Evaluation of single and tri-element adsorption of Pb2+, Ni2+ and Zn2+ ions in aqueous solution on modified water hyacinth (Eichhornia crassipes) fibers

Abstract Water contamination by different toxic ions is a recurring problem due to the increase of anthropic activities. This study aimed to investigate the kinetic and the isotherm of Pb 2+ , Ni 2+ and Zn 2+ ions adsorption in aqueous single and tri-element systems using modified water hyacinth as adsorbent. The water hyacinth fiber was modified and the functional groups were characterized by Fourier Transform Infrared Spectrometer (FTIR) and by the Boehm method. The ions concentrations in the solutions were quantified using an Energy-Dispersive X-ray Fluorescence Spectrometer. The adsorption was analyzed and interpreted using kinetic and isotherm models. The alkali treated water hyacinth was selected to perform the kinetic and the isotherm studies, due to its higher ion adsorption capacity compared to acid-treated water hyacinth and water hyacinth washed with water. The FTIR studies indicated that −OH and −COO − groups are the main ones involved in the adsorption of the Zn 2+ ions while the −COO − groups in the biosorption of the Pb 2+ and Ni 2+ ions. The kinetic model that best fitted the single and tri-element experimental data for all the ions was the pseudo-second order. The single-element adsorption isotherms of Redlich-Peterson, Freundlich and Sips suitably fit the adsorption data, while none of the multi-element models adequately fit the adsorption data. The maximum single-element adsorption capacities of BWH for Ni 2+ , Zn 2+ and Pb 2+ ions were 28.6 ± 3.9, 18.9 ± 1.6 and 76.8 ± 4.7 mg g -1 at 25.0 °C, respectively. The selectivity order of BWH fiber in single and tri-element systems is Pb 2+ >> Zn 2+ ≥ Ni 2+ .