Heterogeneous electro-Fenton Catalyst Research Articles

Accelerated removal of sulfadiazine by heterogeneous electro-Fenton system with Pt-FeOX/graphene single-atom alloy cathodes

Heterogeneous electro-Fenton (EF) process is emerging as an attractive treatment technology for removal of sulfadiazine (SDZ), in which in situ generation of H2O2 and Fe(II) are crucial steps. In this study, Pt-FeOX/G was synthesized as a heterogeneous EF catalyst by incorporating Pt single atoms into a FeOX nanocrystal. The optimized Pt1-FeOX/G cathode exhibited an SDZ conversion of >90% within 30 min over a broad pH range (3–11). The Pt1-FeOX/G cathode under a strong alkaline medium exhibited very prominent selectivity to H2O2 via 2e− oxygen reduction reaction with a maximum H2O2 concentration of 211.93 mg L−1. The hydroxyl radicals in the cathodic chamber were mainly derived from the in situ conversion of generated H2O2 in the heterogeneous EF system. The structure-activity results of Pt-FeOX/G suggested that the SDZ removal efficiency was closely related to the decentralized morphology and electronic configuration of the Pt-FeOX microcrystalline structure. Three possible SDZ degradation pathways, dominated by S–N bond cleavage, were proposed based on the stage products. The toxicity of the major products was determined using the ecological structure-activity relationship model in conjunction with trophic aquatic organisms. This study demonstrated the feasibility of enhancing heterogeneous EF catalysis for antibiotic-polluted water using multifunctional single-atom alloy cathodes.

Highly dispersed FeN-CNTs heterogeneous electro-Fenton catalyst for carbamazepine removal with low Fe leaching at wide pH

Highly dispersed FeN-CNTs heterogeneous electro-Fenton catalyst for carbamazepine removal with low Fe leaching at wide pH

Fe/Fe3C nanoparticles embedded in N-doped porous carbon as the heterogeneous electro-Fenton catalyst for efficient degradation of bisphenol A

Heterogeneous electro-Fenton is a promising technology for the degradation of organic contaminants. To ensure its effectiveness, it is in urgent demand to design cathode materials with the integrated capability of sufficient H2O2 generation and subsequent activation into reactive oxygen species (ROS) together with catalytic stability. Herein, a composite constituted by Fe/Fe3C nanoparticles embedded into N-doped porous carbon (NPC), designated as Fe/Fe3C@NPC, was successfully fabricated from Fe3+-loaded poly(imine dioxime) (PIDO) membrane via the thermal treatment in N2 atmosphere and employed as the heterogeneous electro-Fenton catalyst to degrade bisphenol A (BPA). By optimizing the pyrolysis temperature and loading level of iron species, the catalyst obtained at 800 °C (i.e. Fe/Fe3C@NPC-800) achieved almost 100% of BPA removal efficiency within 120 min via the electro-Fenton system, accompanied by 69.2% of the total organic carbon (TOC) removal rate. Furthermore, the proposed composite catalyst also exhibited satisfactory reusability and stability, as reflected by low decrease in removal efficiency after six successive degradation tests and limited iron leaching (<0.5 mg/L). This work might provide valuable instruction for the rational design of highly efficient and stable heterogeneous electro-Fenton catalysts for organic pollutant control.

Hemin derived iron and nitrogen-doped carbon as a novel heterogeneous electro-Fenton catalyst to efficiently degrade ciprofloxacin

• Hemin derived iron and nitrogen-doped carbon catalyst exhibited high ciprofloxacin degradation and mineralization efficiency. • KHCO 3 -MgO dual-porogen improved the porous characteristics and exposed the iron sites. • Based on degradation intermediates analysis, a possible degradation pathway of CIP was proposed. • It exhibited good stability and potential for treatment of organic pollutants in wastewater. Heterogeneous electro-Fenton (HEF) technology has become a hot topic for degradation of organic pollutants in water. However, it remains a challenge to design effective catalysts for high H 2 O 2 utilization and pollutant degradation. In this work, we explored a novel iron and nitrogen-doped carbon catalyst derived from hemin (Fe-N-C) using KHCO 3 -MgO as dual-porogen. The results suggested that the KHCO 3 -MgO dual-porogen could not only improve the porous characteristics of catalyst, but also expose iron sites and change the proportion of nitrogen species. The pollutant degradation results demonstrated that the Fe-N-C-700/HEF system exhibited high ciprofloxacin degradation efficiency of 93.82% within 50 min and mineralization efficiency of 87.87% within 90 min by low energy consumption. Moreover, cycle experiments and metal ions leaching experiments revealed that the catalyst had good stability and recyclability. Electron spin resonance (ESR) test and radical capturing experiment showed that • OH was the dominant active species in this HEF system. In addition, the Fe-N-C-700/HEF system achieved satisfactory performance in the treatment of real water matrix, indicating the possibility for practical application in wastewater purification.

Degradation of carbamazepine over MOFs derived FeMn@C bimetallic heterogeneous electro-Fenton catalyst

A highly efficient heterogeneous electro-Fenton (Hetero-EF) catalyst with core-shell structure was successfully prepared by calcination of Mn-doped Mil-53 (Fe) precursor at high temperature. FeMn@C-800/2 prepared at pyrolysis temperature of 800 °C and Fe:Mn molar doping ratio of 2:1 showed the best catalytic performance for the degradation of carbamazepine (CBZ). The characterization, properties and stability of FeMn@C-800/2 were systematically investigated, obtaining the apparent first-order reaction rate of Hetero-EF was 8.9 and 17.8 times higher than that on Fe@C-800 and Mn@C-800 at the optimized conditions of current density 10 mA cm−2, catalyst dosage of 50 mg L−1 and initial pH 4.0, respectively. The incorporation of Mn promoted the generation of more Fe0 and Fe3C during the pyrolysis process, and enhanced the internal micro-electrolysis between Fe0 and carbon shell. At the same time, the presence of Mn0 also promoted the regeneration of Fe2+, and improved the activity of iron-carbon heterogeneous catalysis in the EF process, so as to degrade organic pollutants more effectively. This work would help to gain insight into the design of MOFs derived Fe–Mn bimetal catalyst and its mechanism for enhanced heterogeneous electro-Fenton.

Sustainable reuse of nickel converter slag as a heterogeneous electro-fenton catalyst for treating textile dyeing wastewater: Activity, mechanism and stability assessment

The high production and improper disposal of nickel converter slag (NCS) are raising serious concerns about its environmental impact, owing to the waste of resources and the foregone contribution to air, soil and groundwater pollution. This work uncovered that NCS could be reused as a superior catalyst for the treatment of textile dyeing wastewater by the heterogeneous electro-Fenton (hetero-EF) process. The NCS-laterite porous ceramsite (NLPC) catalyst showed the highest activity when the ratio of NCS to laterite was 3:2 and calcined at 900 °C. The methylene blue (MB) removal rate and chemical oxygen demand (COD) removal rate were 98.64% and 87.84%, respectively, after 30 min reaction under optimal operating parameters (100 g L−1 NLPC, 4 V of cell voltage and initial pH 3.0). Compared with the electro-Fenton (EF) system without NLPC catalyst, the degradation rate constant was increased by 223.9% (0.0452–1.464 min−1) and the energy consumption was reduced by 65.84% (2.02–0.69 kWh m−3). After six cycles, the MB removal rate only decreased by 5.35%, and the NLPC mass loss rate was 2.04%. Synergies between Co, Ni, Fe and Cu species to promote reactive oxygen species (ROS) generation were the predominant catalytic mechanism. Two possible pathways of MB degradation were deduced. In addition, the NLPC catalyst also showed excellent effects in different wastewater treatments. This work demonstrated an upgrade strategy for cleaner production of non-ferrous metallurgical by-products.

Single iron atoms embedded in MOF-derived nitrogen-doped carbon as an efficient heterogeneous electro-Fenton catalyst for degradation of carbamazepine over a wide pH

Developing efficient, stable heterogeneous catalysts with wide adaptability to pH is of great significance for the degradation of organic pollutants by electro-Fenton (EF). In this work, a novel heterogeneous EF (Hetero-EF) catalyst, single atomic Fe sites embedded into N-doped porous carbon (Fe-N/C) was prepared using Fe-doped zeolitic imidazolate frameworks as a precursor. Single Fe atoms anchored on N/C were clearly observed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Due to the single-atom dispersion and the highest content of FeNx, the optimized 0.3Fe-N/C exhibited excellent catalytic activity for the removal of carbamazepine (CBZ) over a wide pH between 3∼11 with very low iron leaching (<0.3 mg/L even at pH 3). The turnover frequency in the Hetero-EF process was 1.6–19 times higher than that of most catalysts in literature. Besides, 0.3Fe-N/C showed superior durability in seven cycling tests and wide suitability to various pollutants. The quenching experiments and electron paramagnetic resonance demonstrated that both OH and 1O2 were responsible for the CBZ degradation, which made 0.3Fe-N/C had a strong tolerance to pH. This work provides a new perspective for the application of atomic Fe-based catalysts, improving stability and pH adaptability in Hetero-EF for wastewater treatment.

Synthetic Ilmenite (FeTiO3) Nanoparticles as a Heterogeneous Electro-Fenton Catalyst for the Degradation of Tetracycline in Wastewater

Synthetic Ilmenite (FeTiO₃) Nanoparticles as a Heterogeneous Electro-Fenton Catalyst for the Degradation of Tetracycline in Wastewater

FeMo@porous carbon derived from MIL-53(Fe)@MoO3 as excellent heterogeneous electro-Fenton catalyst: Co-catalysis of Mo

An ultra-efficient electro-Fenton catalyst with porous carbon coated Fe-Mo metal (FeMo@PC), was prepared by calcining MIL-53(Fe)@MoO3. This FeMo@PC-2 exhibited impressive catalytic performance for sulfamethazine (SMT) degradation with a high turnover frequency value (7.89 L/(g·min)), much better than most of reported catalysts. The mineralization current efficiency and electric energy consumption were 83.2% and 0.03 kWh/gTOC, respectively, at low current (5 mA) and small dosage of catalyst (25.0 mg/L). The removal rate of heterogeneous electro-Fenton (Hetero-EF) process catalyzed by FeMo@PC-2 was 4.58 times that of Fe@PC/Hetero-EF process. Because the internal-micro-electrolysis occurred between PC and Fe0, while the co-catalysis of Mo accelerated the rate-limiting step of the Fe3+/Fe2+ cycle and greatly improved the H2O2 utilization efficiency. The results of radical scavenger experiments and electron paramagnetic resonance confirmed the main role of surface-bound hydroxyl radical oxidation. This process was feasible to remove diverse organic contaminants such as phenol, 2,4-dichlorophenoxyacetic acid, carbamazepine and SMT. This paper enlightened the importance of the doped Mo, which could greatly improve the activity of the iron-carbon heterogeneous catalyst derived from metal-organic frameworks in EF process for efficient removal of organic contaminants.

Efficient degradation of diuron using Fe-Ce-LDH/13X as novel heterogeneous electro-Fenton catalyst

• Fe-Ce-LDH was successfully loaded onto the defect sites of molecular sieve (13X). • Excellent diuron removal was achieved with Fe-Ce-LDH/13X in EF process. • The possible heterogeneous degradation pathways for diuron are proposed. • Improved H 2 O 2 utilization was responsible for the efficient catalytic performance. • More active sites were responsible for the efficient catalytic performance. The heterogeneous electro-Fenton process is an effective technology to remove organic pollutants. However, developing efficient heterogeneous electro-Fenton catalysts remains challenging. In this paper, an iron-cerium layered double hydroxide (Fe-Ce-LDH) was successfully loaded via a solvothermal method onto the defect sites of the molecular sieve 13X to form a novel heterogeneous catalyst (Fe-Ce-LDH/13X). The catalytic performance of Fe-Ce-LDH/13X was evaluated in the heterogeneous electro-Fenton (EF) degradation of diuron. Compared with a traditional powder catalyst, this catalyst was easier to recycle and exhibited good stability. The layered structure of the catalyst provided more active sites. Doping with Ce greatly improved the catalytic performance of the catalyst, which was caused by the synergistic effect of Ce and Fe. At a molar Fe to Ce ratio of 7:3, diuron could be completely degraded within 60 min. According to the catalytic mechanism, the hydroxyl radical ·OH is the main reactive species. Possible degradation pathways in the heterogeneous EF process were proposed based on the intermediates identified in the degradation of diuron. Toxicity analysis indicated that the heterogeneous EF process could not only degrade diuron but also reduce toxicity. This work presents a novel preparation method of a composite catalyst with excellent catalytic performance in an EF system, which supports the development of efficient heterogeneous EF catalysts.

Using chitosan-based heterogeneous catalyst for degradation of Acid Blue 25 in the effective electro-Fenton process with rotating cathodes

Herein, the capability of glutaraldehyde cross-linked magnetic chitosan nanoparticles (Fe3O4/CS/GA NPs) was investigated as a heterogeneous electro-Fenton catalyst for the degradation of Acid Blue 25. A cylindrical reactor with rotating cathodes was used for performing the electro-Fenton process. Fe3O4/CS/GA NPs were characterized by Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray (EDX), and Vibrating Sample Magnetometer (VSM). According to the results, the dye removal efficiency reached 94.83% after 90 min under the optimal conditions of Fe3O4/CS/GA NPs with the iron content of 15 mmol Fe/g chitosan and concentration of 0.3 g/L, natural pH of dye (6.8), initial dye concentration of 150 mg/L, the current intensity of 0.7 A, and rotational speed of 100 rpm. Also, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal reached 74.19% and 61.53% after 120 min, respectively. Average oxidation state (AOS) and carbon oxidation state (COS) values were increased after treatment, indicating that wastewater's biodegradability was improved. Moreover, the heterogeneous electro-Fenton process using optimal Fe3O4/CS/GA NPs resulted in about 16% improvement in the removal efficiency compared to the homogeneous process. The catalyst showed good reusability up to 5 cycles. The amounts of leached iron into the solution were much less than allowable amounts of the Iranian wastewater discharge standard, thus no need for secondary treatment. Furthermore, scavengers studies under the optimum conditions showed the dye degradation occurred mainly by surface-bonded hydroxyl radicals. In short, this study proved, Fe3O4/CS/GA NPs are a promising heterogeneous electro-Fenton catalyst due to their low cost, excellent stability and reusability, negligible iron leaching, environmental compatibility, and superior catalytic activity in a wide range of pH.

Degradation of Carbamazepine Over Mofs Derived Femn@C Bimetallic Heterogeneous Electro-Fenton Catalyst

Degradation of Carbamazepine Over Mofs Derived Femn@C Bimetallic Heterogeneous Electro-Fenton Catalyst

Single Iron Atoms Embedded in Mof-Derived Nitrogen-Doped Carbon as an Efficient Heterogeneous Electro-Fenton Catalyst for Degradation of Carbamazepine Over a Wide Ph

Single Iron Atoms Embedded in Mof-Derived Nitrogen-Doped Carbon as an Efficient Heterogeneous Electro-Fenton Catalyst for Degradation of Carbamazepine Over a Wide Ph

Mixed industrial wastewater treatment by the combination of heterogeneous electro-Fenton and electrocoagulation processes

Mixed industrial wastewater treatment efficiency of combined electro-Fenton (EF) and electrocoagulation (EC) processes was investigated in the present study. Alkali modified laterite soil was used as a heterogeneous EF catalyst and found superior performance than the raw laterite soil. Initially, the effect of catalyst dosage, initial pH, and applied voltage on the performance of EF process was carried out. A total of 54.57% COD removal was observed after 60 min of the EF treatment. Further treatment was carried out with EC process at different voltages. A total of 85.27% COD removal after 2 h treatment was observed by combining two electrochemical processes. Performance of EF followed by EC (EF + EC) process was compared with EC followed by EF (EC + EF) process. Even though efficiency is the same, EF + EC is a better strategy than EC + EF as it nullifies the neutralization requirement after EF process in addition to high mineralization efficiency, enhanced biodegradability, and lesser sludge generation.

S-doped MIL-53 as efficient heterogeneous electro-Fenton catalyst for degradation of sulfamethazine at circumneutral pH

The reduced S-modified MIL-53(Fe) was prepared by sulfurizing MIL-53(Fe) at low temperature, which was an efficient electro-Fenton catalyst at wide pH range (3–9) for sulfamethazine (SMT) degradation. The best temperature and MIL-53(Fe)/S ratio were 350 °C and 1:2, at which the BET surface area was much enlarged. The MIL-53(Fe) surface was etched by S to many 2D nanosheets with the thickness of ~50 nm, while S2–2 replaced OH- to coordinate with Fe2+ and increased the Fe2+ content, which improved the catalytic performance. Even at initial pH of 7.0, the SMT removal was 95.8%, and the rate constant (k) in the Hetero-EF process was 16-folds of that in the Homo-EF process. The turnover frequency (TOFd) value of MIL-53(Fe)/S(1:2)−350 was 0.48 L g−1 min−1, which was 6.8 times that of commercial FeS2. The S2–2in catalyst adjusted the pH superfast, and promoted the generation of Fe2+ and thus efficiently activating H2O2 to form surface ·OH, which was verified to be the main radical by EPR and radical scavenger experiments. This catalyst showed promising prospect for environmental application and could be regenerated by sulfidation method. S-doped MIL-53(Fe) was an excellent pH regulator, thus promoting promising application in Hetero-EF processes.

Bifunctional iron molybdate as highly effective heterogeneous electro-Fenton catalyst and Li-ion battery anode

Three-dimensional materials have attracted considerable interest in energy and environmental remediation fields. Iron molybdate (FMO) materials have prepared via a facile hydrothermal technique with glycerol assistance, and their structural and chemical composition confirmed using various physico-chemical techniques. The prepared bi-functional material is a strong candidate for energy storage and electrocatalytic degradation of Methylene blue and Congo red. Experimental results confirmed the synthesized FMO-10 catalyst was extremely efficient for methylene blue and Congo red breakdown, achieving 91 % and 96 % degradation in 36 h, respectively. This high catalytic activity was attributed to FMO significant visible light absorption, and reactive OH formation from H2O2 synergistically triggered by both Fe3+ and MoO42−. Prepared FMO samples demonstrated excellent potential as negative electrode material for lithium ion batteries. Electrode specific capacity initially dropped then rebounded to 1265 mAh g−1 after 100 cycles at 100 mA g−1 change rate between 0.01 and 3.0 V.

Efficient degradation of tetracycline using core–shell Fe@Fe2O3-CeO2 composite as novel heterogeneous electro-Fenton catalyst

Developing efficient heterogeneous electro-Fenton (EF) catalysts for degradation of organic pollutants remains a challenge. Herein, a novel heterogeneous EF catalyst, core–shell Fe@Fe2O3-CeO2 composite, was successfully synthesized in a facile manner for effective degradation of tetracycline (TC) pollutant. The catalytic activity was evaluated by effects of different processes, Fe/Ce molar ratio, catalyst dosage, initial solution pH, applied current and aeration mode. Fe@Fe2O3-CeO2 with 2:1 Fe/Ce molar ratio achieved TC removal efficiency of 90.7% within 1 h and mineralization efficiency of 86.9% within 6 h with such excellent performance attributed to the high utilization efficiency of H2O2 and the synergistic effects between Ce4+/Ce3+ and Fe3+/Fe2+. Moreover, this novel catalyst exhibited good recyclability and stability in successive cycles with low metal leaching. Furthermore, the heterogeneous EF process showed satisfactory catalytic activity towards degradation of other organic pollutants (e.g., metronidazole, diclofenac sodium, and chloramphenicol). Based on the experimental results and analysis, the mechanism of the heterogeneous EF process with Fe@Fe2O3-CeO2 catalyst and possible TC degradation pathways were proposed, which provides insights into the catalytic reaction process and should be of value in facilitating the application of this method in refractory wastewater treatment.

N-doped carbon-coated Fe3N composite as heterogeneous electro-Fenton catalyst for efficient degradation of organics

Herein, the application of a N-doped graphitic-carbon-coated iron nitride composite dispersed in a N-doped carbon framework (Fe3N@NG/NC) is investigated as a heterogeneous electro-Fenton (HE-EF) catalyst for the efficient removal of organics. The simultaneous carbonization and ammonia etching of iron-based metal organic framework (Fe-MOF) materials yielded well-dispersed N-doped carbon-coated Fe3N nanoparticles with a diameter of ~70 nm. The Fe3N and pyridinic N endowed the composite with high HE-EF activity for decomposing the electrogenerated H2O2 to •OH. The Fe3N@NG/NC exhibited outstanding HE-EF performance in removing various organic pollutants with low iron leaching. A removal rate of 97–100% could be obtained for rhodamine B (RhB), dimethyl phthalate, methylene blue, and orange II in 120 min at a pH of 5.0. When the solution pH was set to 3.0, 5.0, 7.0, and 9.0, the removal rate of RhB reached 100%, 96%, 92%, and 81%, respectively, in 60 min at an optimum voltage of 0.0 V (vs. reversible hydrogen electrode (RHE)). Moreover, the concentration of leached iron was expected to be below 0.03 mg/L in a wide pH range of 3.0–9.0. In addition, the RhB removal efficiency remained as high as 90% after six cycles in the reusability experiments. This work highlights the MOF-derived Fe3N composite as an efficient HE-EF catalyst and the corresponding catalytic mechanism, which facilitates its application in wastewater treatment.

Hydrothermal synthesis of FeS2 as a highly efficient heterogeneous electro-Fenton catalyst to degrade diclofenac via molecular oxygen effects for Fe(II)/Fe(III) cycle

In this study, we demonstrated that hydrothermal synthesized FeS2 was highly efficient to catalyze the H2O2 decomposition for diclofenacsodium (DCF) degradation in a wide range of initial pH (3–9) by heterogeneous electro-Fenton (EF) process, and this “Pyrite-EF” showed a better performance for the mineralization of DCF in comparison with the classic EF process. Effect of pyrite content on the hydroxyl radicals generation and iron dissolution produced by the decomposition of hydrogen peroxide (H2O2), and applied current density on the degradation kinetics and mineralization efficiency were studied. Moreover, toxicity assessment by means of microtox method showed the solution toxicity was removed after treatment. Experimental results revealed that the enhancement of DCF degradation rate in the Pyrite-EF process was attributed to the molecular oxygen activation induced by more surface bound ferrous ions on FeS2, generating superoxide anions to accelerate the Fe(II)/Fe(III) cycle on the FeS2 surface, which favored the H2O2 decomposition to generate more hydroxyl radicals for the DCF degradation via a heterogeneous EF-like process. These findings could provide some new insights into the molecular oxygen activation induced by FeS2 and the subsequent heterogeneous Pyrite-EF degradation of organic pollutants from wastewater.

Catalytic activity of LaCu0.5Mn0.5O3 perovskite at circumneutral/basic pH conditions in electro-Fenton processes

A great challenge in electro-Fenton processes is the development of active heterogeneous catalysts at circumneutral or even basic pH in order to avoid the acidification of the wastewater effluents and the generation of an undesirable metallic sludge after the treatment. In this work, LaCu0.5Mn0.5O3 perovskite has been assessed as heterogeneous electro-Fenton catalyst for the removal of methylene blue dye as model pollutant. The catalyst has been tested in a wide range of pH, from acidic (3) to basic (8.5) values. The effect of the catalyst loading, the applied voltage and the air flow was also studied on the efficiency of the electro-Fenton process. LaCu0.5Mn0.5O3 showed a remarkable activity at circumneutral and basic pH, even at the low current density studied of 2.6–0.9 mA/cm2. The durability of the catalyst was also assessed for five successive runs. XRD patterns of the reused catalyst evidenced a high stability of the perovskite structure after the several runs. The low copper leaching of the catalyst in the aqueous phase (< 0.05 mg/L for Cu) also proves the stability of the LaCu0.5Mn0.5O3 perovskite material and its main contribution as heterogeneous catalyst to the overall activity of the electro-Fenton system.