Removal of hydrated silica, fluoride and arsenic from groundwater by electrocoagulation using a continuous reactor with a twelve-cell stack. (November 2018)

• Record Type: Journal Article
• Authors: Rosales, Mario; Coreño, Oscar; Nava, José L.
• Is Part Of: Chemosphere. Volume 211(2018)
• Page Start: 149
• Page End: 155
• Publication Date: 2018-11
• Subjects: Hydrated silica abatement -- Arsenic removal -- Fluoride removal -- Electrocoagulation -- Aluminum sacrificial anode -- Groundwater; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2018.07.113
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The simultaneous removal of hydrated silica, fluoride and arsenic from deep well water (hydrated silica 72 mg L − 1, fluoride 4.4 mg L − 1, arsenic 106.2 μg L − 1, sulfate 50 mg L − 1, phosphate 0.99 mg L − 1, pH = 8.2 and conductivity 659 μS cm − 1 ) by electrocoagulation (EC) was investigated. The EC was performed in a continuous electrochemical reactor using aluminum plates as sacrificial anodes coupled directly to a jar test device. The effect of current density (4 ≤ j ≤ 8 mA cm −2 ) and mean linear flow rates in the EC reactor (0.057 ≤ u ≤ 0.57 cm s −1 ) on the hydrated silica, fluoride, and arsenic removal efficiencies was analyzed. The abatement of hydrated silica was obtained at 8 mA cm −2 and 0.057 cm s −1, while the residual concentrations of F − and As after the same electrolysis were 0.19 mg L − 1 and 9.8 μg L − 1, satisfying the WHO guidelines for F − (≤1.5 mg L − 1 ) and As (≤10 μg L − 1 ). Spectroscopic analyses on aluminum flocs revealed that they are predominantly composed of aluminum silicates. Arsenates adsorb on aluminum flocs and fluoride replaces a hydroxyl group from aluminum aggregates. Highlights: Hydrated silica abatement from real groundwater by electrocoagulation. Aluminum electrodes in an up-flow reactor with twelve cell stack. Hydrated silica reacts with large dose of coagulant to form aluminum silicates. Fluoride replaces a hydroxyl group from flocs, and arsenate adsorbs on aggregates. Fluoride and arsenic concentrations after EC fulfill the WHO guidelines.