- 學位論文
過氯酸溶液中Ce(IV)電再生之研究
Electro-regeneration of Ce(IV) in perchloric acid solutions
摘要
薄膜電晶體液晶顯示器（TFT-LCD）的製程中常會產生大量的鉻蝕刻廢液，其含有高量的鈰，具有回收價值。而新鮮鉻蝕刻液主要以硝酸銨鈰溶於高濃度硝酸或過氯酸配製而成。本研究探討以過氯酸為介質之仿鉻蝕刻廢液中鈰(IV)之電再生，測定過氯酸中Ce(IV)/Ce(III)氧化還原電化學特性及其質傳參數(擴散係數(D))並測試操作參數對過氯酸介質模擬鉻蝕刻廢液中鈰(IV)電再生之影響。 研究結果顯示，在過氯酸中，Pt、BDD及GC電極上Ce(IV)/Ce(III)氧化還原反應的電化學特性皆為準可逆(quasi-reversible)。以循環伏安法(CV)測試所得3種電極上Ce(III)之擴散係數由高至低分別為Pt > BDD > GC (1.00×10-5、4.81×10-6及4.25×10-6cm2/s)。而以線性伏安法(LSV)測試所得2種旋轉盤電極上Ce(III)之擴散係數為Pt (2.85〜3.58×10-5 cm2/s) > GC (5.41~6.08×10-6 cm2/s)。以4cm2之BDD電極在4℃、電流密度1A/cm2及雙槽交換膜為AMX操作條件下，在配製0.2M Ce(III)/10%過氯酸溶液中，Ce(IV)電再生之產率可達到97.4%，其質傳係數(kL)與外顯速率常數(k)值分別為2.19×10-2 cm/s及8.74×10-4 1/s。增加過氯酸的濃度及Ce(III)濃度可增加鈰的產率，而過氯酸中存在Cr(VI)會影響Ce(IV)電再生之產率，且雙槽之Ce(IV)電再生效果明顯優於單槽。
並列摘要
The manufacturing processes of thin film transistor liquid crystal display (TFT-LCD) usually produce a lot of spent Cr-etching solutions which contain abundant cerium and are deserved to be regenerated and recycled. Fresh Cr-etching solutions are often prepared by dissolving Ce(NH4)2(NO3)6 in concentrated nitric or perchloric acid. In this study we explored the electro-regeneration of Ce(IV) in simulated spent Cr-etching solutions (perchloric acid matrix) under different operating parameters and measured the electrochemical characteristics and diffusion coefficients of Ce(III)/Ce(IV) couple on different electrodes. Experimental results show that in perchloric acid solutions, the electrochemical characteristics of Ce(III)/Ce(IV) redox reaction on Pt, BDD, and GC electrodes were quasi-reversible in cyclic voltametry (CV) analysis. According to CV tests, the magnitude of Ce(III) diffusion coefficients for the three electrodes were in the order Pt > BDD > GC (1.00×10-5, 4.81×10-6, and 4.25×10-6cm2/s). In LSV measurements using GC and Pt rotating disk electrodes, the diffusion coefficients of Ce(III) were greater on Pt (2.85−3.58×10-5 cm2/s) than on GC (5.41−6.08×10-6 cm2/s). The Ce(IV) percent yield of Ce(IV) electro-regeneration in prepared 0.2 M Ce(III)/10% perchloric acid solution achieved the highest value (97.4%) at 4oC and 1A/cm2 on BDD (4cm2) in a divided cell installed with an AMX separator. and the mass transfer coefficient (kL) and apparent rate constant (k) were 2.19×10-2 cm/s and 8.74×10-4 1/s, respectively. Increasing the concentration of perchloric acid or Ce(III) increased the Ce(IV) yield. The presence of Cr(VI) in perchlorate acid solution influenced the Ce(IV) yield of Ce(IV) electro-regeneration. The divided cell was better than an undivided one for Ce(IV) regeneration.
參考文獻
延伸閱讀
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