The Efficiency of DSA Anode for Electrochemical Oxidation Wastewater Contains Ammonia

Jul 14, 2022

The Efficiency of DSA Anode for Electrochemical Oxidation Wastewater Contains Ammonia

Wastewater contains ammonia can cause eutrophication and fish kills which disrupt aquatic ecosystems in a severe manner. Ammonia can be oxidized electrochemically into nitrogen gas, nitrate, or nitrite by direct or indirect oxidation processes.

Ti/IrO2-Pt, Lead Dioxide, and BDD-TiO2 Anode have been investigated for electrochemical  oxidation efficiency. It was shown that ammonia is effectively removed from the solution while active chlorine was electrogenerated on a Ti/PtOx-IrO2 electrode. Nitrogen gaseous is the main by-product of ammonia electrolysis.

Direct electrochemical oxidation of ammonia on boron-doped diamond (BDD) electrode occurred mainly when pH value above 8.0 by free ammonia (NH3) oxidation. Otherwise, when the pH value was below 8.0, oxidation of ammonia was mediated by active free chlorine. Thus, active chlorine effectively removes ammonia from an acidic solution, while the formation of by-products such as chlorate and possibly perchlorate is minimized. Electro-oxidation of the ammonia process inhibited the oxygen evolution reaction (OER) as ammonia oxidation products were absorbed on the BDD surface. Nitrogen, nitrous oxide, and nitrogen dioxide were detected as ammonia oxidation products. Nitrogen gaseous was the main product of the oxidation.

The electro-activity of the Pt and DSA (Dimensionally Stable Anode) electrodes and Ni were confirmed by cyclic voltammogram at pH 7.0 and pH 9.4. An anodic polarization showed the electro-activity of graphite. Anodized Al electrodes showed no electro-oxidation activity. The electrochemical activity of Ni electrodes demonstrated this material for ammonia and ammonium ion electrooxidation at both pH values investigated. A disadvantage of the platinum electrode is that their activities are disrupted by the formation of the platinum oxide (PtO) layer at the cathodic electrode surface. Combination of graphite and titanium dioxide electrode considerably enhance the removal efficiency. In general, the anode is believed to be the key factor that affects ammonia removal, and nitrate and nitrite were found to be the side products during the electrochemical ammonia removal.