| 摘要: | 工業製程中常使用化學鍍鎳來進行電子元件的表面處理加工，由於所產生的廢液中有相當高濃度的鎳金屬離子、次磷酸鹽類與檸檬酸等有機螯合劑，導致這些螯合性的含鎳廢液具有高濃度的COD (40,000 ~ 70,000 mg/L)，使得生物難分解。一般處理含鎳廢液的方法為化學混凝沉澱法，由於此法會產生大量的重金屬污泥，造成後續處理負擔，且其中含有重金屬鎳離子，而鎳為有價金屬及鋼鐵工業不可或缺原料來源，若能有效處理，極富經濟效益。因此本研究針對實廠螯合性含鎳廢液進行相關處理探討，利用化學還原法進行鎳離子去除並製備成鎳金屬回收，研究過程中，進行不同反應單體與各項操作變因對其去除率及回收效率之探討，另針對高濃度COD部分，同時利用芬頓氧化程序進行研究，探討各項操作變因對COD降解效率之影響，最後增加超音波芬頓氧化程序進行比較。本研究結果顯示，利用化學還原法可去除廢液中78%的鎳離子並製備成鎳金屬回收，其中顯著影響因子為反應單體、pH、[NaH2PO2]劑量等，最佳操作條件為使用polyimide作為反應單體，將含鎳廢液系統pH控制於6，添加10 g/L的[NaH2PO2]以增加Ni2+還原效率，且輔以觸媒0.3 g/L [PdSO4]投加於廢液中，可降低活化能，增加反應速率，而得最大鎳金屬回收效率。於芬頓系統中，各項操作變因，所產生之氫氧自由基(OH．)，在初始反應的30分鐘內即快速生成(除連續式加藥外)，廢液COD降解效率可達40%。但[Fe2+]加藥量不可大於[H2O2]，如此才能有效催化H2O2，產生適量之氫氧自由基(OH．)以氧化分解有機物，否則會產生大量Fe(OH)3污泥沉澱，最佳加藥量操作條件為[Fe2+]/[H2O2]=30/1800 mM，可得最大COD降解效率> 45%，即[Fe2+]/[H2O2]比例為1:60。在[Fe2+]/[H2O2] = 30/1200 mM相同加藥量條件下，以超音波芬頓系統優於傳統芬頓，但須提供更多[H2O2]加藥量，才能生成更多氫氧自由基(OH．)，提升COD降解效率。;The electroless nickel plating is widely used for the metal finish process of electronic component in various industries. In the waste nickel-containing solution produced from the process, high-concentration of nickel metal ions, hypophosphite and citrate acid organic compounds may result in high COD (40,000 ~ 70,000 mg/L), and cause difficulty for its biodegradation. Chemical precipitation is the most commonly used method for the treatment of waste nickel-containing solution, but it produces precipitation sludge which may lead to heavy loading of the secondary treatment process. However, waste nickel-containing solution, consists of high-concentration nickel metal ions which are indispensable raw material for the steel industry, and so it will bring about economic value if the nickel metal ions can be treated and recovered properly. Therefore, this study aims to develop an effective method for treating waste nickel-containing solution. The chemical reduction method was employed to remove the nickel ions and reclaim the nickel metal. And the effects of the operational conditions on Ni2+ removal rate and nickel metal recovery efficiency are investigated, as well as the efficiency of COD degradation by using Fenton oxidation procedure. Finally, the ultrasonic Fenton method is applied for comparison. The results of the study showed that with the chemical reduction method, the highest removal efficiency of the Ni2+ from the waste nickel-containing solution was 78%. And the most influential factors are the reaction monomer, pH value and [NaH2PO2]. The optimum operating condition was to use the polyimide as the reaction monomer, and to control the pH = 6 of the waste nickel-containing solution. The dosage was as [NaH2PO2] = 10 g/L and the [PdSO4] = 0.3 g/L. Under the optimum operating conditions, the highest nickel metal recovery efficiency could be realized. In the Fenton system, the reactive hydroxyl radicals (OH．) were generated in the initial 30 minutes reaction time, and the maximum COD degradation efficiency was up to 40%. The dosage of [Fe2+] should be precisely controlled to be lower than [H2O2], and H2O2 could be effectively catalyzed to generate hydroxyl radicals (OH．). Otherwise, a large amount of sludge containing Fe(OH)3 would be produced. The optimum operating condition was [Fe2+]/[H2O2] = 30/1800 mM, and it resulted in the maximum COD degradation efficiency up to 45%, which meant the dosing ratio of [Fe2+] and [H2O2] was 1:60. Under the same operation condition of [Fe2+]/[H2O2]=30/1200 mM, the performance of ultrasonic Fenton method was better than traditional Fenton method. Providing higher [H2O2] dosage would generate more hydroxyl radicals (OH．), resulting in higher COD degradation efficiency. |
