Removal of copper ions by the filamentous fungus, Rhizopus oryzae from aqueous solution.

Removal of heavy metals present in wastewaters has been a major concern due to their non-biodegradability and toxicity. Removal of copper ion using NaOH treated Rhizopus oryzae biomass was investigated in a batch reactor. The copper uptake exhibited substantial enhancement both in terms of kinetics of uptake as well as the loading capacity. The copper biosorption by viable and pretreated fungal biomass fit well to a Lagergren's pseudo second order reaction in comparison to pseudo first order kinetics. Investigation on effect of pH indicated improved performance in the range of pH 4-6 in alkali treated biomass. Copper uptake exhibited by viable biomass was highest at 21 degrees C, unlike pretreated biomass that showed maximum uptake across the range of temperature 21-55 degrees C. The maximum copper loading capacity of the viable and pretreated biomass according to Langmuir isotherm was 19.4 and 43.7 mg/g, respectively. Distribution coefficient of pretreated biomass showed improvement at lower residual concentration, indicating a change in the nature of binding by the treated biomass. Copper uptake decreased with an increasing dose of biosorbent, although enhancement in the total metal ion removal was observed at higher dose.

Extracellular biosynthesis of silver nanoparticles using the fungus Aspergillus fumigatus.

Development of reliable and eco-friendly process for synthesis of metallic nanoparticles is an important step in the filed of application of nanotechnology. One of the options to achieve this objective is to use natural processes such as use of biological systems. In this work we have investigated extracellular biosynthesis of silver nanoparticles using Aspergillus fumigatus. The synthesis process was quite fast and silver nanoparticles were formed within minutes of silver ion coming in contact with the cell filtrate. UV-visible spectrum of the aqueous medium containing silver ion showed a peak at 420 nm corresponding to the plasmon absorbance of silver nanoparticles. Transmission electron microscopy (TEM) micrograph showed formation of well-dispersed silver nanoparticles in the range of 5-25 nm. X-ray diffraction (XRD)-spectrum of the silver nanoparticles exhibited 2theta values corresponding to the silver nanocrystal. The process of reduction being extracellular and fast may lead to the development of an easy bioprocess for synthesis of silver nanoparticles.

Thorium biosorption by Aspergillus fumigatus, a filamentous fungal biomass.

Thorium biosorption by Aspergillus fumigatus was carried out in a batch reactor to study the effect of initial pH and metal ion concentration, contact time, biomass dose and kinetics and equilibrium Th uptake. Thorium(IV) uptake by A. fumigatus was pH dependent (pH range, 2.0-6.0) and maximum sorption was observed at pH 4.0. The uptake was rapid and the biosorption process reached equilibrium within 2h of contact times at pH 2-4 and initial Th concentration of 50 and 100mg/L. The kinetics data fitted well to Lagergren's pseudo-second-order rate equation (r(2)>0.99). A maximum initial sorption rate of 71.94 (mg/g min) and second-order rate constant of 7.82 x 10(-2) (g/mg min) were observed at pH 4.0, 50 mg Th/L. The observed maximum uptake of thorium was 370 mg Th/g at equilibrium. Biosorption process could be well described by Langmuir isotherm in comparison to Freundlich and Temkin isotherms. Sodium bicarbonate was the most efficient desorbing reagent with desorption efficiency of more than 99%. Environmental scanning electron micrograph (ESEM) showed that the surface of the biomass after desorption was intact.