現代工業如玻璃、面板、電鍍製程及排煙脫硫工廠所排放廢水中含四氟化硼並同時含有硼與氟等污染物，因此大幅增加水處理難度。本研究針對含四氟化硼廢水(100 mg-B/L)，使用氯化鋁作為混凝劑，調整兩階段pH，以混凝劑的加藥量、溫度作為研究變因，探討四氟化硼的降解及硼與氟的去除率。研究發現在第一階段四氟化硼與鋁離子反應分解為硼酸與鋁氟酸離子，pHI由6.8下降至1.5，並且鋁氟酸離子(AlF2+)繼續解離成鋁離子與氟離子；第二階段調整pHII至6.0，鋁離子(Al3+)形成氫氧化鋁(Al(OH)3)，並與氟離子(F-)反應成為鹼式氟化鋁(AlnFm(OH)3n-m)等混凝劑，進而沉澱掃除水中硼酸(B(OH)3)與氟離子。在最佳操作條件下(初始[BF4-] = 803 mg/L (100 mg-B/L), pHI = 1.5, pHII = 6.0, [Al3+] = 0.08M, 30 °C)，第一階段四氟化硼降解至1 mg/L以下，降解率達99.9%，第二階段硼與氟濃度分別下降至72.9 mg/L與8.38 mg/L，去除率分別達32.6%及98.8%，其中氟已符合放流水標準(< 15 mg/L)。

Tetrafluoroborate ion (BF4-) generally is found in industrial streams, such as flue gas desulfurization in coal-fired power plants and wet-etching of the borosilicate glasses using hydrofluoric acid. This research investigated the chemical coagulation of BF4- (100 mg-B/L), fluoride and boron using aluminum chloride. The experimental parameters included pH, temperature, and dosage of Al(III). Initially, BF4- anions were decomposed effectively in forms of boric acid and fluoroaluminate complexes by aluminum ions at around pH 1.5; afterwards, the derived boric acid and fluoride ions were co-precipitated with aluminum hydroxide (AlOH3(S)) by elevating pH 6.0. Under optimal conditions: 0.08 M [Al3+], 30 °C, 99.9% of BF4- was decomposed, and the removal efficiencies of fluoride and total boron attained 98.8% and 32.6%, respectively, in 2 h. The concentration of residual fluoride in the end solution was 8.38 mg/L.

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