Preparation Of Magnetical Modified Sepiolite And Its Adsorption Characteristics Of Chromium

Sepiolite has become one kind of promising adsorption material in heavy metal waste water treatment because of its unique diameter layer structure and large surface area. But the surface of sepiolite carries negative charges that results in its poor adsorption effect of metal anion and the separation of the powder sepiolite in water solution is very difficult. Those limit the abroad application in heavy metal wastewater treatment of sepiolite which is abundant resources and low price.Magnetically modified sepiolite(MMS) was prepared by chemical co-precipitation process in order to improve the adsorption performance of sepiolite original soil to Cr(Ⅵ) and tackle the difficulty of separating. The optimal process conditions were decided at first. Separaton properties of MMS was researched by stalling settlement experiments with or without magnetic field while the adsorption performance and mechanism of MMS adsorbing Cr(Ⅵ) were studied on emphasis.Accoding to the experimental results, those conclusions were got:(1) The optimal process conditions of MMS were as follows: preparation tempetature 60℃, pH 9.0, mass fraction of Fe loaded 0.28.(2) The adsorption capacity of MMS adsorbing Cr(Ⅵ) was 3.6 mg·g^-1 while it was 0.02 mg·g^-1 of sepiolite, and the surface area of MMS was 160.366 m²·g^-1 while it was 37.534 m²·g-1of sepiolite.(3) After modification the characteristic peak of Fe₃O₄ and Fe-OH appeared in the infrared spectrum. The crystals of Fe₃O₄ with no more iron oxides were found on MMS by XRD. The structure of MMS was unchanged after adsorption. Fe-OH participated in adsorption reactions as it uptook abating after reaction. Not only physical but also complexation adsorption played roles in the adsorption process.(4) The data at different times and temperatures fited the secondary dynamic model. The adsorption rate was controlled by both of the liquid film diffusion and the intraparticle diffusion which play more important role in adsorption. The Freundlich isotherm was the best-fit adsorption isotherm model for the data of adsorption.(5) Mass fraction of Fe loaded was an important factor in separation. Without additional magnetic field, the supermatant fluid volume of the sepiolite and MMS (iron loaded 0.14, 0.22, 0.28) were 50, 72.8, 75.2, 77 mL in one hour. With the additional magnetic field about 50 mT, the turbidity of the MMS (iron loaded 0.14, 0.22, 0.28) were 0.8, 0.5, 0.35 NTU in 10 minutes while the turbidity were 82 NTU of the sepiolite in 72 h.