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COMPLEX DERIVED FROM THE MEDIUM ANIONIC POLYELECTROLYTE AND MEDIUM CATIONIC SURFACTANT - NEW COAGULANTS USED IN WASTEWATER TREATMENT

Mihaela Mihai

Abstract

This paper aims at studying some complex coagulants derived from the medium anionic polymer and medium cationic surfactant in order to evaluate the opportunity to use them in destabilizing and removing th e colloidal systems from water and wastewater. In this respect, medium anionic copolymers of acrylamide and sodium acrylate with commercial Preastol 2540, and a medium cationic surfactant derived from triethanolamine with commercial name of Tetranyl AT-7590 were used in order to obtain these complex coagulants. The formation of the complex coagulants was revealed based on a comparative analysis of some critical concentrations such as critical aggregation concentration and critical micellar concentration corresponding to both polyelectrolyte and surfactant solutions and critical aggregation c oncentration and critical saturation concentration corresponding to the complex solution. The valu es of these critical concentrations were determined from experimental data regard ing the variation of the surface tension of solutions as function of their concentration. The experimental data revealed that for a constant polyelectrolyte concentration lower than the critical micellar concentration and a variable surfactant concentration, the surface tension of the complex solutions remains constant up to a surfactant concentrati on corresponding to its critical aggregation concentration. After this value of the surfactant concentration, the surface tension of the complex solutions significan tly decreases up to a value of the surfactant solution concentration close to its critical micellar concentration and corresponding to the critical saturation concentration of the complex solutions. These results suggest the formation mechanism of the complex by grafting of surfactant micelles on the chain of the polyelectrolyte. Decreasing the surface tensio n of complex solutions as compared to pure polyelectrolyte solutions leads to a better development of solid-liquid interface processes that occur during coagulation-flocculation. Interactions between surfactant micelles an d polyelectrolyte lead to a change in rheological properties of th e solution. To get more insights concerning the flow behaviour of complex resulted from thes e interactions, a rheological study was performed. In this respect, both polyele ctrolyte and comple x solutions were characterized by determining their rheograms. The experimental results suggested that the Praestol 2540 solution is of Bingham pseudoplastic type. These rheological properties of complex solutions confer a be neficial effect on the interaction between 11th International Multidisciplinary Scientific GeoConference SGEM2011 www.sgem.org International Multidisciplinary Scientific GeoConference SGEM 2011 230 colloidal particles and complex coagulant and subsequently, on the entire coagulation – flocculation process.

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DOI resolver: doi.org/10.5593/sgem2011/s20.111

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