Mechanism of Cd(II) adsorption by macrofungus Pleurotus platypus.

The mechanism of Cd(II) uptake by the dead biomass of macrofungus Pleurotus platypus was investigated using different chemical and instrumental techniques. Sequential removal of cell wall components of the biosorbent revealed that structural polysaccharides play a predominant role in the biosorption of Cd(II). The adsorption kinetics fitted well with the pseudo second-order model suggested that the adsorption of Cd(II) on P platypus involved a chemisorption process. Transmission electron microscopy of the cadmium exposed biomass confirmed the deposition of the metal mainly in the cell wall. Fourier transform infrared spectroscopic analysis of the metal loaded biosorbent confirmed the participation of -OH, -NH and C-O-C groups in the uptake of Cd(II). Energy dispersive X-ray analysis of the biosorbent before and after metal uptake revealed that the main mechanism of adsorption was ion-exchange. The effectiveness of CaCl2 in the desorption of cadmium perhaps suggested the exchange of Ca2+ with Cd(II).