Electrochemically-assisted intensification of As(III) removal through integrated alkalization and oxidation process

In response to the need for trace arsenic removal and detoxification, an electro-assisted self-alkalization and oxidant-free processes (ESOP) cell was developed and investigated. It was found that the ESOP removed 90.3% of arsenic and reduced the As(III) concentration from 150 µg L−1 to less than 5 µg L−1 in its cathode chamber. The As removal involved migration of As(III) and As(V) from the cathode to the anode driven by electrical current. In the ESOP cathode, As(III) was dissociated to As(III) oxyanions via alkalization and then oxidized into As(V) by H2O2. Nearly 80% of As(III) migration could be attributed to the oxidation by H2O2 and approximately 20% dissociation by pH alkalization. The voltage-controlled conditions (1.2−1.5 V) achieved a peak cumulative H2O2 concentration of 10.9 mg L−1. The ESOP demonstrated a high As(III) oxidation to As(V) conversion efficiency of 97.0% as well as a low energy cost of 0.013 kWh m−3 at 1.2 V. The migrated arsenic was stabilized onto the anode electrode through in-situ electro-oxidation of As(III) and electrosorption of As(III, V); this would help with the post-treatment waste disposal. Those results have provided important insights into an electrochemical approach for highly efficient arsenic detoxification. Arsenic is a key contaminant in groundwater and its removal is important to water quality and human health. Its low concentration in groundwater makes it challenging to use the conventional removal approaches such as adsorption. Herein, an innovative electrochemical system was proposed and investigated to remove Arsenic from simulated groundwater. Extensive experiments were conducted to evaluate the system performance and explore the potential mechanisms of As removal, which include dissolution, oxidation, and migration, in an electrical field.