Approaches to Enhancing Cathodic Nickel Recovery from Ni-EDTA Containing Synthetic Wastewaters

Ethylenediaminetetraaceticacid (EDTA) is widely employed as achelating agent in the electroless nickel plating industry to formstable metal-organic complexes (e.g., Ni-EDTA). These metal-organiccomplexes cannot be removed from plating wastewaters by traditionaltreatments in a cost-effective way. While electrochemical advancedoxidation processes (EAOPs) have been utilized for the efficient degradationof Ni-EDTA at the anode, challenges remain in the simultaneous andeffective recovery of nickel at the cathode. In this study, we investigatethe efficacy of five cathode materials [i.e., carbon felt (CF), titaniumplate, graphite plate (GP), copper plate, and stainless-steel plate]with respect to Ni recovery. The highest Ni removal efficiency of81.6 & PLUSMN; 0.1% was achieved with the carbon felt cathode which was30% higher than that of the titanium cathode (52.1 & PLUSMN; 1.4%) withthe improvement in performance attributed to the higher rate of masstransport of Ni ions (CF: 4.3 & PLUSMN; 0.4 x 10(-4) s(-1) vs Ti: 1.8 & PLUSMN; 0.2 x 10(-4) s(-1)) toward the nanowire structure of carbon feltand to the large surface area of the carbon felt cathode comparedwith the other cathodes. While the chemical composition of the depositswas independent of the cathodic material or structure, the morphologyof deposition varied with the cathode material. The accumulated Nion the carbon felt surface was successfully recovered either as anickel salt solution by acid leaching or as high purity NiO by calcinatingthe Ni-loaded carbon felt cathode at over 800 & DEG;C. The performanceof the regenerated carbon felt after acid leaching was comparableto that of the fresh cathode even after 10 cycles of use and regenerationvia acid leaching with this result confirming the stability and reusabilityof the carbon felt material. Approachesto optimizing the removal and recovery of nickel,an element of increasing value, from electroless wastewaters via electrochemicalmethods are examined.

Automated summary

In this study, the efficiency of five cathode materials (carbon felt, titanium plate, graphite plate, copper plate, and stainless-steel plate) in recovering nickel was investigated. The highest Ni removal efficiency of 81.6% was achieved with the carbon felt cathode, which was 30% higher than that of the titanium cathode. The chemical composition of the deposits was independent of the cathodic material, but the morphology of deposition varied with the cathode material. The accumulated Ni on the carbon felt surface was successfully recovered either as a nickel salt solution by acid leaching or as high purity NiO by calcinating the Ni-loaded carbon felt cathode at over 800°C. The regenerated carbon felt showed comparable performance to the fresh cathode even after 10 cycles of use and regeneration, confirming its stability and reusability.