| Magnesium silicate with unique crystal structure and high specific surface area can provide molecular field force and form various adsorption centers,so it has great potential applications in the field of adsorption and separation.How to improve the specific surface area and pore volume of magnesium silicate has become research focus in this field.In this paper,the micro/nano hierarchical mesoporous magnesium silicate is constructed by hydrothermal method.The adsorption properties on dye molecules and lead ions are studied.The main contents are as follows:1.Micro/nano layered magnesium silicateThe micro/nano layered magnesium silicate is prepared by sacrificial assisted template-hydrothermal method using SBA-15 as template and magnesium chloride as magnesium source.The results show that magnesium silicate has a micro/nano composite structure composed of nanosheets with a thickness of about 12 nm.The specific surface area of magnesium silicate is 411 m2/g,the pore volume is 0.45 cm3/g,and the average pore diameter of magnesium silicate is 4.18 nm.The maximum adsorption capacities of magnesium silicate on methylene blue(MB)and rhodamine B(RhB)are 353 mg/g and 227 mg/g,respectively.The adsorption process is in accordance with the pseudo-second-order kinetics and the Langmuir adsorption isotherm model.2.Micro/nano ordered mesoporous magnesium silicateThe SBA-15 filled with carbon(C@SBA-15)is obtained by filling sucrose and carbonization and the micro/nano ordered mesoporous magnesium silicate is prepared by hydrothermal method using the C@SBA-15 as both template and silicon source.The results show that magnesium silicate,which is composed of nanopores and nanosheets,has a two-dimensional hexagonal mesoporous structure.The specific surface area of magnesium silicate is 283 m2/g,the average pore size of magnesium silicate is 7.39 nm,and the pore volume is 0.53 cm3/g.The maximum adsorption capacity of MB on micro/nano ordered mesoporous magnesium silicate is 341 mg/g and 203 mg/g for the first time and second time,respectively.This shows a large adsorption capacity,excellent recycling efficiency and high stability of magnesium silicate.In addition,the maximum adsorption capacity of lead ions is 417 mg/g.The pseudo-second-order rate equation and Langmuir adsorption isotherm model are used to study the adsorption process,and the adsorption process is consistent with the Weber-Morris interior diffusion model.3.Monodispersed micro/nano mesoporous magnesium silicateThe SBA-15 containing the surfactant is carbonized to obtain C@SBA-15 with good dispersibility.Mono-dispersed micro/nano mesoporous magnesium silicate is prepared by sacrificial assisted template-hydrothermal method using the C@SBA-15 as both template and silicon source.The dispersant PEG200 is added in the hydrothermal process.The results show that the magnesium silicate displays well dispersity and micro/nano hierarchical structure consisting of nanosheets on surface and the inner pores.The specific surface area and the average pore size of the magnesium silicate area are 424 m2/g and 50 nm,respectively.The volume of the magnesium silicate is 0.53 cm3/g.The maximum adsorption capacity of MB on monodispersed micro/nano mesoporous magnesium silicate is 208.5 mg/g.The adsorption process is in accordance with the pseudo-second-order rate equation,and the adsorption capacity can be analyzed by Langmuir isothermal adsorption model.The study reveals that the micro/nano mesoporous magnesium silicate prepared with mesoporous silica material as both template and silicon source has high specific surface area and large pore volume.The preparation method is simple and easy to operate.The micro/nano mesoporous magnesium silicate has a strong adsorption effect on organic anionic dyes and heavy metal ions.Micro/nano mesoporous magnesium silicate is an excellent adsorbent. |
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