The use of orange wastes, generated in the orange juice industry, for removing cadmium from aqueous solutions has been investigated. The
material was characterized by Fourier transform infrared spectroscopy and batch experiments were conducted to determine the adsorption capacity
of the biomass. A strong dependence of the adsorption capacity on pH was observed, the capacity increasing as pH value rose. Kinetics and
adsorption equilibrium were studied at different pH values (4–6). The adsorption process was quick and the equilibrium was attained within 3 h.
The maximum adsorption capacity of orange waste was found to be 0.40, 0.41 and 0.43 mmol/g at pH 4–6, respectively. The kinetic data were
analysed using various kinetic models – pseudo-first order equation, pseudo-second order equation, Elovich equation and intraparticle diffusion
equation – and the equilibrium data were tested using four isotherm models – Langmuir, Freundlich, Sips and Redlich–Peterson. The data were
fitted by non-linear regression and five error analysis methods were used to evaluate the goodness of the fit. The Elovich equation provides the
greatest accuracy for the kinetic data and the Sips model the closest fit for the equilibrium data.
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