Abstract: The residual metal content of tightly chelated heavy metal-containing effluents is reduced by carrying out a sulfide precipitation process in the presence of a seed material comprising an added unchelated soluble heavy metal salt, preferably with an adjustment of pH to at least above about 9.0, with optional variations including passage through a mixed filter media comprising at least two particulate ingredients and regeneration of the used filter media.

Abstract: Ammoniacal solutions that have been employed in a bath for etching copper such as in the manufacture of printed circuits is reconstituted or regenerated to substantially fully remove copper solute therefrom and retain the ammonia content thereof in such a manner as to enable a continuous reuse of the etching solution. The process is conducted in such a manner that no contaminating metal powder, compounds or sludge are formed. The reconditioning is effected by introducing used ammonia solute containing ammonium etching solution into an electrolytic bath in which cathodic and anodic electrode containing compartments are defined by a cationic permeable membrane therebetween with the cathodic compartment having an electronegative cathode electrode plate therein.

Abstract: A system and process has been devised for measuring and constantly maintaining a desired concentration of soluble sulfides in a processing solution for the purpose of fully maintaining its function. Sulfide regenerating solution is automatically introduced into the processing solution in an amount as constantly determined by concentration variations in the processing solution, to thus provide the processing solution with its most effective sulfide content. A constant take-off flow of processing solution is thoroughly mixed with a sulfide stabilizing solution flow to provide a tempered solution flow that is passed through a flow block having a sulfide measuring electrode and a reference electrode. Variable negative voltage generated on the sulfide electrode is sensed and compared with a substantially constant voltage generated on the reference electrode and is amplified in a controller assembly.