R. Vimala

Biosorption of cadmium (II) and lead (II) from aqueous solutions using mushrooms: a comparative study.

Sorption capacity of oyster mushroom (Pleurotus platypus), button mushroom (Agaricus bisporus) and milky mushroom (Calocybe indica) were evaluated on biosorption of heavy metals, viz. cadmium (II) and lead (II) from aqueous solutions. The optimum sorption conditions were studied for each metal separately. The desired pH of the aqueous solution was found to be 6.0 for the removal of cadmium (II) and 5.0 for removal of lead (II) for all the mushrooms. The percent removal of both the metals was found to increase with the increase in biosorbent dosage and contact time. The fitness of the biosorption data for Langmuir and Freundlich adsorption models was investigated. It was found that biosorption of cadmium (II) and lead (II) ions onto the biomass of the three mushrooms were better suitable to Langmuir than Freundlich adsorption model. P. platypus showed the highest metal uptake potential for cadmium (q(max) 34.96 mg/g) whereas A. bisporus exhibited maximum potential for lead (q(max) 33.78 mg/g). Milky mushroom showed the lowest metal uptake capacity for both the metals. The present data confirms that mushrooms may be used as efficient biosorbent for the removal of cadmium (II) and lead (II) ions from aqueous solution.

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).

Evaluation of tetraethoxysilane (TEOS) sol-gel coatings, modified with green synthesized zinc oxide nanoparticles for combating microfouling.

Green synthesis of zinc oxide nanoparticles (ZnO-NPs) is gaining importance as an eco-friendly alternative to conventional methods due to its enormous applications. The present work reports the synthesis of ZnO-NPs using the endosperm of Cocos nucifera (coconut water) and the bio-molecules responsible for nanoparticle formation have been identified. The synthesized nanoparticles were characterized using UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and Zeta potential measurement. The results obtained reveal that the synthesized nanoparticles are moderately stable with the size ranging from 20 to 80 nm. The bactericidal effect of the nanoparticles was proved by well diffusion assay and determination of minimum inhibitory concentration (MIC) against marine biofilm forming bacteria. Further the green synthesized ZnO-NPs were doped with TEOS sol-gels (TESGs) in order to assess their antimicrofouling capability. Different volumes of liquid sol-gels were coated on to 96-well microtitre plate and cured under various conditions. The optimum curing conditions were found to be temperature 60 °C, time 72 h and volume 200 μl. Antiadhesion test of the undoped (SG) and ZnO-NP doped TEOS sol-gel (ZNSG) coatings were evaluated using marine biofilm forming bacteria. ZNSG coatings exhibited highest biofilm inhibition (89.2%) represented by lowest OD value against Pseudomonasotitidis strain NV1.