Electrocoagulation of tetrafluoroborate (BF4) and the derived boron and fluorine using aluminum electrodes

Jui Yen Lin, Agnes Raharjo, Li Hsin Hsu, Yu Jen Shih, Yao Hui Huang

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7 Citations (Scopus)

Abstract

Tetrafluoroborate anion (BF4) 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 BF4 were studied using metallic aluminum as the sacrificial electrode. The dissolved Al(III) from the anode could efficiently decompose BF4 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 BF4, 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 BF4 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: [BF4]0 = 9.3 mM, [NaCl] = 10 mM, pH = 8.0, current density = 5 mA/cm2, 98.3% of BF4 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 BF4–], B(OH)3 and F in aqueous solution synergically.

Original languageEnglish
Pages (from-to)362-371
Number of pages10
JournalWater Research
Volume155
DOIs
Publication statusPublished - 2019 May 15

All Science Journal Classification (ASJC) codes

  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

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