A physicochemical investigation of the recovery of hydrous tin oxides from electroplating liquors and rinse waters

The solubility of hydrous tin oxides, precipitated from dilute halogen tinplating rinse waters, has been studied. The degree of solubility in a sodium hydroxide solution is shown to be a function of a number of factors. The precipitation time and temperature, the stannous stannic ratio and the presence of specific impurities are shown to affect the physicochemical properties of the precipitate either independently or in conjunction. The solubility of the precipitate was observed to be related to its morphology. It is suggested that this may be the result of an a/3 transformation in the hydrous stannic oxides. However, morphology was not the sole reason for changes in solubility as demonstrated by the affect of impurities. It was also demonstrated that highly soluble, rapid settling precipitates could be produced in the system with the aid of a Polyacrylamide flocculating agent