The effect of surfactants in leaching hydrophobic organic compounds from sand
Date
1997
Authors
Lee, Dal-Heui
Major Professor
Advisor
Cody, Robert D.
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Abstract
Surfactants may aid in remediation of subsoil and aquifers contaminated with hydrophobic organic compounds. The primary goal of this study is to develop a suitable experimental and laboratory system for investigating the efficiency of surfactants in removing hydrophobic contaminants from model soils. Material used as the model soil was Ottawa sand and the organic used as model contaminant was toluene. The experiments were conducted in three phases. The first phase was the search for suitable surfactants. The second phase was column-testing to investigate the removal of toluene from sand. These experiments used under two different conditions : gravity surfactant leaching and continuous washing by pumping. The third phase of the experiments was the investigation of solvent extraction to remove toluene from the used aqueous surfactant solutions. Based on the experimental results, the following conclusions were drawn: 1) In the surfactant selection phase of the investigation, six different surfactants were chosen based on surfactant types, toxicity, and water solubility. These six were reduced to two on the basis of HLB and surface tension study, separatory funnel experiment, shaker table and centrifugation experiments. The two most suitable surfactants were Sandopan JA36 (an anionic surfactant), and Pluronic L44 (a non-ionic surfactant). 2) In the shaker table and centrifugation experiments, the highest recovery of the toluene was 69 % which was obtained with one surfactant wash plus two water rinses using an anionic surfactant, Sandopan JA36, 3) In both methods of column tests, an aqueous surfactant solution containing 1 % anionic (Sandopan JA36) and 1 % non-ionic (Pluronic L44) surfactants was the most effective in removing the toluene. Maximum removal of 80 % of toluene was obtained from the contaminated sand when washed 5 times with the fresh aqueous surfactant solution containing 10 % NaOH by continuous leaching by pumping. Also, in recycled surfactant solution leaching tests, the mixture of 1 % each of anionic and nonionic surfactant solution with NaOH was effective based on surfactant cost, 4) In both counter-current orifice designs of gentle solvent extraction experiments for surfactant recycling, anionic surfactant solution was the most effective in recycling based on surfactant types. This study suggests that counter-current solvent extraction methods may help to recycle anionic surfactant solutions used for remediation of contaminated soil.
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