Two electroplating industrial effluents containing 109 and 52 mg Ni/l, respectively, were treated using Sargassum wightii biomass in batch and column operations. Potentiometric titrations revealed S. wightii contains 2.1 mmol/g of binding sites and has pK(a) values of 4.3 and 8.8. For both effluents, the pH effect on nickel uptake was not well pronounced at higher pH values. Langmuir, Freundlich, Redlich-Peterson and Sips models were used to describe the biosorption isotherm data. The elution efficiency for Ni-desorption from S. wightii was determined for HCl, H2SO4, HNO3, CaCl2, MgCl2, NaCl, KCl, NH4Cl, NaOH, KOH, NH4OH and EDTA (Na). Among these elutants, 0.1 M CaCl2 (in HCl, pH 2.5) exhibited elution efficiencies greater than 98% and also not markedly affected the biomass. The ability of S. wightii to biosorb nickel from effluents was investigated in a packed column. The presence of excess co-ions in effluent-1 affected the nickel uptake by S. wightii biomass. The Sargassuni bed exhibited uptakes of 37.2 and 38.6 mg Ni/g from effluent-1 and effluent-2, respectively, under full column saturation. The data from five regeneration cycles evidenced that reusability of S. wightii biomass in the treatment of nickel-bearing electroplating effluents is viable. (c) 2005 Elsevier Ltd. All rights reserved.