Removing fluoride from hot spring wastewater by an electrolysis system with a perforated plate as a diaphragm. Issue 1 (1st January 2020)

• Record Type: Journal Article
• Authors: Imai, Yuki; Kawakami, Tomonori
• Editors: Cameselle, Claudio
• Is Part Of: Cogent engineering. Volume 7:Issue 1(2020)
• Publication Date: 2020-01-01
• Subjects: Fluoride -- electrolysis -- magnesium -- perforated plate -- co-precipitation; Engineering -- Periodicals; Technology -- Periodicals; Engineering; Technology; Periodicals; 620
• DOI: 10.1080/23311916.2020.1720061
• Languages: English
• ISSNs: 2331-1916

Abstract

Abstract: A continuous electrolysis system using an electrolysis reactor cell separated into an anode cell and a cathode cell by a perforated plate as a diaphragm was operated in a laboratory to remove fluoride (F - ) from hot spring wastewater to meet the Japanese national minimum effluent standard for F - of 8 mg/L. The perforated plate was 5 mm thick and had 740 holes with a diameter of 1.2 mmφ. F - was removed by co-precipitation with magnesium hydroxide (Mg(OH)2 ) produced in the cathode cell. Water from Gero Hot Spring containing 17.0 mg/L of F - was used as a model wastewater. Since Gero Hot Spring water does not contain magnesium (Mg 2 + ), magnesium carbonate (MgCO3 ) was added as a form of slurry into the anode cell with the hot spring water. The hot spring water containing Mg 2+ passed through the perforated plate and flowed into the cathode cell, where Mg(OH)2 was co-precipitated with F - due to hydroxide ion (OH - ) produced by electrolysis. Alkalinity (Alk), which interferes with the precipitation of Mg(OH)2 by forming MgCO3 in the cathode cell, was removed in the anode cell by hydrogen ion (H + ) produced by electrolysis. Various combinations of the added Mg 2+ concentration (Mgi) and the applied current (Ia) were tested to elucidate the effect of these parameters on F - removal (ΔF). It was revealed that, less than 8 mg/L of the F - concentration in treated water (F (treated)), which is the Japanese national minimum standard for wastewater, was achieved when the Mgi was between 85 and 110 mg/L and Ia was more than 90 mA.