Arsenic and hydrated silica removal from underground water by electrocoagulation coupled to a flocculator-settler in continuous mode

Author(s): Juan Felipe Rodriguez Ruiz
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Institution or organization of origin: Universidad de Guanajuato
Country: Mexico


This work deals with the abatement of hydrated silica (HS) and arsenic (As) from natural groundwater collected in Guanajuato (48.63 µg L-1 As, 77.5 mg L-1 HS) by the electrocoagulation (EC) process using a reactor open to the atmosphere in serpentine array reactor with six cells coupled to a flocculator-settler in continuous mode. Three aluminum plates were used as sacrificial anodes. A systematic study of the aluminum dose was carried out using the EC reactor coupled to a jar test before the electrolysis in the flow plant equipped with the flocculator-settler. The influence of both current density (6-9 mA cm-2) and mean linear flow velocity (1.2-4.8 cm s-1) on As and HS removal were examined. The best trial achieved a residual concentration As and HS of 4.2 µg L-1 and 4.5 mg L-1, respectively. The electrolysis carried out at 9 mA cm-2, and 1.2 cm s-1 is comparable to that obtained in the jar test array. The total operating cost of EC considering the electrolytic energy consumption (EEC), aluminum price, pumping costs, and sludge storage was 0.48 USD m-3. Lastly, the flocs characterization was carried out by SEM-EDS, XRF-EDS, XRD, and FTIR. The presence of aluminosilicates formed by the reaction of aluminum and HS was elucidated. On the other hand, arsenic is removal by adsorption onto aluminosilicates flocs.

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