The precipitation of problematic Group 15 elements (As, Sb and Bi) in synthetic and industrial copper electrorefining electrolyte was examined. Using published thermodynamic values, the solubility products of BiAsO4 and SbAsO4 at 65 °C were calculated as 0.69 and 1.50 g2 L−2, respectively. Experiments were performed where solutions were spiked with arsenic, bismuth and/or antimony, and the start of precipitation was determined based on changes in solution turbidity. For arsenic concentrations of 9–13 g L−1, the concentrations of Bi necessary for the beginning of BiAsO4 precipitation were higher for the industrial electrolyte (0.25–0.50 g L−1) than the synthetic electrolyte (0.05–0.10 g L−1) at each arsenic concentration examined. The results indicate that industrial electrolyte has a greater capacity than the synthetic electrolyte with respect to the precipitation of BiAsO4. In the synthetic electrolyte, precipitation occurs at 0.30 g L−1 of Sb(III) in the presence of 9 g L−1 of As(V) without the addition of Bi, and 0.20 g L−1 with the addition 0.15 g L−1 Bi. At 10–12 g L−1 of As(V), a concentration of 0.10 g L−1 of Sb(III) produced precipitation. In industrial electrolyte, the increase in Sb(V) from 0.10 g L−1 to 0.16 g L−1, significantly increased precipitation. The presence of As and Sb in the +3 and + 5 appears to influence the solubility of antimony. Furthermore, the industrial electrolyte has enhanced solubility of Sb(III) up to 0.40 g L−1 before precipitation was detected.