Electrochemical peroxidation using iron nanoparticles to remove arsenic from copper smelter wastewater

• A new electrochemical peroxidation process based on iron nanoparticles and graphite electrodes for arsenic removal is presented.
• Arsenic can by removed totally from copper smelter wastewater by the new process.
• There is an important dependency of the solution pH and oxidation state of the arsenic on the removal efficiency.

In the present work a study of the electrochemical peroxidation process (ECP) was carried out by using carbon electrodes and iron nanoparticles. Arsenic removal from synthetic and real wastewater from copper pyro-metallurgical industry was analyzed. The experiments were carried out in a 2 L batch reactor with agitation by air injection with airflow of approximately 5 L min−1. A fixed current density of 171.7 A·m−2 was used and a drop wise 30% (w/w) hydrogen peroxide dosage of around 0.5–1 mL·min−1 was supplied to the wastewater solution. The evaluated operating parameters were: initial pH of the wastewater that was in the range of 2.0 to 6.5 and the treatment time that was varied from 30 to 180 min. The results when the ECP process was applied for 1 h, in the pH range of 2.0 to 6.5, to treat As(III) synthetic wastewater, showed that the maximum removal of arsenic was 62.4% at a pH of 6.5; being approximately constant when more treatment time was applied. On the other hand, when treating As(V) wastewater, the maximum removal was 99.7% at a pH of 5.0. When working with real wastewater in the pH range of 3.5 to 6.5; the arsenic maximum removal was 96% at pH 6.5. This removal was approximately constant when more treatment time was applied. The ECP process using carbon electrodes and iron nanoparticles showed to be a capable technology to remove high concentrations of arsenic (1300 to 3000 mg·L−1).