Performance of separators used to regenerate Ce(Ⅳ) from simulated spent Cr-etching solutions

in Domestic Conference (poster summary), 國內研討會(摘要海報發表)
標題Performance of separators used to regenerate Ce(Ⅳ) from simulated spent Cr-etching solutions
AuthorsKuo-Lin Huang, 黃國林, Te-San Chen 陳得三, C. Kuei-Jyum Yeh 葉桂君, & Shui-Jen Chen 陳瑞仁
出版日期May 26 2009 12:0

This paper compares the performance of two different types of separators, AMI-7001CR (anion exchange membrane) and CMI-7000CR (cation exchange membrane), used in an divided cell to electrochemically regenerate Ce(IV) from simulated spent Cr-etching solutions that are regarded as hazardous wastes containing high concentrations of protons, Ce(III), and anion impurities (e.g., SO42-, Cl-, and Cr2O72-) generated from TFT-LCD manufacturing processes. A better Ce(IV) yield along with current efficiency (CE) was found using the AMI-7001CR than using the CMI-7000CR for 0.2 M Ce(III) oxidation on a planar Pt electrode at 0.3 A/cm2 in 4 M HNO3 containing multi-impurity (0.025 M SO42- + 0.08 M Cl- + 0.016 M Cr2O72-). This phenomenon is mainly associated with the anion impurities and ion exchange membranes used in this system. At the Pt anode, the chlorine ions released electrons via 2Cl- → Cl2 + 2e- (E0 = 1.358 V) to compete with the Ce(III) oxidation (E0 = 1.610 V), leading to the decline of Ce(IV) yield as well as CE. Moreover, the Cr2O72- might cause passivation of the electrode surface and inhibition of the Ce(III) oxidation reaction. During the electrolytic operation, the AMI-7001CR was useful to exchange anion impurities from anolyte to catholyte, and thus lowered the anion purity concentration in the anolyte, resulting in a lower decrease of Ce(IV) yield and a higher CE. For 300 min electrolysis at 0.3 A/cm2 in the anion exchange membrane assisted system, either Ce(IV) yield or CE was only 2% lower than that in the system without any impurity. Therefore, the anion exchange membrane is more suitable than the cation exchange membrane for the Ce(IV) regeneration in spent Cr-etching solutions from TFT-LCD manufacturing processes.

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