The use of a rotating cylinder electrode to recover zinc from rinse water generated by the electroplating industry

This work concerns the application of a laboratory scale rotating cylinder electrode (RCE) to recover zinc from rinse water generated by the electrolytic zinc process (initially 1,300, 4,400, 50, 20 mg L⁻¹ of Zn(II), Fe(III), Ag(I) and Cr(VI), respectively, at pH 2), although it is also applicable to other electroplating industries. Experimental results demonstrated the convenience of the removal of ferric ions, as (Fe(OH)_3(s)) by a pH adjustment to 4, before zinc electro recovery on the RCE. The generation of smooth zinc deposits on the RCE was obtained at Reynolds numbers within the range of 15,000 ≤ Re ≤ 124,000 and limiting current densities (J_L) in the interval of −4.8 to −13 mA cm⁻². The zinc recovery reached a conversion of 67% in 90 min of electrolysis for Re = 124,000 and J = −13 mA cm⁻², 21% current efficiency, and energy consumption of 9.5 kWh m⁻³. The treated solution can be recycled back through the same rinsing process.