The Research On Selective Separation Of Copper From Spent Ammoniacal Etchant And Its Reuse Process

Alkaline etchant, one of the chemicals used in PCB, is consumed in large amounts and output in a strong corrosive waste containing highly concentration of copper, ammonium chloride, ammonia and etc. Up to now, this spent etchant has been treated on the basis of the final control and result in secondry pollution . In this paper, from the strategy point of cleaner production , the IEM-E(ion exchange membrane-deposition) was used for the first time to selectivly separate copper from the spent etchant, and all the ingredients useful for copper etching were recovered at the same time. Different factors, such as copper contents in the spent etchant, cell voltage, temperature of IEME-E process, were studied by operating the cathode current efficiency. The experiments showed that the optimum condition for the IEM-E process were: copper contents in the cathode chamber =34.1g/L, cell voltage=2. 5v, operating temperatur=30°C, and the current efficiency can be as high as 87. 5% under the condition. The cathode electric current efficiency can be modified to some degree by addition of corrosion inhibitors to the cathode chamber. The shape of the seperated copper from the cathode was dependent on the current density of the IEM-E. The recyling tests showed that the regenerated echant was as good as that of the fresh etchant, and its etching rate and capacity were 0. 339um/s and 149g/L respectively, which can meet the PCB requirements. And these turn into a cleaner production process by using regeneration and reuse the treating method for the ammoniacal etchant in its usage and disposal.