Copper recovery and spent ammoniacal etchant regeneration based on hollow fiber supported liquid membrane technology: From bench-scale to pilot-scale tests

Abstract

One of the key steps in printed circuit board (PCB) production is etching of a thin copper layer. Ammoniacal etching solutions are widely used for this purpose. Earlier we have developed a supported liquid membrane based method to treat wastewater containing ammonia and copper (up to 1 g/L), where the membrane is stable for at least 1 month and can be easily regenerated if necessary [1]. Now we are describing an effective hollow fiber supported liquid membrane (HFSLM) based technology for copper recovery from spent ammoniacal etching solutions, where copper is present in much higher concentrations. A bench-scale HFSLM system with 1.4 m2 effective membrane surface area was firstly used to screen out the optimal hydrodynamic and other operation conditions for potentially practical spent ammoniacal etching solutions treatment. It was found that the excess of ammonia in spent etching solutions had negative effect on copper removal, especially when copper concentration became low in the feed solutions as the result of treatment. Different methods were employed to control the ammonia level and their efficiencies were compared. Finally, successful pilot-scale experiments were conducted on a hollow fiber membrane contactor with a surface area of 130 m2. The process results in copper removal by a factor of ∼3000 from spent etching solution through the membrane and formation of nearly saturated copper sulfate solution in the sulfuric acid, used as a striping phase. Compositions of the regenerated etching solution and purity of CuSO4·5H2O crystals formed in the striping phase were comparable or even better than their commercial analogues. The stability of the pilot-scale system is promising for further industrial scale-up. © 2006 Elsevier B.V. All rights reserved.