Manickam Velan

Application of Two-and Three-Parameter Isotherm Models: Biosorption of Acid Red 88 onto Azolla microphylla

ABSTRACT Biosorption potential of Azolla microphylla for acid red 88 from aqueous solution was investigated under laboratory conditions as a function of initial pH and temperature. The algal biomass exhibited the highest dye sorption capacity at optimum conditions of pH 3 and temperature 30°C. The experimental isotherms were analyzed using five two-parameter models (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Flory-Huggins) and five three-parameter models (Redlich-Peterson, Sips, Khan, Radke-Prausnitz, and Toth). Three error analysis methods were used to evaluate the experimental data: correlation coefficient, residual root mean square error (RMSE), and chi-square test to find the best fitting isotherm. In particular, Langmuir (two-parameter) and Khan (three-parameter) models described the dye biosorption isotherm data well at all pH and temperature conditions examined.

Copper removal from aqueous solution by marine green alga Ulva reticulata

The batch removal of copper (II) ions from aqueous solution under different experimental conditions using Ulva reticulata was investigated in this study. The copper (II) uptake was dependent on initial pH and initial copper concentration, with pH 5.5 being the optimum value. The equilibrium data were fitted using Langmuir and Freundlich isotherm model, with the maximum copper (II) uptake of 74.63 mg/g determined at a pH of 5.5. The Freundlich model regression resulted in high correlation coefficients and the model parameters were largely dependent on initial solution pH. At various initial copper (II) concentrations (250 to 1000 mg/L), sorption equilibrium was attained between 30 and 120 min. The copper (II) uptake by U. reticulata was best described by Pseudo-second order rate model and the rate constant, the initial sorption rate and the equilibrium sorption capacity were also reported. The elution efficiency for copper-desorption from U. reticulata was determined for 0.1 M HCl, H 2 SO 4 , HNO 3 and CaCl 2 at various Solid-to-Liquid ratios (S/L). The solution CaCl 2 (0.1 M) in HCl at pH 3 was chosen to be the most suitable copper-desorbing agent. The biomass was also employed in three sorption-desorption cycles with 0.1 M CaCl 2 (in HCl, pH 3) as the elutant.

Sonoassisted microbial reduction of chromium.

This study presents sonoassisted microbial reduction of hexavalent chromium (Cr(VI)) using Bacillus sp. isolated from tannery effluent contaminated site. The experiments were carried out with free cells in the presence and absence of ultrasound. The optimum pH and temperature for the reduction of Cr(VI) by Bacillus sp. were found to be 7.0 and 37 °C, respectively. The Cr(VI) reduction was significantly influenced by the electron donors and among the various electron donors studied, glucose offered maximum reduction. The ultrasound-irradiated reduction of Cr(VI) with Bacillus sp. showed efficient Cr(VI) reduction. The percent reduction was found to increase with an increase in biomass concentration and decrease with an increase in initial concentration. The changes in the functional groups of Bacillus sp., before and after chromium reduction were observed with FTIR spectra. Microbial growth was described with Monod and Andrews model and best fit was observed with Andrews model.

Electrochemical degradation of specialty chemical industry effluent

Conventional wastewater treatment techniques are inefficient to manage large quantities of refractory organics discharged by specialty chemical industries. It is aimed in the present investigation to compare overall performance of the basic electrochemical reactor configurations such as batch, batch recirculation and continuous recycle reactors, in removing the organic part of wastewater from a medium-scale, specialty chemical industry. The effects of current density, supporting electrolyte concentration, electrolysis duration and fluid flow rate on the pollutant removal and energy consumption performances were critically evaluated. Continuous recycle reactor is found to be the better configuration, because of its flexibility of operation. Circulation flow rate and withdrawal flow rate enable control on transfer coefficients and treatment duration respectively. The ability of artificial neural network (ANN) in predicting the performance of the batch electrochemical treatment has also been demonstrated.

Nickel Recovery from Aqueous Solution Using Crab Shell Particles

The potential use of crab shell as a sorbent for the removal of nickel(II) ions from aqueous solution was investigated. The binding of nickel ions by crab shell was found to be affected significantly by pH, with the maximum sorption capacity being observed at pH 4.5. The sorption isotherm was well represented using the Freundlich model. Nickel(II) ion removal by crab shell was mainly influenced by the removal of calcium carbonate, proteins and chitin, indicating the importance of these components in nickel ion binding. Co-ions such as Cu2+, Co2+, Cd2+, Zn2+ and Mg2+ affected the Ni(II) ion removal efficiency of crab shell. The biosorbed Ni(II) ions were effectively eluted by various mineral acids, EDTA solutions and NH4OH. Of these, the sodium salt of EDTA (0.01 M) in NH4OH appeared to be the best eluant, being capable of desorbing more than 99% of the sequestered Ni(II) ions with insignificant damage to the shell particles. The biosorbent could be regenerated and re-used in five sorption—elution cycles.

Improved biodegradation of Congored by using Bacillus sp.

The biodegradation of Congored, a toxic azo dye, was studied by using a hybrid technique involving sonolysis as pretreatment followed by biological treatment. The experiments were carried out with and without pretreatment using dye solution as a sole source of nutrition with an isolated and acclimatized strain of Bacillus sp. obtained from tannery industry effluent. The pretreatment time was varied as 30, 60, 90, 120, 150 and 180 min and then the pretreated dye solution was subjected to biological treatment. The effectiveness of pretreatment was compared with the results of biological degradation of non pretreated Congored and the results showed that the pretreatment improved the efficiency of the biodegradation of Congored. During the biological degradation, the increase in initial dye concentration decreased the decolorization rate and at high concentrations (1500 and 2000 mg/l), the inhibition was observed. The optimum pH and temperature were determined to be 7.0 and 37 degrees C, respectively. The data obtained through biodegradation experiments were fitted with five different kinetic models and the results were analyzed.

Biosorption of Cr(VI) using a novel microalga Rhizoclonium hookeri: equilibrium, kinetics and thermodynamic studies

AbstractHeavy metal pollution is a major environmental concern in many countries. Among heavy metals, chromium is one of the widely used despite being one of the most toxic metal ions. The present study deals with the evaluation of Cr(VI) biosorption using a novel fresh water alga Rhizoclonium hookeri. Batch experiments were conducted and the maximum adsorption capacity was evaluated as 67.3 mg/g at pH 2 at a biomass dosage of 1 g/L and 1,000 mg/L initial Cr(VI) concentration. Fourier transform infrared spectroscopy analysis of alga before and after biosorption revealed a shift in the carboxylic O–H stretching vibration from 3,401 to 3,373 cm−1, which confirmed its involvement in biosorption of Cr(VI) by R. hookeri. Surface morphology of alga was examined using the scanning electron microscopy, which indicated the highly porous nature of biomass. Non-linear regression analyses of isotherm models revealed that the three-parameter model isotherms (Redlich–Peterson and Sips) better described the experimental...

Electrochemical behaviour of nickel-based electrodes for oxygen evolution reaction in alkaline water electrolysis

NiZnS electrode has been investigated for use in oxygen evolution reaction in alkaline media. Nickel mesh electrode was coated with the ternary composition of NiZnS by four methods, viz., direct current electrodeposition, pulse electrodeposition, sonoassisted direct current electrodeposition and sonoassisted pulse electrodeposition. The oxygen evolution studies carried out using these electrodes resulted in higher current density for the electrode prepared by sonoassisted pulse electrodeposition compared to those prepared by other methods. Effect of plating current density, pulse duty cycle and temperature on the electrochemical parameters of the alloy coating has been studied. Surface morphologies of the various coating were studied using scanning electron microscopy. Long-term stability of the electrodes prepared was studied in alkaline medium. Exchange current density (jo) was found to increase with the increase in temperature and was the highest for sonoassisted pulse electrodeposited electrode.

Utilization of Coconut Oil Cake for the Production of Lipase Using Bacillus coagulans VKL1

The overproduction of enzymes was performed by manipulating the medium components. In our study, solvent-tolerant thermophilic lipase-producing Bacillus coagulans was isolated from soil samples and a stepwise optimization strategy was employed to increase the lipase production using coconut oil cake basal medium. In the first step, the influence of pH, temperature, carbon source, nitrogen source and inducers on lipase activity was investigated by the One-Factor-At-A-Time (OFAT) method. In the second step, the three significant factors resulted from OFAT were optimized by the statistical approach (CCD).The optimum values of olive oil (0.5%), Tween 80 (0.6%) and FeSO4 (0.05%) was found to be responsible for a 3.2-fold increase in the lipase production identified by Central Composite Design.

Sorption behavior of freshwater aquatic fern Azolla filiculoides on redwine dye

Abstract The biosorption of redwine dye from aqueous solution onto aquatic fern Azolla filiculoides has been studied. The factors affecting the sorption process, such as solution pH, contact time and initial concentration, adsorbent size, and dosage were determined in the batch mode. Equilibrium sorption isotherms and kinetics were investigated. Sorption isotherm data were fitted with Langmuir and Freundlich models and Langmuir monolayer coverage was determined as 86.21 mg/g. The kinetic data obtained at different initial concentrations were analyzed using pseudo-first-order and pseudo-second-order equations. Biosorption mechanism using Boyd’s plot confirmed the film diffusion was the rate-limiting step. The morphological characteristics and functional groups responsible for the binding of dyes were done using Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy analysis, respectively. The ability of A. filiculoides to remove redwine dye from aqueous solution was also examined in an up...