Fe when strengthened with other metals (transition) embedded in it, results in a redox reaction with catalytic decomposition, and is favored with the increase in efficacy of the electrocatalytic system to bring about degradation of TPs [53–55]. A figurative description of the functionalized catalytic activity is shown in Figure 1.3.
In a typical report of Cui, L. et al., MO decomposition by H-EF was proved to be accelerated by FNM - Fe3O4/MWCNTs, when prepared by solvothermal process. Degradability of the TP was noted to be 90.3% (3 h) with reusability to 5 runs, at pH (3). This system with two compartments of FNM membrane required no external additives, but had a potency in green wastewater treatment techniques [56]. Zhao, H. et al. reported that Fe3O4@Fe2O3/ACA (activated C aerogel) as cathodic in this EF routine degraded (90%) of OP-pesticide imidacloprid (30 min) and TOC (60 min) in pH range of (3–9) [57]. Haber-Weiss model inferred that Fe2+ aided the decomposition of peroxide to form ·OH. ·OH and ·O2− contribute for the degradation of OP. Mesoporous FNMs MnCo2O4-CF (C felt) as cathodic EF with excellent porosity and large modified surface area prepared showed a powerful degrading capacity for CIP (100%) an antibiotic in 5 h and TOC (75%) in 6 h [58]. Mn2+/Mn3+, Co3+/Co2+ with e− transfers enhanced peroxide decomposition to form ·OH and ·OOH required for five cycles degradation.
Figure 1.3 Electro-Fenton functionalized catalytic degradative activity for water bodies.
Table 1.1 Electro-Fenton (EF)/Hetero-Electro-Fenton (H-EF) catalyst as FNMs.
| FNMs as catalyst | Type | Year | Process | Current/Voltage | Parametric expressions | Solution evolved (% degradation) | Reusable cycles | Remarks | Ref. |
| BGA-GDE | EF | 2019 | Hydrothermal | 4.5 mA cm−2 | pH (3–9) | 60 min | BPA (~89.65%) | 5 TOC (~90%) | 5 | · OH | pseudo-1st-order kinetics | [62] |
| RGO-Ce/WO3 NS/CF | EF | 2018 | Hydrothermal | 300–400 mA | pH (3) | 1h | CIP (100%) | 5 | · O2−, H2O2, ·OH | Ce-WO3 improved adsorption | [63] |
| ACF-HPC | EF | 2019 | Hydrothermal, carbonization | (16, 20, 24) mA cm−2 | pH (3, 7, 9) | 40, 180 min | Phenol (93.8%) | 5TOC (85.7%) | 5 | Enhanced formation of H2O2, ·OH | Low-cost | [64] |
| Fe-C/PTFE | H-EF | 2015 | Ultra-sonification | 100 mA | pH (6.7) |120 min | 2,4-DCP (95%) | | pseudo-1st-order kinetics | promoters: H2O2, ·OH | Cheap | [65] |
| N-C (NF) as (c PANI/GF2) | EF | 2019 | Carbonization (PANI) |−0.6 V | pH (3) |180 min | Mineralization (42%) | Florfenicol (99%)| Phenol (85%) | MO (100%) | 5 | Activation: H2O2 → ·OH | [66] |
| FeOx/NHPC750 | H-EF | 2020 | Hydrothermal, carbonization | (−3.30, −4.42, −3.77) mA cm−2 | −0.6 V | pH (6) |90 min | ATZ (96%) | Rh B (99%) | 2,4-DCP (99%) | Sulfamethoxazole (95%) | Phenol (99%) | 5 | Cleavage of O-O bond | Assists H2O2 | Fe2+ + O2 → Fe3+ + ·O2− | [67] |
| (Co, S, P)/MWCNTs | P-EF |2019 | Hydrothermal | 40 mA cm−2 | pH (3) |360 min | Bronopol (100%) |TOC (77%) | 3 | Contributors: sunlight, ·OH, BDD (·OH) | | [68] |
| Mn/Fe@porous C (PC)-CP cathode | H-EF | 2019 | Carbonization | 40 mA | pH (2–8) |120 min, 240 min | TCS (100%) | TOC (~57%) | 6 | Regeneration: Fe2+/Mn2+/3+| e-transfer: Fe2+/3+, Mn2+/3+/4+, pseudo-0-order kinetics | [69] |
| 3DG/Cu@C | H-EF | 2020 | Hydrothermal, calcination | 30 mA | pH (3–9) | 150 min | Rh B (100%) | CIP (100%) | 2,4-DCP (100%) | PCA (89.8%) | BPA (96.1%) | CAP (82.6%) | 5 | Contributors: ·OH, ·O2− | e- transfer: Cu2+/+ | [70] |
| C felt/Fe-Oxides | H-EF | P-EF | 2016 | Electro-deposition | 21.7 mA cm−2 | pH (3) |120 min | MG (98%) | 10 | ·OH, BDD - activators | UVA | pseudo-1st-order kinetics | | [71] |
| (N-G@CNT | EF | 2108 | Hydrothermal | variable | −0.2 V | pH (3) |180 min | DMP (100%) | 20TOC (40.4%) | Fe2+ + H2O2 → Fe3+ + e− | pseudo-1st-order kinetics | [72] |
| F-rGO/SS membrane | EF | 2019 | Electrophoretic deposition | 170 mA | −0.5 V | pH (3) | | PCM (37%) | 5 | e- transfer-enhanced by rGO | low-cost membrane | [73] |
| G-CNT-CE | EF | 2014 | Electrophoretic deposition | 0.18 A | pH (3) |210 min | Acid Red 14 (91.22%) |Acid Blue 92 (93.45%) |