Jayanta Kumar Basu

Nanofiltration of textile plant effluent for color removal and reduction in COD

Abstract A membrane based separation process (nanofiltration, NF) is used to treat the effluent from a textile plant. The dye mixture contains reactive black dye (Cibacron Black B) and reactive red dye (Cibacron Red RB). An organic membrane with molecular weight cut-off of 400 is used for the experiments. The experiments are conducted in an unstirred batch and a rectangular cross flow cell. Separations with retentions up to 94 and 92% of the two dyes are achieved respectively in the cross flow cell where steady state is attained quickly. It is important to note that NF techniques achieve a sharp reduction in chemical oxygen demand (COD), (up to 94% in cross flow cell), as the dyes are removed from the permeate. A parametric study of the separation process is undertaken to characterize the effects of the operating variables, e.g., trans-membrane pressure, dye concentration in the feed and cross flow velocity in case of cross flow NF.

Studies on adsorption of p-nitrophenol on charred saw-dust

An effective adsorbent developed from common sawdust has been used for the removal of p-nitrophenol from aqueous solution. It is observed that the degree of agitation has a significant effect on the rate of removal of p-nitrophenol. Higher initial concentration and lower temperature are more favorable for the adsorption of p-nitrophenol. The experimental results confirmed that the intraparticle diffusion has a hindering effect on the adsorption rate. An external mass-transfer model has been applied to interpret the rate data. The values of fluid-particle mass-transfer coefficient obtained from the experimental data have been compared with the predicted value. The mass-transfer coefficient is found to decrease with increasing concentration of p-nitrophenol. Adsorption equilibrium data fit most satisfactorily with the Langmuir adsorption isotherm.

Lipase applications in oil hydrolysis with a case study on castor oil: a review.

Lipase (triacylglycerol acylhydrolase) is a unique enzyme which can catalyze various types of reactions such as hydrolysis, esterification, alcoholysis etc. In particular, hydrolysis of vegetable oil with lipase as a catalyst is widely studied. Free lipase, lipase immobilized on suitable support, lipase encapsulated in a reverse micelle and lipase immobilized on a suitable membrane to be used in membrane reactor are the most common ways of employing lipase in oil hydrolysis. Castor oil is a unique vegetable oil as it contains high amounts (90%) of a hydroxy monounsaturated fatty acid named ricinoleic acid. This industrially important acid can be obtained by hydrolysis of castor oil. Different conventional hydrolysis processes have certain disadvantages which can be avoided by a lipase-catalyzed process. The degree of hydrolysis varies widely for different lipases depending on the operating range of process variables such as temperature, pH and enzyme loading. Immobilization of lipase on a suitable support can enhance hydrolysis by suppressing thermal inactivation and estolide formation. The presence of metal ions also affects lipase-catalyzed hydrolysis of castor oil. Even a particular ion has different effects on the activity of different lipases. Hydrophobic organic solvents perform better than hydrophilic solvents during the reaction. Sonication considerably increases hydrolysis in case of lipolase. The effects of additives on the same lipase vary with their types. Nonionic surfactants enhance hydrolysis whereas cationic and anionic surfactants decrease it. A single variable optimization method is used to obtain optimum conditions. In order to eliminate its disadvantages, a statistical optimization method is used in recent studies. Statistical optimization shows that interactions between any two of the following pH, enzyme concentration and buffer concentration become significant in presence of a nonionic surfactant named Span 80.

A generalized shrinking core model applied to batch adsorption

Abstract A two resistance mass transfer model for batch adsorption process has been developed which includes a film mass transfer coefficient and an internal effective diffusivity that controls the internal mass transport process based on the pore diffusion mechanism. This model is based on shrinking core formulation for catalytic reaction. The model proposed here is more generalized, can accommodate wide range of initial adsorbate concentration in feed and the nature of the isotherm. The model is solved numerically and optimized using nonlinear parameter estimation technique in order to match with the experimental kinetic data available in the literature [AIChE J. 39 (1993) 2027; AIChE J. 30 (1984) 692; Adsorp. Sci. Technol. 4 (1987) 58]. In this procedure the process parameters, i.e. the external mass transfer coefficient and internal effective diffusivity are determined for a particular system. Using the estimated parameters, a parametric study has been carried out to observe the effects of initial adsorbate concentration, particle size of adsorbent, mass of adsorbent, etc. on the system kinetics.

Maximization of bioconversion of castor oil into ricinoleic acid by response surface methodology

In this study, response surface methodology was applied to optimize process variables like temperature, pH, enzyme concentration (mg/g oil), and buffer concentration (g/g oil) for hydrolysis of castor oil using Candida rugosa lipase. A 2(4) full factorial central composite design was used to develop the quadratic model that was subsequently optimized and the optimal conditions were as follows: temperature 40 degrees C, pH 7.72, enzyme concentration 5.28 mg/g oil, buffer concentration 1g/g oil and there was 65.5% conversion in 6 h. These predicted optimal conditions agreed well with the experimental results. This is the first report on the application of response surface methodology in castor oil hydrolysis using C. rugosa lipase with higher percentage conversion in 6 h.

Prediction of permeate flux and concentration of two-component dye mixture in batch nanofiltration

Modeling of separation of two-component dye mixture has been carried out in an unstirred bath cell. Nanofiltration of a two-component industrial dye-house effluent containing reactive black dye (Cibacron Black B, molecular weight 924.5) and reactive red dye (Cibacron Red RB, molecular weight 855.5) has been considered using a 400 molecular weight cut-off (MWCO) membrane. An unsteady state mass transfer model is developed using an integral method to predict the permeate flux and the permeate concentration of each component. The experimental profiles of permeate concentration and permeate flux are optimized with the calculated profiles to estimate the model parameters. The predicted results using these optimized parameters are in good agreement with the experimental results.

Prediction of permeate flux and permeate concentration in nanofiltration of dye solution

Abstract Unstirred batch and cross flow nanofiltration have been carried out to separate dye from aqueous solution. The effect of different process parameters on separation of dye is studied. Experiments are conducted with aqueous solution of crystal violet (CV, molecular weight 408) using a 400 molecular weight cut-off membrane. An unsteady state mass transfer model is developed to predict the permeate flux and the permeate concentration in a batch cell. Using the experimental results, the model parameters i.e. the diffusivity of the solute (D) and real retention (Rr) of the membrane are evaluated by optimizing the experimental flux and permeate concentration profiles. Using the estimated D and Rr from the batch cell results, the permeate flux and concentrations are predicted for a cross-flow nanofiltration system using film theory.

Surfactant enhanced ricinoleic acid production using Candida rugosa lipase

In this study, ricinoleic acid was produced on surfactant enhanced castor oil hydrolysis using Candida rugosa lipase. The most effective surfactant was Span 80. Employing fractional factorial design, the most suitable temperature and surfactant concentration were found to be 31 degrees C and 0.257% (w/w in buffer) respectively whereas pH, enzyme concentration, buffer concentration and agitation were identified as the most significant independent variables. A 2(4) full factorial central composite design was applied and the optimal conditions were found to be pH 7.0, enzyme concentration 7.42 mg/g oil, buffer concentration 0.20 g/g oil and agitation 1400 rpm with the maximum response of 76% in 4 h. The most important variable was pH, whereas enzyme and buffer concentrations also showed pronounced effect on response. This is the first report on the application of response surface methodology for optimizing surfactant enhanced ricinoleic acid production using C. rugosa lipase.

Modeling of arsenic adsorption kinetics of synthetic and contaminated groundwater on natural laterite.

A simple shrinking core model is applied to predict the adsorption kinetics of arsenite and arsenate species onto natural laterite (NL) in a stirred tank adsorber. The proposed model is a two-resistance model, in which two unknown parameters, external mass transfer coefficient (K(f)) and pore diffusion coefficient (D(e)) are estimated by comparing the simulation concentration profile with the experimental data using a nonlinear optimization technique. The model is applied under various operating conditions, e.g., initial arsenic concentration, NL dose, NL particle size, temperature, stirring speed, etc. Estimated values of D(e) and K(f) are found to be in the range of 2.2-2.6 x 10(-11)m(2)/s and 1.0-1.4 x 10(-6)m/s at 305K for different operating conditions, respectively. D(e) and K(f) values are found to be increasing with temperature and stirrer speed, respectively. Calculated values of Biot numbers indicate that both external mass transfer and pore diffusion are important during the adsorption. The model is also applied satisfactorily to predict the arsenic adsorption kinetics of arsenic contaminated groundwater-NL system and can be used to scale up.

Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions

Arsenic pollution in groundwater is a worldwide concern due to its chronic effects on human health. Numerous studies have been carried out to obtain cost-effective arsenic removal method. Adsorption using natural materials or its treated forms is found to be cost-effective technology. Raw laterite (RL) or its treated form (TL) is studied recently as arsenic adsorbent for aqueous system. Laterite composition varies with geographical location and extent of lateritization. The study on effects of arsenic adsorption with varying composition of laterite is not explored yet. Four laterite samples with different compositions are examined to remove arsenic from water. These laterite samples are activated using an optimized acid followed by base treatment method in order to determine the effects of RL composition on arsenic adsorption behavior of TL. Higher iron and aluminum containing RL samples show higher arsenic adsorption behavior. Similarly, TL obtained from higher iron and aluminum containing RL sample shows the higher specific surface area (130-180 m(2) g(-1)) and pore volume (0.28-0.35 mL g(-1)). Two household filters using TL are deployed in arsenic affected area of Barasat, 24 Parganas (N), West Bengal, India and their performance is monitored for about a year.