Electro-regeneration of Ce(Ⅳ) in real spent Cr-etching solutions

摘要

This paper presents the electro-regeneration of Ce(Ⅳ) in real (hazardous) spent thin-film transistor liquid-crystal display (TFT-LCD) Cr-etching solutions. In addition to Ce(Ⅲ)＞ Ce(Ⅳ) in diffusivity, a quasi-reversible behavior of Ce(Ⅲ)/Ce(Ⅳ) was observed at both boron-doped diamond (BDD) and Pt disk electrodes. The Ce(Ⅳ) yield on Pt increased with increasing current density, and the best current efficiency (CE) was obtained at 2 A/2.25 cm~2. The performance in terms of Ce(Ⅳ) yield and CE of tested anodes was in order BDD＞Pt＞dimensional stable anode (DSA). At 2A/2.25cm~2 on Pt and 40℃ for 90min, the Ce(Ⅳ) yield, CE and apparent rate constant (k) for Ce(Ⅲ) oxidation were 81.4%, 21.8% and 3.17 x 10~(-4)s~(-1) respectively. With the increase of temperature, the Ce(Ⅳ) yield, CE, and k increased (activation energy = 10.7 kJ/mol), but the specific electricity consumption decreased. The Neosepta CMX membrane was more suitable than Nafion-117 and Nafion-212 to be used as the separator of the Ce(Ⅳ) regeneration process. The obtained parameters are useful to design divided batch reactors for the Ce(Ⅳ) electro-regeneration in real spent Cr-etching solutions.