|摘要: ||本研究以Evercion Red H-E3B反應性染料配製100 mg/L人工色度廢水，以鐵鹽(亞鐵及三價鐵)與過氧化氫加藥量、pH等為操作變數，研究目的為探討鐵鹽（三價鐵）混凝、Fenton、Fenton-like程序去除色度與溶解性有機物（DOC），同時比較各處理程序色度、DOC之去除機制。所有實驗採瓶杯試驗，人工色度廢水含色度及DOC分別為6,500單位(以ADMI方法表示)及16.5 mg/L。此外，各程序去除色度與DOC機制比較實驗之皆控制pH 4。|
研究結果顯示Fe3+混凝與Fenton混凝去除色度、DOC之最佳pH分別為pH 3~5與pH 2~4，色度去除率可達80%以上。Fenton及Fenton-like混凝脫色效果較鐵鹽混凝佳，其單位鐵鹽色度去除量為Fe3+混凝之10.5倍，但鐵鹽混凝、Fenton、Fenton-like 程序於DOC效果上，無明顯差異。Fenton及Fenton-like程序同時具有氫氧自由基氧化及混凝效果，氫氧自由基氧化可有效脫色，但無法礦化DOC。於低鐵鹽加藥量時，脫色主要機制為氧化，色度去除率可達90%以上，DOC主要為氧化去除，但僅有約25%去除率。
於高鐵鹽加藥量時，Fenton及Fenton-like混凝去除率約90%，主要為混凝去除，而非氫氧自由基氧化。比較Fenton及Fenton-like混凝去除色度機制，顯示Fenton程序氧化與混凝脫色比率約4 : 1，相對地Fenton-like程序氧化與混凝脫色比率約為1 : 4。高鐵鹽加藥量時，Fenton及Fenton-like混凝去除色度機制之主要分別為氧化與混凝去除。故Fenton及Fenton-like程序較適用於脫色處理而非去除DOC。
The purposes of this study are to investigate the removals of color and dissolved organic carbon (DOC) by ferric coagulation, the Fenton and Fenton-like coagulation processes, to compare the removal mechanisms of color and DOC among three processes. The synthetic colored wastewater samples were prepared from 100 mg/L of a red reactive azo dyestuff, Red H-E3B, and contained color and DOC were 6,500 uint (expressed by ADMI method) and 16.5 mg/L, respectively. The experimental variables studied include dosages of iron salts (ferrous and ferric) and hydrogen peroxide (H2O2), pH. All experiments were conducted by the Jar test. Furthermore, the experiments for comparing the removal mechanisms among three processes were controlled at pH of 4.
The result showed that optimum pH for color removal occurred at pH 3-5 and at pH 2-4 by ferric coagulation and the Fenton coagulation, respectively. The color removal can reach more than 80% by both ferric and the Fenton coagulation processes. The color removals by the Fenton and Fenton-like coagulation were markedly better than ferric coagulation. The ratio of color removal efficiency, expressed by color removed per iron dosage, between the Fenton, Fenton-like and ferric coagulation was 10.5. However, the DOC removals were the same among three processes. Since the Fenton and Fenton-like coagulation have dual functions of the hydroxyl radical(OH●) oxidation and ferric coagulation, the OH● oxidation can effectively remove color, but the removal of DOC was poor. In the presence of low iron dosages, more than 90% of color can be removed mainly by the OH● oxidation, whereas, only 25% of DOC was poorly removed by the Fenton and Fenton-like coagulation processes.
In the presence of high dosages, the DOC removals can reach to more than 90% by both the Fenton and Fenton-like coagulation processes. Moreover, it was observed that the removal of DOC was mainly by ferric coagulation but the OH● oxidation. Besides, comparing the color removal mechanisms between the Fenton and Fenton-like coagulation processes, the ratio of color removal by the OH● oxidation and ferric coagulation was 4 to 1 for the Fenton coagulation. In contract, it was 4 to 1 for the Fenton-like coagulation. Therefore, it demonstrated that the color removal was mainly by the OH● oxidation and ferric coagulation, respectively, by the Fenton and Fenton-like coagulation. It is concluded that the DOC was mainly removed by ferric coagulation but the OH● oxidation. Both the Fenton and Fenton-like coagulation processes were better used for color removal but DOC removal.