ABSTRACT
Significant research has been conducted on copper corrosion and solubility in drinking water, including the establishment of the "cupric hydroxide model". The model describes the temporal aging and associated solubility changes of copper minerals beginning with the most soluble solid, cupric hydroxide. Although the model explains copper levels in field observations well, there are aspects of the model that are not well understood, including a lack of evidence of the presence of cupric hydroxide in drinking water distribution systems. This study aimed to understand the effect of water chemistry on the solubility and properties of newly precipitated cupric solids, including mineral identification. Bench-scale copper precipitation tests were performed in water under a matrix of pH and dissolved inorganic carbon conditions. Copper solids were analyzed using a combination of materials analysis tools including XRD, FT-IR, TGA, and inorganic carbon analyses. Copper solids were X-ray amorphous, isotropic, and were light blue to blue. Based on repeated analysis, georgeite (Cu2(CO3)(OH)2·6H2O) was conclusively identified as the solid at all test conditions. Georgeite is an extremely rare, amorphous malachite analog, and because of its rarity, very little has been reported on its presence in any environment.
