Removal of fluoride and arsenic from groundwater by capacitive deionization using a continuous flow cell with graphite felt electrodes

Abstract

This paper reports for the first time the removal of fluoride and arsenic from natural groundwater by capacitive deionization (CDI). The CDI trials were performed in a laboratory-scale flow cell, in recirculation mode, equipped with two graphite felts (GFs) as the anode and cathode. The characterization of the cell in terms of anodic applied potential (Eapp, 0-1.3 V vs. SHE) and flow rate (Q, 0.1-0.4 L min−1) was systematically examined in a synthetic solution containing F−, finding Eapp = 1.2 V vs. SHE and Q = 0.2 L min−1 as the best conditions. Afterward, F− and arsenic removal from real groundwater (1.6 mg L−1F−, 19.6 μg L−1 As, 0.4 mg L−1 PO43‒, pH 6.6, and 430 μS cm−1 conductivity) was performed by using Eapp = 1.2 V vs. SHE and Q = 0.2 L min−1. After three rounds of CDI, the solution reached ending values of 1.2 mg L−1F−, 7.4 μg L−1 As, 0.2 mg L−1 PO43‒, with energy consumption (EC) of 0.023 kWh m−3. The treated water fulfills the WHO guidelines (< 1.5 mg L−1F−, and < 10 μg L−1 As). CDI using GF electrodes is an affordable technology to supply safe drinking water.