This study investigated the effects of the initial Ce(III) concentration, nitric acid concentration, anion impurity, and cell device on Ce(IV) regeneration in simulated spent Cr-etching solutions from thin-film transistor liquid crystal display manufacture. Increasing HNO(3) (electrolyte) concentration (0.5-4 M) favored 0.2 M Ce(III) electro-oxidation, Ce(III) diffusion [(0.37-3.32) x 10(-6) cm(2) s(-1)], and internal cell resistance reduction. The amount of Ce(IV) regenerated from Ce(III) electro-oxidation and the current efficiency (CE) at 0.13 A cm(-2) electrolysis on Pt increased with increasing initial Ce(III) concentration in 4 M HNO(3) without impurities in a divided cell with an anion-exchange (AMI-7001) separator. Both Ce(IV) yield and CE were lowered in the copresence of multiple impurities, and the adverse influence of a single anion impurity on the Ce(IV) yield and CE was in the order Cl(-) > SO(4)(2-) > Cr(2)O(7)(2-). The apparent rate constant of Ce(III) oxidation without impurity (1.32 x 10(-4) s(-1)) was approximately fourfold that with multiple impurities; nevertheless, the two cases exhibited similar Ce(IV) yields or CEs at 0.13 A cm(-2) electrolysis for 300 min. For the Ce(IV) regeneration, the divided cell was superior to an undivided cell in the absence/presence of multiple impurities, and the AMI-7001 was better than a cation-exchange separator (CMI-7000). (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3236628] All rights reserved.
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Huang, K.-L., & Chen, T.-S. (2009). Electro-Regeneration of Ce(IV) in Simulated Spent Cr-Etching Solutions Containing Abundant Ce(III). Journal of The Electrochemical Society, 156(12), E192. https://doi.org/10.1149/1.3236628