Optimizing the removal of Chromium from aqueous solution by adsorption using sugarcane bagasse

Abstract

In Ethiopian tannery and textile industries, chromium concentration before treatment ranges from 1000 ppm to 5000 ppm. From this concentration about 95 % of chromium exists in the form of Cr (III), which was toxic when its concentration exceeded 5 ppm and oxidized in to Cr (VI).  This chromium was disposed to environment with effluent in the form of chromium III and chromium VI was highly toxic to humans, animals and plants. Still there was no effective treatment method to remove this high concentration chromium from textile and tannery effluent wastewater. So, this research was done to remove chromium from aqueous solution using sugarcane bagasse through adsorption process. To do adsorption process, first sugarcane bagasse was treated physically and chemically to increase surface area and to activate active sites respectively. Optimization of chromium removal factors was done using 1600 ppm of artificial chromium solution prepared from chromium (III) sulphate and mixed with 20 g /L of activated bagasse. The effect of pH, agitation speed and contact time on adsorption was studied using MINITAB software and the maximum removal efficiency (76.1%) was obtained at pH 2, agitation speed 250 rpm and contact time 120 min. The adsorption isotherm models (Langmuir and Freundlich) isotherms was determined and our adsorption data was fitted with Langmuir isotherm model. Also, adsorption kinetics was determined using Pseudo first and second adsorption kinetics and our adsorption process was fitted with Pseudo second order adsorption kinetics.