Recovery of cupric chloride from spent copper etchant solutions: a mechanistic study

This paper shows a mechanism for recovering cupric chloride salts from spent etchant solution used in printing circuits industry. The tested solution is an ammoniacal copper solution containing 135 g/L Cu ion with minor impurity. Copper is present as the square planar cupprammine complex. The separation method involved decomposition of the cupprammine complex in two ways, The first by hydration, and the second by acidification using concentrated HCl . The mechanism of separation proceeds by second-order bimolecular substitution reactions. Results are explained in the light of a model which assumes that successive intermediate copper compounds are formed, which were identified and separated. The final product was pure cupric chloride crystals free of ammonium ions meeting the standard specification assigned for printing industry. Parameters affecting efficiency of the method such as solution pH, dilution, addition of acid and temperature have been investigated. Maximum extent of extraction amounted to 99%.