Prevention of soils from heavy metal

EPA [10] and [11]. During immobilization process, some additives such as silicates [12], cement, phosphates [13], organic materials [14], [15] and [16], and inorganic sulfides [17] and [18], are frequently used to reduce the mobility of heavy metals according to various mechanisms such as adsorption, precipitation or complexation, decreasing the bioavailability of pollutants in soils. But for these immobilizing agents, several problems must be paid attention to: one is that the volume of the treated waste will be increased when cement or lime are used as stabilization agent; another is that some immobilization products are sensitive to surrounding pH, and heavy metal ions will be released again while the pH value changes [19].