Uptake of Cd(II) Onto Raw Crab Shells: Isotherm, Kinetic, Adsorption Properties And Mechanisms.

  This study focuses on the uptake of cadmium (Cd(II)) ion from water onto raw crab shells acting as a biosorbent. Experimental data were perfectly fitted to the Langmuir and Dubinin-Radushkevich models, while the uptake kinetics are well-described using the pseudo-second-order model. The effects of experimental conditions on the uptake isotherms and kinetics are discussed in detail. A study of uptake thermodynamics has indicated that the Cd(II) uptake onto the crab shell is an endothermic and spontaneous process. For further understanding of this process, possible mechanisms of Cd(II) uptake onto crab shell have been deduced from experimental results. Desorption experiment shows that 93.7% of adsorbed Cd(II) could be recovered with a 0.1 M HNO3 solution. The inhibitory effects of other metal co-ions on the Cd(II) uptake on the crab shell are also discussed.