Abstract
The process of electromembrane transformation of L-lysine monohydrochlorides into their zwitterionic form in four- and two-chamber electrodialysis apparatus was investigated. The process of transformation at various concentrations of lysine monohydrochloride (0.1-0.6 mol.L-1) was studied and it was established that at the optimum density of current optimal concentrations of lysine hydrochloride during electrodyalisis was in the range of 0.2-0.4 mol.L-1. It was determined that the process of total transformation was accomplished when pH of the lysine solution achieved 10. Changes of concentrations of Cl‾ ions and lysine diffused into the neighboring chamber were determined depending on the time. The method developed by us allows adjusting the removal coefficient of Cl‾ ions during transformation to a maximal value, the losses of lysine diffused into the next chamber after its return to the technological cycle being less than 1.0 %. The specific energy consumption during the process of transformation in two- and four-chamber electrodialyzers was 0.19 and 0.205 A.h.kg-1 and the current efficiency was 75.9 and 73.1 %, correspondingly. Study of the process of electromembrane transformation allowed obtaining zwitterionic form of L-lysine from L-lysine monohydrochloride with minimal reagent and energy consumption.
Key Words
electrodialysis; L-lysine monohydrochloride; zwitterion of L-lysine; transformation
Abstract
Emulsion liquid membrane (ELM) process suffers from emulsion instability problem. So far, emulsion produced by mechanical methods such as stirrer and homogenizer has big size and high emulsion breakage. This paper discussed the application of emulsion produced by sonicator to extract cadmium in a batch ELM system. The emulsions consist of N,N-Dioctyl-1-octanamine (trioctylamine/TOA), nitrogen trihydride (ammonia/NH4OH), sorbitan monooleate (Span 80), and kerosene as carrier, stripping solution, emulsifying agent, and organic diluent, respectively. Effects of comprehensive parameters on extraction efficiency of Cd(II) such as emulsification time, extraction time, stirring speed, surfactant concentration, initial feed phase concentration, carrier concentration, volume ratio of the emulsion to feed phase, and pH of initial feed phase were evaluated. The results showed that extraction efficiencies of Cd(II) greater than 98% could be obtained under the following conditions: 15 minutes of emulsification time, 4 wt.% of Span 80 concentration, 4 wt.% of TOA concentration, 15 minutes of extraction time, 250 rpm of stirring speed, 100 ppm of initial feed concentration, volume ratio of emulsion to feed phase of 1:5, and initial feed pH of 1.53.
Key Words
emulsion liquid membrane; extraction efficiency; cadmium; ultrasonication
Address
School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang, Malaysia
Abstract
During cleaning steps, ultrafiltration membranes are mechanically and chemically stressed. This may result in membrane degradations and failures. In this paper, polysulfone membranes were used to evaluate membrane deteriorations by commercial detergents in static conditions. Ageing of the membrane was simulated by immersing samples in solutions containing commercial detergents with various concentrations, temperatures and times defined by experimental designs. Indeed, an innovative approach in the chemical membranes ageing researches, based on methodological tools, was used in order to achieve significant ageing experiments without using an accelerated ageing protocol. The macroscopic changes were monitored by permeability measurements and mechanical strength tests coupled with a microscopic
characterization by ATR-FTIR and HRSEM. The present work details results obtained for three commercial detergents: an alkaline, an acidic and an enzymatic detergent. It was found that the detergents used in the industrial advised conditions (concentration, temperature and time of contact) were not detrimental for membrane properties (permeability and elongation at break) and so for the quality of the produced water. Over the industrial cumulated time of contact, different ageing effects can be observed and compared with the ones induced by NaOCl.
Address
P. Moulin, C. Regula, E. Carretier, Y. Wyart : Aix Marseille Universite, Laboratoire de Mecanique, Modelisation et Procedes Propres (M2P2 – UMR-CNRS 7340), Europole de l\'Arbois, BP. 80, Batiment Laennec, Hall C, 13545 Aix en Provence Cedex 04, France
M. Sergent : Aix Marseille Universite, CNRS (UMR 6263), Institut des Sciences Moleculaires de Marseille,
13397 Marseille Cedex 20, France
G. Gesan-Guiziou : INRA, UMR1253 Science et Technologie du Lait et de l
Abstract
In this study, ageing characteristics of an industrial hollow-fiber membrane module were investigated after 50 months of drinking water production. For this purpose, the industrial module was opened to make 18 smaller modules with hollow-fibers taken from different parts of the industrial module. These modules were probed by the use of a magnetic nanoparticle (NP) challenge test based on magnetic susceptibility (K) measurement of permeate. No magnetic susceptibility was detected in permeate when the
challenge test was performed on an intact membrane module, indicating the complete retention of nanoparticles by the membrane. The compromised membrane module can be successfully detected by means of magnetic susceptibility measurement in permeate. So, this study clearly demonstrates that ageing of ultrafiltration membranes can be monitored by measuring the magnetic susceptibility of permeate from an ultrafiltration membrane module. These results showed that the hollow fibers in the center zones of the bundle would age faster than those in the outer zones around the bundle. This result is in agreement with
numerical simulation (Daurelle et al. 2011).
Key Words
drinking water, ageing characteristics, magnetic nanoparticles, magnetic susceptibility
Address
S. Wang, Y. Wyart, P. Moulin : Aix Marseille Universite, Laboratoire de Mecanique, Modelisation et Procedes Propres
(M2P2 – UMR-CNRS 7340), Europole de l\'Arbois, BP. 80, Batiment Laennec, Hall C, 13545 Aix en Provence Cedex 04, France
J. Perot, F. Nauleau : SAUR, 1 avenue Eugene Freyssinet, 78064 Saint Quentin en Yvelines Cedex, France
Abstract
The pH-dependent inter-conversion of the three free chlorine species (Cl2, HOCl, OCl-) present in the aqueous hypochlorite solution was theoretically investigated. Each species was found overwhelmingly present in a characteristic pH range. Hypochlorite treatment of the polyamide membrane was carried out over these pH ranges and various membrane responses were observed. As pH is less than 8, membrane tends to be N-chlorinated by Cl2 and HOCl, and N-ch lorinated membrane showed reduced water permeance and salt rejection. As pH rises to 10-12, OCl¯ appears to be the dominating chlorine species. Membrane hydrolysis was found to well interpret the improved water permeance and salt rejection. When the pH is between 8-10, both N-chlorination and hydrolysis contribute to the response of the membrane, and the treated membrane showed improved salt rejection but reduced water permeation. Excessive hydrolysis
occurred while the membrane was treated at pH 13 for the much stronger alkalinity.
Key Words
polyamide; hypochlorite treatment; reverse osmosis; salt rejection; water permeance; membrane chemistry; chlorinating species; hydrolysis; N-chlorination
Address
P. Shao : 1Energy, Mining and Environment (EME) Portfolio, National Research Council Canada,
M12, 1200 Montreal Road, Ottawa, ON, Canada K1A 0R6, Canada
C.J. Kurth : NanoH2O Inc. 750 Lairport Street, El Segundo, CA 90245, USA
