| abstract |
Sulfate-free electroless copper baths comprising cupric ions, formaldehyde, formate ions, hydroxyl ions, a copper counterion, e g. preferably a monovalent anion such as acetate, nitrate or formate, and copper chelant such as an alkali metal salt of aminotris(methylenephosphonic acid), biscarboxymethylaspartic acid, ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), gluconic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, mucic acid, D-saccharac acid, tartaric acid and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine are amenable to the recovery of copper, e.g. from purge streams, using the methods and apparatus including solvent extraction, e.g. employing hydroxamic acid extractants, anion filtration, ion-exchange and chelant precipitation. |