Remediation of heavy metals contaminated soils by ball milling

Heavy metals are widespread in urban and industrial areas as a consequence of several anthropic activities. Strong efforts have been made to develop remediation techniques of heavy metals contaminated soils. Typical remediation techniques are constituted by extraction and immobilization processes. Nevertheless, the ex situ extractive technologies are rarely adopted because of high risks and costs related to the use of hazardous reactants and the consequent need of treating secondary effluents. On the other hand immobilization processes are generally preferred as cost-effective technologies for treating heavy metals contaminated soils. Specifically, the immobilization techniques prevent migration of heavy metals into the environment due to leaching by improving soil physical characteristics, increasing and subsequently decreasing surface area, or limiting the solubility or mobility of the hazardous compounds. In the present work, we analyze the efficiency of mechanical treatment for the remediation of real soils contaminated by heavy metals and tailings from the mining area of "Diga su Fangu", SW of Sardinia, Italy. The characterization of possible modification of soil physical, chemical and mineralogical properties induced by the milling process is also addressed. Possible mechanisms involved during the mechanical treatment and responsible of the increase of soil immobilization capacity are discussed.