光碟片回收製程廢水物化處理

國內廢光碟片回收製程中產生高濃度COD及高pH值廢液，而在實廠中有兩股廢液，一股廢液(以下簡稱廢液A)是使用大量液鹼及漂白水攪煮破碎廢光碟片，將光碟片上UV硬化膠、染料及金屬反射層剝離聚碳酸酯樹脂，另一股廢液(以下簡稱廢水B)是將攪煮完之聚碳酸酯樹脂清洗，因廢液A中含有大量懸浮及半溶解性UV硬化膠，所以實驗利用土地面積需求小之物化處理流程處理廢液，並找出較經濟有效之流程、藥劑種類及操作參數，將獲取實用之操作控制參數以應用至實廠操作，以增加現場試驗之成功及符合工業區污水廠進廠限值予以放流。廢液A中COD之來源主要為UV硬化膠，在回收製程中需利用液鹼使UV硬化膠水解而撥離聚碳酸酯樹脂，其單一廢液桶中廢液A經10次取樣分析，pH值及COD分別為pH13±0.5及49,000±1,500mg/L。DVD光碟片大多使用Ag及其他微量金屬做為金屬反射層，經由攪煮過程剝離聚碳酸酯樹脂，而廢液中含有Ag、Zn、Cd、Cu分別為2.57、2.62、0.02、0.007mg/L。而廢水B是清洗攪煮過之破碎聚碳酸酯樹脂，其pH值及COD分別為pH9.8及900mg/L。本實驗將廢液A利用反製程原理降低pH值使懸浮及半溶解性UV硬化膠還原為膠體狀，再利用混凝沉澱方式將膠體狀UV硬化膠去除，藉由硫酸鋁、硫酸鐵及氯化鐵混凝劑做瓶杯試驗，其加藥量分別為1,200mg/L、2,000mg/L及2,000mg/L，pH都控制在4，COD去除率分別為92%、71%及92%，實驗建議最適藥劑種類及操作參數為利用氯化鐵做混凝劑，操作條件為pH控制為4及加藥量為1,200mg/L，其優點為加藥量少且具經濟效益。廢液A經氯化鐵混凝沉澱後，COD濃度可降低至9,000mg/L，仍未符合符合工業區污水廠進廠限值(＜650mg/L)，進而使用氯酸鈉直接氧化法及Fenton法以去除剩餘之COD，其操作條件範圍分別為氯酸鈉加藥量0.5g ~ 100g/L ，而最適加藥量為50g/L，及Fenton法H2O2/Fe2+加藥量範圍為5/2.5g/L~50/25g/L，其最適H2O2/Fe2+加藥量為50/25g/L，兩種方法處理後殘餘COD濃度分別為400mg/L及3300mg/L，去除率約為95%及63%，而依此判斷氯酸鈉氧化處理殘餘COD有較好之效果，且利用氯酸鈉氧化速率快，5分鐘就能有92%去除率，所需水力停留時間較短，由此實驗建議利用氯酸鈉直接氧化處理，最適加藥量為50g/L。處理廢液A在實廠操作流程中建議最先以降低pH值至4，在利用1,200mg/L氯化鐵做為混凝劑，經由1分鐘快混(100rpm)及30分鐘慢混(10rpm)後，藉由混凝沉澱去除廢液中之膠體，再使用50g/L氯酸鈉作為氧化劑，反應時間為5分鐘，氧化殘餘之COD，再利用ORP值為是否達334mV，藉以判斷COD是否達終點。試驗所利用之土地面積要求小，且利用簡單物化處理方法處理廢液，可使設備及操作成本降低，為此試驗之優點。

關鍵字

UV硬化膠；光碟片回收；瓶杯試驗；混凝沉澱；化學氧化

並列摘要

In the disc-recovery plant, the pre-broken disc was first immersed with the alkaline liquid containing hypochlorite to solve the UV lacquer, dye and the metal reflex layer from the poly-carbonate-ester resin, the waste-liquid originated from this step containing high COD concentration and pH was named waste liquid A. The other wastewater defined as wastewater B was produced from the next step of washing the poly-carbonate-ester resin treated at the first step. This study treated both the waste liquid with coagulation and the oxidation process in order to search the operation parameters, which would be applied to design and operate the wastewater treatment process in the plant in order that the effluent quality would meet the criteria standard regulated by the industrial park. After about 10 times of investigation, it was found that the waste liquid A in a sample plastic barrel contained 49,000 ± 1,500 mg/L COD, pH of 13 ± 0.5 , and some metals of Ag, Zn, Cd and Cu contents of 2.57, 2.62, 0.02 and 0.007 mg/L individually, while the waste water B having lower pH of 9.8 and COD of 900 mg/L. The opposite alkaline pH was hypothesized to be able to re-congeal some material that solved in the liquid at the first step for treating the waste liquid. After being soured with hydrogen chloride in the waste liquid A, it was approved that the lower pH from 13 to 2 the much more grey glue material precipitated with the COD removal percentage up to 69 % in the supernatant. It was also found that that the COD removal efficient was increased with the decreasing of the pH value and the increasing addition of coagulant in the jar test with agent of aluminum sulfate, ferric sulfate and ferric chloride individually. The economical suggestion for coagulant addition were 1200, 2000 and 2000 mg/L for aluminum sulfate, ferric sulfate and ferric chloride with the COD removal of 92, 71 and 92 % respectively in the initial liquid pH of 4. After the coagulation and sedimentation in the jar test with ferric chloride, the residual COD in the supernatant was 9000 mg/L which was further oxidized by chloric acid or with Fenton method. The COD removal efficient increased with the increasing of the dosage of chloric acid from 0.5 ~ 100 g/L or the H2O2/Fe2+ from 5/2.5 ~ 50/25 g/L, and the economical dosage were suggested as chloric acid 50 g/L or the H2O2/Fe2+ 50/25 g/L which resulted in the residual COD of 400 and 3300 mg/L individually for 95 and 63 % COD removal percentages. Oxidation test showed that only 5 minutes was needed for 92 % COD removal in the case of chloric acid dosage 50 g/L. It was suggested that the raw waste liquid A was conditioned with hydrogen chloride to pH 4, then dosage of ferric chloride as 1200 mg/L for the rapid mixing 1 minute and slow mixing for 30 minutes, then after further settled in the clarifier for at least 1 ~ 2 hours, the effluent was treated by the oxidation with chloric acid for no more than 10 minuts in the dosage of 50 g/L or the correspond ORP value of 334 mV.