Hierarchical porous MgO is a promising adsorbent for dye removal because of its large Brunauer-Emmett-Teller specific surface area(SBET)and abundant low-coordinated oxygen anions(LCO)sites.As hierarchical porous MgO p...Hierarchical porous MgO is a promising adsorbent for dye removal because of its large Brunauer-Emmett-Teller specific surface area(SBET)and abundant low-coordinated oxygen anions(LCO)sites.As hierarchical porous MgO particles with large SBET values are typically prepared by complicated procedures under harsh conditions,such as high temperatures and high pressures,their large-scale production is impractical.Consequently,the preparation of hierarchical porous MgO with a large SBET value under mild conditions is highly desirable.In this study,a morphology transition engineering strategy is introduced to change the morphology of simple MgO microspheres to an embroidered ball-shaped with a larger SBET value via hydrolysis and calcination without using surfactants as sacrificial templates.During hydrolysis,numerous Mg(OH)_(2)sheets form and attach to the MgO surface,thus increasing the SBET value of the newly obtained MgO that forms by calcination(denoted as NM-x,where x is the hydrolysis time in hours).The sizes of the crystalline sheets were tuned by controlling the hydrolysis time.NM-12 exhibited the highest density of small-sized sheets on its surface and the largest SBET value of 180.17 m^(2)g^(-1),which was 3.51 times that of the MgO precursor(51.89 m^(2)g^(-1)).However,NM-24(134.07 m^(2)g^(-1))had a higher adsorption efficiency for Congo red(CR)than NM-12,despite having a smaller SBET value,which indicates that other factors are involved.NM-24 exhibited a lower probability of exposed(200)and(220)facets which were verified to repulse CR molecules by molecular dynamics simulations,and a greater number of LCO sites,which contributed to adsorption.Thus,this study introduces a facile method for preparing hierarchical porous MgO and examines the effects of LCO sites and exposed facet probabilities on its adsorption properties.展开更多
Laboratory experiments and thermodynamic calculations were performed to investigate the interfacial reactions between the MgO-C refractory and the steel with and without the lanthanum(La)addition.Following a reaction ...Laboratory experiments and thermodynamic calculations were performed to investigate the interfacial reactions between the MgO-C refractory and the steel with and without the lanthanum(La)addition.Following a reaction time of 50 min,a reaction layer comprised MgO and CaS with a thickness of 30μm was observed at the interface between the La-free steel and refractory.The MgO layer was observed in La-bearing steel after just 10 min of reaction.The addition of La to the steel accelerated the formation of the MgO layer.As the reaction time increased,a La-containing layer was formed at the La-bearing steel/refractory interface.This La-containing layer progressed through stages from La_(2)O_(2)S+La2O3→La-Ca-O-S→La-Ca-O→La-Ca-Al-O.Furthermore,the evolution of oxide inclusions in the La-free steel followed the sequence of MgO⋅Al_(2)O_(3),Ti-Ca-Al-O and Ti-Mg-Al-O→MgO·Al_(2)O_(3)and MgO with increasing the reaction time.In contrast,the sequence for the La-bearing steel was:La_(2)O_(2)S and La2O3→La_(2)O_(2)S and La-Ti-Al-Mg-O→La-Ti-Al-Mg-O,MgO and MgO·Al_(2)O_(3).The average penetration depth of the La-bearing steel into the refractory was notably lower than that of the La-free steel,revealing that the incorporation of rare earth element La in steel exhibits a significant inhibitory effect on the penetration of molten steel into the MgO-C refractory.展开更多
基金supported by the National Natural Science Foundation of China(U22A20434)supported by the foundation from Qinghai Science and Technology Department(2023-ZJ-745).
文摘Hierarchical porous MgO is a promising adsorbent for dye removal because of its large Brunauer-Emmett-Teller specific surface area(SBET)and abundant low-coordinated oxygen anions(LCO)sites.As hierarchical porous MgO particles with large SBET values are typically prepared by complicated procedures under harsh conditions,such as high temperatures and high pressures,their large-scale production is impractical.Consequently,the preparation of hierarchical porous MgO with a large SBET value under mild conditions is highly desirable.In this study,a morphology transition engineering strategy is introduced to change the morphology of simple MgO microspheres to an embroidered ball-shaped with a larger SBET value via hydrolysis and calcination without using surfactants as sacrificial templates.During hydrolysis,numerous Mg(OH)_(2)sheets form and attach to the MgO surface,thus increasing the SBET value of the newly obtained MgO that forms by calcination(denoted as NM-x,where x is the hydrolysis time in hours).The sizes of the crystalline sheets were tuned by controlling the hydrolysis time.NM-12 exhibited the highest density of small-sized sheets on its surface and the largest SBET value of 180.17 m^(2)g^(-1),which was 3.51 times that of the MgO precursor(51.89 m^(2)g^(-1)).However,NM-24(134.07 m^(2)g^(-1))had a higher adsorption efficiency for Congo red(CR)than NM-12,despite having a smaller SBET value,which indicates that other factors are involved.NM-24 exhibited a lower probability of exposed(200)and(220)facets which were verified to repulse CR molecules by molecular dynamics simulations,and a greater number of LCO sites,which contributed to adsorption.Thus,this study introduces a facile method for preparing hierarchical porous MgO and examines the effects of LCO sites and exposed facet probabilities on its adsorption properties.
基金the support from the National Key R&D Program(No.2023YFB3709900)the National Key R&D Program(No.2023YFB3709901)+2 种基金the National Natural Science Foundation of China(Grant No.U22A20171)the Hebei Natural Science Foundation(Grant No.52304340)the High Steel Center(HSC)at North China University of Technology.
文摘Laboratory experiments and thermodynamic calculations were performed to investigate the interfacial reactions between the MgO-C refractory and the steel with and without the lanthanum(La)addition.Following a reaction time of 50 min,a reaction layer comprised MgO and CaS with a thickness of 30μm was observed at the interface between the La-free steel and refractory.The MgO layer was observed in La-bearing steel after just 10 min of reaction.The addition of La to the steel accelerated the formation of the MgO layer.As the reaction time increased,a La-containing layer was formed at the La-bearing steel/refractory interface.This La-containing layer progressed through stages from La_(2)O_(2)S+La2O3→La-Ca-O-S→La-Ca-O→La-Ca-Al-O.Furthermore,the evolution of oxide inclusions in the La-free steel followed the sequence of MgO⋅Al_(2)O_(3),Ti-Ca-Al-O and Ti-Mg-Al-O→MgO·Al_(2)O_(3)and MgO with increasing the reaction time.In contrast,the sequence for the La-bearing steel was:La_(2)O_(2)S and La2O3→La_(2)O_(2)S and La-Ti-Al-Mg-O→La-Ti-Al-Mg-O,MgO and MgO·Al_(2)O_(3).The average penetration depth of the La-bearing steel into the refractory was notably lower than that of the La-free steel,revealing that the incorporation of rare earth element La in steel exhibits a significant inhibitory effect on the penetration of molten steel into the MgO-C refractory.
