2014 Volume 93 Issue 6 Pages 542-547
The etching process by copper chloride is widely used in printed wiring board manufacturing. Unfortunately, almost copper waste solution is treated by neutralization method and the precipitated sludge is dumped on the ground without copper recovery. Brown coal has ion exchange ability because it has carboxy groups and hydroxyl groups in it. Using that ability of brown coal, 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 in 9-11.5 and stirring at room temperature. When pH range is in 9-11.5, it is considered that copper and ammonium complex ions such as tetraamminecopper(II) ion [Cu(NH3)4]2+ are produced and exchanged with proton of carboxy groups in brown coal. 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. From XRD analysis at the middle of burning, it is considered that Cu2O plays a role of catalyst of gasification and/or oxidation. It was shown that low energy consuming copper recovery method is feasible by using capability of ion exchange of brown coal and catalysis of Cu-loaded brown coal.