2007_6_Nr6_EEMJ

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TECHNOPOLIS/Environmental Engineering and Management Journal, 6 (2007), 6, 504 ENVIRONMENTAL ASSESSMENT LABORATORY The Environmental Assessment Laboratory was founded in 2006, within a project financed by the INFRATECH Program, administrated by the Ministry of Education and Research. The laboratory operates as a part of Tehnopolis Science and Technology Park Iasi – a consortium having our Technical University “Gh. Asachi “ of Iasi as partner. The laboratory is staffed by some members of the Environmental Engineering and Management Department of the Faculty of Chemical Engineering and Environmental Protection (Technical University “Gh. Asachi “of Iasi). With a rich expertise in environmental engineering and management, the staff is especially competent in: • Environmental monitoring o Specialized in complex environmental analysis such as the identification and quantification of organic pollutants (VOC, POPs, pesticides, PCBs etc.) from air, water and soil; • Environmental impact assessment; • Risk assessment • Environmental consulting (Environmental permitting, Quality management certification for ISO 14.001, Emission reduction plan for VOC; Solvent management plan); The research activity of the group members is illustrated by: • More than 100 scientific articles, published in well-known national and international (ISI); • More than 45 national and international patents; • Books published in Romania (publishers accredited by CNCSIS) and abroad; • PhD thesis approaching new and original topics in environmental engineering and management; • Centers of excellence in research • International collaborations (within programs such as PHARE, EcoLinks, or financed by German Ministry for Education and Research, Swiss Science Foundation, Swedish Institute Stockholm etc) During the last decade of activity, the members of the laboratory have participated in more than 200 research contracts with the industry, on different activities: • Environmental permitting; • Integrated pollution prevention and control; • Technical Inspection Certificates for VOC (according to H.G. 568/2001), being one of the six accredited laboratories in the country); • VOC emission reduction schemes (H.G. 699/2003) • Other projects concerning the cleaning or depollution of different industrial effluents and streams. Facilities and Equipments The laboratory is being organized according to the requirements of the Quality management system ISO /IEC 17025:2000 “General requirements regarding the competence of the testing and calibration laboratories”. The main equipments used in the laboratory, fully compliant with international standard methods, are: • High resolution GC-MS with hyperbolic quadrupole mass analyzer (Agilent) • Thermal desorber (Markes International) • High precision analytical balances • Ovens, automatic pipettes etc In addition to the classical GC-MS/FID methods, our laboratory is especially interested in using the analytical thermal desorption methods for the measurement of trace level volatile and semi-volatile organic chemicals (VOCs and SVOCs). It is the technique of choice for air monitoring (indoor, outdoor, workplace, automobile interior, breath, etc.) and is an invaluable tool for the analysis of soil, polymers, packaging materials, foods, flavors, cosmetics, tobacco, building materials, pharmaceuticals, and consumer products. Indeed, virtually any sample containing volatile organic compounds can be analyzed using some variation of this technique. In this context, we are opened for collaboration with scientific institutions in the areas covered by our laboratory. Cezar Catrinescu Department of Environmental Engineering and Management Faculty of Chemical Engineering “Gh. Asachi” Technical University of Iasi, Romania 504
Environmental Engineering and Management Journal November/December 2007, Vol.6, No.6, 505-509 http://omicron.ch.tuiasi.ro/EEMJ/ “Gh. Asachi” Technical University of Iasi, Romania ______________________________________________________________________________________________ POLYELECTROLYTE – SURFACTANT COMPLEXES Mihaela Mihai ∗ , Gabriel Dabija, Cristina Costache Polytechnica University Bucharest, Faculty of Applied Chemistry and Materials Science, 1 – 7 Polizu Street, Sector 1, 011061 Bucharest, Romania Abstract The formation of the polyelectrolyte – surfactant complexes has been studied. On this purpose has been measured the critical micelle concentration for every polyelectrolyte and surfactant which had been used. The phase behaviour of mixtures of a cationic polyelectrolyte (Praestol 611) and an anionic surfactant (sodium lauryl sulphate – SLS) has been studied. For a given polyelectrolyte concentration, with increasing surfactant concentration, three phase regions were identified. The first region is a single homogeneous phase. Within this region, at some surfactant concentration, above the critical aggregation concentration (cac), stable open – network ‘particles’ form, typically 100 nm in size, which are net positively charged. However, as the surfactant concentration is increased further, these particles aggregate and form a two – phase system: a separated gel phase, containing a high percentage of water co-existing with an aqueous surfactant phase. The rheological consequences of interactions of polyelectrolytes with surfactants of the opposite charge are experimentally studied. Key words: polyelectrolyte, surfactant, complex polyelectrolyte – surfactant, rheologie 1. Introduction Polyelectrolytes are used in a number of technical applications, such as water treatment. With polyelectrolytes can change the surface properties of colloids, rheology of solutions, wettability etc. In particular, cationic polyelectrolytes are used in the water treatment because of their ability to interact with negatively charged surfaces. Using surfactants in combination with polyelectrolytes increases the width of the applications even further, and mixtures of polymers and surfactants in aqueous solution have been used for colloidal stabilization or flocculation as well as rheology control. The interaction between polyelectrolytes and oppositely charged surfactants can be understood considering electrostatic and hydrophobic interactions (Vautrin, 2006). At low concentrations, the surfactant binds individually to the polyelectrolyte through electrostatic interactions. A cooperative association occurs at the critical aggregation concentration, cac, as the concentration is raised due to hydrophobic interactions between the surfactant tails. This aggregation process leads in some cases to a beadand-necklace type structure, where surfactant aggregates are located along the polyelectrolyte chain (Bastardo, 2005). The addition of a simple salt lowers the viscosity of polyelectrolyte solutions because salt screens the electrostatic repulsion that expands the size of the polyelectrolyte. The addition of an equivalent amount of oppositely charged surfactant has a larger effect on viscosity (Abuin and Scaiano, 1986). This is because flexible polyelectrolytes bind to the spherical surfactant micelles by wrapping around the exterior of the micelle, thereby shortening the effective length of the polyelectrolyte chain (Konop, 1997). The polyelectrolyte stabilizes the large charge on the micelle surface and no counterion condensation on the micelle surface is needed (Goddard, 1993). These effects stabilize the spherical micelles, reflected in micelles forming at a much lower concentration when oppositely charged polyelectrolytes are present (Colby, 2000). 2. Experimental The cationic Praestol 611 is a commercial denomination of a copolymer of polyacryl amide with acrylic acid. The association between the cationic ∗ Author to whom all correspondence should be addressed: mihai_mihaela2007@yahoo.com
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