Cetylpyridinium bromide assisted micellar-enhanced ultrafiltration for treating enrofloxacin-laden water.

The presence of a fluoroquinolone base veterinary antibacterial drug enrofloxacin in aqueous media poses a major threat due to its ecotoxicity on aquatic microbiota. Hence, for the first time, an attempt was made to remove enrofloxacin (ENX) from its aqueous solution by employing micellar-enhanced ultrafiltration (MEUF) where cetylpyridinium bromide (CPB), a cationic surfactant was used for micellization. Response surface methodology (RSM) with central composite design (CCD) approach was applied to design the experiment, and to optimize the process parameters, namely, ENX concentration (3-15 mg/L), transmembrane pressure (2-6 kgf/cm2), recirculation flow rate (5.5-7.5 L/min) and CPB concentration (1.4-4.2 mM). The objective of this study was to maximize the permeate flux and rejection coefficient and to find out the optimal process condition for the removal of enrofloxacin from aqueous solution. Though maximum 68.23 L/m2 h of permeate flux and 94.20% of rejection coefficient were achieved at different process conditions, the optimization study reveals that the predicted optimal values of permeate flux and rejection coefficient are 67.53 L/m2 h and 89.67% respectively. Modelling was also carried out with the aid of artificial neural network (ANN) to validate the prediction of RSM. The predictability of the model by RSM and ANN was compared statistically by evaluating root-mean-square error (RMSE), absolute average deviation (AAD) and mean absolute error (MAE), where ANN exhibited better predictability. The following set of parameters was proposed for industrial scale up: ENX concentration of 8.4 mg/L, TMP of 5 kgf/cm2, recirculation flow rate of 6 L/min and CPB concentration of 2.1 mM.

Comprehensive analysis on sorptive uptake of enrofloxacin by activated carbon derived from industrial paper sludge.

The current investigation deals with how chemically activated carbon derived from industrial paper sludge (ACPS) performs on sorptive removal of enrofloxacin (ENF), an antibacterial drug from its water solution. Thermogravimetric (TGA) and proximate analysis of raw paper sludge (RPS) were conducted. ACPS was characterized with proximate analysis, XRD, FT-IR, SEM and BET. The influence of five operational parameters viz. adsorbate concentration (initial), dose of adsorbent, pH, temperature, and contact time on the adsorption of ENF onto ACPS has been conducted using batch experiments. The process of adsorption was optimized through ANN (artificial neural network) in addition to RSM (response surface methodology). The maximum percentage removal (95.85%) was achieved at initial ENF concentration 12 mg/g, adsorbent dose 1.2 g/L, contact duration of 18 h and temperature 20 °C. Kinetic data were best fitted into pseudo-second order kinetic model and adsorption equilibrium study indicates that the adsorption process follows Langmuir isotherm model. Adsorption capacity was noted to have a highest value of 44.44 mg/g. A study on thermodynamics of the adsorption process suggests that it exhibits spontaneity, being essentially exothermic. Cost analysis and reusability study confirm that adsorbent produced from industrial paper sludge is cost-effective and reusable. Therefore, ACPS as adsorbent has potency for removing ENF from aqueous solution.

Extraction of lignin, structural characterization and bioconversion of sugarcane bagasse after ionic liquid assisted pretreatment.

The primary focus of this work was to recover lignin and investigate the structural changes in sugarcane bagasse after pretreatment with ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]oAc). 90% lignin recovery was achieved while bagasse was treated with [EMIM]oAc at 140 °C, 120 min reaction time and 1:20 bagasse to the ionic liquid ratio (w/w). The impact of ionic liquid pretreatment on bagasse was confirmed by qualitative analysis of untreated and pretreated bagasse. Scanning electron microscopy analysis exhibited the porous and irregular structure of bagasse after pretreatment. X-ray powder diffraction analysis verified a decrease in crystallinity as a result of the pretreatment process by showing a 14.7% reduction of Crystallinity index after ionic liquid treatment. The efficacy of [EMIM]oAc on bagasse treatment was also examined by enzymatic hydrolysis which manifested an increase in reducing sugar yield as a result of pretreatment. Maximum yield of 54.3% reducing sugar was obtained after 72 h enzymatic hydrolysis of pretreated bagasse. Recovered lignin was analyzed qualitatively. 1D NMR spectroscopy of lignin revealed the presence of essential functional groups whereas 2D NMR spectroscopy showed the dominance of etherified syringyl unit. Further ionic liquid recovery and reuse were substantiated by Gel permeation chromatography analysis of lignin. Weight average molecular weight (Mw) of lignin extracted by fresh [EMIM]oAc was obtained as 1769 g/mol (in the previous study) while lignin recovered by recycled [EMIM]oAc showed almost equal Mw 1765 g/mol in this study. Thus, the current investigation corroborated satisfactory performance of [EMIM]oAc in lignocellulose processing which further enhanced enzymatic hydrolysis in the subsequent step.

Immobilized biocatalytic process development and potential application in membrane separation: a review.

Biocatalytic membrane reactors have been widely used in different industries including food, fine chemicals, biological, biomedical, pharmaceuticals, environmental treatment and so on. This article gives an overview of the different immobilized enzymatic processes and their advantages over the conventional chemical catalysts. The application of a membrane bioreactor (MBR) reduces the energy consumption, and system size, in line with process intensification. The performances of MBR are considerably influenced by substrate concentration, immobilized matrix material, types of immobilization and the type of reactor. Advantages of a membrane associated bioreactor over a free-enzyme biochemical reaction, and a packed bed reactor are, large surface area of immobilization matrix, reuse of enzymes, better product recovery along with heterogeneous reactions, and continuous operation of the reactor. The present research work highlights immobilization techniques, reactor setup, enzyme stability under immobilized conditions, the hydrodynamics of MBR, and its application, particularly, in the field of sugar, starch, drinks, milk, pharmaceutical industries and energy generation.

Reactive red 120 retention through ultrafiltration enhanced by synthetic and natural polyelectrolytes.

Two cationic chelating polymers, namely synthetic polyethylenimine (PEI), and biopolymer chitosan were employed in the present study to bring about the retention of anionic reactive red 120 (RR 120) from its aqueous solutions by way of polymer enhanced ultrafiltration (PEUF). The effects of process parameters, namely, cross-flow rate, transmembrane pressure, time, polyelectrolyte loading, and ionic strength on dye retention and permeation flux were examined. PEI enhanced ultrafiltration achieved dye retentions as high as 99.9%, and significant permeation fluxes around 148 L/m(2)h. However, in case of chitosan, relatively low retention (88%), and flux (120 L/m(2)h) levels were observed. A careful comparison of the changes induced in the UV-vis spectra of RR 120 by PEI and chitosan indicated a predominant electrostatic interaction between PEI and RR 120, as opposed to the relatively weak and sterically as well as chemically hindered interaction between chitosan and the dye ion. The respective binding constants of PEI-RR 120, and PEI-chitosan complexes, in addition to the relatively more pronounced permeation flux decline witnessed in the presence of chitosan, clearly advocated the use of PEI, rather than chitosan, as the most appropriate complexing agent in the present context.

Remediation of textile effluents by membrane based treatment techniques: a state of the art review.

The textile industries hold an important position in the global industrial arena because of their undeniable contributions to basic human needs satisfaction and to the world economy. These industries are however major consumers of water, dyes and other toxic chemicals. The effluents generated from each processing step comprise substantial quantities of unutilized resources. The effluents if discharged without prior treatment become potential sources of pollution due to their several deleterious effects on the environment. The treatment of heterogeneous textile effluents therefore demands the application of environmentally benign technology with appreciable quality water reclamation potential. These features can be observed in various innovative membrane based techniques. The present review paper thus elucidates the contributions of membrane technology towards textile effluent treatment and unexhausted raw materials recovery. The reuse possibilities of water recovered through membrane based techniques, such as ultrafiltration and nanofiltration in primary dye houses or auxiliary rinse vats have also been explored. Advantages and bottlenecks, such as membrane fouling associated with each of these techniques have also been highlighted. Additionally, several pragmatic models simulating transport mechanism across membranes have been documented. Finally, various accounts dealing with techno-economic evaluation of these membrane based textile wastewater treatment processes have been provided.