Chemical Extraction of Arsenic from Contaminated Soil

A series of batch extraction experiments were conducted using a fortified soil with different extracting solutions such as inorganic acids (hydrochloric acid (HCl), sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), perchloric acid (HClO₄), or nitric acid (HNO₃)), organic acids (acetic acid (C₂H₄O₂), citric acid (C₆H₈O₇)) and alkaline agent (NaOH). Various concentrations were used to investigate the removal efficiency and to optimise the concentration of each extractant. In the present investigation a Kuroboku soil contaminated with arsenite (As(III)) was used as a model soil. Arsenic was extracted most efficiently by 5% H₃PO₄ with a maximum of more than 99% from the model soil. Sulfuric acid also showed high percentage extraction efficiency. On the other hand, C₂H₄O₂ and oxidizing acids such as HNO₃ and HClO₄ showed low efficiency of As extraction compared with C₆H₈O₇. Although, NaOH also showed higher extraction efficiencies compared with organic and oxidizing acids but mainly arsenate (As(V)) was found to be the major component. A significant fraction of the As(III) was oxidized to As(V) during mineral acid and alkaline extraction and extraction efficiency also varied with the concentration of the acid and alkali solution.

Keywords:

• Arsenite
• Arsenate
• Chemical extraction
• Soil contamination
• Soil remediation.