Electro-assisted reduction of chalcopyrite using acetic acid. The feasibility to use weak and less aggressive acids

This work presents for the first time an electrochemical study of the electro-assisted reduction of chalcopyrite using an organic weak acid. The chalcopyrite reduction was assessed at the microelectrolysis level using different electrochemical and characterization techniques. The voltamperometric and FESEM/EDS results revealed that chalcopyrite can be reduced to bornite at more cathodic potentials than -0.25 V vs SHE. When the acetic acid concentration was increased from 0.5 to 3 M, the chalcopyrite reduction kinetics was favored liberating a higher amount of chalcopyritic iron into the bulk solution. The Tafelarian analysis of the system showed that the exchange current density of the chalcopyrite reduction was increased from 1.72x10-7 to 9.71x10-7 A/mm2 at 0.5 and 3 M acetic acid, respectively. A constant Tafel slope of -0.2 V/dec was found in the range of 0.5-3 M acetic acid, which revealed that the same rate determining step (rds) controlled the chalcopyrite reduction. The calculation of the reaction order confirmed that the formation of monoatomic hydrogen from undissociated acetic acid molecules is the rds. The effect of multiple cathodic polarizations was also evaluated on the solid products formed during the chalcopyrite reduction. The X-ray diffraction analysis revealed the formation of less refractory phases. The effect of agitation was studied in the acetic acid system, the results showed that the chalcopyrite reduction kinetics was considerably increased producing metallic copper.

Automated summary

This study presents an electrochemical investigation of the electro-assisted reduction of chalcopyrite using an organic weak acid for the first time. The experimental results reveal that increasing the concentration of acetic acid promotes the reduction of chalcopyrite, resulting in the release of a higher quantity of chalcopyritic iron. It is also found that the rate determining step of the reduction reaction involves the formation of monoatomic hydrogen from undissociated acetic acid molecules.