重金屬廢水由於存在如EDTA的螯合反應變得更加復雜化，這些配體在表面處理或印刷電路板行業的水中普遍存在;通過常見的化學沉澱法產生金屬氫氧化物沉澱去除重金屬已不再是可行的。在本研究中，採常用於生產金屬納米粒子的化學還原法來去除和回收銅離子，產生的金屬納米粒子可以做為載體提高還原的效果及速率。在本研究中，將化學還原法和薄膜過濾程序結合在一起處理含銅和配體的電子廢水，並將其稱為“還原結晶”。中空纖維膜浸沒安裝於封閉反應器中，以隔絕減少空氣中的氧氣對還原過程的影響。 pH和ORP為實驗中的主要對照參數。在這項研究中，研究了pH、ORP，對銅去除效率、銅顆粒大小和薄膜阻塞的影響。
結果顯示，在pH值為5〜8，ORP為-400mV和-500mV的條件下，銅的還原/去除率為87-92％。使用連續性Cu（II）還原系統還原含銅和鎳的廢水；可達近90％的銅去除效率，然而鎳去除率僅只有15％。連續還原系統中薄膜於3天操作後TMP迅速增加。可以發現金屬光澤顆粒懸浮在薄膜槽中及中空纖維膜被一層金屬塗層覆蓋。加入銅金屬顆粒做為結晶種子可以提高了還原/回收速率同時減少薄膜阻塞的影響。TMP保持穩定直到實驗結束。從系統收集的固體樣品中可以鑑定出金屬銅和氧化亞銅(Cu2O)。模擬廢水中同時含有重金屬銅及鎳時，可實現幾乎93％的銅去除效率，符合要求台灣EPA對銅的排放標準。但在鎳的去除上僅達到15％的去除效率，未來需進一步處理。

Treatment of the metal-containing wastewater is complicated by the presence of ligands, such as EDTA, which are ubiquitous in metal-containing wastewaters from surface finishing or printed circuit board industries; the common practice to remove metal through metal hydroxide precipitation is no longer a viable option. Chemical reduction, which has commonly used for the production of metal nanoparticles, was employed to remove and recover copper ions in this study.
In the current study, chemical reduction and membrane filtration are combined to treat electronic wastewater containing copper and ligands, and the process is dubbed as reduction "crystallization process". A closed reactor with submerged type membrane installed was designed to minimize the effect of oxygen from air on the reduction process. Both pH and ORP are used as the control parameters for the treatment process. In this study, effects of pH, hydraulic retention time, solid retention time on copper removal efficiency, the size of copper particles, and membrane fouling were studied. The result shows that 87-92% of copper reduction/ removal was achieved at pH of 5 to 8 and ORP of -400 mV and -500 mV, respectively. The synthetic wastewater containing both copper and nickel ions was treated using the continuous Cu(II) reduction system. Almost 90% of copper removal efficiency is achieved by the system, while it is merely 15% for nickel removal efficiency. In membrane integrated continuous Cu(II) reduction system, the TMP increased rapidly after a 3-day operation. Visually, hollow fiber membranes were covered by a layer of coating and shiny metallic particles suspending in membrane tank can be spotted. Injecting Cu seed particles enhanced the reduction rate of Cu, and the coating of membrane surface can be reduced. TMP remained low and stable until the end of operation. Metallic copper and cuprous oxide (Cu2O) were identified in the solid samples collected from systems. Re-oxidation of metallic copper particles by atmospheric oxygen during sample handling or incomplete reduction of Cu(II) ions during reduction process might also result in the formation of cupric or cuprous oxides.

Catalog	I
List of Figure	III
List of Table	VI
Chapter 1	Introduction	1
Chapter 2	Literature Review	4
2.1	Treatment of heavy metal-containing wastewater	4
2.1.1	Chemical precipitation	4
2.1.2	Ion-exchange method	4
2.1.3	Electrolysis method	5
2.1.4	Membrane separation process	6
2.1.5	Chemical reduction	11
2.2 Sodium dithionite	12
Chapter 3	Material and Methods	16
3.1	Materials and Experimental setup	16
3.1.1	Chemicals and reagents	16
3.1.2	Wastewater qualities	17
3.1.3	Membrane information	18
3.2	Experimental setup and procedures	20
3.2.1	Precipitation of metals by pH adjustment	20
3.2.2	Continuous Cu(II) reduction system	20
3.2.3	Membrane integrated continuous Cu(II) reduction system	23
3.3	Analytical method	25
3.3.1	Scanning electron microscope (SEM)	25
3.3.2	Flame atomic absorption spectrometry (AAS)	25
3.3.3 X-ray Diffraction	25
3.3.4 TOC analyzer	26
Chapter 4	Results and discussion	27
4.1	Metal removal by pH adjustment	27
4.2	Continuous Cu(II) reduction system	32
4.2.1 The effectiveness of solid/liquid separation	33
4.2.2 The effects of pH and ORP	36
4.3	Membrane integrated continuous Cu(II) reduction system	41
4.3.1 Determination of membrane fouling	47
4.3.2 Improving copper removal efficiency and reducing membrane fouling by seed addition	48
4.4	Solid analysis	50
Chapter 5	Conclusion and suggestions	55
5.1	Conclusion	55
5.2	Suggestions	56
Reference	58

 
List of Figure
Figure 1. Schematic comparison of selected separation process [47].	7
Figure 2. The filtration mechanism of membrane.	7
Figure 3. Membrane fouling mechanism.	10
Figure 4. The standard redox potential of various redox couples [69].	15
Figure 5. The module of hollow fiber membranes.	18
Figure 6. The module of experimental membrane.	19
Figure 7. Continuous Cu(II) reduction system	22
Figure 8. Membrane integrated continuous Cu(II) reduction system.	24
Figure 9. Distribution of copper dominant species as a function of pH in the presence of EDTA. Modeled with MINEQL+. Total concentration for copper and EDTA are both 10-3 M.	28
Figure 10. Distribution of nickel dominant species as a function of pH in the presence of EDTA. Modeled with MINEQL+. Total concentration for nickel and EDTA are both 10-3 M.	28
Figure 11. The precipitation of (a) copper sulfate liquid and (b) nickel sulfate liquid. The original pH of copper sulfate and nickel sulfate liquids are 0.98 and 5.05, respectively.	29
Figure 12. Effect of pH on (a) copper removal efficiency and (b) nickel removal efficiency. The original pH of copper sulfate and nickel sulfate liquids are 0.98 and 5.05, respectively.	30
Figure 13. Distribution of nickel dominant species as a function of pH in the presence of citric. Modeled with MINEQL+. Total concentration for nickel and citric are both 10-3 M.	31
Figure 14. The copper removal efficiency as a function of time. ORP of -400 mV and pH of 6.	34
Figure 15. The copper removal efficiency as a function of time. ORP of -500 mV and pH of 6.	34
Figure 16. The average copper removal efficiency as a function of ORP.	35
Figure 17. The average copper removal efficiency as a function of pH.	36
Figure 18. The average ratio of dithionite /Cu molar as a function of pH.	37
Figure 19. The removal efficiency of metal as a function of time. At pH 6.	38
Figure 20. The average metal removal efficiency as a function of ORP.	39
Figure 21. Distribution of mixing condition dominant species as a function of pH in the presence of EDTA. Modeled with MINEQL+. Total concentration for copper, nickel, and EDTA are both 10-3 M.	40
Figure 22. Determination of membrane pressure of chemical reduction. pH of 6, ORP of -400 mV, HRT of 60 min. On/off cycle = 9 min/1 min.	42
Figure 23. Photos of membranes for (a) clean membrane, (b) membrane A after a 5-day operation and (c) membrane B after a 12-day operation.	42
Figure 24. SEM analysis of membrane surface for (a) clean membrane, (b) membrane A, and (c) membrane B.	46
Figure 25. The average removal efficiency of copper as a function of time by membrane integrated continuous Cu(II) reduction system. Experiment condition: pH of 6; ORP of -400 mV; HRT of 60 min.	47
Figure 26. Determination of membrane pressure of chemical reduction with seed added. pH of 6, ORP of -400 mV.	49
Figure 27. The removal efficiency as a function of time at pH 6 and ORP -400 mV, respectively.	49
Figure 28. XRD analysis of solid samples collected from the reduction of wastewater A. (a) continuous Cu(II) reduction system at various pH and ORP value, (b) membrane integrated continuous Cu(II) reduction system at pH 6 and various ORP.	51
Figure 29. XRD analysis of solid samples collected from the reduction of wastewater B at pH 6 and various ORP.	52
Figure 30. Photos of particle size at different days with chemical reduction at pH 5.	53
Figure 31. Photos of particle size at different days with chemical reduction at pH 6.	53
Figure 32. Photos of particle size at different days with chemical reduction at pH 7.	53
Figure 33. Photos of particle size at different days with chemical reduction at pH 8.	53
Figure 34. Zeta potentials of a-alumina, copper and cuprous oxide as a function of pH [71].	54
Figure 35. The new system with membrane filter setup.	57
 
	List of Table	
Table 1. Chemical materials	16
Table 2. The information of wastewater from PCB production process.	17
Table 3. The information of hollow fiber membrane.	19
Table 4. Parameters of particle and fluid are used for Stocks’ law in continuous Cu(II) reduction system.	21
Table 5. Parameters of particle and fluid are used for Stocks’ law in membrane integrated continuous reduction system.	23
Table 6. The mass balance of copper in filtrate and solids. (Unit, mg)	31
Table 7. The coefficient of variation by with filtration and without filtration.	35
Table 8. Membrane fouling resistance.	48

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