It was found that phosphoric acid proved to be most promising as an extractant,
attaining 99.9% arsenic extraction at 9.4% acid concentration in 6 h. Sulfuric acid also attained high
percentage extraction. An environment-friendly and cost-effective extraction method has been studied for
the removal of arsenic from contaminated soil [14]. A yellow-brown forest soil was contaminated with
arsenic (V) and used as a model soil. Among various potassium and sodium salts, potassium phosphate
was most effective in extracting arsenic. Arsenic was efficiently extracted by phosphate solution of pH
6.0 at 300 mM phosphate concentration and at 40°C. Among the extractant, the EDTA can form stable
composite with most heavy metals in the wide pH valve range. A soil washing process was applied to
remediate arsenic (As)-contaminated stream sediments around an abandoned mine in Goro, Korea [15].
Removal efficiencies for fine sediments were >95% after 1 h of washing with 0.2 M citric acid. When
using 0.2 M citric acid mixed with 0.1 M potassium phosphate, the As removal efficiency increased to
100%. It is worth mentioning that, the effect is almost unsatisfactory using single extractant as the many
different pollutants in soil.