Treatment of nickel containing electroplating effluents with Sargassum wightii biomass

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 pKa 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 Sargassum 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.