Adsorption of Pesticides and Heavy Metals from Water on Modified Bentonites

Fourteen modified bentonites prepared using cationic, anionic and combination of both modifiers were screened for their efficiency to remove butachlor, methyl parathion, chlorothalonil, cadmium and lead from water. Normal bentonite and modified bentonite (J-8) were characterised using FTIR, XRD, EDX and SEM techniques and used to study adsorption kinetics of pesticides and heavy metals. Cationic modified clay adsorbed > 80 per cent of all the three pesticides whereas hexametaphosphate modified bentonite adsorbed > 72 per cent lead. Doubly modified bentonite with sodium hexametaphosphate and cetylpyridinium chloride (J-8), cetyltrimethyl ammonium bromide (J-10) and cetrimide (J-11) were found to give removal efficiency of > 90 per cent for the pesticides and 73–83 per cent for lead. Cadmium adsorption capacity was lowest in all the adsorbents. Adsorption data was fitted to Freundlich and Langmuir isotherms. High values of adsorption coefficient (K_d), Freundlich Coefficient (K_F) and Langmuir parameters (q_m) obtained for J-8 revealed its potential as effective adsorbent for pesticides and lead for their removal from contaminated water.