Biosorption of Nickel (II) from Aqueous Solutions and Electroplating Wastewater using Tamarind (Tamarindus indica L.) Bark

The biosorption experiments were carried out in a batch system as a function of pH, contact time, adsorbent dosage and initial concentration of nickel. Biosorption was pH dependent and maximum removal of Ni(II) was obtained at pH 7.0. The uptake of metal was very fast initially, but gradually slowed down and approached steady state after 30 minute during which no significance biosorption was observed. Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models were applied to the equilibrium data. The Langmuir isotherm model was found to be better applicable to the equilibrium data. The maximum biosorption capacity was 15.34 mg/g. From Dubinin-Radushkevich isotherm model, the free energy was calculated as 15.81 kJ/mol indicating that the biosorption of nickel was taken place by chemisorption. Kinetic evaluation of the experimental data showed that the biosorption process followed well pseudo-second order kinetics. The results of the study showed that the tamarind bark powder can be efficiently used as low cost alternative for the removal of divalent nickel from rinsing wastewater of plating factory