“…Several washing agents have been investigated to decontaminate metals from soil, like chloride solutions, chelating agents, surfactants, and reducing and oxidizing agents [7], in which the acid and the chelant are two most prevalent washing agents [8]. Hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid have been studied in bench and field scale experiments for remediaton of contaminated soils, sediments, and sludge [9], hydrochloric acid was efficient in zinc extraction [10] and could achieve high lead extraction efficiency even at low concentration and short mixing time [1], it also exhibit strong ability in extracting cadmium from weathered, heavily cadmium contaminated soils [11] and show certain ability in extracting arsenic from arsenic mine tailings [9]. However, in sites, lead, zinc, cadmium were commonly coexist with arsenic, and hydrochloric acid alone was not sufficient to effectively reduce all metals to lower than required value due to their dissimilar chemical properties [12].…”