Immobilisation of metal(loid)s in building materials made with mine waste

In the framework of the H2020 ETN SULTAN (European Training Network for the Remediation and Reprocessing of Sulfidic Mining Waste Sites) project, the release of metal(loid)s from different building materials, in which mining waste (including mine tailings and waste rock) was used as a raw material, was investigated. The waste rock and mine tailings originated from an active Cu-Zn mine and were characterized by a high content of Cu, Zn, Pb, and As. Part of the waste rock was cleaned by flotation before use, while the mine tailings were used without pre-cleaning. 

Bricks, clinkers, cements, and inorganic polymers in which from 14 wt% up to 100 wt% of primary raw materials had been replaced by mine tailings or (cleaned) waste rock, were subjected to various leaching tests: (i) a single batch leaching test (EN 12457-2), (ii) the Toxicity Characteristic Leaching Procedure (TCLP), and (iii) a cascade leaching test (NEN 7349). The influence of the processing of the mine waste, the pH of the leachates, and the mineralogical composition of the building materials on the immobilisation of metal(loid)s were assessed.

Clinkers and cements were the most efficient building materials to immobilise all metal(loid)s, even when uncleaned waste materials were used as a raw material. For the inorganic polymer produced from uncleaned mine waste rock, the leaching of Zn, Pb, Cu, and As was a point of concern, promoted by the alkaline pH of this material. The bricks had a lower release of metal(loid)s  compared to the inorganic polymers, which also showed the importance of an efficient cleaning procedure before using the mine waste as a raw material.