Heavy metal biosorption by gellan gum gel beads

The Ni2+ accumulation in batch mode from diluted solutions by gel beads of gellan gum (GG), alginate, kappa-carrageenan, agar, agarose, silica gel, polyacrylamide and two mixtures of GG + agar was investigated. All polymeric materials studied accumulated Ni2+, but gel beads of GG were stable, easily obtainable and showed the highest Ni2+ accumulation. The pH of the Ni2+ solution was not critical for Ni2+ accumulation. Accumulation of metals Cu2+, Co2+, Ni2+, Pb2+, Cd2+ and Zn2+ by GG gel beads reached the equilibrium after 24h. The removal of Pb2+ and Cu2+ from the aqueous solution was very efficient, with maximum metal uptake (q(max)) of 0.85 and 0.75 mmol/g dw GG, respectively. The general q(max) sequence was Ph > Cu > Ni approximate to Zn = Co > Cd. In an equimolar metal mixture sorption experiment a clear reduction in accumulation was observed, except for Pb2+ (30%). Heavy metals were desorbed with 100mM sodium citrate. (C) 2002 Elsevier Science Ltd. All rights reserved.