Claymetal interactions a study with respect to kaolinite and montmorillonite with and without pillaring

Abstract

The tremendous increase in the use of heavy metals over the past few decades has inevitably resulted in an increased flux of metallic substances in aquatic environment. Heavy metals have taken the center-stage due to their non-degradable, hazardous and toxic nature. The toxic metals, viz., As(III), Cd(II), Cr(VI), Co(II), Cu(II), Hg(II), Pb(II), Ni(II), Zn(II), etc., are found in the aquatic systems through wastewater from metal industries. Hence, the elimination of heavy metals from water and wastewater is of utmost importance to protect public health. Adsorption process is promising in this regard as it achieves higher level of removal over a wider range of solution concentrations and generally reduce the quantity of solid residual that need to be disposed of. Activated carbons and synthetic resins have found ample use as adsorbent, however, the high cost of preparation and regeneration of activated carbon and synthetic resins prohibit their large-scale use in wastewater treatments. To overcome this problem, extensive studies have been done to find cheaper adsorbent materials. A large number of conventional and non-conventional adsorbents have been reported in literature, namely, bone charcoal, silica gel, natural and modified zeolites, natural and modified oxides, sawdust, rice husk, wheat bran, fly-ash, red mud, blast furnace slag and sludge, fertilizer waste slurry, peat, coal, chitin and chitosan, banana pith, waste tea leaves, orange peel, etc. The present work has been designed for using natural and modified clays as adsorbents with the following objectives: (i) To prepare adsorbents from common clay minerals such as kaolinite and montmorillonite by calcination under controlled conditions, (ii) To prepare other adsorbents from kaolinite and montmorillonite by intercalating with polyoxo and quaternary ammonium cations, and also by acid treatment, (iii) To characterize the adsorbents with XRD, FTIR and to determine such properties as specific surface area, cation exchange capacity (CEC), etc., (iv) To use...