In situ coagulation-electrochemical oxidation of leachate concentrate: A key role of cathodes
Huankai Li, Qian Zeng, Feixiang Zan, Sen Lin, Tianwei Hao
Abstract
To efficiently remove organic and inorganic pollutants from leachate concentrate, an in situ coagulation-electrochemical oxidation (CO-EO) system was proposed using Ti/Ti 4 O 7 anode and Al cathode, coupling the “super-Faradaic” dissolution of Al. The system was evaluated in terms of the removal efficiencies of organics, nutrients, and metals, and the underlying cathodic mechanisms were investigated compared with the Ti/RuO 2 –IrO 2 and graphite cathode systems. After a 3-h treatment, the Al-cathode system removed 89.0% of COD and 36.3% of total nitrogen (TN). The TN removal was primarily ascribed to the oxidation of both ammonia and organic-N to N 2 . In comparison, the Al-cathode system achieved 3–10-fold total phosphorus (TP) (62.6%) and metal removals (>80%) than Ti/RuO 2 –IrO 2 and graphite systems. The increased removals of TP and metals were ascribed to the in situ coagulation of Al(OH) 3 , hydroxide precipitation, and electrodeposition . With the reduced scaling on the Al cathode surface, the formation of Al 3+ and electrified Al(OH) 3 lessened the requirement for cathode cleaning and increased the bulk conductivity, resulting in increased instantaneous current production (38.9%) and operating cost efficiencies (48.3 kWh kg COD −1 ). The present study indicated that the in situ CO-EO process could be potentially used for treating persistent wastewater containing high levels of organic and inorganic ions.