The research progress on the application of magnesium compounds (magnesium hydroxide,light calcined magnesia,magnesium chloride,sea water,brine,dry brine,etc.) which were represented by magnesium hydroxide in the wast...The research progress on the application of magnesium compounds (magnesium hydroxide,light calcined magnesia,magnesium chloride,sea water,brine,dry brine,etc.) which were represented by magnesium hydroxide in the wastewater treatment filed was comprehensively commentated.Meanwhile,the prospects of application were discussed.Considering the magnesium resources in China were characterized with rich classes,abundant reserves,vast distribution and high quality,it's important to make great efforts to research and exploit magnesium products,especially the exploitation of their meticulous use way.It had the practical significance for the sustainable development of economy in China.展开更多
Hydrophobic magnesium hydroxide(MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream–rotating packed bed(IS-RPB) reactor. The reactant sol...Hydrophobic magnesium hydroxide(MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream–rotating packed bed(IS-RPB) reactor. The reactant solutions were simultaneously and continuously pumped into the IS-RPB reactor, and then Tween80 was added as a surface modifier. The morphology, structure, and properties of blank and hydrophobic MH were characterized. The effects of MH nanoparticles on the flame retardancy, thermal stability, and mechanical properties of PP/MH composites were also studied. We found that the obtained MH nanoparticles exhibited hexagonal lamella with a mean size of 30 nm, excellent hydrophobic properties(e.g., high water contact angle of 112°), and improved thermal stability of MH. The limiting oxygen index(LOI) further showed that increased MH loading can significantly improve flame-retardant performance, which reached 29.3% for PP/MH composites with 30 wt% hydrophobic samples. The thermal stability and mechanical properties of the PP/MH composites with hydrophobic samples were also much higher than those of PP/MH composites with blank MH. Results showed that the one-step synthesis had high potential application in the large-scale production of hydrophobic MH nanoparticles.展开更多
Magnesium alloys are nontoxic and promising as orthopedic metallic implants,but preparing a biocompatible Mg(OH)_(2)layer with high corrosion protection ability remains challenging.It is generally believed that the Mg...Magnesium alloys are nontoxic and promising as orthopedic metallic implants,but preparing a biocompatible Mg(OH)_(2)layer with high corrosion protection ability remains challenging.It is generally believed that the Mg(OH)_(2)layer,especially that formed in a natural condition,cannot provide desirable corrosion resistance in the community of corrosion and protection.Here,several Mg(OH)_(2)coatings were prepared by changing the pH values of sodium hydroxide solutions.These coatings were composed of innumerable nanoplatelets with different orientations and showed distinguished capability in corrosion resistance.The nanoplatelets were well-oriented with their ab-planes parallel to,instead of perpendicular to,the magnesium alloy surface by raising the pH value to 14.0.This specific orientation resulted in the optimal coating showing long-term corrosion protection in both in vitro and in vivo environments and good osteogenic capability.These finds manifest that the environment-friendly Mg(OH)_(2)coating can also provide comparable and better corrosion protection than many traditional chemical conversion films(such as phosphate,and fluoride).展开更多
Magnesium hydroxide(Mg(OH)2)has been considered as a potential solvent for CO2 removal of coal-fired power plant and biomass gas.The chemistry action and mass to transfer mechanism of CO2-H2O-Mg(OH)2 system in a slurr...Magnesium hydroxide(Mg(OH)2)has been considered as a potential solvent for CO2 removal of coal-fired power plant and biomass gas.The chemistry action and mass to transfer mechanism of CO2-H2O-Mg(OH)2 system in a slurry bubble column reactor was described,and a reliable computational model was developed.The overall mass transfer coefficient and surface area per unit volume were obtained using experimental approach and simulation with software assistance.The results show that the mass transfer process of CO2 absorbed by Mg(OH)2 slurry is mainly liquid-controlled,and slurry concentration and temperature are main contributory factors of volumetric mass transfer coefficient and liquid side mass transfer coefficient.High concentration of CO2 has an adverse effect on its absorption because it leads to the fast deposition of MgCO3·3H2O crystals on the surfaces of unreacted Mg(OH)2 particles,reducing the utilization ratio of magnesium hydroxide.Meanwhile,high CO3^2– ion concentration limits the dissolution of MgCO3 to absorb CO2 continually.Concentration of 0.05 mol/L Mg(OH)2,15%vol CO2 gas and operation temperature at 35℃are recommended for this CO2 capture system.展开更多
In this work, we demonstrate an in situ phase conversion from basic magnesium chloride（BMC） into magnesium hydroxide whisker by using polar organic solvent at low temperature. The morphology and phase composition of...In this work, we demonstrate an in situ phase conversion from basic magnesium chloride（BMC） into magnesium hydroxide whisker by using polar organic solvent at low temperature. The morphology and phase composition of magnesium hydroxide whiskers prepared at different reaction temperature, alkali concentration and organic solvent were analyzed by X-ray diffraction（XRD） and scanning electronic microscope（SEM）. It was found that when one of the organic solvents such as absolute ethyl alcohol, butanol, polyethylene glycol（PEG-400）, acetone, et al. was selected as the template, the precursor BMC can transform into whisker-like magnesium hydroxide through precipitate transformation in low temperature and non-hydrothermal system. It can be reasonably explained that the regulation of Mg^2＋ solubility by those organic solvents and the sustained release of Mg^2＋ dissolution by organic adsorption played a significant role in the formation of magnesium hydroxide whisker via BMC whisker as the precursor.展开更多
Hydrophobic Mg(OH)_2nanoparticles were successfully synthesized via an in situ surface modification method in a novel impinging stream-rotating packed bed(IS-RPB) reactor using oleic acid(C_(17)H_(33)COOH, OA) as a su...Hydrophobic Mg(OH)_2nanoparticles were successfully synthesized via an in situ surface modification method in a novel impinging stream-rotating packed bed(IS-RPB) reactor using oleic acid(C_(17)H_(33)COOH, OA) as a surface modifier, magnesium chloride hexahydrate in the presence of ethanol as a precursor, and sodium hydroxide as a precipitant. The products were characterized by Fourier transform infrared spectroscopy(FTIR), Field emission scanning electron microscopy(FESEM), X-ray diffraction(XRD), and thermogravimetry-differential scanning calorimetry(TG-DSC). Compatibility with organic solutions was determined by sedimentation tests. The prepared nanoparticles exhibited regular hexagonal lamella with an average diameter of 30 nm when OA is added to the reaction system; this result indicates that OA regulates the morphology of the Mg(OH)_2nanoparticles.XRD revealed that the high-purity Mg(OH)_2product presents a brucite structure, and the I_(001)/I_(101) of hydrophobic Mg(OH)_2(0.86) was higher than that of the blank Mg(OH)_2(0.63). FTIR analysis showed that OA bonded to the surface of the Mg(OH)_2. Compared with the blank Mg(OH)_2product, the product obtained through the proposed method possesses excellent hydrophobic properties, including a high water contact angle of 101.4° and good compatibility with liquid paraffin. TG-DSC analysis indicated that the total percentage of mass loss of hydrophobic Mg(OH)_2(40.88%) was higher than that of the blank Mg(OH)_2product(33.18%). The in situ surface modification method proposed in this work presents potential use in the large-scale production of Mg(OH)_2nanoparticles.展开更多
Magnesium hydroxide(MH) whiskers were modified via in situ polymerization of n-butyl acrylate and maleic anhydride. Sodium dodecyl sulfonate was used as emulsifier. The modifying effect was evaluated by using contact ...Magnesium hydroxide(MH) whiskers were modified via in situ polymerization of n-butyl acrylate and maleic anhydride. Sodium dodecyl sulfonate was used as emulsifier. The modifying effect was evaluated by using contact angle and activation index. The thermal stability,functional groups, structure, morphology, phase composition and surface element valence of MH whiskers were characterized by thermogravimetry-differential scanning calorimetry(TG-DSC), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). Results reveal that the contact angle and activation index of modified MH whiskers are 105°and 76.5%, the thermal stability shows little change, and the decomposition temperature ranges between 38 and419 ℃. The copolymer of n-butyl acrylate and maleic anhydride absorbed on the surface of MH whiskers leads to the increased diameter and makes the surface of whiskers be rougher. Furthermore, the absorption of element C on the surface of MH whiskers increases, and the diffraction intensity of C 1 s spectra increases; thus, the compatibility of whiskers in the organic phase can be improved significantly. Lastly, the surface molecular model of MH whiskers modified via in situ copolymerization of n-butyl acrylate and maleic anhydride is established.展开更多
The yield of magnesium hydroxide was investigated via response surface methodology using bischofite and aqueous ammonia as raw materials. The experimental results indicated that the effects of reaction temperature,mag...The yield of magnesium hydroxide was investigated via response surface methodology using bischofite and aqueous ammonia as raw materials. The experimental results indicated that the effects of reaction temperature,magnesium ion and aqueous ammonia concentrations on the yield of magnesium hydroxide gradually decreased. In particular,reaction temperature and magnesium ion concentration had a significant influence on the yield. After the regression and fitting of the response value and each factor,the regression equation was obtained. As proven by experiments,the predicted value and actual value showed a good fit. The products of the center experiment were characterized by particle size analysis,scanning electron microscopy,and X-ray diffraction. The results show that the morphology is irregular and shows a lamellar structure. The particles have a narrow size distribution ranging from 0.64 to 0.68 μm of D50 size. The difference in particle size of D10 and D90 is less than 0.91 μm,and the purity very high.展开更多
Magnesium hydroxide(MH),which is commonly used as a halogen-free flame retardant filler in composite materials,was modified by silanization reaction with γ-aminopropyltriethoxysilane (γ-APS) in aqueous solution at d...Magnesium hydroxide(MH),which is commonly used as a halogen-free flame retardant filler in composite materials,was modified by silanization reaction with γ-aminopropyltriethoxysilane (γ-APS) in aqueous solution at different pH values (pH range from 8.0 to 12.0). The surface properties of grafted γ-APS on MH surface as a function of solution pH value were studied using elemental analysis,Fourier transform infrared spectroscopy and zeta potential measurement. The results show that hydrolysis and condensation of γ-APS are activated in alkaline solution and lead to multilayer adsorption of γ-APS molecules on the surface of MH. The type of adsorption orientation of γ-APS on MH surface is a function of coverage density that is altered by changing solution pH value. At low coverage density (e.g. 55 nm-2),γ-APS molecules are preferentially adsorbed to the surface with the silicon moiety towards the surface,and increasing coverage density (e.g. 90 nm-2) leads to parallel orientation. At an even higher coverage density (e.g. 115 nm-2),γ-APS molecules bond to the surface with the amino moiety towards the surface.展开更多
Functional polymers such as polyethylene grafted glycidyl methacrylate （PE-g-GMA） and ethylene-methyl acrylate-glycidyl methacrylate terpolymer （E/MA/GMA） were used as compatibilizers in the preparation of highly ...Functional polymers such as polyethylene grafted glycidyl methacrylate （PE-g-GMA） and ethylene-methyl acrylate-glycidyl methacrylate terpolymer （E/MA/GMA） were used as compatibilizers in the preparation of highly filled composites of polyethylene/magnesium hydroxide（PE/MH）. Comparative studies were performed on the effect of magnesium hydroxide and stearic acid on the interface within polymer and magnesium hydroxide composites. The effect of polymeric compatibilizers on the properties of the composites was studied using tensile and impact tests, torque rheological analysis, differential scanning calorimetry and environmental scanning electron microscopy （ESEM）. The microstructure of highly filled PE/MH composites changed after the addition of functional polymers. The mechanical properties of the composite material increased after compatibilization. The compatibilization processes of PE-g-GMA and E/MA/GMA were different. The grafted polymer was more compatible with polyethylene, which led to a polar polymer phase. In contrast, the tercopolymer tended to adhere to the surface of MH particles.展开更多
Efficient lubrication of magnesium alloys is a highly challenging topic in the field of tribology.In this study,magnesium silicate hydroxide(MSH)nanotubes with serpentine structures were synthesized.The tribological b...Efficient lubrication of magnesium alloys is a highly challenging topic in the field of tribology.In this study,magnesium silicate hydroxide(MSH)nanotubes with serpentine structures were synthesized.The tribological behavior of AZ91D magnesium alloy rubbed against GCr15 steel was studied under lubricating oil with surface-modified MSH nanotubes as additives.The effects of the concentration,applied load,and reciprocating frequency on the friction and wear of the AZ91D alloy were studied using an SRV-4 sliding wear tester.Results show a decrease of 18.7–68.5%in friction coefficient,and a reduction of 19.4–54.3%in wear volume of magnesium alloy can be achieved by applying the synthetic serpentine additive under different conditions.A suspension containing 0.3 wt.%MSH was most efficient in reducing wear and friction.High frequency and medium load were more conducive to improving the tribological properties of magnesium alloys.A series of beneficial physical and chemical processes occurring at the AZ91D alloy/steel interface can be used to explain friction and wear reduction based on the characterization of the morphology,chemical composition,chemical state,microstructure,and nanomechanical properties of the worn surface.The synthetic MSH,with serpentine structure and nanotube morphology,possesses excellent adsorbability,high chemical activity,and good self-lubrication and catalytic activity.Therefore,physical polishing,tribochemical reactions,and physicalchemical depositions can occur easily on the sliding contacts.A dense tribolayer with a complex composition and composite structure was formed on the worn surface.Its high hardness,good toughness and plasticity,and prominent lubricity resulted in the improvement of friction and wear,making the synthetic MSH a promising efficient oil additive for magnesium alloys under boundary and mixed lubrication.展开更多
Magnesium hydroxide with high purity and uniform particle size distribution was synthesized by the direct precipitation method using MgCl_(2) and NaOH as reactive materials and NaCl as additive to improve the crystall...Magnesium hydroxide with high purity and uniform particle size distribution was synthesized by the direct precipitation method using MgCl_(2) and NaOH as reactive materials and NaCl as additive to improve the crystallization behavior of the product.The particle size distribution,crystal phase,morphology,and surface area of magnesium hydroxide were characterized by Malvern laser particle size analyzer,X-ray diffraction(XRD),scanning electron microscope(SEM)and Branauer-Emmett-Teller(BET)method,respectively.The purity of products was analyzed by the chemical method.The effects of synthesis conditions on the particle size distribution and water content(filtration cake)of magnesium hydroxide were investigated.The results indicated that feeding mode and rate,and reaction temperature had important effects on water content and the particle size distribution of the product,and sodium chloride improved the crystallization behavior of magnesium hydroxide.The ball-like magne-sium hydroxides with the particle size distribution of 6.0–30.0μm and purity higher than 99.0%were obtained.This simple and mild synthesis method was promising to be scaled up for the industrial production of magnesium hydroxide.展开更多
The use of magnesium hydroxide(Mg(OH)_(2))was proposed as a filler to replace part of the calcium carbonate(CaCO_(3))in cigarette paper and reduce the toxicity of the smoke from cigarettes.Physical property changes an...The use of magnesium hydroxide(Mg(OH)_(2))was proposed as a filler to replace part of the calcium carbonate(CaCO_(3))in cigarette paper and reduce the toxicity of the smoke from cigarettes.Physical property changes and smoke reducing ability of this possible substitution were effectively studied.The results showed that adding 10%Mg(OH)_(2) could meet the requirements of the physical property of the cigarette paper.Moreover,with the addition of Mg(OH)2 as a filler in the cigarette paper,the pyrolysis temperature of the cigarette paper decreased,while the porosity and specific surface area increased.As a result,the main-stream smoke had a lower smoke total particle matter(STMP),tar,nicotine and carbon monoxide content,and the side-stream smoke also had a lower STMP.展开更多
In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxide...In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.展开更多
The IEP of magnesium aluminum hydroxide was predicted with the modified Yoon′s equation, and the effect of electrolyte on the Y- potential of the sol was studied by electrophoresis method. The results showed that ...The IEP of magnesium aluminum hydroxide was predicted with the modified Yoon′s equation, and the effect of electrolyte on the Y- potential of the sol was studied by electrophoresis method. The results showed that the calculated IEP values with the modified Yoon′s equation agreed well with the experimental ones. With the increase of the ionic radius of monovalent anions (Cl -, Br -, I -) the ζ potential decreased. The same was true for CO 2- 3, SO 2- 4 but the sign of the Y- potential reversed from positive to negative. For Al 3+ , Ca 2+ , Mg 2+ , however, the ζ potential increased with the increase of the concentration of Al 3+ , Ca 2+ , Mg 2+ .展开更多
The coordination structure of aluminum in magnesium aluminum hydroxide was studied by 27Al NMR. The result showed that tetrahedral aluminum (AlIV) existed in magnesium aluminum hydroxide, and the contents of AlIV inc...The coordination structure of aluminum in magnesium aluminum hydroxide was studied by 27Al NMR. The result showed that tetrahedral aluminum (AlIV) existed in magnesium aluminum hydroxide, and the contents of AlIV increased with the increase of the ratio of Al/Mg and with the peptizing temperature. AlIV originated from the so-called Al13 polymer with the structure of one Al tetrahedron surrounded by twelve Al octahedrons.展开更多
Yoon's equation which predicted point of zero charge of complex oxide should predict the zero point of net charge (ZPNC) of mixture of variable and permanent charge rather than the point of zero charge (PZC) of th...Yoon's equation which predicted point of zero charge of complex oxide should predict the zero point of net charge (ZPNC) of mixture of variable and permanent charge rather than the point of zero charge (PZC) of the variable charge component. The calculated values with modified Yoon's equation agreed with the experimental values.展开更多
Producing magnesium hydroxide is the basic way to utilize magnesium resources of natural brines. However, the effect of lithium on properties of product is always neglected. The interaction between ions in magnesium c...Producing magnesium hydroxide is the basic way to utilize magnesium resources of natural brines. However, the effect of lithium on properties of product is always neglected. The interaction between ions in magnesium chloride solution containing lithium was illustrated based on the experimental results, and the effect of lithium on the crystallization of magnesium was clarified. The results of X-ray diffraction（XRD）, scanning election microscope（SEM）, Fourier transform infrared spectroscopy（FTIR）, thermogravimetry analysis（TGA） and laser particle size analysis indicate that the effect of lithium is not obvious on the crystal phase and morphology of the products. But the XRD relative intensity of（001） surface of magnesium hydroxide declines, the specific surface area reduces apparently and the additive mass of lithium affects the heat loss rates of precipitations obviously. Quantum chemical calculations on the interactional systems of Mg（H2O）2＋6 and Li（H2O）＋4 were performed using B3LYP/6-311 G basis set. The results show that when the distance of Mg2＋ and Li＋ is 7-10 , the interaction energy is high and the trend of solvation is strong, which would make hydroxide ions easier to combine with hydrogen ions in ammonia precipitation process. And the absolute value of solvation free energy reduces significantly in MgCl2 solution（1 mol/L） containing lithium ion.展开更多
A new biobased flame retardant(MHPA)with remarkable compatibility was synthesized via a facile and low-cost neutralization reaction of magnesium hydroxide(MH)and phytic acid(PA).By blending the prepared MHPA into ethy...A new biobased flame retardant(MHPA)with remarkable compatibility was synthesized via a facile and low-cost neutralization reaction of magnesium hydroxide(MH)and phytic acid(PA).By blending the prepared MHPA into ethylene vinyl acetate(EVA),the fire retardancy,smoke suppression and mechanical properties of the composites were significantly improved.When 50 wt%of MH was added into EVA matrix,the value of limiting oxygen index(LOI)reached 26.1%.Whereas,when 10 wt%MH in the EVA composites(with initial 50 wt%MH)was replaced by MHPA,the resulted EVA composites had a LOI value of 30.8%,indicating high efficiency of addition of MHPA to improve flame retardancy.Moreover,the heat release rate(HRR)and total smoke production(TSP)of the EVA composites reduced by 54.4%and 27.6%,respectively,suggesting that incorporation of MHPA could effectively hinder rapid degradation of EVA composites during burning process.The fire-retardant mechanism may reside in that the MHPA combined with MH can present the excellent carbonization and expansion effects.This study illustrates that the biobased MHPA has a broad application prospect to develop flame-retardant EVA composites.展开更多
基金Supported by The National Science Research Guidance Plan Project of Education Department in Hebei Province (Z2009110 )The Science & Technology Research and Development Guidance Plan of Baoding City in 2009 (the Second Batch) (09ZF075)The Natural Science Funds of Hebei Province (B2005000105)
文摘The research progress on the application of magnesium compounds (magnesium hydroxide,light calcined magnesia,magnesium chloride,sea water,brine,dry brine,etc.) which were represented by magnesium hydroxide in the wastewater treatment filed was comprehensively commentated.Meanwhile,the prospects of application were discussed.Considering the magnesium resources in China were characterized with rich classes,abundant reserves,vast distribution and high quality,it's important to make great efforts to research and exploit magnesium products,especially the exploitation of their meticulous use way.It had the practical significance for the sustainable development of economy in China.
基金Supported by the National Natural Science Foundation of China(21376229)the Science and Technology of Shanxi Province(2015031019-5)the Natural Science Foundation for Young Scientists of Shanxi Province(2015021033)
文摘Hydrophobic magnesium hydroxide(MH) nanoparticles were prepared by a one-step synthesis method in a high-gravity environment generated by a novel impinging stream–rotating packed bed(IS-RPB) reactor. The reactant solutions were simultaneously and continuously pumped into the IS-RPB reactor, and then Tween80 was added as a surface modifier. The morphology, structure, and properties of blank and hydrophobic MH were characterized. The effects of MH nanoparticles on the flame retardancy, thermal stability, and mechanical properties of PP/MH composites were also studied. We found that the obtained MH nanoparticles exhibited hexagonal lamella with a mean size of 30 nm, excellent hydrophobic properties(e.g., high water contact angle of 112°), and improved thermal stability of MH. The limiting oxygen index(LOI) further showed that increased MH loading can significantly improve flame-retardant performance, which reached 29.3% for PP/MH composites with 30 wt% hydrophobic samples. The thermal stability and mechanical properties of the PP/MH composites with hydrophobic samples were also much higher than those of PP/MH composites with blank MH. Results showed that the one-step synthesis had high potential application in the large-scale production of hydrophobic MH nanoparticles.
基金supported by the National Natural Science Foundation of China(NSFC,52271073)the Sichuan Science and Technology Program(2024NSFJQ0034)+3 种基金the Central Government Guided Special Program(No.2021ZYD0049)the Young Elite Scientists Sponsorship Program by CAST(YESS,2018QNRC001)the GDPH Supporting Fund for Talent Program(KY0120220137)the Scientific and Technological Projects of Guangzhou,China(202002030283).
文摘Magnesium alloys are nontoxic and promising as orthopedic metallic implants,but preparing a biocompatible Mg(OH)_(2)layer with high corrosion protection ability remains challenging.It is generally believed that the Mg(OH)_(2)layer,especially that formed in a natural condition,cannot provide desirable corrosion resistance in the community of corrosion and protection.Here,several Mg(OH)_(2)coatings were prepared by changing the pH values of sodium hydroxide solutions.These coatings were composed of innumerable nanoplatelets with different orientations and showed distinguished capability in corrosion resistance.The nanoplatelets were well-oriented with their ab-planes parallel to,instead of perpendicular to,the magnesium alloy surface by raising the pH value to 14.0.This specific orientation resulted in the optimal coating showing long-term corrosion protection in both in vitro and in vivo environments and good osteogenic capability.These finds manifest that the environment-friendly Mg(OH)_(2)coating can also provide comparable and better corrosion protection than many traditional chemical conversion films(such as phosphate,and fluoride).
基金Project(21878338)supported by the National Natural Science Foundation of ChinaProject(2015BAL04B02)supported by the National key Technology R&D Program of China+1 种基金Project(2018K2038)supported by the key Research and Development Project of Hunan Province,ChinaProject supported by Hunan Collaborative Innovation Center of Building Energy Conservation&Environmental Control,China
文摘Magnesium hydroxide(Mg(OH)2)has been considered as a potential solvent for CO2 removal of coal-fired power plant and biomass gas.The chemistry action and mass to transfer mechanism of CO2-H2O-Mg(OH)2 system in a slurry bubble column reactor was described,and a reliable computational model was developed.The overall mass transfer coefficient and surface area per unit volume were obtained using experimental approach and simulation with software assistance.The results show that the mass transfer process of CO2 absorbed by Mg(OH)2 slurry is mainly liquid-controlled,and slurry concentration and temperature are main contributory factors of volumetric mass transfer coefficient and liquid side mass transfer coefficient.High concentration of CO2 has an adverse effect on its absorption because it leads to the fast deposition of MgCO3·3H2O crystals on the surfaces of unreacted Mg(OH)2 particles,reducing the utilization ratio of magnesium hydroxide.Meanwhile,high CO3^2– ion concentration limits the dissolution of MgCO3 to absorb CO2 continually.Concentration of 0.05 mol/L Mg(OH)2,15%vol CO2 gas and operation temperature at 35℃are recommended for this CO2 capture system.
基金Supported by the National Basic Research Program of China(2010CB933501,2013CB934302)the Outstanding Youth Fund(21125730)+3 种基金the National Science Foundation Grant(21273237,21103191)the Knowledge Innovation Program of the Chinese Academy of Sciences(KJCX2-YW-N50,KJCX2-EW-J02)the Technology Key Project of Fujian Province(2013H0058)the Fund of Fujian Key Laboratory of Nanomaterials(2006L2005)
文摘In this work, we demonstrate an in situ phase conversion from basic magnesium chloride（BMC） into magnesium hydroxide whisker by using polar organic solvent at low temperature. The morphology and phase composition of magnesium hydroxide whiskers prepared at different reaction temperature, alkali concentration and organic solvent were analyzed by X-ray diffraction（XRD） and scanning electronic microscope（SEM）. It was found that when one of the organic solvents such as absolute ethyl alcohol, butanol, polyethylene glycol（PEG-400）, acetone, et al. was selected as the template, the precursor BMC can transform into whisker-like magnesium hydroxide through precipitate transformation in low temperature and non-hydrothermal system. It can be reasonably explained that the regulation of Mg^2＋ solubility by those organic solvents and the sustained release of Mg^2＋ dissolution by organic adsorption played a significant role in the formation of magnesium hydroxide whisker via BMC whisker as the precursor.
基金Supported by the National Natural Science Foundation of China(No.21376229)
文摘Hydrophobic Mg(OH)_2nanoparticles were successfully synthesized via an in situ surface modification method in a novel impinging stream-rotating packed bed(IS-RPB) reactor using oleic acid(C_(17)H_(33)COOH, OA) as a surface modifier, magnesium chloride hexahydrate in the presence of ethanol as a precursor, and sodium hydroxide as a precipitant. The products were characterized by Fourier transform infrared spectroscopy(FTIR), Field emission scanning electron microscopy(FESEM), X-ray diffraction(XRD), and thermogravimetry-differential scanning calorimetry(TG-DSC). Compatibility with organic solutions was determined by sedimentation tests. The prepared nanoparticles exhibited regular hexagonal lamella with an average diameter of 30 nm when OA is added to the reaction system; this result indicates that OA regulates the morphology of the Mg(OH)_2nanoparticles.XRD revealed that the high-purity Mg(OH)_2product presents a brucite structure, and the I_(001)/I_(101) of hydrophobic Mg(OH)_2(0.86) was higher than that of the blank Mg(OH)_2(0.63). FTIR analysis showed that OA bonded to the surface of the Mg(OH)_2. Compared with the blank Mg(OH)_2product, the product obtained through the proposed method possesses excellent hydrophobic properties, including a high water contact angle of 101.4° and good compatibility with liquid paraffin. TG-DSC analysis indicated that the total percentage of mass loss of hydrophobic Mg(OH)_2(40.88%) was higher than that of the blank Mg(OH)_2product(33.18%). The in situ surface modification method proposed in this work presents potential use in the large-scale production of Mg(OH)_2nanoparticles.
基金financially supported by the National Natural Science Foundation of China (No.51272163)
文摘Magnesium hydroxide(MH) whiskers were modified via in situ polymerization of n-butyl acrylate and maleic anhydride. Sodium dodecyl sulfonate was used as emulsifier. The modifying effect was evaluated by using contact angle and activation index. The thermal stability,functional groups, structure, morphology, phase composition and surface element valence of MH whiskers were characterized by thermogravimetry-differential scanning calorimetry(TG-DSC), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). Results reveal that the contact angle and activation index of modified MH whiskers are 105°and 76.5%, the thermal stability shows little change, and the decomposition temperature ranges between 38 and419 ℃. The copolymer of n-butyl acrylate and maleic anhydride absorbed on the surface of MH whiskers leads to the increased diameter and makes the surface of whiskers be rougher. Furthermore, the absorption of element C on the surface of MH whiskers increases, and the diffraction intensity of C 1 s spectra increases; thus, the compatibility of whiskers in the organic phase can be improved significantly. Lastly, the surface molecular model of MH whiskers modified via in situ copolymerization of n-butyl acrylate and maleic anhydride is established.
基金Supported by the Department of Science and Technology of Qinghai Province(No.2010-G-221A)
文摘The yield of magnesium hydroxide was investigated via response surface methodology using bischofite and aqueous ammonia as raw materials. The experimental results indicated that the effects of reaction temperature,magnesium ion and aqueous ammonia concentrations on the yield of magnesium hydroxide gradually decreased. In particular,reaction temperature and magnesium ion concentration had a significant influence on the yield. After the regression and fitting of the response value and each factor,the regression equation was obtained. As proven by experiments,the predicted value and actual value showed a good fit. The products of the center experiment were characterized by particle size analysis,scanning electron microscopy,and X-ray diffraction. The results show that the morphology is irregular and shows a lamellar structure. The particles have a narrow size distribution ranging from 0.64 to 0.68 μm of D50 size. The difference in particle size of D10 and D90 is less than 0.91 μm,and the purity very high.
基金Projects(50574104 50574102) supported by the National Natural Science Foundation of China
文摘Magnesium hydroxide(MH),which is commonly used as a halogen-free flame retardant filler in composite materials,was modified by silanization reaction with γ-aminopropyltriethoxysilane (γ-APS) in aqueous solution at different pH values (pH range from 8.0 to 12.0). The surface properties of grafted γ-APS on MH surface as a function of solution pH value were studied using elemental analysis,Fourier transform infrared spectroscopy and zeta potential measurement. The results show that hydrolysis and condensation of γ-APS are activated in alkaline solution and lead to multilayer adsorption of γ-APS molecules on the surface of MH. The type of adsorption orientation of γ-APS on MH surface is a function of coverage density that is altered by changing solution pH value. At low coverage density (e.g. 55 nm-2),γ-APS molecules are preferentially adsorbed to the surface with the silicon moiety towards the surface,and increasing coverage density (e.g. 90 nm-2) leads to parallel orientation. At an even higher coverage density (e.g. 115 nm-2),γ-APS molecules bond to the surface with the amino moiety towards the surface.
文摘Functional polymers such as polyethylene grafted glycidyl methacrylate （PE-g-GMA） and ethylene-methyl acrylate-glycidyl methacrylate terpolymer （E/MA/GMA） were used as compatibilizers in the preparation of highly filled composites of polyethylene/magnesium hydroxide（PE/MH）. Comparative studies were performed on the effect of magnesium hydroxide and stearic acid on the interface within polymer and magnesium hydroxide composites. The effect of polymeric compatibilizers on the properties of the composites was studied using tensile and impact tests, torque rheological analysis, differential scanning calorimetry and environmental scanning electron microscopy （ESEM）. The microstructure of highly filled PE/MH composites changed after the addition of functional polymers. The mechanical properties of the composite material increased after compatibilization. The compatibilization processes of PE-g-GMA and E/MA/GMA were different. The grafted polymer was more compatible with polyethylene, which led to a polar polymer phase. In contrast, the tercopolymer tended to adhere to the surface of MH particles.
基金support from the National Natural Science Foundation of China(grant number 52075544)Innovation Funds of Jihua Laboratory(X220971UZ230)+1 种基金Basic and Applied Basic Research Foundation of Guangdong Province(2022A1515110649)Funds from Research Platforms of Guangdong Higher Education Institutes(2022ZDJS038).
文摘Efficient lubrication of magnesium alloys is a highly challenging topic in the field of tribology.In this study,magnesium silicate hydroxide(MSH)nanotubes with serpentine structures were synthesized.The tribological behavior of AZ91D magnesium alloy rubbed against GCr15 steel was studied under lubricating oil with surface-modified MSH nanotubes as additives.The effects of the concentration,applied load,and reciprocating frequency on the friction and wear of the AZ91D alloy were studied using an SRV-4 sliding wear tester.Results show a decrease of 18.7–68.5%in friction coefficient,and a reduction of 19.4–54.3%in wear volume of magnesium alloy can be achieved by applying the synthetic serpentine additive under different conditions.A suspension containing 0.3 wt.%MSH was most efficient in reducing wear and friction.High frequency and medium load were more conducive to improving the tribological properties of magnesium alloys.A series of beneficial physical and chemical processes occurring at the AZ91D alloy/steel interface can be used to explain friction and wear reduction based on the characterization of the morphology,chemical composition,chemical state,microstructure,and nanomechanical properties of the worn surface.The synthetic MSH,with serpentine structure and nanotube morphology,possesses excellent adsorbability,high chemical activity,and good self-lubrication and catalytic activity.Therefore,physical polishing,tribochemical reactions,and physicalchemical depositions can occur easily on the sliding contacts.A dense tribolayer with a complex composition and composite structure was formed on the worn surface.Its high hardness,good toughness and plasticity,and prominent lubricity resulted in the improvement of friction and wear,making the synthetic MSH a promising efficient oil additive for magnesium alloys under boundary and mixed lubrication.
基金supported by the Shanghai Natural Science Foundation(No.09ZR147900)the Program for New Century Excellent Talents in University(NCET-08-0776).
文摘Magnesium hydroxide with high purity and uniform particle size distribution was synthesized by the direct precipitation method using MgCl_(2) and NaOH as reactive materials and NaCl as additive to improve the crystallization behavior of the product.The particle size distribution,crystal phase,morphology,and surface area of magnesium hydroxide were characterized by Malvern laser particle size analyzer,X-ray diffraction(XRD),scanning electron microscope(SEM)and Branauer-Emmett-Teller(BET)method,respectively.The purity of products was analyzed by the chemical method.The effects of synthesis conditions on the particle size distribution and water content(filtration cake)of magnesium hydroxide were investigated.The results indicated that feeding mode and rate,and reaction temperature had important effects on water content and the particle size distribution of the product,and sodium chloride improved the crystallization behavior of magnesium hydroxide.The ball-like magne-sium hydroxides with the particle size distribution of 6.0–30.0μm and purity higher than 99.0%were obtained.This simple and mild synthesis method was promising to be scaled up for the industrial production of magnesium hydroxide.
文摘The use of magnesium hydroxide(Mg(OH)_(2))was proposed as a filler to replace part of the calcium carbonate(CaCO_(3))in cigarette paper and reduce the toxicity of the smoke from cigarettes.Physical property changes and smoke reducing ability of this possible substitution were effectively studied.The results showed that adding 10%Mg(OH)_(2) could meet the requirements of the physical property of the cigarette paper.Moreover,with the addition of Mg(OH)2 as a filler in the cigarette paper,the pyrolysis temperature of the cigarette paper decreased,while the porosity and specific surface area increased.As a result,the main-stream smoke had a lower smoke total particle matter(STMP),tar,nicotine and carbon monoxide content,and the side-stream smoke also had a lower STMP.
基金Vietnam National University-Ho Chi Minh City under grant number A2020-16-01.
文摘In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.
文摘The IEP of magnesium aluminum hydroxide was predicted with the modified Yoon′s equation, and the effect of electrolyte on the Y- potential of the sol was studied by electrophoresis method. The results showed that the calculated IEP values with the modified Yoon′s equation agreed well with the experimental ones. With the increase of the ionic radius of monovalent anions (Cl -, Br -, I -) the ζ potential decreased. The same was true for CO 2- 3, SO 2- 4 but the sign of the Y- potential reversed from positive to negative. For Al 3+ , Ca 2+ , Mg 2+ , however, the ζ potential increased with the increase of the concentration of Al 3+ , Ca 2+ , Mg 2+ .
基金This research is supported by NNSFC No:20273041.
文摘The coordination structure of aluminum in magnesium aluminum hydroxide was studied by 27Al NMR. The result showed that tetrahedral aluminum (AlIV) existed in magnesium aluminum hydroxide, and the contents of AlIV increased with the increase of the ratio of Al/Mg and with the peptizing temperature. AlIV originated from the so-called Al13 polymer with the structure of one Al tetrahedron surrounded by twelve Al octahedrons.
文摘Yoon's equation which predicted point of zero charge of complex oxide should predict the zero point of net charge (ZPNC) of mixture of variable and permanent charge rather than the point of zero charge (PZC) of the variable charge component. The calculated values with modified Yoon's equation agreed with the experimental values.
基金Projects(51104185,51134007)supported by the National Natural Science Foundation of ChinaProject(2010QZZD003)supported by the Key Project of Central South University of Fundamental Research Funds for the Central Universities of China
文摘Producing magnesium hydroxide is the basic way to utilize magnesium resources of natural brines. However, the effect of lithium on properties of product is always neglected. The interaction between ions in magnesium chloride solution containing lithium was illustrated based on the experimental results, and the effect of lithium on the crystallization of magnesium was clarified. The results of X-ray diffraction（XRD）, scanning election microscope（SEM）, Fourier transform infrared spectroscopy（FTIR）, thermogravimetry analysis（TGA） and laser particle size analysis indicate that the effect of lithium is not obvious on the crystal phase and morphology of the products. But the XRD relative intensity of（001） surface of magnesium hydroxide declines, the specific surface area reduces apparently and the additive mass of lithium affects the heat loss rates of precipitations obviously. Quantum chemical calculations on the interactional systems of Mg（H2O）2＋6 and Li（H2O）＋4 were performed using B3LYP/6-311 G basis set. The results show that when the distance of Mg2＋ and Li＋ is 7-10 , the interaction energy is high and the trend of solvation is strong, which would make hydroxide ions easier to combine with hydrogen ions in ammonia precipitation process. And the absolute value of solvation free energy reduces significantly in MgCl2 solution（1 mol/L） containing lithium ion.
基金Financial support of Zhejiang Outstanding Youth Fund(No.LR22E080007)National Natural Science Foundation of China(Nos.52070170,51978628)Zhejiang Provincial Ten Thousand Talent Program(No.ZJWR0302055)。
文摘A new biobased flame retardant(MHPA)with remarkable compatibility was synthesized via a facile and low-cost neutralization reaction of magnesium hydroxide(MH)and phytic acid(PA).By blending the prepared MHPA into ethylene vinyl acetate(EVA),the fire retardancy,smoke suppression and mechanical properties of the composites were significantly improved.When 50 wt%of MH was added into EVA matrix,the value of limiting oxygen index(LOI)reached 26.1%.Whereas,when 10 wt%MH in the EVA composites(with initial 50 wt%MH)was replaced by MHPA,the resulted EVA composites had a LOI value of 30.8%,indicating high efficiency of addition of MHPA to improve flame retardancy.Moreover,the heat release rate(HRR)and total smoke production(TSP)of the EVA composites reduced by 54.4%and 27.6%,respectively,suggesting that incorporation of MHPA could effectively hinder rapid degradation of EVA composites during burning process.The fire-retardant mechanism may reside in that the MHPA combined with MH can present the excellent carbonization and expansion effects.This study illustrates that the biobased MHPA has a broad application prospect to develop flame-retardant EVA composites.
