Priya Banerjee

Optimization and modelling of synthetic azo dye wastewater treatment using Graphene oxide nanoplatelets: Characterization toxicity evaluation and optimization using Artificial Neural Network

Azo dyes pose a major threat to current civilization by appearing in almost all streams of wastewater. The present investigation was carried out to examine the potential of Graphene oxide (GO) nanoplatelets as an efficient, cost-effective and non-toxic azo dye adsorbent for efficient wastewater treatment. The treatment process was optimized using Artificial Neural Network for maximum percentage dye removal and evaluated in terms of varying operational parameters, process kinetics and thermodynamics. A brief toxicity assay was also designed using fresh water snail Bellamya benghalensis to analyze the quality of the treated solution. 97.78% removal of safranin dye was obtained using GO as adsorbent. Characterization of GO nanoplatelets (using SEM, TEM, AFM and FTIR) reported the changes in its structure as well as surface morphology before and after use and explained its prospective as a good and environmentally benign adsorbent in very low quantities. The data recorded when subjected to different isotherms best fitted the Temkin isotherm. Further analysis revealed the process to be endothermic and chemisorption in nature. The verdict of the toxicity assay rendered the treated permeate as biologically safe for discharge or reuse in industrial and domestic purposes.

Potential of biosorbent developed from fruit peel of Trewia nudiflora for removal of hexavalent chromium from synthetic and industrial effluent: Analyzing phytotoxicity in germinating Vigna seeds

Chromium (VI) removal efficiency of a biosorbent prepared from fruit peel of Trewia nudiflora plant was studied. The effect of pH, sorbent dose, initial metal concentration and temperature was studied with synthetic Cr+6 solution in batch mode. About 278 mg/g of Cr+6 sorption was obtained at 293 K at an optimum pH of 2.0 and biosorbent dose of 0.75 g/L. Equilibrium sorption data with varying initial concentration of Cr+6 (22–248 mg/L) at three different temperatures (293–313 K) were analyzed by various isotherms. Biosorption kinetics and thermodynamics were described using standard model equations. Encouraging results were obtained by the application of the biosorptive treatment for removal of Cr+6 from wastewater collected from common effluent treatment plant of tannery industry. In addition, Cr+6 desorption behavior was studied on different systems. Biosorbent was characterized by FESEM, FT-IR and XRD, etc. Effect of the biosorptive treatement with respect to the phytotoxicity of Cr+6 was analyzed by studying the seed germination behavior and enzyme activity of a pulse seed (Vigna radiata L.). Different concentrations of Cr+6 solution in both synthetic medium, as well as, in tannery effluent was employed and the results were compared with that of biosorbent treated medium. The study showed that due to efficient removal of Cr+6 from aqueous phase, considerable enhancement of seed germination, as well as, increase in root length was obtained for the biosorbent treated solutions which were close to that of the control values. Significant decrease (P < 0.01) in POD activity was observed in seeds irrigated with biosorbent treated wastewater compared to untreated wastewater. The study showed that the novel biosorbent prepared might be utilized for abatement of heavy metal toxicity, i.e., Cr+6 from industrial effluent.

Assessment on linear and non-linear analysis for the estimation of pseudo-second-order kinetic parameters for removal of dye using graphene nanosheet

AbstractGraphene nanosheets were used as adsorbent for the removal of crystal violet dye from its aqueous solution. The equilibrium kinetic data were analyzed using pseudo-second-order kinetic model. A comparison between linear and non-linear methods of estimating the kinetic parameters was examined. Four pseudo-second-order kinetic linear equations have been discussed here. The coefficient of determination and chi-square test were employed as methods of error analysis for determining the best-fitting equation. The results revealed that the non-linear method proved to be a significantly better alternative for obtaining the kinetic parameters in comparison with the linear form of the model. In addition, the test was found to be a better method for determination of the best-fitting model.

Treatment of cosmetic effluent in different configurations of ceramic UF membrane based bioreactor: Toxicity evaluation of the untreated and treated wastewater using catfish (Heteropneustes fossilis).

Extensive usage of pharmaceutical and personal care products (PPCPs) and their discharge through domestic sewage have been recently recognized as a new generation environmental concern which deserves more scientific attention over the classical environmental pollutants. The major issues of this type of effluent addressed in this study were its colour, triclosan and anionic surfactant (SDS) content. Samples of cosmetic effluent were collected from different beauty treatment salons and spas in and around Kolkata, India and treated in bioreactors containing a bacterial consortium isolated from activated sludge samples collected from a common effluent treatment plant. Members of the consortium were isolated and identified as Klebsiella sp., Pseudomonas sp., Salmonella sp. and Comamonas sp. The biotreated effluent was subjected to ultrafiltration (UF) involving indigenously prepared ceramic membranes in both side-stream and submerged mode. Analysis of the MBR treated effluent revealed 99.22%, 98.56% and 99.74% removal of colour, triclosan and surfactant respectively. Investigation of probable acute and chronic cyto-genotoxic potential of the untreated and treated effluents along with their possible participation in triggering oxidative stress was carried out with Heteropneustes fossilis (Bloch). Comet formation recorded in both liver and gill cells and micronucleus count in peripheral erythrocytes of individuals exposed to untreated effluent increased with duration of exposure and was significantly higher than those treated with UF permeates which in turn neared control levels. Results of this study revealed successful application of the isolated bacterial consortium in MBR process for efficient detoxification of cosmetic effluent thereby conferring the same suitable for discharge and/or reuse.

Algal Biomass as Potential Biosorbent for Reduction of Organic Load in Gray Water and Subsequent Reuse: Effect on Seed Germination and Enzyme Activity

ABSTRACT Biosorptive treatment using algal biomass of Rhizoclonium riparium was proposed for higher-loading gray water for its effective utilization. A batch sorption study was conducted using composite wastewater having a wide range of initial chemical oxygen demand (COD) values (2400–44,800 mg/L). The study showed an optimum dose of 5 g/L of biosorbent resulted in 96% reduction of COD for wastewater with an initial COD of 10,500 mg/L. The equilibrium isotherm data at different temperatures were fitted to linear and nonlinear isotherms. Biosorption kinetics was studied by various kinetic models. Chemical composition and surface morphology of the biosorbent were characterized by infrared, x-ray diffraction, and scanning electron microscopy techniques before and after biosorption. Applicability of the biosorbent-treated wastewater in agricultural uses was explored by studying the effect of untreated and treated wastewater on the germination of two seeds, i.e., Vigna radiata and Lens esculenta, and subsequently the activity of peroxidase (POD) enzymes were studied to understand the toxicity in plants. The study revealed that compared with seeds treated with different dilutions of untreated wastewater, germination (%) was significantly higher for biosorbent-treated wastewater, with a reduced level of POD activity, indicating positive response of the seeds towards the biosorptive treatment.

Assessment on the decolourization of textile dye (Reactive Yellow) using Pseudomonas sp. immobilized on fly ash: Response surface methodology optimization and toxicity evaluation

This study focuses on the investigation of removal of textile dye (Reactive Yellow) by a combined approach of sorption integrated with biodegradation using low cost adsorbent fly ash immobilized with Pseudomonas sp. To ensure immobilization of bacterial species on treated fly ash, fly ash with immobilized bacterial cells was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and fluorescence microscopy. Comparative batch studies were carried out using Pseudomonas sp, fly ash and immobilized Pseudomonas sp on flyash and were observed that immobilized Pseudomonas sp on flyash acted as better decolourizing agent. The optimized pH, temperature, and immobilized adsorbent dosage for highest percentage of dye removal were observed to be pH 6, 303 K, 1.2 g/L in all the cases. At optimum condition, the highest percentage of dye removal was found to be 88.51%, 92.62% and 98.72% for sorption (flyash), biodegradation (Pseudomonas sp) and integral approach (Pseudomonas sp on flyash) respectively. Optimization of operating parameters of textile dye decolourization was done by response surface methodology (RSM) using Design Expert 7 software. Phytotoxicity evaluation with Cicer arietinum revealed that seeds exposed to untreated dye effluents showed considerably lower growth, inhibited biochemical, and enzyme parameters with compared to those exposed to treated textile effluents. Thus this immobilized inexpensive technique could be used for removal of synthetic dyes present in textile wastewater.

Phenol Adsorption onto Various Soil Composite Membranes: Insight into Process Kinetics, Modelling and Optimisation Using Response Surface Methodology

The present study investigates the potential of soil and soil composites for removal of phenol from solution on a comparative scale. Different experimental parameters were optimized with a novel approach of response surface methodology (RSM) and a central composite design (CCD) for achieving maximum efficiency. Maximum adsorption efficiency (1.44 mg g-1) was obtained at initial pH 5.5, an adsorbent dosage of 7.5 g L-1 and a treatment time of 32.5 mins at a temperature of 313 K as predicted by the RSM design. The phenomenon best fitted the Temkin isotherm at different temperatures. The process was guided by the pseudo-secondorder kinetic model and was analyzed to be spontaneous, endothermic and chemisorption in nature. Characterization of soil particles using Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy showed the changes in its structure and surface morphology both before and after use and explained it’s prospective as a good and environmentally benign adsorbent in very low quantities. Hence, this adsorbent can be implemented as an efficient liner material for the removal of phenol and phenolic compounds from wastewater.

Preparation and Characterization of Single Layer Ultra Filtration Alumina Membrane Directly over Porous Clay-Alumina Tubular and Capillary Support for Textile Effluent Treatment

Clay-alumina porous tubular supports of 8/6 mm for outside diameter/inside diameter (OD/ID) were prepared by extrusion and sintering at 1450°C for 110 min to obtain an average pore size of 1 µm and porosity of 40%. Slip casting slurry was prepared by peptization of boehmite (AlO(OH)) powder with 1.5 N nitric acid and mixing it with γ-Al2O3 powder of 40 nm particle size along with PVA and PEG in determined weight percentage. Clay alumina porous support tubes of 3.1/1.9 and 8/6 mm (OD/ID) were coated with the slip casting slurry and sintered at 550°C for 60 min to obtain γ-alumina membrane directly over the supports in a single step. The membrane layer prepared over both the support tubes were without any intermediate layer. The membranes presented a pore diameter distribution centered at 7.0 nm on 3.1/1.9 mm (OD/ID) and 5.5 nm on 8/6 mm (OD/ID) supports, which was in ultrafiltration (UF) range. The prepared UF membranes were studied for treatment of bio-treated synthetic and real textile effluent in the side stream mode. About 98% decolorization of synthetic dye solution and 95.6% colour removal of real textile effluent were obtained by the combined effect of UF membrane and bioreactor.

Urban wood waste as precursor of activated carbon and its subsequent application for adsorption of polyaromatic hydrocarbons

A novel activated carbon with well-developed porous structure was fabricated from waste wood filings using H3PO4 as an activating agent. The activated carbon so prepared was further investigated for adsorption of polyaromatic hydrocarbons like acenapthene and naphthalene from their aqueous solution. Adsorption studies were optimized with response surface methodology. Data obtained in batch adsorption studies were also subjected to analysis of adsorption kinetics, isotherms and thermodynamics. Activated carbon reported in this study was found to be capable of removing 98% (approximately) of both PAHs considered in this study. The adsorption process was found to be guided by Temkin isotherm and pseudo-second-order kinetics. Results also indicated that the process of adsorption was spontaneous, endothermic and chemisorption in nature. Overall results indicated that the activated carbon prepared from waste wood filings could efficiently remove polyaromatic hydrocarbons from their respective aqueous solutions in highly reduced contact time and dosage.

Treatment of textile effluent using bacteria-immobilized graphene oxide nanocomposites: evaluation of effluent detoxification using Bellamya bengalensis

Recent studies have reported graphene-based nanomaterials as novel scaffolds for the development of vigorous biocatalytic systems. The present study investigated polyacrylic acid-linked graphene oxide (GO)–gelatin nanocomposite for the immobilization of moderately halotolerant engineered bacterial consortium consisting of Dietzia sp., Bacillus sp. and Pseudomonas mendocina. This biocatalyst was subsequently applied for treatment of hypersaline textile effluents collected from local textile manufacturing and processing units. Effluent treatment efficiency of this biocatalyst was assessed in terms of its dye, surfactant and salt-removal abilities from collected effluents. High metabolic activity recorded in the case of immobilized bacterial cells indicated that immobilization had stimulated improved growth as well as electrolyte and pH tolerance in bacterial cells. Examination of the treated effluents suggested approximately 99% removal of COD, color (dyes), electrolytes and surfactant. Probable cyto-genotoxic potential and oxidative stress inducing the ability of both untreated and treated effluents was determined with Bellamya bengalensis (fresh water snail). Comet formation in hepatopancreatic cells of snails exposed to untreated effluent was significantly higher than in individuals exposed to treated effluents which in turn were similar to organisms treated as control. Hence, results of this study indicated efficient performance of GO-based biocatalyst in augmenting biodegradation and detoxification of textile effluent. The low cost incurred during the synthesis and application of bacteria-immobilized GO nanocomposite and its reusability potential determined herein established the process of effluent treatment reported in this study as a promising approach for commercial wastewater treatment.