Removal of copper(II) and chromium(VI) from aqueous solution using sorghum roots (S-bicolor): a kinetic and thermodynamic study

Biosorption of toxic metal ions from industrial effluents using different plant parts is an important branch of environmental chemistry. Biosorption of copper(II) and chromium(VI) ions from aqueous solution onto sorghum root (SR) powder have been investigated under batch mode. The optimum pH and temperature for biosorption of both the metals was found to be 2 and 20 A degrees C, respectively. The maximum biosorption capacity q (e) for Cu(II) and Cr(VI) is 18.6 and 18.39 mg/g, respectively. The Langmuir model gave a better fit than other two models. The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second-order model. The thermodynamic parameters were also calculated and the values indicated that the biosorption process was exothermic, spontaneous, and feasible in nature. Desorption experiments with 1 M HCl and 1 M HNO3 inferred the reusability of biomass. The results showed that SRs have excellent adsorption properties and thus can be used as an effective and low cost biosorbent for the removal of Cu(II) and Cr(VI) ions from aqueous solution.