Kinetics of Copper Cementation by Aluminum Powder from Sulfate Solution under Ball Milling Conditions

Despite a great thermodynamic driving force¡ copper cementation by aluminum from sulfate solutions involves a relatively slow kinetics due to the presence of the passive oxide film on the surface of aluminum. The previous studies have confirmed the positive effect of the presence of small amounts of chloride ion on reducing the scale of this problem. In this paper¡ the effect of concurrent ball milling on the kinetics of this process has been investigated. The cementation experiments were carried out in a polyamide jar with alumina balls inside by planetary ball milling. The studied parameters were ball number (0¡ 4)¡ temperature (25-55 °C) and time (0-240 s). All experiments were conducted at constant condition of [Cu2] = 6 g/L¡ [Cl−] = 75 mg/L¡ rotation speed of 160 rpm¡ average aluminum particle size of 279 µm and [H] = 1.94×10-3. The results showed that concurrent ball milling reduces the induction period of the cementation process to less than 120 s. The apparent rate constant of cementation showed the positive influence of simultaneous milling on the kinetics of the studied cementation process. Moreover¡ activation energies of the induction and main periods were calculated to be respectively 86 and 26 kJ.mol-1¡ indicating the shift of the reaction mechanism from chemical control to mass transfer control.