Department of Chemical Engineering

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Supported Liquid Membrane (SLM) is an emerging trace metal pre-concentration technique. It has the ability to decontaminate radionuclides even from lean secondary effluent. SLM can be considered as a part of process intensification, which implies a closed loop operation. It has reduced space requirement as well as minimised secondary effluent generation and the number of unit steps. Proper selection of molecular design criteria helps in deciding performances such as selectivity, compatibility, permeability, etc., that is attributed to both feed and desired strippant characteristics, and great effort has been applied for nuclear plant waste treatment generated in the uranium metal plant of Trombay, India. This paper articulates basic views of SLM, selection of carrier by experimental verification with respect to both feed and strippant for further processing, and structural aspects with evidences (from FT-IR studies). © 2011 Inderscience Enterprises Ltd.

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International Journal of Nuclear Desalination

Selection and design criteria of supported liquid membrane for the treatment of rad-waste

The heavy metals, such as uranium and vanadium, are some of the valuable metals in desalination effluents. Metal Chelate Embedded Polymers (MCEP) in leaflet form were prepared using the post-irradiation induced graft polymerisation technique, with different non-woven thermally bonded fibrous substrate materials. The novel sorbents, synthesised by using accelerator energy beams of 1.25 MeV and 2 MeV, were characterised for their radiation, chemical and mechanical characteristics. The novel sorbent was evaluated under different parametric conditions, in order to study the influence of grafting levels, initial concentration, dissolved solids and contact time. The standard isotherm and diffusion models were fitted to the experimental sorption data and model parameters were evaluated. The sorption characteristics of MCEP for recovery of heavy metals such as uranium and vanadium from desalination effluents were investigated. © 2011 Inderscience Enterprises Ltd.

Sorption kinetic studies using metal chelate embedded polymers for recovery of heavy metals from desalination effluents

In this study, we report the effect of different additives added with amine reactants on aliphaticaromatic and aromatic-aromatic types thin-film composite (TFC) polyamide reverse osmosis membranes performance that are prepared by in-situ interfacial polymerization. Aliphatic-aromatic polyamide membranes are prepared using polyethylene imine and 1, 3-benzene dicarbonyl chloride whereas aromatic-aromatic polyamide membranes are prepared using 1,4-phenylene diamine and 1,3,5-benzene tricarbonyl chloride. Additives used with amine reactants for TFC membrane preparation are (a) acid acceptors like sodium hydroxide, trisodium phosphate and triethyl amine, (b) aqueous soluble organic additives like isopropyl alcohol and dimethyl sulfoxide and (c) inorganic salts like feme chloride and copper sulfate. The performances of prepared composite membranes are evaluated with respect to separation characteristics of sodium chloride and magnesium sulfate solutes. It is found that presence of inorganic and organic acid acceptors in amine solution has different impacts on aliphatic-aromatic and aromatic-aromatic type polyamide composite membrane performances. Change in membrane performance is more for aromaticaromatic polyamide in presence of aqueous soluble organic additives but it is more for aliphaticaromatic polyamide in presence of inorganic salt additives in amine solution. © MD Publications Pvt. Ltd.

Journal of Polymer Materials

Effect of additives in amine solution on performance of aliphatic-aromatic and aromatic-aromatic polyamide composite reverse osmosis (RO) membranes

Thin film composite type positively charged nanofiltration membrane developed by in situ polymerisation of functionalised polyethyleneimine and acid chloride has been used in various aqueous stream separations. The membrane contained fixed quaternary ammonium moieties which contributed to its positive charge. The membrane was tested for its performance in single solute feed systems containing salts of various combinations of univalent and bivalent ions (NaCl, Na2SO4, CaCl2 and MgSO4) in test cells as well as spiral module where it gave differential separation profile for these solutes with high rejection for CaCl2 and low rejection for Na2SO4. The 2512 spiral module of the membrane was further used for separation of a simulated effluent solution containing uranyl nitrate, which is a common effluent generated in the nuclear industry. The membrane gave a high separation for uranyl nitrate and low separation for ammonium nitrate indicating that both the solutes can be fractionated by the membrane when they are present together in the nuclear effluent. © 2011 Inderscience Enterprises Ltd.

Thin film composite type positively charged nanofiltration membrane for separation of aqueous streams and nuclear effluents

A filament stretching rheometer is used to investigate the extensional flow-induced crystallization of two commercial grade isotactic poly-1-butene samples. The degree of crystallinity of the stretched fibers is quantified using differential scanning calorimetry measurements as a function of extension rate and accumulated Hencky strains. All the measurements are performed using the Janeschitz-Kriegel protocol. The samples are first melted to erase their thermal and mechanical history. They are then quickly quenched to T=98°C after which the stretch is imposed. The deformed filament is then allowed to crystallize fully at T=98°C. The extensional rheology of both the samples shows only minimal strain hardening. For the case of the lower molecular weight sample, the percent crystallinity increases from 46% under quiescent conditions to a maximum of 63% at an extension rate of ε̇ =0.05 s-1. This corresponds to an increase of nearly 50% above the quiescent case. The high molecular weight sample shows similar trends achieving an increase in crystallinity of 25%. The experiments show an optimal extension rate for which the extensional flow has the maximum impact on the polymer crystallinity. The percent crystallinity of both the samples is observed to increase with increasing strain for a fixed extension rate. Small angle X-ray scattering shows that the observed increase in crystallinity is likely due to the increasing orientation and alignment of the polymer chains in extensional flows which enhances the thread-like precursors responsible for the formation of the crystals in the shish-kebab morphology. © 2011 The Society of Rheology, Inc.

Journal of Rheology

Extensional flow-induced crystallization of isotactic poly-1-butene using a filament stretching rheometer

Recovery of water from spent aqueous streams is well known through the use of reverse osmosis (RO) but the extent of recovery is limited primarily by the scaling potential of dissolved species and the osmotic pressure of the concentrate stream. Mining industries, particularly the ones which use sulphuric acid leaching, discharge large quantities of effluents containing dissolved solutes with significant amounts of calcium and sulphate. Chemical method for the removal of sulphate is economically prohibitive to meet the discharge norm. The effluents therefore are often diluted and discharged or sent to dry areas for solar evaporation. Application of RO for the recovery of water is restricted by the scaling of sparingly soluble calcium sulphate. The use of commercial antiscalants does not help as they do not reduce the quantity of sulphates in the discharge stream. Experiments were carried out using nanofiltration (NF) membrane process with commercially available membrane element primarily to remove sulphates with minimal scaling problems. Furthers based on commercial software the performance of RO was assessed to estimate the extent of water recovery for reuse. The studies have indicated that it is possible to recover significant quantity of water for reuse. The sulphates in the concentrate stream can be converted to a solid form in a lime column. The stream depleted of sulphate can be recycled through NF. The paper presents the salient features of our bench scale studies, a precursor for field trials indicating the technical feasibility of achieving 'zero-liquid discharge (ZLD)' through membrane processes. © 2011 Desalination Publications. All rights reserved.

Desalination and Water Treatment

Recovery of water from saturated solutions by membrane processes

Water is the natural resource on which human life, food security and the health of ecosystems depend. The requirement for water is increasing rapidly owing to progressive increase in the demand for irrigation, rapid industrialisation, population growth and improving living standards. The existing water resources are diminishing due to (a) unequal distribution of rain leading to drought, (b) excessive exploitation of groundwater sources and (c) deterioration of water quality owing to the discharge of domestic and industrial effluents without adequate treatment. A large number of villages in India and several other parts of the world are known to be suffering from excess salinity, fluoride, iron, arsenic and microbial contaminations of ground water. There are areas that face perennial water shortage. Thus, the sustainable management of water is one of the key challenges that our society is facing today. This paper discusses different challenges and approaches to integrated water resource management. © 2011 Inderscience Enterprises Ltd.

Challenges and approach to integrated water resource management

Nanotechnology is a potential augmentation to the existing water purification technologies. Four different types of functional nanomaterials, like carbon nanotubes, metal/metal oxide nanoparticles, dendrimers and zeolites, are currently under evaluation for water purification application. Nanomaterials offer excellent opportunities because of high surface area (surface/ volume ratio), but the challenge is to build up an integrated scalable system. Membranes, because of being energy-economic and having the ability to get associated to different processes as a pretreatment or post-treatment stage, fi nd tremendous applications in the field of water purification. Nanostructured materials serve as a wonderful tool towards development of high flux, high selective membranes. Here attempts are made to develop biofouling resistant membrane. Nanoparticles of silver, copper and silver–copper mixture were impregnated on to the polysulfone host matrix and the biofouling resistance behavior of each membrane surface was examined. The performance of the membranes was evaluated in terms of pure water permeability and solute rejection studies. The membranes were characterized using scanning electron microscopy, energy dispersive X-ray, water contact angle and atomic force microscopy studies. The authors conclude that the silver impregnated membranes possess the best biofouling resistant behavior. The present paper discusses the potential of nanoparticles for water purifi cation and explains briefly the R&D work carried out in the research centre towards development of a biofouling resistant nanocomposite membrane. © 2011 Taylor & Francis Group, LLC.

Potential of nanoparticles for water purification: A case-study on anti-biofouling behaviour of metal based polymeric nanocomposite membrane

Thin film composite (TFC) type positively-charged nanofiltration membranes, bearing fixed quaternary ammonium moieties, have been developed and studied. Branched polyethyleneimine (PEI) was functionalized by reaction with glycidyl trimethyl ammonium chloride (GTACl) to introduce quaternary ammonium chloride. Positively-charged TFC membranes were prepared by in situ interfacial polymerization of functionalized PEI and terephthaloyl chloride. The effects of variation of chemical compositions and other experimental conditions such as curing temperature and duration of curing on the performances of the membrane were studied. ATR FT-IR spectroscopy was done to establish the presence of charge-bearing groups in the membrane. The membranes were tested using single solute feed solutions of NaCl, Na2SO4, CaCl2, and MgSO4. Positive charges on the membranes were estimated in terms of their ionexchange capacities (IEC). The values were also correlated to the solute-rejection properties of the membranes. © Taylor &amp; Francis Group, LLC.

Separation Science and Technology

Development, characterization and performance evaluation of positively-charged thin film-composite nanofiltration membrane containing fixed quaternary ammonium moieties

Permeation of U(VI) from nitric acid solution has been studied across supported liquid membrane (SLM) using bis[2,4,4 trimethyl pentyl] phosphinic acid (Cyanex 272) either alone or in combination with neutral donors like Cyanex 923 (a mixture of four trialkyl phosphine oxides viz. R3PO, R2R′PO, RR′2PO, and R′3PO where R: n-octyl and R′: n-hexyl chain), TBP (tri-n-butyl phosphate), and TEHP (tris-2-ethylhexyl phosphate) dissolved in n-paraffin as carriers. Effect of various other parameters such as nature and concentration of receiver phase, feed acidity, uranium concentration, pore size, and membrane thickness on U(VI) transport across SLM were investigated. Transport behavior of U(VI) was also compared with other derivatives of phosphoric acids like 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A), dinonyl phenyl phosphoric acid (DNPPA) under identical conditions and it followed the order: Cyanex 272 &gt; PC88A &gt; DNPPA. 2 M H2SO4 was suitable for effective U(VI) transport across SLM. Presence of neutral donors in carrier showed significant enhancement in U(VI) permeation in the order: Cyanex 923 &gt; TBP &gt; TEHP. U(VI) transport decreased with increased membrane thickness as well as decrease in pore size. The optimized conditions were tested for recovery of U(VI) from uranyl nitrate raffinate (UNR) waste generated during purification of uranium. © Taylor &amp; Francis Group, LLC.

Uranium permeation from nitrate medium across supported liquid membrane containing acidic organophosphorous extractants and their mixtures with neutral oxodonors