Effective removal of zinc ions from aqueous solutions using crab carapace biosorbent

The carapace of the crab (Cancer pagurus), a waste material disposed of by the seafood industry, has recently been shown to have potential as a biosorbent for the removal of metals from aqueous media. Crab carapace in the particle size ranges 0.25-0.8 mm and 0.8-1.5 mm were used to investigate the effects of agitation speed, contact time, metal concentration and initial pH on the removal of Zn2+. In sequential-batch process Zn2+ uptakes of 105.6 and 67.6 mg/g were recorded for 0.25-0.8 mm and 0.8-1.5 mm particles, respectively, while values of 141.3 and 76.9 mg/g were recorded in fixed-bed column studies. Binary-metal studies showed that the presence of Cu2+ or Pb2+ significantly suppressed Zn2+ uptake. This study confirms that crab carapace may be considered a viable and cost-effective alternative to commercial activated carbon or ion-exchange resins for the removal of metals from aqueous media.