Electrochemical nitrate reduction by using a novel Co3O4/Ti cathode. (1st September 2017)

• Record Type: Journal Article
• Authors: Su, Liuhua; Li, Kan; Zhang, Hongbo; Fan, Maohong; Ying, Diwen; Sun, Tonghua; Wang, Yalin; Jia, Jinping
• Is Part Of: Water research. Volume 120(2017)
• Page Start: 1
• Page End: 11
• Publication Date: 2017-09-01
• Subjects: Electrochemical denitrification -- Co3O4/Ti cathode -- Total nitrogen removal -- ClO− oxidation -- Actual textile wastewater; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2017.04.069
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Co3 O4 film coated on Ti substrate is prepared using sol-gel method and applied as cathode material for electrochemical denitrification in this research. Preparation conditions including precursor coating times and calcination temperature are optimized based on NO3 − -N removal, NO2 − -N generation, NH4 + -N generation and total nitrogen (TN) removal efficiencies. The influences of electrolysis parameters such as current density and NO3 − -N initial concentration are also investigated. In comparison with other common researched cathodes (Ti, Cu and Fe2 O3 /Ti), Co3 O4 /Ti exhibits better NO3 − -N removal and NH4 + -N generation efficiencies. In order to remove NO3 − -N completely from water, Cl − is added to help further oxidize NH4 + -N to N2 . TN removal after 3 h treatment increases from 65% to 80%, 90% and 96% with the increase of Cl − from 0 mg L −1 to 500, 1000 and 1500 mg L −1, respectively. The mechanisms of NO3 − -N reduction on cathode and NH4 + -N oxidation on anode in the absence and presence of Cl − are investigated in a double-cell reactor. Actual textile wastewater containing both NO3 − and Cl − is also treated and the Co3 O4 /Ti cathode exhibits excellent stability and reliability. It is interesting to find out that FeCl2 -H2 O2 Fenton pretreatment is needed to remove extra COD and provide more Cl − to help oxidize NH4 + -N to N2 at the same time. Graphical abstract: Highlights: Co3 O4 film coated on Ti plate is used as cathode for electrochemical denitrification. The NO3 − -N reduction performance of Co3 O4 /Ti is better than Cu and Fe2 O3 /Ti. In order to complete remove NO3 − -N, Cl − is added to help oxidize NH4 + -N to N2 . Actual textile wastewater containing both NO3 − and Cl − can be effectively treated. FeCl2 -Fenton is needed to remove extra COD and provide more Cl − in wastewater.