Jaya Sikder

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.

Response surface-optimized removal of Reactive Red 120 dye from its aqueous solutions using polyethyleneimine enhanced ultrafiltration

Retention of toxic dyes with molecular weights lower than the molecular weight cut-off (MWCO) of the ultrafiltration membranes can be improved through selective binding of the target dyes to a water-soluble polymer, followed by ultrafiltration of the macromolecular complexes formed. This method, often referred to as polymer enhanced ultrafiltration (PEUF), was investigated in the present study, using polyethyleneimine (PEI) as the chelating agent. Model azo dye Reactive Red 120 was selected as the poorly biodegradable, target contaminant, because of its frequent recalcitrant presence in colored effluents, and its eventual ecotoxicological impacts on the environment. The effects of the governing process factors, namely, cross flow rate, transmembrane pressure polymer to dye ratio and pH, on target dye rejection efficiency were meticulously examined. Additionally, each parameter level was statistically optimized using central composite design (CCD) from the response surface methodology (RSM) toolkit, with an objective to maximize performance efficiency. The results revealed high dye retention efficiency over 99%, accompanied with reasonable permeate flux over 100L/m(2)h under optimal process conditions. The estimated results were elucidated graphically through response surface (RS) plots and validated experimentally. The analyses clearly established PEUF as a novel, reasonably efficient and economical route for recalcitrant dye treatment.

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

Abstract 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.

Nanofiltration based water reclamation from tannery effluent following coagulation pretreatment

Coagulation-nanofiltration based integrated treatment scheme was employed in the present study to maximize the removal of toxic Cr(VI) species from tannery effluents. The coagulation pretreatment step using aluminium sulphate hexadecahydrate (alum) was optimized by response surface methodology (RSM). A nanofiltration unit was integrated with this coagulation pre-treatment unit and the resulting flux decline and permeate quality were investigated. Herein, the coagulation was conducted under response surface-optimized operating conditions. The hybrid process demonstrated high chromium(VI) removal efficiency over 98%. Besides, fouling of two of the tested nanofiltration membranes (NF1 and NF3) was relatively mitigated after feed pretreatment. Nanofiltration permeation fluxes as high as 80-100L/m(2)h were thereby obtained. The resulting permeate stream quality post nanofiltration (NF3) was found to be suitable for effective reuse in tanneries, keeping the Cr(VI) concentration (0.13mg/L), Biochemical Oxygen Demand (BOD) (65mg/L), Chemical Oxygen Demand (COD) (142mg/L), Total Dissolved Solids (TDS) (108mg/L), Total Solids (TS) (86mg/L) and conductivity levels (14mho/cm) in perspective. The process water reclaiming ability of nanofiltration was thereby substantiated and the effectiveness of the proposed hybrid system was thus affirmed.

Modeling and optimization of polymer enhanced ultrafiltration using hybrid neural-genetic algorithm based evolutionary approach

Display Omitted Reactive red 120 dye was separated via Polymer enhanced ultrafiltration (PEUF).ANN model was developed to predict Membrane performance index (PFI).GA method used for PFI optimization was based on genetics and evolutionary biology.The hybrid ANN-GA strategy was upgraded by using hill-climbing (HC) algorithm.A PFI of 143.8L/m2h was achieved under optimal PEUF process factor settings. A stochastic genetic algorithm (GA) based strategy along with artificial neural network (ANN) was applied to optimize the retention of reactive red 120 (RR 120) dye from its aqueous solutions by way of polymer (polyethyleneimine (PEI)) enhanced ultrafiltration (PEUF). The optimal feed forward back propagation ANN (4-10-1) model network, trained initially through LevenbergMarquardt (LM) algorithm, was suitably manoeuvred by the GA approach to predict the membrane performance index (PFI) response, evaluated as the product of dye rejection and permeation flux, for a randomly generated population of chromosomes. Each chromosome was constituted by four principal genes, namely, cross-flow rate, transmembrane pressure, polymer to dye ratio, and pH. The local exploitation capacity of the canonical GA was enhanced further by combining hill-climbing (HC) local search with the optimization levels of standard GA. The near-optimal and economically feasible factor levels were predicted by the hybrid ANN-GA-HC strategy, keeping PFI maximization and the constrained PEUF process dynamics in perspective; the optimal process factor settings experimentally yielded a pragmatic PFI of 143.8L/m2h, corresponding to high (99.9%) dye rejection, and a satisfactory permeation flux (144L/m2h).

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.

Photocatalytic Membrane Reactor for Sustainable Environmental Remediation

The photo mineralization of organics by semiconductor photocatalysts is an area of intensive research, ideally the end products of these processes should be carbon dioxide, water, and inorganic mineral salts, which have a minimum environmental impact.

Improving Cellulose Structure for Bioconversion: Sugarcane Bagasse Pretreatment Accompanied by Lignin Recovery and Ionic Liquid Recycle

Bioethanol, derived from biomass has established itself as one of the leading biofuels in the global market (Sarkar et al. in Renew Energ 19:19–27, 2012). Lignocellulosic biomass has proved to be one of the most abundant and cost effective renewable resource which is non-polluting agricultural residue and potential to be converted into biofuel.