Environmental Impact of Ether Carboxylic Derivative Surfactants

The ultimate aerobic biodegradability and toxicity of three ether carboxylic derivative surfactants having different alkyl chains and degrees of ethoxylation were investigated. Ultimate aerobic biodegradability was screened by means of dissolved organic carbon determinations at different initial surfactant concentrations. For comparison, the characteristic parameters of the biodegradation process, such as half-life, mean biodegradation rate, and residual surfactant concentration, were determined. Increased surfactant concentrations decreased mineralization and lengthened the estimated half-life. The results demonstrate that the ultimate aerobic biodegradability is higher for the surfactants with the shortest alkyl chain and highest degree of ethoxylation. Toxicity values of the surfactants, and their binary mixtures, were determined using three test organisms, the freshwater crustacea Daphnia magna, the luminescent bacterium Vibrio fischeri and the microalgae Selenastrum capricornutum. The toxicity is lower for the surfactants with the shortest alkyl chain and highest degree of ethoxylation. The toxicity of binary mixtures of the three ether carboxylate surfactants at a 1:1 weight ratio was also measured. The least toxic mixture is formed by the surfactants having lower individual toxicity.