Removal of lindane and malathion from wastewater using bagasse fly ash--a sugar industry waste.

The bagasse fly ash, obtained from the local sugar industry, has been used as inexpensive and effective adsorbent for the removal of lindane and malathion from wastewater. The optimum contact needed to reach equilibrium was found to be 60 min. Maximum removal takes place at pH 6.0. The removal of the pesticides increases with an increase in adsorbent dose and decreases with adsorbent particle size. The optimum adsorbent dose is 5 g/l of particle size 200-250 microm. Removal of the two pesticides was achieved up to 97-98% under optimum conditions. The material exhibits good adsorption capacity and follows both Langmuir and Freundlich models. Thermodynamic parameters also indicate the feasibility of the process. The adsorption was found to be exothermic in nature. At lower concentrations, adsorption is controlled by film diffusion, while at higher concentrations, it is controlled by particle diffusion mechanisms. The adsorbent is a very useful and economic product for the removal of lindane and malathion.