Preparation Of Inorganic-Compound-Intercalated Montmorillonite And It's Adsorption Behavior And Mechanism Of Cr(VI)in Waste Water

This subject is launched to enlarge the appliance of nonmetallic minerals in environmental protection. Up to now, the study of appliance of intercalated montmorillonite in waste water treatment is mostly about the adsorption of organic pollutants on organic-compound-intercalated montmorillonite . Little sdudy is done about the adsorption of inorganic pollutants and especially hazardous anion.In this thesis, The preparation of inorganic-compound-intercalated montmorillonite and it's adsorption behavior and mechanism of Cr( VI) in waste water are investigated.Liaoning aluminium-intercalated montmorillonite and Liaoningaluminium-chronmium-intercalated montmorillonite are prepared. The results show that sllury concentration affects the interplanar spacing of Liaoning aluminium-intercalated montmorillonite, the optimun sllury concentration is 1.5% and the interplanar spacing and specific surface area of Liaoning aluminium-intercalated montmorillonite prepared under this condition (LA) reach 1.9620 nm and 180.4770 m2/g. Cr/Al ratio affects the interplanar spacing of Liaoning aluminium-chronmium-intercalated montmorillonite , the optimun Cr/Al ratio is 0.10 and the interplanar spacing and specific surface area of Liaoning aluminium-chronmium -intercalated montmorillonite prepared under this condition (LAC) reach 1.9194nm and 165.675 m2/g. When calcined at 300 and 500 ,the interplanar spacing of LA and LAC decreases but both present good crystal structure .It showes that they posess good thermal stability at this temperature. When calcined at 700, the structure of LA and LAC is destroyed.Adsorption of Cr(â…¥) on inorganic-compound-intercalated montmorillonite is investigated.The results show that the adsorption rate is affected by pH, reacting time inventory of adsorbents and waste water concentration. Calcination of adsorbents affects the adsorption rate. The optimum pH of XA and LA is 4 , adsorption equilibrium time of XA and LA is 40 min and 80 min, the adsorption rate of Cr(â…¥) on XA in 25 mg/L Cr(â…¥) waste water is 94% when the inventory of XA is 9.6 g/100mL. The adsorption rate of Cr(â…¥) on LA in 4 mg/L Cr(â…¥) waste water is 90% when the inventory of LA is 4 g/100mL and the residual concentration of Cr(â…¥) decreases to 0.4 mg/L. The adsorption rate of LA is reduced when sodium chloride and sodiumphosphate exist. The adsorption rate of LA is reduced after calcination..The adsorption of Cr(â…¥) on XA and LA fits Langmuir adsorption isotherm. The max apparent adsorption capacity of XA and LA is 4.5 mg/g and 1.46 mg/g, monomolecular layer saturation adsorption capacity of XA and LA is 5.14 mg/g and 1.69 mg/g. The adsorption mechanism includes three facets: l)Specific surface area and thus the effective contact area are magnified, so adsorption rate is enhanced. 2)The negtive charge of montmorillonite is reduced after intercalation and thus the electrostatic repulsion between Cr(â…¥) and montmorillonite is reduced. 3) The adsotption of Cr(â…¥) is the complex reaction between Cr(â…¥) and surface hydroxyl radicals,hydroxyl surface is formed on interlayer pillars in solution and thus the sum of surface hydroxyl radicals is enhanced,so the adsorptive capacity is enhanced after intercalation.The adsorption process is controlled by membrane diffusion dynamics.