Studies of Anode Slime Sintering/Coalescence and Its Effects on Anode Slime Adhesion and Cathode Purity in Copper Electrorefining

Four series of copper electrorefining tests were performed using four different types of anodes, which have different inclusion types. Test results show that the high impurity anodes and the scrap cycle anodes have more inclusions associated with the Pb-Bi-S compounds that show evidence of sintering at 50 degrees C, whereas the low impurity anodes and the strip cycle anodes have more inclusions related with the Pb-Bi-S-As compounds that demonstrate evidence of sintering above 65 degrees C. Inclusion (slime) particles sinter and adhere to the anode surface, which happens at lower temperatures for the high impurity anodes and the scrap cycle anodes. Correspondingly, there are different slime distributions for each type of anode. The anode slimes layers in front of anode surfaces for different types of anodes were observed and analyzed by SEM/EDS. Results show significant effects of particle sintering near anode surfaces, which was also demonstrated by slime size distributions at different cell temperatures. Experimental results demonstrate that slime particle sintering and coalescence can improve anode slime adhesion and reduce the amount of suspended slimes, which are a major source of copper cathode contamination. Arsenic content in copper anode and cell temperature are major factors affecting slime sintering and coalescence. (C) The Author(s) 2015. Published by ECS.