不同犧牲金屬電極之電混凝法及不同金屬混凝劑之化學混凝法處理含硼廢水比較

本研究採用鋁和鐵電極作為犧牲陽極之電混凝法處理包括人工合成的含硼廢水和燃煤火力發電廠中煙道脫硫所產生的實廠含硼廢水。實驗中探討了不同參數，如:電流密度、pH值、溫度和電導度對除硼效率的影響。並同時比較化學混凝法與電混凝法之除硼效率。除了以批次系統探討上述影響因子外，本研究中也建構了連續式處理系統，由三座反應槽組成，針對實廠廢水施做了固定鋁硼莫爾比，無pH值及溫度控制之去除程序，探討連續系統用於處理實廠廢水的除硼效率。在使用鋁電極的部分，電流密度、電導率和固定溶液 pH 值對硼去除效率的影響可以忽略不計，最高去除率約為 80%，而溶液溫度顯著影響硼的去除效率，在 20 oC 和 50 oC 的溫度下，除硼效率分別為 65% 和 50%。在鐵電極的部分，pH值對於硼的去除效率有著顯著地影響，pH為7、8和9的去除效率分別為15%、35和30%。另一方面，連續系統在第一反應器、第二反應器和第三反應器中的去除率分別達到約 70、85 和 90%。整體來說，化混法的除硼效率在本研究中較優於電凝法。使用化混法在鋁硼莫爾比為 15:1 時，硼的去除效率為 70%。而使用電凝法時，鋁硼的莫爾比需要約為 35:1，才能達到約 80% 的除硼效率。對於鐵電極，化混法在鐵硼莫爾比為 5:1 時達到了約 67%的去除率，而使用電凝法在鐵硼莫爾比為 20:1 時僅去除了 31% 的硼，這是因為電生成的二價鐵離子主要以氫氧化亞鐵的形式沉澱，可能對硼酸鹽的結合能力較低。所以在經過一系列的實驗及探討之後，在批次實驗的部分使用三價鐵混凝劑的化學混凝法對於除硼效率有著最適合用且最具經濟性的效果，而電混凝法則可使用鋁犧牲電極之連續式系統來處理實廠的含硼廢水。

關鍵字

電混凝法、硼去除效率、鋁犧牲電極、鐵犧牲電極、化學混凝法

並列摘要

In this study, electrocoagulation process using aluminum and iron plates as sacrificial anodes was employed to treat synthetic boron-containing wastewater and actual wastewater collected from a flue-gas desulfurization process at a coal-fired power plant. The effects of different parameters such as current density, pH value, temperature, and electrical conductivity on boron removal efficiency were investigated. Both batch and continuous systems were constructed. For Al plate as an anode, the effect of current density, conductivity and fixed solution pH on boron removal were negligible with the highest removal of around 73%. The solution temperature significantly affects the removal of B with the efficiency of 65% and 50% for the temperature of 20 oC and 50 oC, respectively. For iron anode, pH value significantly affects the removal efficiency of B with the efficiency of 15%, 35 and 30%, respectively for the pH of 7, 8 and 9. A continuous EC system with three reactors connected in series for the removal of B from FGD wastewater was investigated. The overall B removal efficiency reached around 70, 85 and 90% for the first reactor, second reactor and third reactor, respectively. In general, the B removal efficiency using CC process was better than that of EC process. The B removal efficiency was 70% at Al:B molar ratio of 15:1 using CC process. The Al:B molar ratio around 35:1 was required to obtain the B removal efficiency around 72% using EC process. For iron system, CC process obtained around 67% of B removal at Fe(III):B molar ratio of 5:1, while only 31% of B was removed at Fe:B molar ratio of 20:1 using EC process because the electrogenerated Fe(II) ions mainly precipitate as Fe(OH)2 which might have a low adsorption ability toward of borate. After a series of experiments, it was concluded that chemical coagulation method of batch system using Fe(III) coagulant to remove B-containing wastewater is the most applicable and economical method. Electrocoagulation using an aluminum sacrificial electrode is applicable for the continuous system.