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Electrolytic Nickel Bath Rinsewaters by Membrane Electrolysis
Renocell apparatus for the removal of metals ions from plating effluents
The recovery of metals and the maintenance of process solutions used in the metal finishing industry has become an essential component of the plating operation not only due to stricter environmental compliance regulations but also as a means of recovering the metal and increasing competitiveness.
Schematic of the cross-section of membrane electrolysis cell
The goal of this project is to investigate pollution prevention technologies that can reduce the costs of the nickel rinse water recovery process at small plating shops. At present our laboratory is conducting studies with a mid sized plating facility in Cincinnati on removing nickel from a nickel Watts bath rinse water using a combination of a high surface area electrowinning cell and a weak base anion-exchange unit. The electrowinning unit electrochemically reduces the nickel on a carbon felt cathode and the anion exchange unit replaces sulfate and chloride ions with hydroxide ions keeping the rinse water pH in.The drawback to this dual system is the necessity of regenerating the ion exchange resin at intervals with its associated labor costs and downtime and the disposal of the sodium sulfate and sodium chloride from the regeneration.It is envisioned that the dual electrowinning and ion exchange units could be replaced by a single-step membrane electrolysis unit (see schematic).The membrane electrolysis unit would be constructed by simply replacing the current cation exchange membrane in the electrowinning cell with an anion exchange membrane.The nickel solution would be passed through the catholyte compartment and the nickel metal plated on the cathode.The sulfate ions would pass through the anion exchange membrane into the anolyte compartment and by combining with the hydrogen ions produced at the anode would generate sulfuric acid which can then be reused by the plating shop in the pre-rinse steps for metal plating parts.
Contact Information:
Contact:Michael Gonzalez
(513) 569-7180
gonzalez.michael@epa.gov
>Postal Address:
26 West Martin Luther King Drive
Mail Stop 443
Cincinnati, Ohio 45268