Removal of zinc ions from wastewater using industrial waste sludge: A novel approach

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This article presents sorption of zinc by a novel adsorbent derived from steel plant waste sludge. The batch experiments were carried out to investigate the influence of process parameters such as pH, contact time, adsorbent dose, and the initial metal ion concentration. The equilibrium and kinetic study were performed to investigate the adsorption potential of the waste sludge. The maximum adsorption of 7.26 mg/g of Zn(II) on waste sludge was obtained at an initial pH value of 5.0. Particle size range of 75–150 μm yielded the best adsorption capacity for Zn(II). The pseudo-second-order rate equation fitted the adsorption kinetic data better than pseudo-first-order rate equation. The rate constants and coefficient of determination were determined for the waste sludge. The equilibrium data for the adsorption of Zn(II) on waste sludge was tested with various adsorption isotherm models viz. Langmuir, Freundlich, Redlich–Peterson, and Tempkin. The Langmuir isotherm model was found to be the most suitable one followed by nonlinear Redlich–Peterson isotherm model. The characteristic of the prepared waste sludge was found comparable to the other technically as well as economically feasible and environmentally benign activated carbon. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 576–586, 2013