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Abatement of As and hydrated silica from natural groundwater by electrocoagulation in a continuous plant having an electrolyzer and a flocculator-settler

2021; Elsevier BV; Volume: 281; Linguagem: Inglês

10.1016/j.seppur.2021.119895

1873-3794

Álvaro Gutiérrez, Juan F. Rodrı́guez, Locksley F. Castañeda, José L. Nava, Oscar Coreño, Gilberto Carreño,

Mine drainage and remediation techniques

This paper shows the elimination of arsenic (As) and hydrated silica from natural groundwater (48.63 µg L−1 arsenic, 77.5 mg L−1 hydrated silica, 0.33 mg L−1 phosphate, 5 mg L−1 sulfate, 240 mg L−1 alkalinity, 89.5 mg L−1 hardness, pH 8.44 and 450 µS cm−1 conductivity) by electrocoagulation (EC). The flow plant employed a parallel plates EC reactor in series with a flocculator-settler. Aluminum was used as the sacrificial electrode. Before the electrolysis in the flow plant, a systematic study of the aluminum dose was carried using the EC reactor adapted to a jar test. The influence of the mean linear flow velocity (1.2–4.8 cm s−1) and current density (6–9 mA cm−2) on the removal of As and hydrated silica was addressed. The residual concentration of As and hydrated silica in the flow plant was CAs = 4.2 µg L−1 and Chs = 4.5 mg L−1, respectively, at 9 mA cm−2 and 1.2 cm s−1, which agree well with that obtained in the jar test array. The residual As concentration fulfills the World Health Organization (WHO) recommendation (<10 μg L−1). The total operating cost of EC was 0.48 USD m−3, considering electrolytic energy consumption, aluminum price, pumping costs, and sludge confinement. Flocs analyses performed by SEM-EDS, XRF-EDS, XRD, and FTIR showed the existence of aluminosilicates formed by the reaction of aluminum and hydrated silica. At the same time, As, phosphates and sulfates were separated by adsorption on flocs.