Chromium Detoxification by Using Mango ( Mangifera indica ) and Neem ( Azadirachta indica ) Leaves

Abstract

Water is one of the most vital natural resource, and is crucial for survival of all living organism. One of the major polluting sources of this water is the industrial effluents. In developing countries, most of the industries are operated in small and medium scales and some of these like electroplating and tannery industries discharge waste which is rich with Cr (VI) salts. Such untreated effluents have raised several ecological concerns. Chromium has been considered as one of the most toxic pollutant primarily because of its carcinogenic and teratogenic nature. The present work was focused on investigation into suitable biological remediation of such effluents without subsequent secondary pollution. It involved effect of concentration, contact time and pH variation on ability of the neem and mango leaves in removing chromium ions form aqueous solution. The dried leaves were washed with deionised water, air-dried and ground using ball mill. The leaf powders were added to 10 ppm stock metal ion solution made from potassium dichromate where chromium exist as Cr (VI). These mixtures were shaken at a constant rate of 150 rpm, filtered and analyzed by Atomic Absorption Spectrophotometer. The maximum adsorption was obtained at pH 5.5, agitation rate of 150 rpm, particle size, of ground dry leaves, was 5 mm, initial concentration of Cr (VI) ions of 10 mg/l and contact time 24 hrs to 48 hrs. The maximum adsorption capacity was found to be 10 ppm Cr (VI) ion concentration and 5.0 g/L of mango leaf powder (MLP) at pH 5.5. However, pH 7.0 was chosen as the optimum pH (to prevent secondary pollution due to acidic pH of treated effluent). Better adsorption did not occur at higher solution temperatures. The neem leaf powder was less effective in removing Cr(VI) ions from solutions. The adsorption mechanism followed a pseudo second order kinetics.