Surface functionalization of Aspergillus versicolor mycelia: in situ fabrication of cadmium sulphide nanoparticles and removal of cadmium ions from aqueous solution

Xanthate functionalization of Aspergillus versicolor mycelia (AVM) was carried out to synthesize cadmium sulphide (CdS) nanoparticles and for the removal of cadmium ions from aqueous solution. The synthesized nanoparticles were characterized by spectroscopic and microscopic techniques. Fourier transform infrared (FTIR) spectroscopy and elemental detection X-ray analysis (EDXA) results confirmed the binding of cadmium with sulphur groups of the functionalized mycelia. Scanning electron and atomic force microscopic studies revealed alteration of surface morphology following binding of cadmium, while high resolution transmission electron microscopy (HRTEM) and fluorescence micrographs demonstrated formation of CdS nanoparticles on AVM surface. Formation of 3.0 +/- 0.2 nm size CdS nanoparticles was confirmed from HRTEM images. The maximum adsorption capacity of the functionalized mycelia for Cd+2 was enhanced to 141.5 mg g(-1) from the corresponding value of 70.5 mg g(-1) for pristine mycelia. An increase in adsorption capacity was attributed to cadmium binding affinity of sulfur atoms due to soft acid-base reaction and supported by a -Delta G value. The experimental results thus suggest that xanthate functionalization of AVM provides a feasible approach for CdS nanoparticle synthesis and also for efficient removal of heavy metal ions.