representing contact time, the square of H2O2 concentration, the square of contact time, and the product of malonic and H2O2 concentrations respectively were lower than 0.05 (Table ) which means that these terms are significant in influencing the efficiency of Cu leaching. However, the p-value of the model terms X1, X2, X1 2 , X1X3, and X2X3 are greater than 0.05 indicating that these model terms are not significant in the determination of Cu leaching efficiency. Therefore, amongst the independent variables, the contact time has the single highest influence on the leaching efficiency of Cu.