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CONTENTS
Volume 4, Number 2, April 2013
 

Abstract
In the present investigation, were synthesized composite membranes prepared by simultaneous casting of two polymer solutions using the technique of phase inversion by immersion / precipitation. The support layer was prepared using polyethersulfone and polysulfone as base polymer and for the top layer was used sulfonated polysulfone (SPSU) with 50% sulfonation degree. The morphology of the resulting membranes were characterized by scanning electron microscopy (SEM). The final results showed that it is possible to prepare composite membranes by simultaneous casting of two polymer solutions with adherence between the two layers. Regarding the permeation tests, the developed membranes presented values of hydraulic permeability within the range of commercial nanofiltration (NF) membranes. Values rejection of 80% ammonium ions can be increased by using a SPSU with a greater degree of sulfonation.

Key Words
polysulfone sulfonated; composite membrane; ammonium rejection

Address
Edna T.R. Bastos and Celina C.R. Barbosa: Instituto de Engenharia Nuclear (IEN / CNEN), Rua Helio de Almeida 75 - 21941-906 - Rio de Janeiro - Brazil; Jaciara C. Silva and Vanessa B.C. Queiroz: Bolsista CT/Petro; Delmo S. Vaitsman: Departamento de Quimica Analitica, Instituto de Quimica, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos, 149, room A-519 - 21941-909 - Rio de Janeiro - Brazil

Abstract
Metal ions exist in seawater, groundwater and industrial wastewaters. These source waters can be recycled if their concentrations are reduced. A number of processes can be applied for this purpose. Liquid-liquid extraction is one of the promising methods. In this paper, experimental results are presented on the removal of Cr(VI) using Aliquat-336, a reactive carrier, in sunflower oil (a non-toxic solvent). The performance of this new system is compared with those of kerosene (a toxic solvent). The extent of removal of Cr(VI) from samples with high and low concentrations are presented. The process was upgraded to a bench-scale module that can selectively remove about 50-90% Cr(VI) from samples of groundwater. Thus this process can produce water within the acceptable range for recycling and for use in secondary purposes such as irrigation.

Key Words
ground waters; liquid membrane contactor; removal; chromium; sunflower oil; solvent

Address
Md M Hossain: Department of Chemical & Petroleum Engineering, United Arab Emirates University, P.O. Box 17555, Al Ain, UAE

Abstract
Surface modification by low-pressure ammonia (NH3) plasma on commercial thin-film composite (TFC) membranes was investigated in this study. Surface hydrophilicity, total surface free energy, ion exchange capacity (IEC) and zeta (ζ)-potentials were determined for the TFC membranes. Qualitative and quantitative analyses of the membrane surface chemistry were conducted by attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy. Results showed that the NH3 plasma treatment increased the surface hydrophilicity, in particular at a plasma treatment time longer than 5 min at 50 W of plasma power. Total surface free energy was influenced by the basic polar components introduced by the NH3 plasma, and isoelectric point (IEP) was shifted to higher pH region after the modification. A ten (10) min NH3 plasma treatment at 90 W was found to be adequate for the TFC membrane modification, resulting in a membrane with better characteristics than the TFC membranes without the modification for water treatment. The thin-film chemistry (i.e., fully-aromatic and semi-aromatic nature in the interfacial polymerization) influenced the initial stage of plasma modification.

Key Words
thin-film composite; modification; membranes; NH3 plasma; physico-chemical properties

Address
Eun-Sik Kim: Department of Civil & Environmental Engineering, University of Missouri, Columbia, MO 65211, USA; Baolin Deng: Department of Chemical Engineering, University of Missouri, Columbia, MO 65211, USA

Abstract
In order to investigate the significance of \"salting-out\" and \"pore swelling\" effects on the nanofiltration of neutral solutes, rejection properties of two NF ceramic and polymeric membranes were studied with single polyethyleneglycol (PEG) solution and mixed PEG/inorganic electrolyte solutions. For both membranes, the rejection rate of PEG was found to decrease significantly in the presence of ions. In the case of the ceramic membrane (rigid pores), this phenomenon was imputed to the sole partial dehydration of PEG molecules induced by the surrounding ions. This assumption was confirmed by the lowering of the PEG rejection rates which followed the Hofmeister series. Experimental data were used to compute the resulting decrease in the Stokes radius of PEG molecules in the presence of the various salts. Concerning the polymeric membrane, the decrease in the rejection rate was found to be systematically higher than for the ceramic membrane. The additional decrease was then ascribed to the swelling of the pores. The experimental data of rejection rates were then used to compute the variation in the mean pore radius in the presence of the various salts. The pore swelling phenomenon due to accumulation of counterions inside pores was supported by electrokinetic charge density measurements.

Key Words
dehydration; salting-out; hofmeister effects; pore swelling; nanofiltration; ceramic membrane; organic membrane; salts; streaming potential

Address
Aurelie Escoda, Patrick Fievet and Sebastien Deon: Institut UTINAM, Universite de Franche-Comte, 25030 Besancon cedex, France; Saliha Bouranene: Universite Mohamed Cherif Messaadia, Souk-Ahras, 41000, Algerie; Anthony Szymczyk: Universite de Rennes, Institut des Sciences Chimiques de Rennes, 35042 France

Abstract
Four membranes were used to separate Chlorella sp. from their culture medium in cross-flow microfiltration (MF) experiments: cellulose acetate (CA), cellulose nitrate (CN), polypropylene (PP) and polyvinylidenefluoride (PVDF). It was found that the hydrophilic CA and CN membranes with a pore size of 1.2

Key Words
cross-flow microfiltration; Chlorella sp.; flux decline; pore blocking

Address
A.L. Ahmad, N.H. Mat Yasin, C.J.C. Derek and J.K. Lim: School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Seberang Perai Selatan, Pulau Pinang, Malaysia


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