From copper concentrate to Cu-based metal oxides for thermochemical heat storage: Impurity impact analysis and redox performance optimization

Abstract

Copper oxide is a promising material for thermochemical heat storage, but its high cost remains a challenge for large-scale applications. To address this issue, we explore using relatively cheap copper concentrate as a starting material. We heat treat the concentrate and find that it mainly consists of CuO and CuFe2O4. Our thermogravimetric analysis shows that the re-oxidation performance of the concentrate is poor, with only 12.5 % reaction, which is about 32.5 % lower than that of commercial copper oxide (≥99.5 %). Our investigation reveals that impurities in the concentrate inhibit the re-oxidation of copper oxide, and their removal is essential to improve performance. Based on these findings, we optimize the existing purification process that removes impurities to less than 0.1–0.5 wt%. The resulting copper oxide has a content above 99 % and an extraction rate of over 97 %, which can minimize the waste of raw materials and reduce the influence of impurities. The redox properties of the purified copper oxide are comparable to those of commercially available copper oxide. On this basis, the self-made CuO was modified by doping with cheap MgO and Al2O3, whose reduction conversion rate and reoxidation rate could still reach 97.0 % and 96.3 % after 250 redox cycles.