Munusamy Thirumavalavan

Effective adsorption of heavy metal ions (Cu2+, Pb2+, Zn2+) from aqueous solution by immobilization of adsorbents on Ca-alginate beads

The performance of adsorbent system consisting of orange peel cellulose (OPC), banana peel cellulose (BPC), orange peel cellulose immobilized Ca-alginate beads (OPCCA) and banana peel cellulose immobilized Ca-alginate beads (BPCCA) for the removal of Cu2+, Pb2+, and Zn2+ from an aqueous solution was tested. The widely used Langmuir isotherm model was utilized to describe the adsorption equilibrium process. OPC and BPC were characterized by SEM and Fourier transform infrared spectroscopy (FT–IR) techniques. The concentration of metal ions was varied in order to obtain optimum concentration level. The effect of pH was studied at different pH values. The role of cellulose in the case of OPC and BPC and the role of alginate in OPCCA and BPCCA were well understood leading to two different mechanisms in native and immobilized cellulose. OPC was found to be a better adsorbent among OPC and BPC, and Cu2+ was considered to be adsorbed more effectively than Pb2+ and Zn2+. The extent of enhancement of adsorption capacity in the case of BPC was greater than that of OPC after immobilization. For the same amount of adsorbents used, OPC and OPCCA showed enhanced activity than BPC and BPCCA.

Preparation and Morphology Studies of Nano Zinc Oxide Obtained Using Native and Modified Chitosans

Nano zinc oxide (ZnO) with moderate surface area and high pore volume were prepared using a facile preparation method. Chitosan was utilized as both chelating and structure directing agent. The application of chitosans in this study suggested that even biowastes can be served in a productive manner economically. The surface modification of chitosan was carried out in order to increase the interaction between chitosan and zinc ions. The effect of sodium chloroacetate and isopropyl alcohol on the surface modification process was also explored. FT-IR (Fourier transform-infrared spectrometer) and TGA (Thermogravimetric analyses) analyses revealed that modified chitosans are more stable than those of unmodified chitosan. Among surface modified chitosans, CMC1 (1.5 M sodium chloroacetate and 75% isopropyl alcohol) showed enhanced surface properties. Freundlich adsorption isotherms as preliminary studies confirmed that modified chitosan showed enhanced interaction with zinc ions. The interaction of zinc salt with chitosans produced a zinc-chitosan polymer. This finally cleaved upon calcination to produce nano ZnO. The effects of different calcination temperatures indicated that 450 °C is the optimum calcination temperature to produce the nano ZnO with favored surface area (15.45 m2/g) and pore size (221.40 nm). SEM (Scanning electron microscope) and TEM (Transmission electron microscope) of ZnO indicated that uniform particle and shape distributions were obtained at low calcination temperature (450 °C).

A versatile chitosan/ZnO nanocomposite with enhanced antimicrobial properties.

Porous chitosan membrane was fabricated by casting method using silica particles. Simultaneously nano ZnO was synthesized by green-synthesis method using tung ting oolong tea extract. Chitosan membrane was combined with nano ZnO in order to increase its antimicrobial activity. Through observations obtained from various techniques such as XRD, SEM, FT-IR, UV-visible and fluorescence emission analyses, chitosan was seen to be able to incorporate nano ZnO in the nanocomposite membrane. A blue shift (from 360 to 335 nm) was observed in the UV-visible spectrum of nanocomposite and fluorescence emission intensity of nanocomposite was considerably lower than that of nano ZnO. Gram negative organism Klebsiella planticola (MTCC2727) and Gram positive organism Bacillus substilis (MTCC3053) were used to test the antibacterial and antifouling activities of newly synthesized nanocomposite chitosan/ZnO membrane. The nanocomposite chitosan/ZnO membrane promisingly inhibited the bacterial growth when compared with as-synthesized chitosan. Gram negative K. planticola (MTCC2727) was comparatively more susceptible for inhibition than that of Gram positive Bacillus substilis (MTCC3053). In conclusion, nanocomposite obtained in this study showed enhanced antibacterial and antifouling activities. We believed that the enhanced physical properties of nanocomposite achieved by incorporating nano ZnO in the chitosan matrix could be beneficial in various applications.

Effects of humic acid and suspended soils on adsorption and photo-degradation of microcystin-LR onto samples from Taiwan reservoirs and rivers

This article covers the adsorption capacity of microcystin-LR (MC-LR) onto natural organic matter (NOM) or suspended solids of water samples from reservoirs (Emerald and Jade reservoirs) and rivers (Dongshan, Erhjen and Wukai rivers) in Taiwan to determine the fate, transport behavior and photo-degradation of microcystins in natural water systems. Langmuir adsorption and photo-degradation studies were carried out and the capability of samples for MC-LR adsorption was confirmed. Among these, samples collected from reservoir showed enhanced MC-LR adsorption than that of river samples and the greater adsorption behavior was always favored by larger content of organic matter and suspended particles in the system. It is obvious from the experimental results that the adsorption of MC-LR was influenced by suspended particles (turbidity), humic acid (HA), organic matter content and other pollutants. The effective photo-degradation of MC-LR was achieved using higher energy, lower wavelength (254 nm) UV light within 60 min. The presence of humic acid and turbidity affected the photo-degradation process. These data provide important information that may be applied to management strategies for improvement of water quality in reservoirs and rivers and other water bodies in Taiwan.

Synthesis of ZnO/Zn nano photocatalyst using modified polysaccharides for photodegradation of dyes

A complete set of experiments in two aspects of studies combining the various factors affecting both the preparation and photocatalytic activity of ZnO/Zn nanocomposite obtained using corn starch and cellulose (native and modified) as chelating agents for the photodegradation of methylene blue, and congo red was carried out and discussed. The resulting ZnO/Zn nanoparticles obtained using modified polysaccharides exhibited super catalytic capability. The ZnO/Zn nanoparticles possessed favored surface area (11.8443-15.7100m(2)/g) and pore size (12.3473-13.7453nm). The photocatalytic degradation of nano ZnO/Zn was directly proportional to the surface area of nano ZnO/Zn. Regardless of the dye pollutants, nano ZnO/Zn obtained using modified corn starch showed enhanced catalytic activity than that of cellulose and methylene blue had comparatively faster degradation rate. Our findings shed light on the optimization of both preparation conditions of photocatalysts and their photocatalytic experimental conditions.

Effects of PAH biodegradation in the presence of non-ionic surfactants on a bacterial community and its exoenzymatic activity

The influence of two non-ionic surfactants (TX-100 and Brij 35) on a bacterial community and its exoenzymatic activity during polycyclic aromatic hydrocarbon (naphthalene, phenanthrene and pyrene) biodegradation was evaluated in this study. The result indicated the addition of the non-ionic surfactants altered the profiles of the microbial populations and produced exoenzymes. Fluorescence in situ hybridization found that, as PAH biodegradation progressed in the presence of non-ionic surfactant, the proportion of Bacteria presents increased significantly from the range 54.79%–57.00% to 64.17%–73.4% and there was parallel decrease in Archaea. The trends in five phyla/subclass of Bacteria, namely α -, β -, or γ -Proteobacteria, HGC bacteria and LGC bacteria, were influenced significantly by the addition of Brij 35 as either monomers or micelles. A change was ascribed to different cohesive energy density (CED) value between the PAH and surfactant. The percentage of genera Pseudomonas 4.76%–12.67%, which included two signals, namely most true Pseudomonas spp. and Pseudomonas aeruginosa, were dominant during biodegradation. For exoenzymaztic activities, trends were identified by principle component analysis of the API ZYM enzymatic activity dataset. The additions of non-ionic surfactant were identified strong activities of three esterase (esterase, esterase lipase and lipase), α -glucosidase, β -glucosidase, leucine arylamidase and acid phosphatase during PAH biodegradation. These enzymes are selected as possible organic pollutant indicators when the in situ bioremediation was monitored in the presence of non-ionic surfactant additives.

Development of silica gel-supported modified macroporous chitosan membranes for enzyme immobilization and their characterization analyses.

The present work was aimed at developing stability enhanced silica gel-supported macroporous chitosan membrane for immobilization of enzymes. The membrane was surface modified using various cross-linking agents for covalent immobilization of enzyme Bovine serum albumin. The results of FT-IR, UV–vis, and SEM analyses revealed the effect of cross-linking agents and confirmed the formation of modified membranes. The presence of silica gel as a support could provide a large surface area, and therefore, the enzyme could be immobilized only on the surface, and thus minimized the diffusion limitation problem. The resultant enzyme immobilized membranes were also characterized based on their activity retention, immobilization efficiency, and stability aspects. The immobilization process increased the activity of immobilized enzyme even higher than that of total (actual) activity of native enzyme. Thus, the obtained macroporous chitosan membranes in this study could act as a versatile host for various guest molecules.

A facile approach for achieving an effective dual sorption ability of Si/SH/S grafted sodium montmorillonite

In this study, sodium montmorillonite was functionalized with SH, S and Si functional groups using four different soil modifiers, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane [BAT], 3,3′-tetrathiobis(propyl-triethoxysilane) [TP], thiodiglycol bis(3-aminocrotonate) [TDBA] and (3-mercaptopropyl)trimethoxysilane [MPTMS], for the effective uptake of both organic and inorganic pollutants. The uptake of inorganic (Cu2+, Zn2+) and organic [benzene, toluene, ethylbenzene and p-xylene (BTEX)] pollutants was studied with individual as well as binary mixtures. Based on the experimental results, the soil modifier MPTMS best improved the sorption characteristics and, among two metal ions, Cu2+ showed enhanced adsorption. Sorption of BTEX was not correlated with a single parameter and hence it differed for the different cases based on the organic matter content. The obtained log KOC and log KOM values of BTEX in this study for modified montmorillonite are comparatively larger than those of unmodified montmorillonite or natural soil. Sorption carried out in the binary mixtures showed that there is no interaction between these pollutants and the presence of one did not retard the adsorption of another. The uptake phenomenon was influenced by various combined factors such as the nature, surface charge and surface area of the modified soils.

A Short Review on Chitosan Membrane for Biomolecules Immobilization

Chitosan is an important natural polymer that occurs in the world. Chitosan is soluble in acidic aqueous media and it can be obtained in various forms. It is widely used for many applications. Hence, we briefly describe the role of chitosan in membrane form, an important area of research in which a variety of synthetic methods has been proposed and their significance is explained. Thus, this review emphasizes the papers on the high value-added applications of these chitosan membranes in diverse fields such as medicine, biological, cosmetics and nanotechnology.

A facile approach to the isolation of proteins in Ferula asafoetida and their enzyme stabilizing, anti-microbial and anti-oxidant activity

The objective of the present study was to identify the proteome pattern, isolate and study the functions of selective proteins from Ferula asafoetida root exudate using chromatographic techniques. The root exudate proteins were fractionated using ion-exchange and gel filtration chromatography. A range of bioactive protein fractions were then separated in sufficient quantity which is the focus of this study. Based on studies, here we report three main proteins with molecular weights 14kDa, 27kDa, and 39kDa. The biological and pharmacological activities of both purified and unpurified proteins obtained were extensively studied to understand their significance. The study revelaed that 27kDa protein interestingly stabilized trypsin activity in 24h of time and retained about 64% of the enzyme activity. Analyses confirmed 40°C and pH 8.0 are the optimum temperature and pH respectively. The 39kDa protein remarkably increased the activity of chymotrypsin and the 14kDa protein showed anti-bacterial activity against Pseudomonas aeruginosa. Invariably all of the three purified proteins showed enhanced anti-oxidant activity. In conclusion, results here obtained suggested that the primary metabolites (proteins) in asafoetida are mainly responsible for its versatile biological and pharmacological activities.