REDUCTION OF LEACHING VALUE BY REMOVING A FINE-GRAINED FRACTION FROM NATURALLY OCCURING ARSENIC-CONTAMINATED SOIL

Abstract

 The objective of this study was to develop a better understanding of the effects of pH and the arsenic content in naturally occurring arsenic-contaminated soil on leaching behavior with regard to removing a fine-grained fraction from soil. The arsenic contents of feed soils ranged from 6.6 to 13.1 mg/kg and the leaching values were between 0.005 and 0.057 mg/L. Soil slurry was separated into a fine-grained fraction and a coarse fraction by decanter centrifugation. A leaching test was applied to investigate leaching behavior of both a coarse fraction and a fine-grained fraction in a wide pH region by alkali/acid adding. As a result of this study, following observations were made; 1) the load-curve test results showed that the smaller the grain size, the greater both the arsenic content and the leaching value, 2) the applied leaching test provided a magnified observation of leaching behavior which is difficult to determine in a neutral region, 3) removal of a fine-grained fraction from soil slurry showed a possibility to produce clean soil that satisfied the environmental standard, and 4) increasing cut sizes of centrifugal separation, that is, decreasing the arsenic content in a coarse fraction was very effective in reduction of the leaching value in a coarse fraction that became clean soil.