Nitrogen doped Graphene Nano sheets (N−Gns) as Electrocatalyst for Electro‐Fenton Process for the Degradation of Highly Toxic Chlorophenoxy acid Herbicides from Water

Abstract

For the development of a highly active and energy‐effective electro‐Fenton process, highly efficient 2e−pathway oxygen reduction reaction electrocatalytic materials forin situelectrochemical synthesis of H2O2are extremely important. A novel nitrogen‐doped graphene nanosheets (N‐Gns) is prepared, characterized, investigated for the oxygen reduction reaction, and employed for highly toxic chlorophenoxy acid herbicides degradation in water. Herein, we report novel nitrogen‐doped graphene nano sheets (N‐Gns), which exhibit superior electrocatalytic activity and stability for oxygen reduction reaction (ORR) in acidic medium, which is utilized for Electro Fenton's reaction. The effects of operating parameters such as applied current, pH of the solution, inter‐electrode distance, ferrous ion concentration, oxygen flow rate and initial concentration of herbicides were investigated. The herbicides such as 2,4‐dichlorophenoxyacetic acid (2,4‐D), 2‐(2,4‐ dichlorophenoxy) propanoic acid (2,4‐DP), 4‐chloro‐2‐methylphenoxyacetic acid (MCPA), 2,4,5‐Trichlorophenoxyacetic acid (2,4,5‐T), 2‐(2‐methyl‐4‐chlorophenoxy) propionic acid (MCPP) were degraded by electro‐Fenton process. All the herbicides exhibited the total organic carbon removal efficiency greater than 95 % within 240 minutes. The four various places of Madurai district, Tamil Nadu, India, real water samples were collected and spiked with standard 2,4‐D solution and its degradation was studied by as‐prepared electrodes. The degradation efficiency was greater than 95 % with 300 min. It is comparatively less high than synthetic waste water (herbicides). It is due to the presence of natural organic matter in the real water samples. Hence the herbicides 2,4‐D, 2,4‐DP, 2,4,5‐T, MCPA and MCPP were successfully removed by the as‐synthesizedN doped graphene nano sheets (N‐Gns). The as‐prepared (N‐Gns) exhibits high activity and desirable stabilityand represents a potential candidate material as electro‐Fenton cathode for energy‐effective water treatment.

Fenton‐Like Reaction: Recent Advances and New Trends

“…Both Fe 3 + and Fe 2 + ions can be used as alternative iron sources for three-dimensional carbonaceous materials because the rapidly regenerated Fe 2 + can react with electrically generated H 2 O 2 in large quantities, resulting in the continuous generation of large amounts of * OH. [39,40] Boron doped diamond (BDD) serves as an effective anode in electron-Fenton reaction. [41] M( * OH) is more effective in oxidizing BDD then the classical electrodes such as Pt, SnO 2 , PbO 2 , IrO 2 , RuO 2 , etc.…”

“…The selection of the iron source depends strongly on the nature of the cathode. Both Fe 3+ and Fe 2+ ions can be used as alternative iron sources for three‐dimensional carbonaceous materials because the rapidly regenerated Fe 2+ can react with electrically generated H 2 O 2 in large quantities, resulting in the continuous generation of large amounts of ⋅OH [39,40] …”

Adsorption characteristics of N‐rGO for multiple representative trace antibiotics in water

“…Kamaraj et al (2015) used electrochemical and adsorption methods to remove antibiotics and herbicides in water and achieved good results. Compared with the electrochemical method, adsorption has the advantages of simple operation, low cost, and good removal effect (Kamaraj et al, 2014a(Kamaraj et al, , 2014b(Kamaraj et al, , 2015(Kamaraj et al, , 2018(Kamaraj et al, , 2021Pandiarajan et al, 2017). Different adsorbents have been developed to improve the adsorption capacity of antibiotics, among which some carbon (C)-based adsorbents are the most notable, including active C and reduced graphene oxide (rGO).…”