Electrochemical reactor with rotating cylinder electrode for optimum electrochemical recovery of nickel from plating rinsing effluents

摘要

This study is devoted to analyze the metallic electrochemical recovery of nickel from synthetic solutions simulating plating rinsing discharges, in order to meet the water recycling policies implemented in these industries. These effluents present dilute Ni(Ⅱ) concentrations (100 and 200 ppm) in chloride and sul-fate media without supporting electrolyte (397-4202 μSm~(-1)), which stems poor current distribution, limited mass transfer, ohmic drops and enhancement of parasitic reactions. An electrochemical reactor with rotating cylinder electrode (RCE) and a pH controller were utilized to overcome these problems. The pH control around 4 was crucial to yield high purity nickel, and thus prevent the precipitation of hydroxides and oxides. Macroelectrolysis experiments were systematically conducted to analyze the impacts of the applied current density in the recovery efficiency and energy consumption, particularly for very diluted effluents (100 and 200 ppm Ni(Ⅱ)), which present major recovery problems. Promising nickel recoveries in the order of 90% were found in the former baths using a current density of -3.08 mA cm~(-2), and with overall profits of 9.64 and 14.69 USD kg~(-1), respectively. These estimations were based on the international market price for nickel ($18 USD kg~(-1)).