Presented paper

IMWA2019 Students work

Electrochemical Treatment Of Mining Waters

Mamelkina, Maria; Tuunila, Ritva; Sillänpää, Mika; Häkkinen, Antti
LUT University, Finland

Mining waters are often heavily contaminated with anionic and cationic species. Among the most prevalent and harmful compounds are toxic metals and anionic contaminants, such as sulfate, nitrate, chloride and cyanide. It is essential to treat discharged wastewaters and bring the concentrations of harmful dissolved contaminants to acceptable discharge levels. Another mining wastewater management concept is to reuse and recycle water within the process sections. Firstly, it makes mining operation more economically and environmentally feasible. Secondly, it allows for treating water only to a level suitable for a certain process rather than to an acceptable discharge level.

This research is intendent to study the removal of cyanide, sulfate, chloride and nitrate from mining waters using electrochemical treatment. Electrolysis and electrocoagulation using different electrodes materials (iron, aluminum for electrocoagulation, DSA, DDB and carbon for electrolysis) resulted in favouring of anions removal. The tests were performed in batch and continuous modes with real and synthetic mining waters. Additionally, performances comparison of electrolysis, electrocoagulation and chemical coagulation for cyanide removal was completed.

Sulfate was almost completely removed when iron and aluminum electrodes were tested as anode and cathode respectively. The cyanide removal of 99% was achieved during electrocoagulation using Fe-Fe pair and during electrolysis with DSA as an anode. Continuous electrochemical treatment of cyanide with iron electrodes resulted in high cyanide removal and a shorter treatment time when compared with batch operation. Current charge has been chosen as a scale-up parameter. Under applied experimental conditions, nitrate and chloride were not removed, but its concentration was maintained at the same level during the tests.

The conducted research on the electrochemical removal of anions from mining waters has provided an understanding of the phenomenon occurring during the process. The knowledge about the removal mechanisms of the anionic contaminants from mining waters favors the possible development of electrochemical treatment technologies and scale-up of the existing units.