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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2007.09.001 Byline: P.K. Tewari, V.S. Batra, M. Balakrishnan Abstract: Agro-based pulp and paper mills in India are one of the most polluting industries; in addition, they are high consumers of raw water. Growing scarcity of high quality freshwater as well as stringent regulatory standards is compelling these units to explore appropriate water management options. Based on data obtained through a questionnaire survey and plant visits, this work provides an overview of the water use and effluent treatment status in Indian agro-residue and recycled pulp and paper mills. The challenges faced by this sector are reviewed and practices adopted by progressive units to minimize freshwater use are illustrated through case studies. Author Affiliation: The Energy and Resources Institute (TERI), Darbari Seth Block, India Habitat Center, Lodhi Road, New Delhi 110003, India Article History: Received 20 March 2007; Revised 18 August 2007; Accepted 15 September 2007

A novel sorbent, poly-acryl hydroxamic acid was prepared in-house from acrylamide monomer by solution polymerization method. Surface morphology and energy dispersive X-ray spectroscopy revealed that the sorbent was capable of encaging uranium from aqueous solution. Sorption potentials of uranium ions were investigated using the sorbent in dilute alkaline aqueous solution by varying pH of solution, sorbent quantities, contact time, initial uranium ion concentration and temperature of solution. Results from batch sorption experiment with simulated nuclear plant effluent showed the sorbent could remove uranium(VI) ions efficiently in presence of competitive ions such as Ca(II), Mg(II), Mn(II), Cu(II), Fe(III) and nitrate. Sorption characteristics were studied using Langmuir and Freundlich isotherms. The evaluated thermodynamic parameters indicated the present sorption process was endothermic and spontaneous. This work provided a promising and new sorbent for removing hazardous material like uranium from industrial wastewater. [ABSTRACT FROM AUTHOR]

Summary: The importance as well as impact of application of carbon nanotube (CNT) membranes in the area of water technology development is tremendous. A substantial amount of work have been carried out with impregnation of CNTs (simply as one of the reinforcements for incorporation of better properties like antibiofouling and/or better strength, etc.) in polymer host matrix. However, the volume of work enabling CNTs as flow channels (in a membranous structure) is not significant and that is where the potential benefits of CNTs lie. Moreover, from impressive works carried out in this direction, it is quite obvious that still significant challenges have to be addressed to align the CNTs, to reinforce it in a suitable host matrix without disturbing the alignment and inhibiting the agglomeration (adoption of suitable nanocomposite fabrication route), to open the tips preferentially and to scale up favorably. It is believed that the innovative attributes put forth by CNTs and the application areas identified with CNTs are getting matured, while the area of development of CNT (based) membranes is far from being matured and it still needs to be looked into in the light of involvement of materials as well as process challenges. [ABSTRACT FROM AUTHOR]

This work compares the filtration performance of low cost filters for wastewater treatment in a submerged MBR. Two filters viz. commercial nylon mesh of 30μm pore size and 2–6μm macroporous ceramic filters prepared from bagasse fly ash were investigated. Critical flux was measured by flux stepping method, and the MBR filtration performance was monitored in terms of flux, transmembrane pressure (TMP) build-up and permeate quality. It was observed that both the nylon mesh and the ash filter are good solid–liquid separators with low TMP build-up. However, the ash filter displayed higher critical flux that was comparable to commercial microporous membranes; it also does not require the formation of a secondary filtration layer to ensure consistently high suspended solids retention. [Copyright &y& Elsevier]

Four chelating matrices prepared by coupling Amberlite XAD-2 with chromotropic acid (AXAD-2-CA or 1), pyrocatechol (AXAD-2-PC or 2) and thiosalicylic acid (AXAD-2-TSA or 3) through azo spacer and impregnation of Amberlite XAD-7 with xylenol orange (AXAD-7-XO or 4) have been studied for enrichment of lead(II). All the four resins quantitatively sorb Pb(II) at pH 3.0–8.0 when the flow rate is maintained between 2 and 10 ml min−1. HNO3 (0.5–4.0 M) instantaneously elutes Pb(II) from all the four chelating resins. The sorption capacity is in the range 16.0–186.0 μmol g−1 and loading half time (t1/2) between 3.2 and 15.5 min. The tolerance limits of electrolytes (NaCl, NaBr, NaNO3, Na2SO4, Na3PO4) and cations (Ca and Mg) are reported. Phosphate interferes in the sorption with 3 and 4. The limit of detection and limit of quantification have been found to be in the ranges 2.44–7.87 and 2.76–8.64 ng ml−1, respectively. Lead has been determined in river (RSD ∼2.6–12.8%) and tap (RSD ∼1.8–7.2%) water samples. [Copyright &y& Elsevier]

Abstract: This study aims at understanding the role the velocity profile can play in affecting the performance of the electorneutral bulk of a continuous flow electrolyser. Numerical simulations have been carried out by solving Navier–Stokes (NS) equations together with the Nernst–Planck (NP) equations. Performance of different geometries in which velocity profile has been altered by putting different types of obstacles has been evaluated. Performance of electrolysers having moving cathode has also been evaluated. Role played by inlet channel has also been investigated. The results obtained for different geometries suggest that it is possible to enhance the performance of the electroneutral bulk by putting obstacles in the flow path but this enhancement may not be very significant. An electrolyser with the cathode moving co-currently with the electrolyte is found to perform better than an electrolyser with cathode moving counter-currently with the electrolyte. Performance of an electrolyser with the inlet channel is found to be better than an electrolyser without inlet channel. [Copyright &y& Elsevier]

A distinctive and impactful idea has been materialized to develop high-performance mixed-matrix ultrafiltration (UF) membranes using non-solvent induced phase inversion technique, utilizing various optimized compositions of polymer – polysulfone (Psf) and bactericidal nanostructured material, i.e. , silver nanoparticles (Ag-nps). Membranes in sheet-configuration with high void volumes were synthesized employing large amount of polyvinyl pyrrolidone (PVP) as porogen. The resultant porous morphology and surface chemistry, i.e. , surface hydrophilicity and electrokinetic features were assessed by instrumental techniques. The notable separation performances were observed as the membranes exhibited very high solvent throughput with reasonable anti-microbial activity. It has been substantiated that the nanoparticles upon impregnation within such a benign matrix of polymer exerted more pronounced mechanistic role towards anti-microbial efficacy on Escherichia coli , since as a survival mechanism the bacteria undergoing flagellar locomotory motion started experiencing negative chemotactic responses under the modified circumstances. With an objective of applying the salient features of such membranes, the facile methodical attempt was utilized in fabricating a domestic water purification device, with the membrane in candle-configuration for treatment of environmentally relevant aquatic media. It has been corroborated that our impactful approach towards development of an efficient water purification methodology (solvent throughput: 2500 LMH/bar and bacterial rejection: 99.99%) confirms the significance of membrane technology as a green and sustainable process with provision of easy scale up, energy and cost efficiency. [ABSTRACT FROM AUTHOR]

Hydrogen production by water splitting method is one of the promising solutions for the future energy systems. Among all hydrogen production processes, thermo-chemical Iodine–Sulfur process is one of the efficient and environmentally attractive methods. Iodine–Sulfur process consists of three chemical reactions: (i) Bunsen reaction, which is the acid production step, (ii) sulfuric acid decomposition to produce oxygen and (iii) hydrogen iodide decomposition to produce hydrogen. A detailed parametric study of Bunsen reaction has been carried out through semi-batch experiments. Experiments are carried out in a metallic tubular Bunsen reactor at different pressure and temperature with pure sulfur dioxide (SO 2 ). It has been observed that the overall reaction rate increases with increase in pressure and decreases with increase in temperature. Further studies have been carried out with nitrogen in SO 2, to understand the effect of gas film resistance on the overall reaction rate and conversion. [ABSTRACT FROM AUTHOR]

Numerical simulations to develop an understanding of transport processes inside PBMRs (packed bed membrane reactors) and to evaluate effectiveness of PBMRs in increasing the conversion of HI (hydrogen iodide) decomposition reaction of IS (iodine–sulfur) thermochemical cycle are reported. The computational approach used in the simulations has been validated using the data reported for HI decomposition in a packed bed reactor (PBR). The validated computational approach has been used for parametric studies. Effects of different parameters (temperature, pressure, space velocity, membrane permeability, permselectivity, packed bed porosity and reactor diameter) on HI conversion are reported. The parameters having the maximum impact on the conversion are identified. The findings show that using a PBMR instead of a PBR leads to significant enhancement in conversion and the parameters having high impact on conversion are wall temperature, feed temperature, reactor diameter and packed bed porosity. Based on the findings of parametric studies, ranges of the parameters having maximum impact on conversion are suggested, e.g. the reactor wall temperature is recommended to be in the range of 690–700 K, the bed porosity is recommended to be in the range of 0.2–0.4. [ABSTRACT FROM AUTHOR]

Abstract: Thermochemical cycle using water as raw material and nuclear/renewable energies as sources of energy is believed to be a safe, stable and sustainable route of hydrogen production. Amongst the well-studied thermochemical cycles, the sulfur–iodine (S–I) cycle is capable of achieving an energy efficiency of 50%, making it one of the most efficient cycles among all water-splitting processes. The SI cycle is characterized by three basic reactions as shown below. [1.] I2 + SO2 + 2H2O → 2HI x  + H2SO4 (120 °C) [2.] 2H2SO4 → 2SO2 + 2H2O + O2 (830 °C) [3.] 2HI x  → I2 + H2 (450 °C) The third section, that is the HI x (HI + I2 + H2O) processing section, is the most intricate step in terms of the process efficiency as it has got the lowest overall rate and very complicated separations. In order to overcome the low efficiency due to the poor equilibrium decomposition of HI, ongoing research is dedicated toward development of a hydrogen-permselective membrane reactor. Proper identification of suitable membranes and introduction of membrane reactor is proposed to improve the efficiency of the overall cycle and make hydrogen production more economical. The experimental procedure has already been optimized toward development of an asymmetric silica membrane. The authors presently intend to use the membrane in the form of a packed bed membrane reactor for the enhancement of equilibrium decomposition of HI. The present paper discusses the challenges and intricacies associated toward development of a membrane reactor which can be applied in highly corrosive environment like HI under a high temperature of about 500 °C. [Copyright &y& Elsevier]