Metal Removal and Cyanide Destruction in Plating Wastewaters Using Particle Bed Electrodes.

摘要

A small (0.5gpm) pilot-plant unit for metal and cyanide removal was constructed and demonstrated by operation on cadmium and zinc rinsewaters at a plating plant. With single-stage operation 73% of an initial 22ppm cadmium and 79% of an initial 44ppm cyanide were removed. Retreatment of the effluent (equivalent to two-stage operation) gave overall removals of 95% of the cadmium and 94% of the cyanide. Similar two-stage treatment of zinc rinsewater gave overall removal of 75% of an initial 57ppm zinc and 78% of an initial 195ppm cyanide. The heart of the unit is an electrolytic cell with tin cathode and graphite anode particle bed electrodes and a cellophane separator. Sequential water flow through the electrodes gives concurrent removal of metal and cyanide under action of applied DC voltage. Design of the unit was based on design of and test results with a laboratory scale apparatus. Best removals were obtained with added NaCl as supporting electrolyte and anode bed effluent recirculation. Estimated total treatment costs,derived from a subsequent corporate-funded study,are $1.64/1000sq ft plated,with cadmium plating rinsewater use at 3.5gpm for 2500sq ft/hr and 40hr/week operation.