Extraction of Selenium from a Contaminated Forest Soil Using Phosphate

Abstract

Laboratory batch experiments were conducted to develop an environment-friendly and cost-effective technique for the treatment of selenium contaminated soils. A yellow brown forest soil was artificially contaminated with sodium selenite (Na2SeO3) and used as a model contaminated soil sample. Among various potassium and sodium salts, potassium phosphate exhibited a pronounced effect in extracting selenium, attaining more than 55% extraction in the pH range of 4 to 6, with minimum damage to the soil properties. Based on the sorption selectivity between phosphate and selenite, an exchange mechanism is proposed for the extraction of selenium from soil by phosphate. The results of sequential extraction show that phosphate is effective in extracting selenium, NH4F-extractable and NaOH-extractable fractions. The CH3COOH-extractable and residual fractions were poorly extracted by phosphate. Selenium was most efficiently extracted at 40°C with a 300 mM (pH 6) phosphate solution.