Terrestrial environment

Arsenic removal from contaminated soil using phosphoric acid and phosphate


ZENG Min , LIAO Bohan , LEI Ming , ZHANG Yong , ZENG Qingru , OUYANG Bin

DOI:

Received March 09, 2007,Revised May 14, 2007, Accepted , Available online

Volume 20,2008,Pages 75-79

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Laboratory batch experiments were conducted to study arsenic (As) removal from a naturally contaminated soil using phosphoric acid (H3PO4) and potassium dihydrogen phosphate (KH2PO4). Both H3PO4 and KH2PO4 proved to reduce toxicity of the soil in terms of soil As content, attaining more than 20% As removal at a concentration of 200 mmol/L. At the same time, acidification of soil and dissolution of soil components (Ca, Mg, and Si) resulted from using these two extractants, especially H3PO4. The e ectiveness of these two extractants could be attributed to the replacement of As by phosphate ions (PO43-). The function of H3PO4 as an acid to dissolve soil components had little e ects on As removal. KH2PO4 almost removed as much As as H3PO4, but it did not result in serious damage to soils, indicating that it was a more promising extractant. The results of a kinetic study showed that As removal reached equilibrium after incubation for 360 min, but dissolution of soil components, especially Mg and Ca, was very rapid. Therefore dissolution of soil components would be inevitable if As was further removed. Elovich model best described the kinetic data of As removal among the four models used in the kinetic study.

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