Preparation And Adsorption Properties Of Spherical Magnesium Silicate

In this thesis,the hydrothermal method was used to synthesize porous spherical magnesium silicate with magnesium ions by using silica microspheres produced by hydrolysis of ethyl orthosilicate as template and reactants.SEM,BET,XRD,FT-IR,TPD,methylene blue and Rhodamine B adsorption were used to study how the calcination temperature,molar ratio of magnesium to silicon and the time when magnesium ions are added affect the morphology,structural parameters,surface acid and base sites of magnesium silicate samples and the adsorption properties.The results show:1.The petal-like spherical magnesium silicate prepared by the simultaneous addition method using tetraethyl orthosilicate and magnesium chloride as the main raw materials has the structure of talc.After the sample is calcined at 400?,the specific surface area and total pore volume are increased.However,after the sample was calcined at a temperature of 450?600?,the structural parameters showed a decreasing trend.Among them,when the calcination temperature is 400?,the sample has a maximum specific surface area of 532.51 m2·g-1,the most acid-base active sites,and the highest adsorption capacity for methylene blue and rhodamine B,and the maximum adsorption amount is 177.26 mg·g-1 and 227.32 mg·g-1.2.A series of petal-like spherical magnesium silicate samples were prepared by simultaneous feeding method under different conditions of molar ratio of magnesium to silicon.When n(Mg):n(Si)=0.1,the prepared sample was amorphous silica.As the magnesium to silicon ratio increased to 0.2,a distinct magnesium silicate phase began to appear.The samples synthesized by different silicon-magnesium ratios have a porous structure,and the structural parameters first increase and then decrease.Among them,the sample with n(Mg):n(Si)=0.6 has the largest specific surface area and the largest total pore volume.The maximum specific surface area is 606.01 mg·g-1,and the maximum total pore volume is 0.704 cm3·g-1.With the increase of the ratio of silicon to magnesium,the acid-base activity of the sample decreased first and then increased,and the strength of the acid-base active center remained basically unchanged.The sample with a magnesium to silicon ratio of 0.6 had the highest adsorption of methylene blue and rhodamine B,which were 238.26 mg·g-1 and 273.92 mg·g-1,respectively.3.A series of porous spherical magnesium silicate samples were prepared by using the delayed feeding method under different conditions of molar ratio of magnesium to silicon.When the ratio of magnesium to silicon was 0.1,the sample did not show a distinct magnesium silicate phase.When the ratio of magnesium to silicon increased to 0.2,the sample began to show a magnesium silicate phase with a distinct talc structure.At 400?,the specific surface area and total pore volume of the sample after calcination increased compared with the uncalcined sample,and the specific surface area increased from 339.411 mg·g-1 to 357.98 mg·g-1.As the ratio of magnesium to silicon increases,the number of acid-base active sites in the sample increases.The sample with a silicon to magnesium ratio of 1.0 had the highest adsorption of methylene blue and rhodamine B,which were 177.26 mg·g-1 and 174.47 mg·g-1,respectively.