Susmita Dutta

Removal of mercury from its aqueous solution using charcoal-immobilized papain (CIP).

In the present work mercury has been eradicated from its aqueous solution using papain, immobilized on activated charcoal by physical adsorption method. Operating parameters for adsorption of papain on activated charcoal like pH, amount of activated charcoal, initial concentration of papain in solution have been varied in a suitable manner for standardization of operating conditions for obtaining the best immobilized papain sample based on their specific enzymatic activity. The immobilized papain sample obtained at initial papain concentration 40.0 g/L, activated charcoal amount 0.5 g and pH 7 shows the best specific enzymatic activity. This sample has been designated as charcoal-immobilized papain (CIP) and used for further studies of mercury removal. Adsorption equilibrium data fit most satisfactorily with the Langmuir isotherm model for adsorption of papain on activated charcoal. Physicochemical characterization of CIP has been done. The removal of mercury from its simulated solution of mercuric chloride using CIP has been studied in a lab-scale batch contactor. The operating parameters viz., the initial concentration of mercury in solution, amount of CIP and pH have been varied in a prescribed manner. Maximum removal achieved in the batch study was about 99.4% at pH 7, when initial metal concentration and weight of CIP were 20.0mg/L and 0.03 g respectively. Finally, the study of desorption of mercury has been performed at different pH values for assessment of recovery process of mercury. The results thus obtained have been found to be satisfactory.

Removal of mercury (II) from aqueous solution using papain immobilized on alginate bead: Optimization of immobilization condition and modeling of removal study

Papain having the characteristics of metal binding ability is immobilized on alginate bead. Design Expert Software (Version 7.1.6) uses Response Surface Methodology (RSM) for statistical designing of operating condition for immobilization of papain on alginate bead considering concentration of papain, concentration of sodium alginate, concentration of calcium chloride and pH as numeric factors and Specific Enzymatic Activity (SEA) of immobilized papain sample as response. Immobilization using 25.96 g/L papain, 20 g/L sodium alginate and 20 g/L calcium chloride at pH 7 gives the desired product as indicated by ANOVA (Analysis of Variance). Three parameters viz., initial concentration of mercury (II), amount of AIP and pH are varied in a systematic manner. Maximum 98.88% removal of mercury (II) has been achieved within 8 min when simulated aqueous solution of mercury (II) with initial concentration of 10mg/L has been contacted with 5 g of AIP at pH 9 and at 35 degrees C in a batch contactor. A mathematical model has been developed and the value of equilibrium constant for binding of mercury (II) with AIP has been found to be 126797.3.

Studies on encapsulation of Rifampicin and its release from chitosan-dextran sulfate capsules

Biodegradable capsules of size around 350 nm were prepared by layer-by-layer (L-b-L) assembly of oppositely charged chitosan and dextran sulfate on silica particles and the subsequent removal of template. The resulting capsules were loaded with rifampicin, an anti-tuberculosis drug under modest conditions, as demonstrated by scanning electron microscopy (SEM). Maximum encapsulation of rifampicin was found to be about 82 μg at 25 °C and pH of 3. Release studies were done in-vitro mode by semiautomatic release protocol, with different pH solutions in water and phosphate buffered saline (PBS). The microcapsules exhibited a slow and sustained release over 72 hours and maximum release was obtained at a pH of 1.2 in water and a pH of 7.4 in PBS. The size of silica particle was analyzed by dynamic light scattering method. Scanning electron microscopy (SEM) measurements showed the surface morphology of the hollow capsules. UV spectroscopy was employed to monitor the drug release processes in both solutions. The kinetics of drug release mechanism was studied using Ritger-Peppas and Higuchi models.

Adsorptive removal of phenol from coke-oven wastewater using Gondwana shale, India: experiment, modeling and optimization

AbstractThe aim of this study is to explore the effectiveness of Gondwana shale for the removal of phenol from coke-oven wastewater. The phenol concentration in coke-oven plant effluent varies from 2 mg/L to 10 mg/L depending on the extent of final treatment in the effluent treatment plant. Kinetics of the removal of phenol from industrial effluent having different initial phenol concentration using Gondwana shale has been studied in a batch contactor by varying different parameters. Morris Webber model has been found to fit the kinetic data. Langmuir isotherm model has been found to fit the equilibrium data with value of 0.986 and adsorption capacity of 0.0334 mg g−1. Response surface methodology has been employed to optimize the removal condition of phenol using shale. The spent shale obtained by removing phenol at optimum condition is used for recovery study. Finally, to see whether the shale is efficient with much higher concentration of phenol, it is contacted with untreated industrial wastewater com...

Evaluation of fluoride bioremediation and production of biomolecules by living cyanobacteria under fluoride stress condition

Application of microalgae for defluoridation has gained interest in recent years. In the present study, bioremediation of fluoride using living cyanobacteria, Starria zimbabweensis, collected from wastewater of coke-oven effluent treatment plant, Durgapur, India, has been investigated. Initially, the cyanobacterial strain was grown in BG11 medium at 25°C, 45μmol/m2/s irradiation in 18h: 6h light:dark cycle in an algal incubator. Samples were withdrawn after 2 days interval and analyzed for its dry biomass and lipid content. Optimum inoculum size of 10% and age of 16th day were assessed based on maximum dry biomass (9.307 ± 0.01g/L) and lipid (244.05 ± 0.02mg/L) production. SEM-EDX and FTIR studies of both native and fluoride treated biomass were done to emphasize the changes. During kinetic study of defluoridation, initial fluoride concentration was varied in the range of 10-50mg/L. Maximum fluoride removal (66.6 ± 0.11%) and dry biomass (18.19 ± 0.12g/L) were obtained at 10mg/L fluoride concentration using 10% of 16th days inoculum. Biomass and lipid content were found to increase 2 and 4 folds, respectively under fluoride stress condition. Furthermore, chlorophyll, carbohydrate and protein content of the biomass were also compared between control and fluoride contaminated conditions. Fatty Acid Methyl Ester (FAME) analysis was done using Gas Chromatography (GC) to compare the lipid profile of native and fluoride loaded strain.

Studies on removal of lead(II) by Alginate Immobilized Bromelain (AIB)

AbstractThe work is based on augmentation of active sites of calcium alginate bead by immobilizing bromelain to remove lead(II) from simulated solution. The optimum immobilization condition as specified by response surface methodology is as follows: initial concentration of sodium alginate, bromelain, and calcium chloride are 20, 21.09, and 20 g/L, respectively, at pH 7 and 35°C and the sample, thus prepared, is termed as alginate immobilized bromelain (AIB). Maximum 99.5% lead(II) has been removed when 30 mL lead(II) solution having initial concentration of 0.0048 mmol L−1 has been treated with 5 g of AIB at pH 7 and 35°C. 77.9% lead(II) has been recovered when 1 g of spent adsorbent is stirred in 100 mL of solution having pH 2 for 30 min. The removal of lead(II) using AIB and, thereby, simultaneous inhibition of enzyme have been modeled both statistically and empirically.

Optimization of process factors for the efficient generation of biogas from raw vegetable wastes under the direct influence of plastic materials using Taguchi methodology

Abstract In this investigation, the combined process efficiency with respect to biogas generation was evaluated by Taguchi robust design using raw vegetable wastes (RVW) and waste plastics (WP) as the key components. The signal-to-noise (S/N) ratio was used to estimate the main effects, interaction effects, and optimal levels of the process factors. Among the various experimental combinations, statistical analysis of the optimized result showed that enhanced biogas production could be achieved with the plastic content (15%), height to diameter (h/D) ratio (30), water content (125 ml), and digestion period (18 week). The Taguchi methodology predicted a maximum biogas (24.83 m3/ton of RVW) could be generated with those selected process parameters under optimized condition. The experimental data showed that enhanced biogas production (24.16 m3/ton of RVW) was found with the optimized conditions.

Bioremediation of methylene blue dye using Bacillus subtilis MTCC 441

Methylene blue (MB) commonly found in the textile industry effluent has been chosen as a model dye to investigate bioremediation using Bacillus subtilis MTCC 441. Both free cells and calcium alginate immobilized cells have been used to remove MB from the effluent. The operating variables of initial concentration of dye (20-60 mg/L), inoculum size (4-8%) and temperature (25-35 °C) have been varied judiciously during the kinetic study in a batch contactor. A maximum removal of 91.68% is obtained when 20 mg/L MB solution was inoculated with 8% inoculum and cultured for 6 h at 30 °C. Continuous removal of MB has been studied in a fixed bed contactor using immobilized cells as packing materials. Influent concentration (10-30 mg/L) was varied and breakthrough parameters have been determined. With increase in influent concentration from 10 mg/L to 30 mg/L, percentage removal of dye decreases from 72.44% to 49.62%.

Sequestration of carbon dioxide and production of biomolecules using cyanobacteria

A cyanobacterial strain, Synechococcus sp. NIT18, has been applied to sequester CO2 using sodium carbonate as inorganic carbon source due to its efficiency of CO2 bioconversion and high biomass production. The biomass obtained is used for the extraction of biomolecules - protein, carbohydrate and lipid. The main objective of the study is to maximize the biomass and biomolecules production with CO2 sequestration using cyanobacterial strain cultivated under different concentrations of CO2 (5-20%), pH (7-11) and inoculum size (5-12.5%) within a statistical framework. Maximum sequestration of CO2 and maximum productivities of protein, carbohydrate and lipid are 71.02%, 4.9 mg/L/day, 6.7 mg/L/day and 1.6 mg/L/day respectively, at initial CO2 concentration: 10%, pH: 9 and inoculum size: 12.5%. Since flue gas contains 10-15% CO2 and the present strain is able to sequester CO2 in this range, the strain could be considered as a useful tool for CO2 mitigation for greener world.

Phycoremediation of cyanide from coke–oven wastewater using cyanobacterial consortium

Abstract Owing to the presence of several toxic pollutants such as cyanide, phenol, ammonium, coke–oven wastewater is being considered as hazardous stream and needs to be treated properly. In the present study, cyanobacterial consortium of Dinophysis acuminata and Dinophysis caudata, collected from East Kolkata Wetland, was used for the treatment of both synthetic cyanide solution and real coke–oven wastewater. The growth kinetics was studied considering nitrate as substrate. Since consortium showed growth in cyanide solution, a model was proposed considering both nitrate and cyanide as substrates. The simulated data match quite well with experimental ones. Two coke–oven wastewater samples were collected—untreated one from equalization tank and another from secondary clarifier effluent and treated with consortium separately. Lipid was extracted from biomass of native cyanobacterial consortium, biomass treated with raw coke–oven wastewater and biomass treated with secondary clarifier effluents. Fatty acid methyl ester of such lipid samples was analyzed using gas chromatograph.