Removal of Cd(II) from Aqueous Solution Using Dried Plant (Azadirachta indica) Biomass

Abstract

INTRODUCTIONHeavy metals build up as metal-organic complexes in living organisms and eventually increase their concentration in biological cycles [1]. Issues related to metal contamination and management are common due to human activities and subsequent impact on the environment. Environmental contamination due to heavy metals accumulation from anthropogenic sources is one of the major areas of concern. Various industries viz., manufacturing, mining, power generating significantly contribute to water pollution through the generation of effluents containing higher concentrations of heavy metals. If left untreated, these contaminated effluents may pollute both surface and sub-surface water. Inadequate treatment of effluents from industries impacts both health and environment [2]. Their removal being a prerequisite, various physical, chemical and biological techniques have been brought forth. Several methods, like precipitation, coagulation/flocculation, chemical reduction, ion exchange, electrodialysis, reverse osmosis, filtration, etc.[3] are followed for the decontamination of wastewater. However, these methods cannot be always implemented due to capital investments and operating costs. Adsorption is a physical technique used for the removal of toxic metals [3] and known for its simple usage and availability of wide range of adsorbents. Adsorption plays a significant role in the effective removal of pollutants not only from the aqueous sources but also from In the present study, we have used neem (Azadirachta indica) leaf powder as a non-conventional biosorbent for the removal of Cd(II) from aqueous solutions. Batch experiments were conducted to identify equilibrium time, equilibrium adsorbent dosage and equilibrium metal concentration. The data were analyzed by applying Freundlich, Langmuir and Temkin isotherm models. The kinetics of adsorption was studied from the data obtained through pseudo-first-order and pseudo-second-order equations. The adsorption data best fitted for Freundlich isotherm and the process obeyed pseudo-second-order. The adsorption of Cd(II) was rapid initially and reached the peak at 180 min of agitation (96.9 %). The adsorbent dose indicated instantaneous adsorption (92.8 %) at 0.4 g and reached equilibrium at 1.6 g (97.4 %). The adsorption was rapid initially (99.6 %) at Cd(II) concentration of 60 mg L -1 and decreased (96.2 %) at 200 mg L -1 . It was revealed that neem leaf powder has effective potential for the removal of Cd(II) from aqueous solution. Removal of Cd(II) from Aqueous Solution Using Dried Plant (Azadirachta indica)