Quasi-in situ observation of single nodule morphology and current response characteristics during short-circuit processes in copper electrorefining

Abstract During the copper electrorefining process, short circuits between anodes and cathodes caused by nodules lead to significant current efficiency losses and product quality degradation. By investigating the morphological evolution and current response characteristics during the growth of a single nodule, we can gain a deeper understanding of the short-circuit formation mechanism, establishing a theoretical framework for real-time current monitoring. This study investigated the morphological changes of a single pre-set artificial nodule throughout its growth-to-short-circuit process using a laboratory-scale copper electrolytic refining cell, and analyzed the influence of nodule growth on cathode current. The results showed that once a nodule begins to grow, its surface becomes rough, with dense spherical and worm-like protrusions forming at the middle and neck zones. Subsequently, an annular structure parallel to the cathode plate gradually develops around the nodule neck. As electrolysis proceeds, the nodule head expands into a distinct cauliflower-like shape. Eventually, short circuits occur when individual branches contact an anode, triggering a sharp rise in cathode current followed by high-amplitude oscillations and transient disconnection events. After short-circuiting, radial growth at the nodule root and middle zones essentially ceases, while the dominant branches at the head develop a finger-like structure. The length and diameter of the finger-like structure exhibited a linear relationship with the cumulative electrolysis time. The unstable point-contact between the finger-like structure and the anode resulted in frequent transient disconnections.