Development and Characterisation of Nanoclays from Indian Clays

Indian clays are known for their smecticity. One such clay sample collected from Bhuj (Gujarat) was characterised and modified by successive sedimentation processes for different time intervals. The non-plastic components of clay, viz., quartz, illite, iron oxide, CaO, MgO, and organic matter were removed in different steps, as the heavy impurities in the clay-water suspensions, settle down during sedimentation. The free iron oxide present in clay suspension was reduced by giving sodium citrate-bicarbonate-dithionite treatment and iron content was further reduced from 12–15 per cent to 5–7 per cent respectively. The organic matter was removed by sodium acetate-H₂O₂ treatment. The modified clay so obtained was characterised by thermal analysis, FTIR, and XRD, SEM and TEM. The cation exchange capacities of original and modified clays were determined both by methylene blue method and ammonium acetate method. The cation exchange capacity is found to enhance from 120–130 meq/100 g to 135–145 meq/100 g. Using the above procedure, 92 per cent smecticity was obtained. Organophilisation of purified clay (smectite) was carried out by intercalation with alkyl ammonium salt. The XRD analysis showed enhancement of interlamellar spacing from 1.294 nm to 2.855 nm.