Study On Modification Of Bentonite And Its Adsorption Of Heavy Metal

Bentonite is a montmorillonite clay for major compositions and is abundant in nature. Montmorillonite has the huge adsorption potential because of its own unique layered aluminosilicate structure. If we use different methods through the varying modification, the surface area of montmorillonite will be greatly improved, thus its adsorption properties will be significantly improved.This topic's goal is to improve the adsorption performance of montmorillonite and it will be applied to the removal of metal ions in waste water. The relevance between the surface properties of montmorillonite and its adsorption performance was studied.Based on the external-intercalation which is the traditional method of intercalation , the synthesis process was analyzed and a new method of inner-intercalation was put forward.The interlayer distance of post-pillared montmorillonite,surface area, distribution of pore size and other physical parameters were studied,too. The paper made the following aspects:Bentonite as raw material from commercial, was modified by the inner- intercalation to prepare pillared montmorillonite and according to the nitrogen adsorption - desorption isotherms of pillared samples in 77K , the BET equation was used to analyze and calculate the surface area , pore volume and distribution of pore size. The effect on the surface area and pore size of montmorillonite of slurry solid content, reaction time, pH and reaction temperature during the preparation of pillared montmorillonite, was deeply discussed. The results showed: pH and reaction temperature were the main elements affecting the surface area and pore structure parameters of montmorillonite. Pillared by the optimum conditions, the pillared montmorillonite was prepared with the specific surface area and the average pore volume being as high as 223.12 m² / g and 0.4 981 cm³ /g, respectively.Compared with original soil and pillared montmorillonite by the traditional methods,montmorillonite pillared by method of inner-intercalation obtained high adsorption performance. For the solution of mercury and lead, inner-intercalated bentonite get the best adsorption on pH of 7 and 6, respectively, and best adsorption time of 90 min and 60 min, respectively. Under the best adsorption conditions, 100 mL concentration for 10 mg/L mercury and lead solution can be completely adsorbed by 250 mg inner-intercalated bentonite,while traditional external-intercalation bentonite and the original soil were 300 mg and 800 mg respectively, namely the capability of adsorption of montmorillonite pillared by method of inner-intercalation was 1.2 times and 3.2 times,respectively,more than montmorillonite obtained by traditional methods of external-intercalation and original soil.The adsorption dynamics follows the laws of pseudo second-order kinetics and Elovich equation,and the chemical adsorption control the speed of the adsorption processes. The relationship between adsorption capacity(q_eq) and equilibrium mass concerntration(C_eq) is in accord with the isothermal adsorption equation of Langmuir.