Biosorption of chromium(VI) from aqueous solutions using waste plant biomass

Abstract

Metal biosorption on plant-based materials and agricultural wastes is a well practiced but a complex process affected by several factors. The biosorption of chromium(VI) from aqueous solution onto waste plant biomass of Portulaca Oleracea was studied in the present work. Batch studies were carried out to examine the effects of process parameters. Influence of altering various process parameters was studied. The biosorption process was fast, and equilibrium was achieved in 45 min of contact time. It was found that the biosorption capacity of plant material depends on many factors mainly on solution pH, with a maximum biosorption capacity for chromium at pH 2. The biosorption kinetics was tested with pseudo-first-order and pseudo-second-order reaction, and results showed that biosorption followed pseudo-second-order rate expression. Experimental equilibrium data were applied to two different isotherm models. Isotherm tests showed that equilibrium sorption data were better represented by Langmuir model, and the sorption capacity of plant biomass was found to be 54.945 mg/g. Thermodynamic parameters like ∆G 0, ∆H 0 and ∆S 0 were also evaluated, and it was found that the biosorption was spontaneous and endothermic in nature. Plant biomass was found to be an effective adsorbent for chromium(VI) from aqueous solution. This study indicated that plant biomass could be used as an efficient, cost-effective and environmentally safe biosorbent for the treatment of chromium containing aqueous solutions.