A comparative study of copper(II) biosorption on Ca-alginate, agarose and immobilized C-vulgaris in a packed-bed column

Little attention has been paid to investigating the effect of operating variables on the metal-ion sorption characteristics of agarose and agarose-micro-organism systems in a fixed bed, although some fragmentary studies related to Ca-alginate and Ca-alginate-micro-organism systems have been reported in the literature. In this study a comparative biosorption of copper(II) ions to Ca-alginate, agarose biopolymers and immobilized C, vulgaris, a green alga, was investigated in a packed-bed column operated in continuous mode, as a function of the flow rate and inlet metal-ion concentration. The quantities of Cu(II) ions removed relative to the effluent volumes were determined by evaluating the breakthrough curves obtained at different flow rates and different inlet Cu(II) concentrations. The data confirmed that early saturation and lower Cu(II) removal was observed at higher flow rates and higher Cu(II) concentrations for all packing materials. Ca-alginate is a good adsorbent of Cu(II) ions and immobilization of C. vulgaris to Ca-alginate only marginally increased the biosorption yield. However, agarose-immobilized C. vulgaris clearly increased the biosorption capacity. Agarose and agarose-algae systems showed a rapid Cu(II) uptake initially while Cu(II) ion adsorption to Ca-alginate and Ca-alginate-algae systems was limited initially by the diffusion of the solute through the pores. Total Cu(II) removal by Ca-alginate and immobilized C. vulgaris was higher than that of agarose and agarose-C. vulgaris systems over longer time periods. (C) 1998 Elsevier Science Ltd. All rights reserved.