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Cu recovery from industrial wastewater using brown coal

Fuel Processing Technology
DOI: 10.1016/j.fuproc.2014.09.029
  • Copper Recovery
  • Brown Coal
  • Wastewater
  • Low Temperature Combustion
  • Catalyst
  • Chemistry


Abstract The etching process by copper chloride is widely used in printed wiring board manufacturing. Unfortunately, almost all copper waste solution is treated by neutralization method and the precipitated sludge is dumped into the ground without copper recovery. 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 8.5wt.% by adding ammonium hydroxide, adjusting pH to 9–11.5 and stirring the solution at room temperature. When pH range is adjusted to 9–11.5, it is considered that ion exchange is the main mechanism of the copper loading and 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 0.5–1.0μm copper oxide particles are formed as the residue. In order to commercialize the copper recovery system, control factors of the copper particle size, the chemical structure, the purity or contaminants, the process cost and scale-up factors should be clarified. Since Cu-loading amount in brown coal 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 8.6wt.%, it is estimated that the activation energy is reduced to 56% of that of the raw coal.

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