Arumugam Sivasamy

Biosorption of an Azo Dye by Aspergillus niger and Trichoderma sp. Fungal Biomasses

Biosorption is an eco-friendly and cost-effective method for treating the dye house effluents. Aspergillus niger and Trichoderma sp. were cultivated in bulk and biomasses used as biosorbents for the biosorption of an azo dye Orange G. Batch biosorption studies were performed for the removal of Orange G from aqueous solutions by varying the parameters like initial aqueous phase pH, biomass dosage, and initial dye concentration. It was found that the maximum biosorption was occurred at pH 2. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms, and it was found that both the isotherm models best fitted the adsorption data. The monolayer saturation capacity was 0.48xa0mg/g for Aspergillus niger and 0.45xa0mg/g for Trichoderma sp. biomasses. The biosorption kinetic data were tested with pseudo first-order and pseudo second-order rate equations, and it was found that the pseudo second-order model fitted the data well for both the biomasses. The rate constant for the pseudo second-order model was found to be 10–0.8 (g/mgxa0min−1) for Aspergillus niger and 8–0.4 (g/mgxa0min−1) for Trichoderma sp. by varying the initial dye concentrations from 5 to 25xa0mg/l. It was found that the biomass obtained from Aspergillus niger was a better biosorbent for the biosorption of Orange G dye when compared to Trichoderma sp.

Synthesis and characterization of maleimide-functionalized polystyrene-SiO2/TiO2 hybrid nanocomposites by sol-gel process.

Maleimide-functionalized polystyrene (PSMA-SiO2/TiO2) hybrid nanocomposites were prepared by sol–gel reaction starting from tratraethoxysilane (TEOS) and titanium isopropoxide in the solution of polystyrene maleimide in 1,4-dioxane. The hybrid films were obtained by the hydrolysis and polycondensation of TEOS and titanium isopropoxide in maleimide-functionalized polystyrene solution followed by the Michael addition reaction. The transparency of polymer (PSMA-SiO2/TiO2) hybrid was prepared from polystyrene titanium isopropoxide using the γ-aminopropyltriethoxy silane as crosslinking agent by in situ sol–gel process via covalent bonding between the organic–inorganic hybrid nanocomposites. The maleimide-functionalized polystyrene was synthesized by Friedel-Crafts reaction from N-choloromethyl maleimide. The FTIR spectroscopy data conformed the occurrence of Michael addition reaction between the pendant maleimide moieties of the styrene and γ-aminopropyltriethoxysilane. The chemical structure and morphology of PSMA-SiO2/TiO2 hybrid nanocomposites were characterized by FTIR, nuclear magnetic resonance (NMR), 13u2009C NMR, SEM, XRD, and TEM analyses. The results also indicate that the inorganic particles are much smaller in the ternary systems than in the binary systems; the shape of the inorganic particles and compatibility for maleimide-functionalized polystrene and inorganic moieties are varied with the ratio of the inorganic moieties in the hybrids. Furthermore, TGA and DSC results indicate that the thermal stability of maleimide-functionalized polystyrene was enhanced through the incorporation of the inorganic moieties in the hybrid materials.

Kinetic studies on anaerobic co-digestion of ultrasonic disintegrated feed and biomass and its effect substantiated by microcalorimetry.

Studies were carried out on anaerobic co-digestion of primary and secondary excess sludge obtained from tannery effluent treatment plant. Anaerobic biomass collected from a treatment plant was used as the source of micro-organisms. The optimum feed to micro-organism ratio was evaluated as 0.7 on the basis of volatile solids reduction cum gas production. Both feed and anaerobic biomass were subjected to ultrasonic pre-treatment in order to enhance the digestion process. Experiments carried out on batch mode showed significant increase in the gas production for pre-treated feed and biomass. Optimum pre-treatment durations were evaluated as 5xa0min for feed and 3xa0min for anaerobic biomass. Heat flow analyses of the anaerobic biomass using isothermal microcalorimetry throw light on different stages of digestion process. The effect of ultrasonic pre-treatment on anaerobic biomass was also substantiated using this technique. The heat energy released by pre-treated and untreated anaerobic biomass was evaluated as 16.3 and 7.6xa0kJ/kg, respectively. Kinetic analysis revealed that the overall rate constant of digestion process increased by 1.5 times due to pre-treatment. However, the initial lag time increased by about 20xa0% for the optimally pre-treated sample compared to untreated sample. Modified Gompertz equation was used to model, and the parameters were evaluated. The significance of this work lies on energy production (bio gas) and at the same time increasing the maintenance metabolism rate thereby minimizing excess sludge biomass generation.

Synthesis and Characterization of 3,3′-bis (3-maleimidophenyl) Phenyl Phosphine Oxide (BMI)/1, 3-Cyanatobenzene Epoxy Inter-crosslinked Matrices for Engineering Applications

Cyanate ester (CE) -3,3′-bis (3-maleimidophenyl) phenyl phosphine oxide (BMI)-modified epoxy matrices were made by using epoxy resin (DGEBA) and 1,3-dicyantobenzene and diaminodiphenyl methane as a curing agent. The properties of BMI-CE epoxy matrices were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis, scanning electron microscopy, water absorption behavior and heat deflection temperature. The matrices were also characterized for their mechanical properties such as tensile strength, flexural strength and unnotched Izod impact strength by ASTM methods. The mechanical and tensile properties were improved by increasing the percentage of the CE in the epoxy resin. DSC thermograms of 1,3-dicyantobenzene as well as BMI-modified epoxy resin showed an unimodal reaction exothermicity.

High-performance N-doped MWCNT/GO/cellulose hybrid composites for supercapacitor electrodes

A nitrogen-doped MWCNT/GO/cellulose hybrid composite was prepared via an in situ hydrothermal process, and its electrochemical performance was evaluated by conducting cyclic voltammetry (CV). The synthesized ternary hybrid nanocomposite was characterized using Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission transmission electron microscope (FE-TEM), and thermogravimetric (TGA) analysis. The structural and morphological properties of the hybrid composite show it is possible to control the morphology and achieve thermal stability for hybrid nanocomposites. The electrochemical characteristics of the hybrid composites were investigated via cyclic voltammetry, Galvanostatic charge–discharge and electrochemical impedance spectroscopy. The hybrid composites were capable of delivering a high specific capacitance of ∼264 F g−1 at a current density of 6 A g−1, and this increases the energy density with an excellent cycling stability (98%) after 10u2006000 continuous charge–discharge cycles, this shows that the hybrid composites can be promising electrode materials to achieve high-performance supercapacitors.

Optimization and biokinetic studies on pretreatment of sludge for enhancing biogas production

Excess sludge generation is a major problem in biological effluent treatment processes. Utilization of excess sludge for gas production is an attractive route, which could be enhanced by pretreatment methods. This study involves two sets of experiments. The first set covers mechanical pretreatment of both feed and inoculum. The second set involves alkaline and mechanical treatments of feed and only mechanical treatment of inoculum. Response surface methodology was used for experimental design, analysis and optimization. The optimized mechanical treatment volume of feed was found to be 50%. Diligent mechanical treatment of inoculum resulted in enhanced microbial activity and improved gas production. Reduction in volatile solids, proteins and carbohydrates was observed to a maximum of 63, 84 and 78.5%, respectively. Feed was subjected to alkali treatment in order to reduce mechanical energy input and to improve solubilization. Compared to mechanical treatment alone, enhanced gas production of about 15% was observed at an optimized pH of 11.8 and SRT of 21xa0days. A biokinetic model was formulated, simulated and validated for the degradation of organics and gas production.

Ultrasonic sludge disintegration in the presence of iron (II) as catalyst

Increasing environmental awareness worldwide and subsequent regulations have led to the application of improved and novel technologies in excess sludge treatment. Sludge is the by-product of wastewater treatment plants rich in organic carbons, pathogens and metals. To enhance the ultrasonic sludge disintegration, a new method by introducing (Fe (II)) as a catalyst in the process has been explored. Studies were conducted to elucidate the parameters governing the disintegration process. The disintegration profiles shows two phases, disruption of micro-organisms resulting release of organic-substances and mineralisation of dissolved organic substances. The optimal level of process parameters results in better solubilisation and mineralisation.

Synthesis of Octa(maleimidophenyl) silsesquioxane–SiO2/TiO2 Hybrid Nanocomposites: Adsorption Behavior for the Removal of an Organic Methylene Blue Dye and Antimicrobial Activity against Pathogens

ABSTRACT In this study, a sol–gel process was used to prepare hybrid nanocomposite consisting of octa(maleimidophenyl) silsesquioxane-silica/titania (maleimide–POSS (polyhedral oligomeric silsesquioxanes)–SiO2/TiO2) to use in methylene blue (MB) adsorption and as an antibacterial agent. The structure, surface, and morphological characteristics were confirmed through Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The optical and thermal stabilities were studied by conducting UV–visible and thermogravimetric analysis–differential scanning electron calorimetry analysis. The experimental results showed a maximum dye adsorption capacity of 92% achieved using 0.5u2009g of hybrid nanocomposite after 2.5u2009h at pH 9. We also investigated the effect that the adsorbent dosage, pH, and contact time had on the removal efficiency of the MB dye in aqueous solution. The recycling experiment showed a good adsorption capacity of the MB dye, even after five repeated cycles. Furthermore, the hybrid nanocomposite was tested against pathogenic bacteria, such as Bacillus cereus, Lactobacillus, Escherichia coli, and Pseudomonas aeruginosa. The nanocomposite was observed to be highly sensitive to E. coli, B. cereus, and P. aeruginosa, as confirmed by the size of the zone inhibition. GRAPHICAL ABSTRACT