Sagnik Chakraborty

Batch and continuous (fixed-bed column) biosorption of crystal violet by Artocarpus heterophyllus (jackfruit) leaf powder.

In this study, batch and fixed-bed column experiments were performed to investigate the biosorption potential of Artocarpus heterophyllus (jackfruit) leaf powder (JLP) to remove crystal violet (CV) from aqueous solutions. Batch biosorption studies were carried out as a function of solution pH, contact time, initial dye concentration and temperature. The biosorption equilibrium data showed excellent fit to the Langmuir isotherm model with maximum monolayer biosorption capacity of 43.39 mg g(-1) at pH 7.0, initial dye concentration=50 mg L(-1), temperature=293 K and contact time=120 min. According to Dubinin-Radushkevich (D-R) isotherm model, biosorption of CV by JLP was chemisorption. The biosorption kinetics followed the pseudo-second-order kinetic model. Thermodynamic analysis revealed that biosorption of CV from aqueous solution by JLP was a spontaneous and exothermic process. In order to ascertain the practical applicability of the biosorbent, fixed-bed column studies were also performed. The breakthrough time increased with increasing bed height and decreased with increasing flow rate. The Thomas model as well as the BDST model showed good agreement with the experimental results at all the process parameters studied. It can be concluded that JLP is a promising biosorbent for removal of CV from aqueous solutions.

Biosorption of Basic Green 4 from aqueous solution by Ananas comosus (pineapple) leaf powder.

Biosorption characteristics of Ananas comosus (pineapple) leaf powder was investigated for decolorization of Basic Green 4 (BG 4), a cationic dye from its aqueous solutions employing a batch experimental set-up. Parameters that influence the sorption process such as pH, biosorbent dosage, contact time, initial dye concentration and temperature were systematically studied. The optimum conditions for removal of BG 4 were found to be pH 9.0, contact time=150 min, biosorbent dosage=5.0 g L(-1), initial dye concentration=50 mg L(-1). The temperature had a strong influence on the biosorption process. Further, the biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett, Teller (BET) surface area and pore size analysis. Experimental biosorption data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The biosorption process followed the Langmuir isotherm model with high coefficients of correlation (R(2)>0.99) at different temperatures. The pseudo second order kinetic model fitted well in correlation to the experimental results. Activation energy of the biosorption process (E(a)) was found to be 45.79 kJ mol(-1) by using the Arrhenius equation, indicating chemisorption nature of BG 4 sorption onto pineapple leaf powder. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic in nature. Overall, the present findings suggest that this environmentally friendly, efficient and low-cost biosorbent may be useful for the removal of BG 4 from aqueous media.

Artificial neural network (ANN) modeling of dynamic adsorption of crystal violet from aqueous solution using citric-acid-modified rice (Oryza sativa) straw as adsorbent

Rice straw, an abundant, lignocellulosic agricultural residue worldwide, was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The morphological and chemical characteristics of rice straw and acid-modified rice straw were investigated by scanning electron microscopy, surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared spectroscopy. The modification process leads to the increase in the specific surface area and pore size of rice straw. In order to investigate the application potential of the prepared adsorbent to remove a cationic dye (Crystal violet) from its aqueous solution, a continuous adsorption study was carried out in a laboratory scale fixed-bed column packed with acid-modified rice straw. Effect of different flow rates and bed heights on the column breakthrough performance was investigated. Results show that with increasing bed height and decreasing flow rate, the breakthrough time was delayed. In order to determine the most suitable model for describing the adsorption kinetics of Crystal violet in the fixed-bed column system, the Bed Depth Service Time model as well as the Thomas model was fitted to the experimental data. An artificial neural network (ANN) based model for determining the dye concentration in the column effluent was also developed. An extensive error analysis was carried out between experimental data and data predicted by the models using the following error functions: correlation coefficient (R2), average relative error (ARE), sum of the absolute error (SAE), and χ2 statistic test. Based on the values of the error functions, the ANN model was most appropriate for describing the dynamic dye adsorption process.

Arsenic Separation by a Membrane-Integrated Hybrid Treatment System: Modeling, Simulation, and Techno-Economic Evaluation

A modeling and simulation study along with economic analysis was carried out for arsenic separation by a membrane-integrated hybrid treatment system that consisted of an oxidation unit integrated with a cross flow nanofiltration membrane module. About 96–98% arsenic removal efficiency was achieved in the membrane module after pre-oxidation. When pH was increased from 3 to 10, arsenic rejections reached as high as 98.5%. The dynamic mathematical model developed for the system used Extended Nernst-Plank equation as the basis for the nanofiltration model. A linearized approach in modeling was adopted that reduced the computation time significantly. Model predictions were found to corroborate very well with the experimental findings as indicated in the small relative errors of the order of only 0.003 and Willmott d-index of 0.993 reflecting very good model performance. Thus the developed model is expected to be very useful in scale-up, design and optimization of the membrane-integrated hybrid treatment system for removal of arsenic from contaminated groundwater.

Batch Removal of Crystal Violet from Aqueous Solution by H2SO4 Modified Sugarcane Bagasse: Equilibrium, Kinetic, and Thermodynamic Profile

Batch adsorption studies were carried out using H2SO4 modified sugarcane bagasse (HMSB) for the removal of hazardous Crystal Violet (CV) dye from aqueous solutions. The effects of initial solution pH, adsorbent dose, and temperature on the adsorption process were investigated. The Langmuir isotherm model well described the equilibrium dye uptake while the pseudo-second-order kinetic model showed good agreement with the experimental kinetic data. Gibbs free energy change (ΔG0) was spontaneous for all interactions, and the adsorption process exhibited endothermic enthalpy values. Results suggest that HMSB is an effective adsorbent for the removal of CV from wastewater.

Adsorption of Crystal Violet From Aqueous Solution by Citric Acid Modified Rice Straw: Equilibrium, Kinetics, and Thermodynamics

Rice straw, an abundant, lignocellulosic agricultural residue was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The application potential of the prepared adsorbent to remove hazardous Crystal Violet dye from its aqueous solution was investigated. The morphological and chemical characteristics of the adsorbent were established by scanning electron microscopy (SEM), surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared (FTIR) spectroscopy. Batch adsorption studies were carried out as a function of solution pH, adsorbent dose, initial dye concentration, and temperature, in order to get insights into the effect of these independent parameters on the adsorption process. The Langmuir, Freundlich, and Dubinin–Radushkevich models were used to describe the equilibrium adsorption data. The sorption mechanism was also evaluated in terms of kinetics and thermodynamics. The adsorption equilibrium data was well described by the Langmuir isotherm model. The adsorption process followed the pseudo-second-order rate kinetics. Thermodynamic study showed spontaneous and exothermic nature of the adsorption process.

Biosorption of hazardous textile dyes from aqueous solutions by hen feathers: Batch and column studies

The biosorption potential of hen feathers (HFs) to remove hazardous textile dyes, namely congo red (CR) and crystal violet (CV), from their aqueous solutions was investigated in batch and dynamic flow modes of operation. The effect of biosorption process parameters such as solution pH, initial dye concentration, temperature, feed flow rate and bed height was studied. Biosorption equilibrium data were well described by the Langmuir isotherm model. Kinetic studies at different temperatures showed that the rate of biosorption followed the pseudo second-order kinetics well. A thermodynamic study showed that biosorption of both CR and CV was spontaneous and endothermic. Breakthrough time increased with increase in bed height but decreased with increase in flow rate. The Thomas model showed good agreement with the dynamic flow experimental data. Overall, the results suggest the applicability of HFs as an efficient biosorbent for removal of carcinogenic textile dyes from aqueous media.