Chromium removal by phytoremediation and biosorption

Abstract

The possibility of using phytoremediation and biosorption with weed plant species in Thailand to remove chromium (Cr) from soil and water was investigated. Six plant species, Cynodon dactylon, Pluchea indica, Phyllanthus reticulatus, Echinochloa colonum, Vetiveria nemoralis and Amaranthus viridis, were chosen for their abilities to accumulate total chromium (TCr). TCr accumulation capacities of these plants were 152.1, 151.8, 101, 77, 69 and 0 mg/kg, respectively, at a hexavalent Cr[Cr(VI)] concentration of 100 mg Cr(VI)/kg soil. Within 30 days of dosing, Cr(VI) accumulation by Pluchea indica occurred mainly in roots, stems and leaves at 29, 35 and 73 mg/kg biomass on a dry weight basis, respectively, whereas 38, 18 and 0 mg/kg accumulated in the roots, stems and leaves of Cynodon dactylon, respectively. Biosorption experiments were conducted in both batch and column reactors. A synthetic solution containing 50 ppm of Cr(VI) was used to represent Cr(IV) contaminated water. Phyllanthus reticulates, Pluchea indica and Echinochloa colonum showed the maximum Cr(VI) adsorption capacities of 53, 45 and 37 mg/g biomass, respectively, at a pH of 2 and an equilibrium time of 24 hours. Leaves were found to have the maximum adsorption capacity. In the column experiments, leaves of Pluchea indica had the maximum Cr(VI) adsorption capacity of 51.3 mg/g biomass at a pH of 2, a breakthrough time of 102 hours, and a flow rate of 1.3 ml/min. The relationship of Cr removal capacities of phytoremediation with living plants and biosorption using non living biomass are discussed. Leaves of Pluchea indica had greater Cr(VI) accumulation and adsorption than the other plants and are therefore the most effective for Cr phytoremediation and biosorption.