Mixed Acids Leaching of Heavy Metals from Contaminated Soils

• Main Authors: Chun-Cheng Lai, 賴俊成
• Other Authors: Jao-Jia Horng
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/64979651410042160013

碩士 === 國立雲林科技大學 === 環境與安全工程系碩士班 === 90 === Many lands in Taiwan were polluted by heavy metals. Various remediation methods were developed in the past; soil washing is one of the solutions that could effectively remove these metals from soils. This study evaluated several acids including nitrate, sulfuric, phosphoric, acetic, hydrochloric and citric acid, etc. and their mixtures for soil washing purpose. The texture of study soil was between sandy and silt loam with few organic and low hydrous materials. The results of sequential extraction indicated that the pollutants of Pb, Cd, Cr and Zn in soil mainly existed mostly in the form of Fe-Mn oxides bond. Some Cd in soil existed as the forms of carbonate-bonded and of exchangeable forms. The mixture of hydrochloric and citric acids (0.05 M:0.05 M) was found to be most effective in metal extraction and with less damage to the soil medium. The desirable soil and extraction solution ratios were 1 to 5. The chemical equilibrium software Mineql+ 3.0 was used to interpreted the extraction results.