Étude sur la rétention d'arsenic de solutions aqueuses utilisant un traitement au polymère suivi d'une séparation par membrane d'ultrafiltration.

Abstract

A new hybrid method incorporating selective polymeric binding and membrane separation was used to remove arsenic from a synthetic solution representing surface water. Two types of exploitation of this process have been investigated. The first series of experiments were performed in an ultrafiltration Amicon stirred cell, and two types of polymers were used poly-(dially dimethyl ammonium chloride) and polyethylenimine. The second was performed with two different continuous processes, either in a thin channel plate and frame module or in the Amicon stirred cell, using only polyethylenimine. All the solutions were made from $\rm Na\sb2HAsO\sb4$. 7H$\sb2$O which represents the most common degree of oxydation of arsenic in surface water, i.e. As(V). The analysis of arsenic was obtained by combining a hybrid generator with the standard atomic absorption equipment. The evaluation performed to date have demonstrated that the combined method of polymeric binding/ultrafiltration can be used for the removal of arsenic from contaminated water. The proposed technique could be used as a single step method for water treatment or as a post-treatment step after reagent precipitation. Arsenic removal depends on various factors: polymer concentration, pH, anions concentration and types of anions present in the system. The efficiencies obtained during the first series of experiments in presence of salts, NaCl, NaNO$\sb3$, $\rm Na\sb2SO\sb4$, and $\rm Na\sb2CO\sb3$, using Amicon stirred cell varied between 15% at high salt concentrations to 88% at low salt concentrations. The two continuous systems were investigated, feed & bleed and feed only, which represent an industrial process. A maximum efficiency exceeding 99.9% was obtained, even in the presence of 1,000 ppm of sodium chloride. (Abstract shortened by UMI.)