also tested. The experimental results show that, in the presence of FGD gypsum, the setting times are much slower than those of pastes in the absence of FGD gypsum. The combination of FGD gypsum and slag powder provides synergistic benefits above that of slag powder alone. The addition of FGD gypsum provides benefit by promoting ettringite formation and forms a compact microstructure, increasing the compressive strength and reduces the drying shrinkage of cement mortar and concrete.
文摘The microstructure, phase composition, and thermal characteristics of various natural gypsums and the high-strength gypsum──the converted product of natural one are analysed.The formation mecbanism of high-strength gypsum is further discussed. It is found that the high-streugth gypsum is of hollow irregular hexagonal prism structure, which is almost free from tbe (010) and (100) cleavages and can form clustered fibrous crystals with high-strength.
基金supported by the State Key Laboratory of Mineral Processing Science and Technology Open Fund(BGRIMM-KJSKL-2017-16)Liaoning Provincial Department of Education Youth Project(LJ2017QL028)Coal Resource Safety Mining and Clean Utilization Engineering Research Center Open Fund(LNTU15KF18)。
文摘In this paper,the solid waste desulfurization gypsum produced by coal-fired power plants was used as a raw material to prepare calcium sulfate whiskers with high application prospects.Calcium sulfate whiskers with uniform morphology and high aspect ratio can be prepared by hydrothermal method in sulfuric acid solution.A new process of desulfurization gypsum activated by high-energy grinding to reduce the reaction temperature and sulfuric acid concentration was developed.Through the comparison of product morphology,the best grinding time was determined to be 3.5 h.The mechanism of desulfurization gypsum through physical–chemical coupling to reduce energy consumption was clarified.The activation of desulfurization gypsum by grinding and the acidic environment provided by the sulfuric acid solution made the calcium sulfate solution reached rapid saturation and accelerated the nucleation rate.By calculating the conversion and crystallization rate of calcium sulfate whiskers,it was found that there were obvious"autocatalytic"kinetic characteristics during the crystallization process.
基金Project(50974018)supported by the National Natural Science Foundation of ChinaProject(108007)supported by Key Project of the Ministry of Education of China
文摘Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was added into the CaCl2 solution by slow titration or in multiple stages over 2-8 h followed by 2 h equilibration.In order to regenerate KCl solution as concentrated as possible,K2SO4 solid was added into the given CaCl2 solution instead of K2SO4 solution,obtaining gypsum crystals with almost the same quality by multistage addition with[SO4 2-]/[Ca 2+]molar ratio no larger than 0.8.However,impurity of K2SO4·CaSO4·H2O was detected by XRD and was further confirmed by SEM-EDS in the produced crystals when the[SO4 2-]/[Ca 2+] ratio increased to 1.1.It is proved that appearance of the double sulfate is attributed to the relatively high concentration of K2SO4.So,it is essential to properly control the[SO4 2-]/[Ca 2+]ratio and make sure[Ca 2+ ]in excess to suppress the solubility of CaSO4 even at the expense of low calcium removal rate.
