微胞加強超過濾結合化學還原法去除水中重金屬

Integration of MEUF and chemical reduction for metal removal

劉凡華(Fan-Hua Liu)

指導教授 ： 李奇旺

淡江大學/工學院/水資源及環境工程學系碩士班/碩士(2016年)

https://doi.org/10.6846/TKU.2016.01053

摘要

印刷電路板業(PCB)是用水需求極高的產業，製程中會產生大量含有重金屬的廢水，如未妥善處理即排放，對人體及自然環境皆會造成重大影響。本研究利用低亞硫酸鈉當還原劑，還原MEUF濃縮液中的金屬。在實驗中先以固定的SDS/Metal莫耳比(5/1)，改變整體濃度(銅及SDS的濃度)探討其對於銅去除率的影響。再分別探討於pH6及pH7的操作條件下，去除率的差異。最後以連續式系統探討薄膜阻塞之影響。此外經由還原所產生的銅顆粒，另以XRD及SEM分析了解其化學組成及外觀結構。
在實驗結果中發現，以化學還原法去除MEUF濃縮液中的銅，當銅濃度在5.1 mM時，利用0.45μm濾紙過濾，其去除率可達97%。而鎳在8.5 mM時，利用0.45μm濾紙過濾，去除率也有56%。但是當整體濃度下降時(Cu=1.7mM)，去除率也跟著大幅降低。因此為了解去除率下降的原因，實驗再利用粒徑分析儀分析，得知尚未添加還原劑時，粒徑分析儀所分析出的微胞大小約20奈米 (SDS濃度8.5、12.75、17mM)，當界面活性劑的濃度增加到25.5 mM及42.5 mM時，有5%的微胞增加到600及800奈米。添加還原劑後，銅濃度在1.7 mM時，粒徑大小增加至200奈米，雖然銅離子有被還原劑還原成銅顆粒，但是仍因粒徑低於0.45μm，仍不能被0.45μm的膜阻擋，這也是實驗結果中，銅去除率偏低的原因。另外為了解還原顆粒的組成成份與外觀，另以XRD分析，測得其為氧化亞銅 (Cu2O)，再由SEM及TGA瞭解其外觀及不同溫度下其重量損失的變化。於TGA的結果中發現大約有30%的SDS會黏在銅顆粒上。
最後將此程序應用於連續式的一次添加低亞硫酸鈉 (單向垂直過濾系統)及連續添加低亞硫酸鈉(掃流過濾系統)中，當銅濃度為1.7 mM時 (約為108 mg/L)，剛開始兩組系統的去除率皆接近100%，兩小時後，將低亞硫酸鈉一次添加時，銅的去除率為0%；但是在連續添加的系統中，銅之去除率為78%，銅殘留濃度約24 mg/L。顯示連續添加還原劑有較高的使用率及對銅較佳的去除率。

關鍵字

化學還原 ； 銅 ； 低亞硫酸鈉 ； SDS ； MEUF

並列摘要

Various industry sectors, such as semiconductor, printed circuit board (PCB), surface finishing, and electroplating, generate heavy metal containing wastewater. Inappropriate handling of the wastewaters will cause severe impact on the environment. In this study, chemical reduction was employed to treat synthetic metal-containing wastewater prepared to simulate the retentate stream of MEUF.

Under the fixed SDS:copper:dithionite molar ratio of 5:1:3, increasing copper concentration (from 1.7 mM to 5.1 mM) increases copper removal efficiency (from 28% to 97%). Since residual copper concentration was obtained after samples filtered with 0.45 μm filter, the discrepancy of copper removal efficiency at various copper concentration might be due to the formation of nano-sized particles. Particle size analysis was employed to elucidate the underlying reason. Result shows that micelle particle diameter growth with increasing initial copper concentration from 20 nm to 800 nm. Although, reducing process generated copper particles, the diameter of particles is only 200 nm and is smaller than the pore size of membrane filter for sample filtration. These small particles in the filtrate were dissolved by acids and were detected by AA, causing low copper removal efficiency. Both XRD and TGA were used to analyze the obtaining reduced copper particles, revealing that the obtained particles were copper oxide (Cu2O) and around 30% of SDS attached to the solids.

Combining MEUF and chemical reduction for copper removal was studied under two reductant dosing schemes, namely (1) one time chemical dosing (Stirred cell Millipore 8200) and (2) continuously chemical dosing (cross flow CF042). Higher copper removal efficiency with 78% was discovered in continuously chemical dosing method.

並列關鍵字

Chemical reduction ； copper ； dithionite ； SDS ； MEUF

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