Department of Chemical Engineering, National Cheng Kung University, Tainan, 701, Taiwan.
Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung, 804, Taiwan.
Water Res. 2019 May 15;155:362-371. doi: 10.1016/j.watres.2019.02.037. Epub 2019 Feb 27.
Tetrafluoroborate anion (BF) is found in the streams of flue-gas desulfurization and borosilicate glasses etching which deteriorates water quality through slow hydrolysis into boric acid and fluoride. Decomposition and electrocoagulation (EC) of BF were studied using metallic aluminum as the sacrificial electrode. The dissolved Al(III) from the anode could efficiently decompose BF in forms of fluoroaluminate complexes, and the derived boric acid and fluoride ion were removed by sweep flocculation. Major variables were investigated to optimize EC, including the reaction pH, initial concentration of BF, current density and electrolyte type. The mechanism of EC process was elucidated with the kinetics of consecutive reactions. Experimental results suggested that the removal of BF and total fluoride were less influenced by pH, and that of total boron reached a maximum at pH 8 which favored the surface complexation between borate species and EC precipitates. Under the conditions: [BF] = 9.3 mM, [NaCl] = 10 mM, pH = 8.0, current density = 5 mA/cm, 98.3% of BF was decomposed and the removal of total fluoride and boron attained 98.2% and 74.1%, respectively within 3 h. EC using the Al electrode outperformed the conventional chemical coagulation and reduced the levels of BF, B(OH) and F in aqueous solution synergically.
四氟硼酸根（BF）存在于烟气脱硫和硼硅酸盐玻璃蚀刻的溪流中，它通过缓慢水解成硼酸和氟化物而使水质恶化。使用金属铝作为牺牲电极研究了 BF 的分解和电凝聚（EC）。来自阳极的溶解 Al（III）可以有效地将 BF 分解为氟铝酸盐配合物，并且衍生的硼酸和氟离子通过扫集絮凝去除。研究了主要变量以优化 EC，包括反应 pH、BF 的初始浓度、电流密度和电解质类型。通过连续反应动力学阐明了 EC 过程的机理。实验结果表明，BF 和总氟化物的去除受 pH 的影响较小，而总硼的去除在 pH 8 时达到最大值，有利于硼酸盐物种与 EC 沉淀物之间的表面络合。在以下条件下：[BF] = 9.3 mM，[NaCl] = 10 mM，pH = 8.0，电流密度 = 5 mA/cm，在 3 h 内，98.3%的 BF 被分解，总氟化物和硼的去除率分别达到 98.2%和 74.1%。使用 Al 电极的 EC 优于传统的化学混凝，并协同降低水溶液中的 BF、B（OH）和 F 水平。
