A design of experiment approach on NaOH-Na 2 S 2 O 8 alkali-oxidising leaching of copper from Cu-As ore

Current copper reserves exhibit more complex mineralogy, including higher concentrations of detrimental elements such as arsenic. This trend underscores the need for efficient processing routes for Cu–As ores to sustain copper production. In this study, alkali–oxidising leaching process is investigated as a potential method for Cu extraction from arsenic-bearing minerals. Statistical analysis, through the design of experiment approach, shows that all three main effects, temperature, NaOH concentration, and Na2S2O8 concentration, are significant. Interactions between temperature-NaOH concentration and NaOH-Na2S2O8 interaction are also significant. Increasing temperature may increase Cu recovery up to an optimum point. Higher temperatures coupled with excess NaOH addition inhibits Cu extraction. Meanwhile, increasing persulfate concentration promotes Cu recovery. The optimum settings were found to be 81.85°C, 1.166 mol/L NaOH, and 0.757 mol/L Na2S2O8 which yielded a predicted Cu recovery of 89.92%. Kinetic modelling through the shrinking core model for heterogeneous reactions shows that the leaching of Cu is controlled by mixed diffusion through the product layer and pores of the ore particles. Overall, the design of experiment approach through central composite design is successfully implemented in the optimisation of alkali oxidising leaching of Cu from Philippine Cu-As ore.