High-Performance Spherical Magnesium Silicate Adsorption Material:Fabrication And Adsorption Behaviour

With the rapid development of China’s economy and the continuous improvement of the industrialization level,the problem of environmental pollution is gradually exposed.This problem is not only threatening the ecological environment and human health,but also becoming a constraint on economic development.Printing and dyeing wastewater is one of the most serious environmental problems.Among many treatment methods of printing and dyeing wastewater,adsorption method has the advantages of simple operation and high benefits,and has become the preferred method of sewage treatment.The processing capacity and efficiency of adsorption method are closely related to the types of adsorption materials,pore structure and so on.Therefore,it is of great scientific significance and practical application value to design and construct advanced,highefficiency and green porous adsorption materials.This thesis aims at the controllable preparation of high-efficiency magnesium silicate hollow spheres and the search for suitable molding solutions.Through the sacrificial template method,adjusting the feed ratio of the raw materials,adding morphology control agents and modifiers,a series of high-efficiency modified magnesium silicate hollow spheres with high specific surface area are prepared.Further by immersion precipitation method,membrane shaping is achieved to construct porous adsorption membrane material.Moreover,Congo red dye is used as a probe to systematically investigate the influence laws of pore structure,spherical shell thickness,surface properties,film forming of porous magnesium silicate on the adsorption properties of Congo red,which reveals the structure-activity relationship between its porous magnesium silicate structure and the adsorption properties.The main research contents,innovation points and results of this paper are as follows:(1)Based on the principle of in-situ phase inversion,the microspherical SiO2 sacrificial template method was developed to prepare a series of hollow spherical magnesium silicate adsorption materials with different shell thicknesses by adjusting the Mg/Si feeding ratio.With the increase of the Mg/Si feeding ratio,the particle size of the hollow spheres increased from 509 nm to 819 nm,the thickness of the spherical shell increased from 71 nm to 212 nm,and the specific surface area decreased from 547 m2·g-1 to 448 m2·g-1.The adsorption capacity of magnesium silicate hollow spheres for Congo red increased with the decrease of shell thickness(the increase of specific surface area),and the maximum adsorption capacity was 1411.4 mg·g-1.(2)The CTAC surface modification method was developed to prepare a series of functionalized magnesium silicate hollow spheres by adjusting the CTAC/Mg feeding ratio,and the surface of hollow spheres was positively charged.With the increase of the CTAC/Mg feed ratio,the particle size of the hollow sphere gradually increased from 538 nm to 856 nm,the thickness of the spherical shell increased from 101 nm to 323 nm,and the specific surface area increased to 139 m2·g-1,and then decreased.The functionalized magnesium silicate hollow spheres with the largest specific surface area had the strongest adsorption performance for Congo red,the maximum adsorption capacity was 2283.1 mg·g-1,which was much more than that of the unmodified magnesium silicate hollow spheres.(3)The immersion precipitation method was developed to prepare a series of hybrid membranes with different magnesium silicate content by using PVDF as the membrane material.The adsorption capacity of the hybrid membrane for Congo red increased with the increase of the doping amount of magnesium silicate hollow spheres.The maximum adsorption capacity of the PM hybrid membrane was 139.1 mg·g-1,and the maximum adsorption capacity of the PCM hybrid membrane was 300.3 mg·g-1.The more the doping amount of MSHS was,the worse the hydrophilicity of the PM hybrid membrane became,and the adsorption equilibrium time was 60 h;The more the doping amount of CM was,the better the hydrophilicity of the PCM hybrid membrane became,and the adsorption equilibrium time was 13 h.The group C-N+component played an important role in promoting the adsorption of Congo red.