Arthur Raj Binupriya

Bioreduction of trivalent aurum to nano-crystalline gold particles by active and inactive cells and cell-free extract of Aspergillus oryzae var. viridis.

Bioreduction efficacy of both active (AB) and inactive (IB) cells/biomass of Aspergillus oryzae var. viridis and their respective cell-free extracts (ACE and ICE) to convert trivalent aurum to gold nanoparticles were tested in the present study. Strong plasmon resonance of gold nanoparticles was observed between 540 and 560 nm in the samples obtained from AB, IB, ACE and ICE. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were performed to examine the formation of gold nanoparticles. Comparing all four forms of A. oryzae var. viridis, ICE showed high gold nanoparticle productivity. The nanoparticles formed were quite uniform in shape and ranged in size from 10 to 60 nm. In addition some triangle, pentagon and hexagon-shaped nanoplates with size range of 30-400 nm were also synthesized especially at lower pH. Organics from the inactive cells are believed to be responsible for reduction of trivalent aurum to nano-sized gold particles. Organic content of the ICE was found to be double the amount of ACE. High productivity of gold nanoparticles by metabolic-independent process opens up an interesting area of nanoparticle synthesis using waste fungal biomass from industries.

Biocrystallization of silver and gold ions by inactive cell filtrate of Rhizopus stolonifer

Microbes and their cell filtrates are known to synthesize metal nanoparticles. But maintenance of aseptic conditions and irregularly shaped and sized nanoparticles are major drawbacks of the system. In this study cell filtrate from inactive biomass of Rhizopus stolonifer was used for the first time to produce near uniformly sized and shaped Ag and Au nanoparticles at room temperature. The size of Ag and Au nanoparticles were found in the range of 25-30 nm and 1-5 nm, respectively. UV-vis spectrum, TEM and XRD measurements confirmed the formation of Ag and Au nanoparticles.

Sequestration of Reactive Blue 4 by free and immobilized Bacillus subtilis cells and its extracellular polysaccharides

Bacillus subtilis a gram positive bacteria and its extracellular polysaccharide were used in free form as well as immobilized form as biosorbent for sequestration of an anionic dye, Reactive Blue 4 (RB) in aqueous phase. The dye uptake enhanced with decrease in pH. Extracellular polymeric substances (EPS) and free cells were found to be better adsorbents when compared to alginate immobilized cells (IC) and EPS (IEPS). The presence of functional groups in free cells and EPS was confirmed by FT-IR analysis. Immobilization resulted in poor adsorption performance due to increase in mass transfer resistance by the polymeric matrix. High Q(max) and b values were noted in the case of free cells and free EPS in contrast to IC and IEPS. From the kinetic experiments, the adsorption system was found to be a pseudo-first-order reaction at low dye concentration. Desorption of RB was found to be 100% in 1N NaOH. However, the alginate beads were found to be unstable under high alkaline conditions of NaOH.

Preservation of kombucha tea-effect of temperature on tea components and free radical scavenging properties.

Kombucha tea is sugared black tea fermented with a consortium of acetic acid bacteria and yeasts (tea fungus) for 14 days. The tea tastes slightly sweet and acidic. The formation of tea fungal biofilms during storage is a big problem when kombucha tea is being stored and commercialized. Various thermal treatments have been tried for long-term storage of kombucha tea. The present study revealed the influence of heat on the biochemical constituents and the free radical scavenging properties of kombucha tea. Heat treatment at 60, 65, and 68 degrees C for 1 min controlled biofilm formation in kombucha tea without changing its clarity, taste, and flavor. However, tea polyphenols and black tea quality parameters showed varying stability during the storage period. A decrease in free radical scavenging properties was also found during the storage period. Because the biological activities of kombucha tea depended on the biochemical constituents, it was concluded that heat treatment was not a suitable method for kombucha tea preservation.

Porogen effect on characteristics of banana pith carbon and the sorption of dichlorophenols

Banana pith was used as precursor material to prepare carbon with and without porogens. Characterization of the carbons showed higher BET surface area (1285 m2/g) for ZnCl2-treated carbon, comparatively. Adsorption experiments were conducted to study the removal of 2,4-dichlorophenol (DCP) from aqueous solutions using the carbons under varying experimental conditions. Decrease in pH increased the percentage removal. All the carbons studied showed greater percentage of DCP removal with decrease in the initial concentration of DCP. Kinetic studies showed that the adsorption of DCP on the carbons was a rapid process. Nonlinear forms of pseudo-first-order and pseudo-second-order models were used to fit the experimental data. Among these the pseudo-first-order model described the data with high correlation coefficients and low percentage error values. Four nonlinear isotherm models including the Langmuir, Freundlich, Toth, and Sips were used to analyze the experimental DCP isotherms under different pH (2-4) conditions. Adsorption capacities (Qmax) from the Langmuir model were found to be 129.4, 67.7, and 49.9 mg/g for ZnCl2-treated, KOH-treated, and porogen-free carbon, respectively, at pH 2. From desorption studies it seemed that chemisorption played a major role in the adsorption process. The results indicated that ZnCl2-treated carbon could effectively remove phenols from wastewater.

Organic micro-pollutant removal in liquid-phase using carbonized silk cotton hull.

Phenolic compounds constitute one of the major pollutants in the modern world. Although many physical and chemical treatment technologies for their removal exist, most of them are economically not feasible. The present study was aimed at using silk cotton hull, a potent agricultural waste as an adsobent for removal of 2,4-dichlorophenol (2,4-DCP), which was used as a model phenolic compound. The process parameters were investigated and optimized conditions were determined. The equilibrium time was found to be 60 and 80 min for 10 and 20 mg/L and 100 min for 30 and 40 mg/L 2,4-DCP concentrations, respectively. Among the kinetic models applied, pseudo-second order model fitted well. The maximum adsorption capacity was 16.0 mg/g by Langmuir isotherm. Acidic pH was found favorable for the adsorption of 2,4-DCP. Studies on pH effect and desorption seemed to show that chemisorption played a major role in the adsorption process. In thermodynamic study, the change in entropy (DeltaS0) and heat of adsorption (DeltaH0) of silk cotton hull carbon (SCHC) was estimated as 14.01 J/(mol x K) and 3.04 kJ/mol, respectively. SCHC as adsorbent for removal of 2,4-DCP from aqueous solution, is effective, inexpensive, indigenous, reusable, has low treatment time and is easily available in large quantities as waste there by significantly lowers the cost of wastewater treatment.

Carbaryl Sorption by Porogen-treated Banana Pith Carbon

This paper reports the adsorption ability of banana pith activated carbon, with ZnCl2 as the porogen, towards carbaryl (1-naphthyl-N-methylcarbamate) from aqueous solution. The pH-edge experiments revealed that carbaryl adsorption onto ZnCl2-treated banana pith activated carbon (ZTC) was a pH-dependent process with maximum adsorption occurring at pH 11. The adsorption isotherm obtained at pH 11 revealed that ZTC possessed a maximum adsorption capacity of 45.9 mg/g. The adsorption isotherms were well described by the Langmuir and Freundlich models. The kinetic data obtained at different initial carbaryl concentrations were modelled using pseudo-first- and -second-order models. Acetone successfully desorbed carbaryl with a 99.8% elution efficiency.