TREATMENT OF AQUEOUS ALCOHOL ETHOXYLATES SOLUTION BY TiO2/UV-A PHOTOCATALYTIC OXIDATION

Alcohol ethoxylates (AEs) are a class of non-ionic surfactants widely used as detergents, emulsion stabilizers, foaming agents and wetting enhancers. These properties allow large industrial application as additives in the formulation of pesticides, pharmaceuticals, paints and cosmetics, as well as in mineral separation, biotechnology etc. Although there is no known toxic effect of AEs, their concentrations are often relatively high in aquatic environment. Until now, only few publications have been devoted to the degradation of AE with advanced oxidation processes (AOPs). Using semiconductor, more especially TiO2related catalysts, to oxidize organic chemicals is a promising AOP which has received much attention recently. Considering the above mentioned facts, in the present experimental study, the photocatalytic degradation of aqueous poly (oxyethylene) (4) loryl ether (commercial name Brij30) being selected as a model AE, using UV-A irradiation in the presence of TiO2 photocatalyst was investigated. The degradation extent has been evaluated by measurements of Brij30 and total organic carbon (TOC). Photocatalytic oxidation experiments were conducted to treat 20mgL aqueous Brij30 solution at different initial pH values (3.0 and solution’s original pH 6.0), different initial TiO2 dosages (1.0, 1.5 gL) and different reaction periods varying between 5 to 480 minutes. Effect of pH on the photocatalytic reaction was conducted at initial pH values of 3.0 and 6.0, with the Aeroxide P25 dosages of 1.0 gL and 1.5 gL.At initial pH 3.0, for 1.0 gLAeroxide P25 dosage, ~64% Brij30 and ~68% TOC removals were obtained after 10 and 480 minutes of reaction time, respectively. At original aqueous Brij30 pH (6.0), 83% Brij30 removal was observed after 10 minutes reaction time whereas ~ 65% TOC removal was realized after 480 minutes treatment. The effect of Aeroxide P25 dosage was investigated at pH3.0 and 6.0 at two different TiO2 loads being 1.0 and 1.5 gL. For initial pH value of 3.0, increasing the Aeroxide P25 dosage from 1.0 gLto 1.5 gL increased the Brij30 removal from 64% to 79%, respectively. 480 minutes reaction time provided 68% and 88% TOC removals for 1.0 gL and 1.5 gL TiO2 dosages, respectively. For initial pH value of 6.0, increasing the Aeroxide P25 dosage to 1.5 gL also increased the TOC removal efficiency up to ~86% for a reaction period of 480 minute. The experimental results showed that by using photocatalytic oxidation it is possible to achieve complete degradation of Brij30 accompanying with high TOC removals under investigated reaction conditions. Even in short reaction periods (15 minutes) high rates of Brij30 removals were achieved however longer oxidation periods (240-480 minutes) were needed in order to obtain significant TOC removals.