Cu recovery from industrial wastewater using brown coal

• In the range of pH 9–11.5, the ion exchange is the main mechanism of copper loading.
• Initial volatile matter combustion is accelerated by copper loading.
• The activation energy of initial combustion is affected by Cu-loading amount.
• When Cu-loading is 8.6 wt.%, the activation energy is an estimated 56% of raw coal.

The etching process by copper chloride is widely used in printed wiring board manufacturing. Brown coal has an ion exchange ability because it has carboxy groups and hydroxyl groups in it. Using this ability of brown coal, the copper recovery from the waste etching solution by low energy consumption method is studied.　Copper ion in the waste solution can be loaded on Loy Yang brown coal around 8.5 wt.% by adding ammonium hydroxide, adjusting pH to 9–11.5 and stirring the solution at room temperature. Cu-loaded brown coal can be burnt at extremely low temperature; 160–180 °C, and 0.5–1.0 μm copper oxide particles are formed as the residue. In order to commercialize the copper recovery system, since Cu-loading amount and low temperature combustion of Cu-loaded brown coal are key factors of this process cost, Cu-loading conditions and the reaction kinetics of low temperature combustion of Cu-loaded brown coal by TG analysis are studied. By the kinetic analysis using TG data, activation energy of initial combustion is affected by Cu-loading amount. When Cu-loading is 8.6 wt.%, it is estimated that the activation energy is reduced to 56% of that of the raw coal.