Abstract
The capability of cow hoof (CH) to remove Zn(II) from aqueous solution under the influence of sorbent size, solution pH, contact time, and sorbent dosage was investigated through batch studies. Equilibrium studies were conducted at three different temperatures (298, 308, and 318 K) by contacting different concentrations of Zn(II) solution with a known weight of cow hoof. The biosorption of Zn onto cow hoof was found to increase with increase in the mass of sorbent used while the biosorption efficiency was found to decrease with increase in sorbent particle size. The optimum conditions of pH 4 and contact time of 60 minutes were required for maximum removal of Zn(II) by cow hoof (mesh size 212 µm). The equilibrium data were modelled using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. The data were best fitted by Langmuir model. The kinetic data were analysed using Lagergren kinetic equations and these were well fitted by the pseudo-second-order kinetic model. The thermodynamic parameters showed that the biosorption process was feasible, spontaneous, and endothermic.
Highlights
Water is an essential life-sustaining natural resource and as such, its fitness for life sustenance should be constantly maintained and preserved
The equilibrium amount of Zn adsorbed onto the cow hoof at different temperatures was examined to obtain thermodynamic parameters such as Gibbs free energy change (ΔG0), enthalpy change (ΔH0), and entropy change (ΔS0)
The biosorption of Zn(II) by powdered cow hooves can be described by both physical and chemical adsorption since the mean energy evaluated from the D-R isotherm model had earlier suggested that the removal of Zn from aqueous solution using cow hooves was dominated by physisorption
Summary
Water is an essential life-sustaining natural resource and as such, its fitness for life sustenance should be constantly maintained and preserved. This means that industries need to develop on-site or in-plant facilities to their own effluents and minimize the contaminant concentrations to acceptable limits prior to their discharge [7] This necessity has seriously enhanced the demand for new technologies for metal removal from wastewater [8]. These include reduction and precipitation, coagulation, ion exchange, reverse osmosis, and evaporation Most of these treatment technologies have their attendant limitations which include high chemical demand, high capital and operational cost, and generation of toxic sludge or other secondary wastes. These methods are ineffective at low metal concentrations, in the range of 1–100 mg/L [9]. The equilibrium data obtained were analysed and modelled using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models
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