The effects of salinity and temperature on phase transformation of copper-laden sludge

► Formation of CuAl2O4 was enhanced by elimination of salt content. ► CuAl2O4 was formed at 700-1100 °C and transformed into CuAlO2 at 1200 °C. ► Formation of CuAl2O4 is a temperature-dependent and energy-favored reaction. ► Leaching level of copper ions coincided with the formation of CuAl2O4. ► More than 95% of copper ion was stabilized at 1000 °C for 3 h.