A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_(2),a by-product of potassium extraction from the salt lake.The eff...A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_(2),a by-product of potassium extraction from the salt lake.The effect of MgO on the microstructure and properties of magnesium oxychloride cement was investigated under different calcination temperatures and time of hydromagnesite,and the hydration process,pore structure and hydration products of the materials were investigated by isothermal calorimeter,MIP,XRD,and SEM,and the mechanical properties of the materials were examined by compressive strength test.The compressive strength test shows that under the optimal conditions(800℃-2 h),the compressive strength of MOC is 75.65 MPa for 7 d and 87.98 MPa for 28 d in the indoor environment.The main exothermic period of MOC is delayed by about 10 h compared with that of 500℃-2 h and extended by about 30 h in the process of MOC preparation,which led to the alleviation of the exothermic concentration phenomenon,and the initial solidification time of the MOC specimens is 5.25 h,and the final solidification time is 11.82 h.The MOC phase maintained in indoor air for 28 d mainly consist of P5 and unreacted MgO,and the P5 in the matrix shows the slat-like shape and fills the gaps in the form of needles and rods,and the total porosity is 18.55%.展开更多
A preparation technology of MgO powder used in special silicon steel from hydromagnesite mineral has been developed. The preparation technology includes the following steps： （1） calcining the hydromagnesite at 700-...A preparation technology of MgO powder used in special silicon steel from hydromagnesite mineral has been developed. The preparation technology includes the following steps： （1） calcining the hydromagnesite at 700-750°C for 1.5-2 h; （2） hydrating the calcined hydromagnesite to be slurry containing the solid-liquid ratio of 15-20 g？L？1; （3） acquiring Mg（HCO3）2 solution by carbonating the slurry, the carbonation temperature, CO2 pressure, and end point PH value of carbonation are less than 40°C, 0.4-0.6 MPa, and 7 respectively during the carbonation process; （4） preparing precipitated basic magnesium carbonate by thermally decomposing the Mg（HCO3）2 solution at 90-100°C; （5） obtaining the MgO product by calcining the precipitated basic magnesium carbonate at 850-950°C for 30-60 min, and adopting flowing nitrogen during the cooling process. By using this technology, more than 80wt% magnesium in hydromagnesite mineral can be extracted, and high-performance MgO products used in special silicon steel can be ob- tained.展开更多
Valorization of multiple low value streams including CO_(2)emissions and magnesium-hydroxide bearing mine tailings to produce magnesium carbonate through reactive CO_(2)capture and mineralization provides a less explo...Valorization of multiple low value streams including CO_(2)emissions and magnesium-hydroxide bearing mine tailings to produce magnesium carbonate through reactive CO_(2)capture and mineralization provides a less explored opportunity to manage several gigatons of CO_(2)emissions.To resolve the feasibility of converting magnesium hydroxide to magnesium carbonate through reactive CO_(2)capture and mineralization,CO_(2)capture solvents such as sodium glycinate are harnessed to capture CO_(2)and react directly with Mg(OH)_(2)to produce hydromagnesite(Mg_(5)[(CO_(3))_(4)(OH)_(2)]·4H_(2)O).This approach eliminates the energy-intensive step of producing high purity CO_(2)associated with regenerating the solvent,and redissolving CO_(2)to produce magnesium carbonate.Interestingly,while temperatures below 50℃facilitate CO_(2)capture,the mineralization kinetics are slow.However,at higher temperatures,accelerated carbon mineralization is favored by the faster kinetics of Mg(OH)_(2)dissolution and precipitation of magnesium carbonate.Reacting Mg(OH)_(2)at 90℃with 15 wt%solids in the presence of 2.5 M sodium glycinate after 3 hours under well-stirred conditions results in an extent of carbon mineralization of 75.5%.The theoretical maximum extent of carbon mineralization when hydromagnesite is formed is 80%.Pre-loading CO_(2)on the solvent is also an effective approach to ensure that sufficient CO_(2)is available for reactive CO_(2)capture and mineralization,particularly when dilute CO_(2)and N_(2)mixtures are used.Higher extents of carbon mineralization are associated with an increase in the particle size and a reduction in the cumulative pore volume.These insights unlock the feasibility of harnessing reactive CO_(2)capture and mineralization as a pathway to convert magnesium-hydroxide bearing resources into industrially relevant magnesium carbonate products.展开更多
The effects of Ti-and Mg-bearing minerals on the crystal structure,morphology,particle size distribution,and formation mechanism of efficient desilication product of hydroandradite(HA)during hydrothermal conversion in...The effects of Ti-and Mg-bearing minerals on the crystal structure,morphology,particle size distribution,and formation mechanism of efficient desilication product of hydroandradite(HA)during hydrothermal conversion in a synthetic sodium aluminate solution were investigated via X-ray diffractometer,scanning electron microscope and particle size analyzer.During HA formation,anatase,rutile,and periclase dissolved in sodium aluminate solution engage in ion substitution reactions between Ti4+and Si4+,and between Mg^(2+)and Ca^(2+),respectively.However,dissolved hydromagnesite cannot enter into the HA.The content of HA after the hydrothermal reactions changes slightly with the increase of anatase and periclase contents,but it notably decreases with increased quantities of rutile and hydromagnesite.Ti-bearing minerals reduce the particle size and enhance the specific surface area of HA,whereas Mg-bearing minerals exert the opposite effect.The morphology of HA with Ti-and Mg-bearing minerals changes from spherical particles to flocculent structure and hexagonal plate-like particles.展开更多
基金Funded by the Xining Key R&D and Transformation Program(No.2024-Y-11)the Qinghai Province“Kunlun Talents-Highend Innovation and Entrepreneurship Talents”Top Talents。
文摘A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_(2),a by-product of potassium extraction from the salt lake.The effect of MgO on the microstructure and properties of magnesium oxychloride cement was investigated under different calcination temperatures and time of hydromagnesite,and the hydration process,pore structure and hydration products of the materials were investigated by isothermal calorimeter,MIP,XRD,and SEM,and the mechanical properties of the materials were examined by compressive strength test.The compressive strength test shows that under the optimal conditions(800℃-2 h),the compressive strength of MOC is 75.65 MPa for 7 d and 87.98 MPa for 28 d in the indoor environment.The main exothermic period of MOC is delayed by about 10 h compared with that of 500℃-2 h and extended by about 30 h in the process of MOC preparation,which led to the alleviation of the exothermic concentration phenomenon,and the initial solidification time of the MOC specimens is 5.25 h,and the final solidification time is 11.82 h.The MOC phase maintained in indoor air for 28 d mainly consist of P5 and unreacted MgO,and the P5 in the matrix shows the slat-like shape and fills the gaps in the form of needles and rods,and the total porosity is 18.55%.
基金the Science and Technology Program Project of Hunan Province, China (No.06SK2011).
文摘A preparation technology of MgO powder used in special silicon steel from hydromagnesite mineral has been developed. The preparation technology includes the following steps： （1） calcining the hydromagnesite at 700-750°C for 1.5-2 h; （2） hydrating the calcined hydromagnesite to be slurry containing the solid-liquid ratio of 15-20 g？L？1; （3） acquiring Mg（HCO3）2 solution by carbonating the slurry, the carbonation temperature, CO2 pressure, and end point PH value of carbonation are less than 40°C, 0.4-0.6 MPa, and 7 respectively during the carbonation process; （4） preparing precipitated basic magnesium carbonate by thermally decomposing the Mg（HCO3）2 solution at 90-100°C; （5） obtaining the MgO product by calcining the precipitated basic magnesium carbonate at 850-950°C for 30-60 min, and adopting flowing nitrogen during the cooling process. By using this technology, more than 80wt% magnesium in hydromagnesite mineral can be extracted, and high-performance MgO products used in special silicon steel can be ob- tained.
基金supported by the U.S.Department of Energy(DOE):DE-AC36-08GO28308the use of shared facilities at the Cornell Center for Materials Research(CCMR).G.G.and P.L.gratefully acknowledge the support of the NSF Partnerships for Innovation(PFI)program(NSF Award#:2141091)+2 种基金support of Ivan Kuzmenko and Jan Ilavsky at APS for assisting in this effortThis research used resources of the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of Science user facility at Argonne National Laboratorysupported by the U.S.DOE Office of Science-Basic Energy Sciences,under Contract No.DE-AC02-06CH11357.
文摘Valorization of multiple low value streams including CO_(2)emissions and magnesium-hydroxide bearing mine tailings to produce magnesium carbonate through reactive CO_(2)capture and mineralization provides a less explored opportunity to manage several gigatons of CO_(2)emissions.To resolve the feasibility of converting magnesium hydroxide to magnesium carbonate through reactive CO_(2)capture and mineralization,CO_(2)capture solvents such as sodium glycinate are harnessed to capture CO_(2)and react directly with Mg(OH)_(2)to produce hydromagnesite(Mg_(5)[(CO_(3))_(4)(OH)_(2)]·4H_(2)O).This approach eliminates the energy-intensive step of producing high purity CO_(2)associated with regenerating the solvent,and redissolving CO_(2)to produce magnesium carbonate.Interestingly,while temperatures below 50℃facilitate CO_(2)capture,the mineralization kinetics are slow.However,at higher temperatures,accelerated carbon mineralization is favored by the faster kinetics of Mg(OH)_(2)dissolution and precipitation of magnesium carbonate.Reacting Mg(OH)_(2)at 90℃with 15 wt%solids in the presence of 2.5 M sodium glycinate after 3 hours under well-stirred conditions results in an extent of carbon mineralization of 75.5%.The theoretical maximum extent of carbon mineralization when hydromagnesite is formed is 80%.Pre-loading CO_(2)on the solvent is also an effective approach to ensure that sufficient CO_(2)is available for reactive CO_(2)capture and mineralization,particularly when dilute CO_(2)and N_(2)mixtures are used.Higher extents of carbon mineralization are associated with an increase in the particle size and a reduction in the cumulative pore volume.These insights unlock the feasibility of harnessing reactive CO_(2)capture and mineralization as a pathway to convert magnesium-hydroxide bearing resources into industrially relevant magnesium carbonate products.
基金financial supports from the National Key R&D Program of China (No.2022YFC2904401)the National Natural Science Foundation of China (Nos.22078055,51774079)the Fundamental Research Funds for the Central Universities,China (No.N2225002)。
文摘The effects of Ti-and Mg-bearing minerals on the crystal structure,morphology,particle size distribution,and formation mechanism of efficient desilication product of hydroandradite(HA)during hydrothermal conversion in a synthetic sodium aluminate solution were investigated via X-ray diffractometer,scanning electron microscope and particle size analyzer.During HA formation,anatase,rutile,and periclase dissolved in sodium aluminate solution engage in ion substitution reactions between Ti4+and Si4+,and between Mg^(2+)and Ca^(2+),respectively.However,dissolved hydromagnesite cannot enter into the HA.The content of HA after the hydrothermal reactions changes slightly with the increase of anatase and periclase contents,but it notably decreases with increased quantities of rutile and hydromagnesite.Ti-bearing minerals reduce the particle size and enhance the specific surface area of HA,whereas Mg-bearing minerals exert the opposite effect.The morphology of HA with Ti-and Mg-bearing minerals changes from spherical particles to flocculent structure and hexagonal plate-like particles.
