Comparison of Two Single Acid Extractants in Simultaneously Removing Heavy Metals from an Artificial Copper-，Zinc-，and Arsenic-Contaminated Soil

摘要

In recent years，soil acid Washing technique is gradually used for the remediation of heavy metal contaminated soil in Taiwan．However,few studies were conducted to assess the effectiveness of using single acid solution for simultaneously removing high contents of both cationic and oxyanionic metals from soil．An artificial heavy metal contaminated soil (Cu 1,930 mg／kg，Zn 5,450 mg／kg，As 239 mg／kg)Was prepared and two acid solutions under various soil-to-acid ratios and stirring time were assessed to investigate the best parameter and the feaSibility of the acid washing technique．The soil-to-acid ratios of 1：3 and 20 minutes for stirring showed the best heavy metal removing efficiency．Phosphoric acid had better heavy metal removal ability than hydrochloric acid，especially for arsenic．The contaminated soil washed one time with O．1M phosphoric acid Can reach the removal rate of 86％ Cu，88％Zn，and 89％As under soil-to-acid ratio of 1：3 for 20 minutes．After washing two times，all the heavy metal concentration of the soil (Cu 67 mg／kg，Zn 87 mg／kg，and As not detectable by ICP-OES) were lower than the‘Soil Pollution Monitoring Standards’(Cu 220 mg／kg，Zn 1000 mg／kg，and As 30mg/kg) announced by Taiwan Environmental protection departments．HoweveL the pH of acid washed soil is between 2 and 3．Some soil management practices such as applying lime materials and composts were required to recover the soil functions．In the case of soil contaminated with multiple heavy metals including As，phosphoric acid is a promising extractant for simultaneously remove both cationic and oxyanionic metals from contaminated soils．