Phenol Degradation Pathway Research Articles

A Novel Cu/Fe Cathode Prepared by a Facile Redox Pathway for Phenol Degradation Electrocatalytically via the Electro-Fenton assisted Electro-Chlorination Process

A Novel Cu/Fe Cathode Prepared by a Facile Redox Pathway for Phenol Degradation Electrocatalytically via the Electro-Fenton assisted Electro-Chlorination Process

The preparation and characterization of WS2 nanomaterials with different morphologies and the mechanistic study of peroxymonosulfate activation for phenol degradation

Transitional metal chalcogenides like WS2 play a significant role as cocatalysts in activating PMS (peroxymonosulfate) due to their high reductivity. Three WS2 samples with different morphologies, specific surface areas, and 1 T phase contents were prepared in this study. Characterizations by SEM, TEM, BET, XRD, Raman, XPS, and catalytic degradation experiments confirmed that the a-WS2 sample exhibited the richest morphology, the largest specific surface area, the highest 1 T phase content, and the best cocatalytic performance. The a-WS2/Fe(II)/PMS system efficiently degraded 20 mg/L phenol within 15 minutes and was also effective in degrading pollutants like RhB (Rhodamine B) and OFX (Ofloxacin). Characterization predicted the degradation pathway of phenol and revealed 10 intermediate products. The degradation mechanism indicated that the presence of WS2 accelerated the conversion of Fe(III) to Fe(II), thereby further promoting the activation of PMS. ·SO4−, ·OH, and ·O2− were identified as the main active radicals in this system. a-WS2 exhibits characteristics such as high catalytic performance, good stability, high recyclability, and a low ion leaching rate, and it generates sulfur vacancies during use. This system shows promising prospects in the treatment of high-concentration organic wastewater.

Unveiling superior phenol detoxification and degradation ability in Candida tropicalis SHC-03: a comparative study with Saccharomyces cerevisiae BY4742.

This study examined the phenol degradation capabilities and oxidative stress responses of Candida tropicalis SHC-03, demonstrating its metabolic superiority and resilience compared to Saccharomyces cerevisiae BY4742 in a culture medium with phenol as the sole carbon source. Through comparative growth, transcriptomic, and metabolomic analyses under different phenol concentrations, this study revealed C. tropicalis SHC-03's specialized adaptations for thriving in phenol as the sole carbon source environments. These include a strategic shift from carbohydrate metabolism to enhanced phenol degradation pathways, highlighted by the significant upregulation of genes for Phenol 2-monoxygenase and Catechol 1,2-dioxygenase. Despite phenol levels reaching 1.8 g/L, C. tropicalis exhibits a robust oxidative stress response, efficiently managing ROS through antioxidative pathways and the upregulation of genes for peroxisomal proteins like PEX2, PEX13, and PMP34. Concurrently, there was significant upregulation of genes associated with membrane components and transmembrane transporters, enhancing the cell's capacity for substance exchange and signal transduction. Especially, when the phenol concentration was 1.6 g/L and 1.8 g/L, the degradation rates of C. tropicalis towards it were 99.47 and 95.91%, respectively. Conversely, S. cerevisiae BY4742 shows limited metabolic response, with pronounced growth inhibition and lack of phenol degradation. Therefore, our study not only sheds light on the molecular mechanisms underpinning phenol tolerance and degradation in C. tropicalis but also positions this yeast as a promising candidate for environmental and industrial processes aimed at mitigating phenol pollution.

Fe/Ni bimetallic magnetic nano-alloy (INBMNA): An efficient heterogeneous catalyst for photo-Fenton-like degradation of phenol in aqueous environment

A lot of attention has been drawn to photo-Fenton-like catalysis among advanced oxidation processes for environmental remediation applications. Herein, we have successfully fabricated iron-nickel bimetallic magnetic nano-alloy (INBMNA) as an efficient heterogeneous photo-Fenton-like catalyst using the chemical reduction method and characterized by several analytical techniques. The characterization results show that the catalyst has a spherical shape with a mesoporous nature and contains a large specific surface area. The impact of various parameters was investigated and optimized to check the catalytic performance of INBMNAs and the found results showed that excellent photo-Fenton-like activity persisted under 6.0 pH conditions for the degradation of hazardous pollutant (phenol) under solar light exposure and microwave radiation power, respectively. Additionally, the exposed INBMNA/H2O2 system provided continuous redox cycles of Fe3+/Fe2+ and Ni2+/Ni0 pair in the Fenton-active species for stable operation. The photo-Fenton-like activity was also performed to check the effect of different inorganic anions which significantly hinder phenol reduction. Besides, the steady performance of the catalyst to remove phenol was performed in tap water and river water. Free radical trapping experiments were tested to know the role of important radicals in the photo-Fenton process. Moreover, the mechanism and possible degradation pathways of phenol were checked. By cyclic degradation experiments, the performance of the catalyst is stable and almost unchanged and can be reused several times. This study provides a promising INBMNA/H2O2 system, which encourages its widespread use in environmental remediation applications.

A novel paraffin-based N/P controlled-release material for biostimulation of phenol biodegradation in groundwater

To address the problem of the weak natural restoration ability of oligotrophic groundwater environments, a novel N/P controlled-release material (CRM) for biostimulation, prepared by an improved method, was developed. CRMs can encapsulate N and P (N/P) salts for sustained release in aquifers. Paraffin-based CRMs can be used to control N/P release rates by adjusting the particle size of CRMs and the mass ratio of the paraffin. The developed CRMs had a more remarkable adaptability to groundwater than other materials. Specifically, 0.4-cm CRMs released N/P stably and efficiently over a wide temperature range (7–25 ℃), and the release properties of various CRMs were not affected by pH. The release of N/P followed Fickian diffusion, and a dissolution-diffusion model was established to elucidate the mechanism of the controlled release. In contrast to bare N/P, CRMs obviously enhanced the biodegradation rate of phenol and prolonged the effectiveness of supplying N/P. The degradation rate of phenol in the CRM system increased by 20.8 %. The different supply modes of N/P, CRMs and bare N/P, resulted in differences in salinity. Metagenomic analysis showed that this difference changed the proportion of various phenol-degrading genera and thus changed the abundance of genes associated with the phenol degradation pathway.

Nanobubbles improve peroxymonosulfate-based advanced oxidation: High efficiency, low toxicity/cost, and novel collaborative mechanism

Cl- activated peroxymonosulfate (PMS) oxidation technology can effectively degrade pollutants, but the generation of chlorinated disinfection byproducts (DBPs) limits the application of this technology in water treatment. In this study, a method of nanobubbles (NBs) synergistic Cl-/PMS system was designed to try to improve this technology. The results showed the synergistic effects of NBs/Cl-/PMS were significant and universal while its upgrade rate was from 12.89% to 34.97%. Moreover, the synergistic effects can be further improved by increasing the concentration and Zeta potential of NBs. The main synergistic effects of NBs/Cl-/PMS system were due to the electrostatic attraction of negatively charged NBs to Na+ from NaCl, K+ from PMS, and H+ from phenol, which acted as a "bridge" between Cl- and HSO5- as well as phenol and Cl-/HSO5-, increasing active substance concentration. In addition, the addition of NBs completely changed the oxidation system of Cl-/PMS from one that increases environmental toxicity to one that reduces it. The reason was that the electrostatic attraction of NBs changed the active sites and degradation pathway of phenol, greatly reducing the production of highly toxic DBPs. This study developed a novel environmentally friendly oxidation technology, which provides an effective strategy to reduce the generation of DBPs in the Cl-/PMS system.

Modulation of morphology and phase of magnetically separable 1T-WS2/CuFe2O4 heterojunctions for acceleration of peroxymonosulfate decomposition for rapid degradation of phenol

Transition metal sulfides are often used as cocatalysts to activate Peroxymonosulfate (PMS) in Fenton-like systems, but the problems include difficulties in recycling and the need to inject iron ions. In this paper, a self-synthesized magnetically recoverable heterogeneous 1 T-WS2/CuFe2O4 composites was prepared for the first time via a two-step hydrothermal method, and the content of the 1 T phase in WS2 was adjusted by controlling the hydrothermal temperature. Analytical techniques, such as XRD, Raman, SEM, TEM, BET, XPS, and VSM, showed that the composite catalyst was prepared with good particle shapes and high content of the 1 T phase. At the optimal dosage, this material activated PMS degraded to 93.6 % of 20 mg/L phenol in 50 min. The system exhibited high degradation efficiency, excellent interference resistance and good cycling stability under different conditions, and sulfur vacancies were generated during the process. ESR, quenching experiments, and other analyses confirm that SO4−, OH and 1O2 are the main active species in the system, with 1O2 making the greatest contribution. The degradation pathway of phenol was analyzed, and the formation of 12 intermediate products was qualitatively identified. Additionally, a simulation analysis of the toxicity of intermediate products was conducted. The degradation mechanism indicated that the three redox couples, Cu+/Cu2+, Fe2+/Fe3+ and W4+/W6+, provided synergistic activation of PMS. The self-synthesized 1 T-WS2/CuFe2O4 composite showed high catalytic performance, good stability, a high magnetic recovery rate and a low ion leaching rate and shows promise for treating concentrated organic wastewater.

Nitrogen-Doped Biochar for Enhanced Peroxymonosulfate Activation to Degrade Phenol through Both Free Radical and Direct Oxidation Based on Electron Transfer Pathways.

Nowadays, super nitrogen-doped biochar (SNBC) material has become one of the most promising metal-free catalysts for activating peroxymonosulfate (PMS) to degrade organic pollutants. To understand the evolution of SNBC properties with fabrication conditions, a variety of SNBC materials were prepared and characterized by elemental analysis, N2 adsorption-desorption, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. We systematically investigated the activation potential of these SNBC materials for PMS to degrade phenol. SN1BC-800 with the best catalytic performance was obtained by changing the activation temperatures and the ratio of biochar to melamine. The effects of catalyst dosage, the PMS concentration, pH, and reaction temperature on phenol degradation were studied in detail. In the presence of 0.3 g/L SN1BC-800 and 1 g/L PMS, the removal rate of 20 mg/L phenol could reach 100% within 5 min. According to electron paramagnetic resonance spectra and free radical quenching experiments, a nonfree radical pathway of phenol degradation dominated by 1O2 and electron transfer was proposed. More interestingly, the excellent catalytic performance of the SN1BC-800/PMS system is universally applicable in the degradation of other typical organic pollutants. In addition, the degradation rate of phenol is still over 80% after five reuses, which shows that the SN1BC-800 catalyst has high stability and good application prospects in environmental remediation.

Development of a 3D Ni-Mn binary oxide anode for energy-efficient electro-oxidation of organic pollutants

The depletion of clean water resources and the consequent accumulation of contaminants in aquatic systems must be urgently addressed by means of innovative solutions. Electro-oxidation (EO) is considered a promising technology, prized for its versatility and eco-friendliness. However, the excessively high prices and the toxicity associated with some of the materials currently employed for EO impede its broader application. This study introduces cost-effective Ni-Mn binary oxide anodes prepared on Ni foam (NF) substrate. A scalable synthesis route that enables a 35-fold increase in the production of active material through a single optimization step has been devised. The synthesized binary oxide material underwent electrochemical characterization, and its effectiveness was assessed in an electrochemical flow-through cell, benchmarked against single Ni or Mn oxides and more conventional alternatives like boron-doped diamond (BDD) and dimensionally-stable anode (DSA). The novel binary oxide anode demonstrated exceptional performance, achieving complete removal of phenol at very low current density of 5 mA cm−2, along with an 80% of chemical oxygen demand (COD) decay within only 60 min. The NF/NiMnO3 anode outperformed the BDD and DSA when using comparable projected surface areas, owing to its high porosity and ability to produce hydroxyl radicals, as confirmed from the degradation profiles in the presence of radical scavengers. Furthermore, GC/MS analysis served to elucidate the degradation pathways of phenol.

Interface-engineered dual Z-scheme of BiVO4/NH2-MIL-125(Ti)/POF photoanode with enhanced photoelectrochemical performance

The key factors that restrain the decomposition activity of photoelectrocatalysis (PEC) are poor redox ability and low charge separation rate. In this work, the dual Z-scheme BiVO4/NH2-MIL-125(Ti)/POF (BiVO4/NM125(Ti)/POF) heterojunctions were successfully established for visible-light driven PEC degradation of phenol. As expected, the optimum BiVO4/NM125(Ti)/POF photoanode exhibited outstanding PEC performance with near-total degradation of phenol within 2 h of illumination. The evaluated activity was assigned to high charge transfer rate and dual Z-scheme heterostructures with double electron transport channels. The fabrication of dual Z-scheme heterojunctions improved a more efficient separation of photo-induced charge carriers while holding a higher redox ability to generate more reactive oxygen species (ROS) such as O2•− and •OH to decompose organic pollutants. In addition, excellent chemical stability and recyclability were also achieved after five times cycles, and the degradation pathway of phenol was also put forward. Finally, the quantitative structure-activity relationship (QSAR) was applied to forecast phenol and its degradation products toxicity. This research gives novel insights into establishing highly effective photoanode with promising applications for organic contaminants degradation, and offers in-depth understanding of charge separation and migration in PEC process.

Degradation of aqueous phenol by combined ultraviolet and electrochemical oxidation treatment

The industrial wastewater containing phenol is characterized by its elevated toxicity, resistance to biodegradation, and pronounced bioaccumulation. Traditional treatment methods frequently fall short in effectively removing phenol. In this study, a UV photoelectrochemical synergistic catalytic oxidation process was employed for the efficient elimination of phenol. The investigation systematically assessed the impact of various factors, including electrolyte type, concentration, current density, and initial pH, on phenol degradation. Furthermore, the degradation products were analyzed using high-performance liquid chromatography and gas chromatography-mass spectrometry. The results indicate that the oxidation and degradation of phenol in the UV photoelectrochemical synergistic catalytic system adhere to a first-order kinetic equation. Moreover, the combined UV and electrochemical catalytic degradation process demonstrated a synergistic effect, significantly enhancing the efficiency of phenol degradation. This study aimed to elucidate the mechanism of UV combined electrochemical catalytic degradation of phenol and provide reasonable speculation on the degradation pathway of phenol under UV electrochemical co-catalytic oxidation.

Catalytic activation of peroxodisulfate using shape-controlled cerium-manganese composite oxide for phenol degradation: Kinetics and degradation pathway investigation

Phenol-containing wastewater is typical organic wastewater, and its treatment is arduous. An advanced method to treat this type of wastewater is persulfate activation. Environmentally friendly cerium-manganese composite oxide materials were synthesized by hydrothermal method and applied to the phenol degradation process. Various ratios of cerium and manganese, as well as the amount of sodium hydroxide, were investigated. The solid solutions of cerium and manganese were formed and confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). H2-temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) were utilized to analyze the synergistic effect of cerium and manganese. It is found that there is a transformation between Ce4+/Ce3+ and Mn2+/Mn3+, which makes the material more trivalent manganese and thereby increases the catalytic activity. The effect of materials in catalyzing phenol degradation by peroxodisulfate (PDS) under various preparation conditions is discussed and high-efficiency removal of phenol can be achieved and the removal rate at 180 min is close to 100%. The kinetic of this process was investigated and activation energy of phenol degradation is 62.35 kJ/mol. The degradation pathway of phenol was studied and it is found that PDS can be activated by low metal ions and the ·OH and SO4·– radicals play crucial roles according to the quenching experiments.

Prussian blue analogues-derived zero valent iron to efficiently activate peroxymonosulfate for phenol degradation triggered via reactive oxygen species and high-valent iron-oxo complexes

It is of great significance to develop the effective technique to treat phenol-containing wastewater. Herein, Fe-based prussian blue analogues-derived zero valent iron (ZVI) was successfully synthesized by one-step calcination method. Owing to high specific surface area and rich active sites, ZVI-2 possessed excellent performance in charge transfer. Notably, in comparison with conventional ZVI and Fe2+, ZVI-2 can effectively activate peroxymonosulfate (PMS) for achieving rapid degradation of phenol, and the highest removal efficiency of phenol reached 94.9% within 24 min. More importantly, developed ZVI-2/PMS oxidation system with good stability displayed strong anti-interference capability. Interestingly, Fe0 loaded on the surface of ZVI-2 can efficiently break the O–O bond of PMS to generate reactive oxygen species (i.e., SO4•−, OH•, O2•− and 1O2). As main adsorption sites of PMS, the existence of oxygen vacancy promote the formation of high-valent transition metal complexes (namely ZVI-2≡Fe4+=O). Under the combined action of reactive oxygen species and ZVI-2≡Fe4+=O, phenol can be eventually degraded into CO2 and H2O. The possible degradation pathways of phenol were also investigated. Furthermore, proposed ZVI-2/PMS oxidation system displayed great potential for application in the field of wastewater treatment. All in all, current work provided a valuable reference for design and application of Fe-based catalysts in PS-AOPs.

Ball-milled layer double hydroxide as persulfate activator for efficient degradation of organic: Alkaline sites-triggered non-radical mechanism

Considerable efforts have been put into enhancing the activation performance of peroxydisulfate (PDS) by catalysts toward oxidative degradation of organic pollutants, while the oxidative selectivity is somehow overlooked. Here, we reported an enhanced non-radical oxidation pathway of PDS, activated by ball-milled Mg/Al-layered double hydroxide (BM-LDH), to reconcile the selectivity and reactivity. EPR and quenching experiments suggested that 1O2 dominated the oxidative pathway for phenol degradation without generating carcinogenic halide by-products. Multiple interfacial characterizations and density functional theory (DFT) calculations revealed that BM-LDH played dual roles in PDS activation: (1) the interlaminar BM-LDH allowed PDS intercalation to form complexed PDS, resulting in decreases in the activation barrier of PDS; (2) abundant terminal hydroxyls in the layers of BM-LDH acted as alkaline-activation sites that can efficiently activate PDS to generate 1O2 toward phenol degradation. Ball-milling treatment of LDH refined the structural hierarchy of LDH to create pore volumes, which greatly enhanced the diffusion of phenol to the intercalated PDS, resulting in more than twice the reaction rate for phenol degradation. This study provided a promising approach to simultaneously control over the reactivity and selectivity toward PDS activation that are critical for the degradation of organic pollutants particularly in drinking water treatment.

Microbial electricity-driven anaerobic phenol degradation in bioelectrochemical systems

Microbial electrochemical technologies have been extensively employed for phenol removal. Yet, previous research has yielded inconsistent results, leaving uncertainties regarding the feasibility of phenol degradation under strictly anaerobic conditions using anodes as sole terminal electron acceptors. In this study, we employed high-performance liquid chromatography and gas chromatography-mass spectrometry to investigate the anaerobic phenol degradation pathway. Our findings provide robust evidence for the purely anaerobic degradation of phenol, as we identified benzoic acid, 4-hydroxybenzoic acid, glutaric acid, and other metabolites of this pathway. Notably, no typical intermediates of the aerobic phenol degradation pathway were detected. One-chamber reactors (+0.4 V vs. SHE) exhibited a phenol removal rate of 3.5 ± 0.2 mg L−1 d−1, while two-chamber reactors showed 3.6 ± 0.1 and 2.6 ± 0.9 mg L−1 d−1 at anode potentials of +0.4 and + 0.2 V, respectively. Our results also suggest that the reactor configuration certainly influenced the microbial community, presumably leading to different ratios of phenol consumers and microorganisms feeding on degradation products.

Heterogeneous catalytic degradation of phenol by CuFe2O4/Bi12O15Cl6 photocatalyst activated peroxymonosulfate

In this study, Bi12O15Cl6 and CuFe2O4 were synthesized by solvothermal and sol-gel methods, respectively, and the binary composite CuFe2O4/Bi12O15Cl6 was successfully synthesized by heat treatment. The structure and morphology were characterized by a series of tests such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). And the effects of catalysts of different composite proportions, peroxymonosulfate (PMS) dosage, anionic environment and initial pH on the photocatalytic degradation of phenol were investigated. The experimental results showed that BCF-30 had the highest photocatalytic activity with 97.8% removal of phenol at 30 min and a pseudo primary kinetic constant k = 0.13539 min−1. The stability and reusability of the CuFe2O4/Bi12O15Cl6 composites were demonstrated by cycling experiments. The results of free radical analysis indicated that SO4•−, •O2−, h+ and •OH were the main active species, and on this basis, the mechanism of PMS activation and phenol degradation by CuFe2O4/Bi12O15Cl6 under visible light conditions was proposed. In addition, the intermediate products degraded by phenol were detected by liquid chromatography and mass spectrometry (LC-MS). Density functional theory (DFT) calculations were used to expound the phenol degradation and conversion pathways.

Confining manganese-based peroxymonosulfate activation in carbon nanotube membrane for phenol degradation: Combined effect of oxygen vacancy defects and nanoconfinement

In this study, an open ends carbon nanotube (OCNT) membrane, which confined fine-tuned oxygen vacancy defects (Odef) modified MnOx inside OCNT (MnOx-in-OCNT), was developed for enhancing peroxymonosulfate (PMS) activation towards phenol (PE) removal. The MnOx-in-OCNT membrane filtration coupled with PMS activation process (MFPA process) achieved outstanding removal (100%) of PE at a high permeate flux of 585.0 L m2 h−1 bar−1 (residence time of only 8.8 s). The unit degradation rate (2 min running time) and mass transfer rate of MnOx-in-OCNT were 2.0 and 8.4 times higher than that of CCNT (closed caps CNT) membrane with surface-loaded MnOx (MnOx-out-CCNT) MFPA process, and its catalytic performance was much superior to MnOx-in-OCNT powder reactions and MnOx-in-OCNT membrane batch reactions. The PMS activation mechanism experienced an obvious enhancement yield of reactive oxygen species (ROS) from MnOx-out-CCNT to MnOx-in-OCNT MFPA process. The enhanced PMS activation and boosted ROS yield of MnOx-in-OCNT was mainly attributed to the co-effect of the fine-tuned Odef and nanoconfinement. The contact frequency between PMS, pollutant and Odef was greatly enhanced via nanoconfinement effect, leading to the enhanced yield of SO4•− and •OH. Meanwhile, the O2 was enriched and reacts with enhanced Odef under nanoconfined-space to produce O2•− and 1O2. Then, the co-enhanced ROS (SO4•−, •OH, 1O2 and O2•−) displayed wide applicability for phenolic pollutants removal owing to their presence of –OH. Finally, the possible degradation pathway of PE was deduced by DFT calculations and HPLC analysis.

Whole Genome Sequence Analysis of Cupriavidus necator C39, a Multiple Heavy Metal(loid) and Antibiotic Resistant Bacterium Isolated from a Gold/Copper Mine.

Here a multiple heavy metal and antibiotic resistant bacterium Cupriavidus necator C39 (C. necator C39) was isolated from a Gold-Copper mine in Zijin, Fujian, China. C. necator C39 was able to tolerate intermediate concentrations of heavy metal(loid)s in Tris Minimal (TMM) Medium (Cu(II) 2 mM, Zn(II) 2 mM, Ni(II) 0.2 mM, Au(III) 70 μM and As(III) 2.5 mM). In addition, high resistance to multiple antibiotics was experimentally observed. Moreover, strain C39 was able to grow on TMM medium containing aromatic compounds such as benzoate, phenol, indole, p-hydroxybenzoic acid or phloroglucinol anhydrous as the sole carbon sources. The complete genome of this strain revealed 2 circular chromosomes and 1 plasmid, and showed the closest type strain is C. necator N-1T based on Genome BLAST Distance Phylogeny. The arsenic-resistance (ars) cluster GST-arsR-arsICBR-yciI and a scattered gene encoding the putative arsenite efflux pump ArsB were identified on the genome of strain C39, which thereby may provide the bacterium a robust capability for arsenic resistance. Genes encoding multidrug resistance efflux pump may confer high antibiotic resistance to strain C39. Key genes encoding functions in degradation pathways of benzene compounds, including benzoate, phenol, benzamide, catechol, 3- or 4-fluorobenzoate, 3- or 4-hydroxybenzoate and 3,4-dihydroxybenzoate, indicated its potential for degrading those benzene compounds.

ReaxFF-MD simulation investigation of the degradation pathway of phenol for hydrogen production by supercritical water gasification

Wastewater from the thermochemical conversion of coal and biomass contains a significant amount of phenolic structures compounds. The degradation of these phenolic compounds to hydrogen-rich gasses can prevent environmental pollution and save energy. Supercritical water (SCW) gasification of phenol is experimentally studied and a reactive force field molecular dynamics (ReaxFF-MD) simulation is conducted to investigate the catalytic mechanism of Ni/Al2O3 in the phenol degradation. The experimental results indicate that Ni/Al2O3 facilitates the conversion of phenol to 1-ethoxy butane via ring opening, which is a crucial step for complete gasification. The ReaxFF-MD simulation demonstrated that Ni facilitates the formation of H3O free radicals and Ni-phenol intermediates. H3O free radicals can be decomposed into H2 and OH free radicals. Both the generated OH free radical and Ni-phenol intermediate promote the ring-opening reaction of phenol. Ni promotes the direct decomposition of phenol into C1, C2, and C3 fragments, which is beneficial for further complete gasification.

Tangyuan-like structure N-doped C shell Fe0 as an efficient catalyst for organic degradation in groundwater: N–Fe synergistic strengthening effect, and activation mechanism

Zero valent iron (Fe0)-based biochar prepared using Fe salts as the Fe source has low yield and is readily oxidized, which limit its practical applications. In this study, a Tangyuan-like structure N-doped C shell Fe0 composite (Fe0@NC-0.8–0.6–800) was prepared via a “hydrothermal coating-pyrolysis reduction” strategy using glucose, ferroferric oxide (Fe3O4), and urea as raw materials to activate persulfate (PS) for organic contaminant degradation. The results revealed that Fe0@NC-0.8–0.6–800, prepared by pyrolyzing 0.8 g Fe3O4 and 0.6 g urea at 800 °C, removed 100% phenol within 20 min with 0.204 min−1 reaction rate constant (kobs), which was 2.4 times higher than that of Fe0@C-0.8–0-800 without N-doping (0.0866 min−1). The primary Fe0@NC-0.8–0.6–800 facilitation mechanisms include enhanced adsorption capacity, increased number of active sites on the C surface, electron transfer, and Fe2+ regeneration. Moreover, the synergistic effect between Fe0 and N defects (graphitic N and pyridinic N) in Fe0@NC-0.8–0.6–800 is the main reason for promoting non-radical pathway (1O2) generation. Based on the intermediates detected, five possible phenol degradation pathways were identified. The toxicity of phenol and degradation byproducts was evaluated by ECOSAR program. Through recycling experiments, and application in real groundwater, Fe0@NC-0.8–0.6–800 was found to show promising potential and offers a new strategy for treating organic matter-contaminated groundwater.