Efficient Activation Of Persulfate Research Articles

Highly dispersed single-atom Fe and Fe3O4 clusters anchored hierarchical-pore carbon as efficient persulfate activation catalyst

The selective removal of Fe particles from carbonized Fe-MOFs presents an intriguing strategy for developing efficient peroxydisulfate (PDS) activators. It is commonly accepted that their outstanding performance is largely attributed to the high specific surface area/pore volume. However, our investigation into the structure–function relationship of these materials has revealed new insights. In this study, a highly dispersed single-atom Fe and Fe3O4 clusters anchored hierarchical-pore carbon (CM88-H) was obtained via post-acid treatment of carbonized MIL-88B (CM88). Various characterizations were comparatively conducted to highlight the beneficial effects of iron dissolution. The CM88-H/PDS system achieved a notable BPA degradation efficiency, with a reaction rate of 0.323 min−1, which is 3.94 times higher than that of the CM88/PDS system. DFT calculations indicate that the Fe3O4 clusters optimize the charge distribution around single-atom Fe, promoting favorable PDS adsorption and facilitating a higher oxidation state of CM88-H. As a result, BPA can be completely degraded within 10 min with 0.1 g/L CM88-H and 0.05 g/L PDS via both radical and non-radical pathways. The CM88-H/PDS/BPA system performs effectively under various conditions, with a general reduction in toxicity. Furthermore, the CM88-H/PDS system shows broad oxidation activity towards BPA substitutes and pollutants with high ionization potential (IP). Notably, the CM88-H sponge-based fixed-bed catalytic reactor demonstrated satisfactory BPA degradation, highlighting the promising application of CM88-H in water purification. This study provides a sustainable solution for water treatment and accelerates the practical application of powdered nanocatalysts to improve water quality.

Synthesis of novel zeolite-supported zinc-cobalt bimetallic catalyst by co-precipitation-calcination method for efficient activation of persulfate to degrade tetracycline hydrochloride

Synthesis of novel zeolite-supported zinc-cobalt bimetallic catalyst by co-precipitation-calcination method for efficient activation of persulfate to degrade tetracycline hydrochloride

Sustainable hydrochar as an efficient persulfate activator for cost-effective degradation of bisphenol A

This study explored Mason pine-derived hydrochar (MPHC) as an effective adsorbent and persulfate (PS) activator for degrading bisphenol A (BPA). Increasing MPHC dosage from 0.25 to 2.0 g L−1 raised BPA removal from 42% to 87%. Similarly, at the same MPHC dosage range and fixed PS concentration (8 mM), BPA removal by MPHC/PS increased from 66% to 91%. Additionally, at a fixed MPHC dosage (1.0 g L−1), higher PS concentrations (2–32 mM) resulted in an overall BPA removal increase from 78% to 99%. The optimal pH for BPA removal by MPHC was at pH 3, while for MPHC/PS was at pH 9. BPA degradation by MPHC was optimal at pH 3, whereas MPHC/PS was at pH 3 and pH 9. Additionally, pH 7 favored BPA adsorption for both MPHC and MPHC/PS. The study also considered the influence of coexisting anions and humic acid (HA). PO43− and NO3− influence adsorption on MPHC, but these anions' effect on MPHC/PS is limited. Furthermore, the existence of HA had minimal influence on BPA removal by MPHC/PS. The contributions of different reactive species by MPHC for BPA degradation are as follows: electron-hole (h+) 2%, singlet oxygen (1O2) 7%, superoxide radicals (O2•–) 13%, electron (e–) 2%, hydroxyl radical (•OH) 3%, whereas the remaining 48% removal was the contribution of adsorption. For MPHC/PS, adsorption accounted for 39 %, more reactive species were involved in degradation, and the donations are (h+) 3%, sulfate radicals (SO4•–) 3%, (1O2) 19%, (O2•–) 15%, (e–) 2%, and (•OH) 2%. Additionally, the performance of MPHC remains stable after three operational cycles. The preparation cost of MPHC is 3.01 € kg−1. These results highlight the potential of MPHC as an environmentally friendly material for activating PS and removing organic pollutants, suggesting its promising application in future environmental remediation efforts.

Efficient activation of persulfate for tetracycline hydrochloride degradation by biochar prepared from corn stover doped with organic phosphorus sources

Proposed to prepare phosphorus-doped biochar catalyst materials by impregnation pyrolysis method using corn stover and different phosphorus source precursors as raw materials, and the batch-wise research revealed that the phosphorus source precursor, the doping ratio, and the pyrolysis temperature had a significant influence on the biochar properties. The biochar material Pb-C-4–600 prepared with (C4H9)3PO4 as phosphorus source precursor, 1:4 doping ratio, and pyrolysis temperature of 600 ℃ had an ID/IG = 0.914, pore size of 4.91 nm, and specific surface area of 173.9845 m²/g, which was 93.4 times higher than that of the pure biochar. The removal rate of TCH reached 99.77 % in 30 min under the reaction conditions of PMS concentration of 2 g/L, Pb-C-4–600 dosage of 1 g/L, and pH 3. Comparing the efficacy of Pb-C-4–600 and different catalysts for the degradation of TCH by activated PMS under the same reaction conditions, the degradation reaction rate of Pb-C-4–600 was 0.17663 min−1, which was 1.48 times higher than that of N-bio, 1.67 times higher than that of S-bio, and 2.64 times higher than that of B-bio, which further demonstrating the advantages of Pb-C-4–600 in similar composites. The oxidative degradation performance of other typical organic pollutants (BPA, phenol, AO7) was also good. The prominent reactive oxidizing radical in the system of Pb-C-4–600/PMS was SO4·−, and the system could adapt to a wide pH range.

Roles of iron and manganese in bimetallic biochar composites for efficient persulfate activation and atrazine removal

As for Atrazine (C8H14ClN5) degradation in soil, iron (Fe)-manganese (Mn) bimetallic biochar composites were proved to be more efficient for persulfate (PS) activation than monometallic ones. The atrazine removal rates of Fe/Mn loaded biochar + PS systems were 2.17–2.89 times higher than Fe/Mn loaded biochar alone. Compared with monometallic biochar, the higher atrazine removal rates by bimetallic biochar (77.2–96.7%) were mainly attributed to the synergy degradation and adsorption due to the larger amounts of metal oxides on the biochar surface. Atrazine degradation in Fe-rich biochar systems was mainly attributed to free radicals (i.e., SO4·-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{SO}}_{4}^{ \\cdot - }$$\\end{document} and ·OH) through oxidative routes, whereas surface-bound radicals, 1O2, and free radicals were responsible for the degradation of atrazine in Mn-rich biochar systems. Furthermore, with a higher ratio of Fe(II) and Mn(III) formed in Fe-rich bimetallic biochar, the valence state exchange between Fe and Mn contributed significantly to the more effective activation of PS and the generation of more free radicals. The pathways of atrazine degradation in the Fe-rich bimetallic biochar systems involved alkyl hydroxylation, alkyl oxidation, dealkylation, and dechlorohydroxylation. The results indicated that bimetallic biochar composites with more Fe and less Mn are more effective for the PS-based degradation of atrazine, which guides the ration design of easily available carbon materials targeted for the efficient remediation of various organic-polluted soil.Graphical

Fe3O4/biochar modified with molecularly imprinted polymer as efficient persulfate activator for salicylic acid removal from wastewater: Performance and specific recognition mechanism

In this study, a novel Fe3O4-based biochar coupled surface-imprinted polymer was constructed via simple hydrothermal route for salicylic acid recognition and degradation in advanced oxidation processes. The material exhibited excellent adsorption capability, up to 118.23 mg g−1, and efficient degradation performance, 87.44% removal rate within 240 min, based on integrating the advantages of both huge specific surface area as well as abundant functional groups from biochars and specific recognition sites from imprinted cavities. Moreover, high selectivity coefficient (11.67) showed stable recognition in single and binary systems. SO4•− and •OH were confirmed as reactive oxygen species in catalytic reaction according to quenching experiments and EPR analysis. The degradation mechanism and pathway were unraveled by DFT calculations and LC-MS. Furthermore, the results of toxicity evaluation, stability and reusability demonstrated application potential in the field of water environment restoration. This study confirmed that molecular imprinting provided a promising solution to targeted removal of emerging environmental pollutants by degrading after the enrichment of pollutants to the composites surface.

Interfacial complexation between Fe3+ and Bi2MoO6 promote efficient persulfate activation via Fe3+/Fe2+ cycle for organic contaminates degradation upon visible light irradiation

To address the observed decrease in efficiency during Fe2+-mediated persulfate (PDS) activation caused by slow electron transfer rates and challenges in cycling between Fe3+/Fe2+ states, we devised a strategy to establish interfacial complexation between Fe3+ and Bi2MoO6 in the presence of PDS. The proposed approach facilitates more efficient capture of photogenerated electrons, thereby accelerating the rate-limiting reduction process of the Fe3+/Fe2+ cycle under visible light irradiation and promoting PDS activation. The Bi2MoO6/Fe3+/PDS/Vis system demonstrates complete degradation of organic pollutants, including Atrazine (ATZ), carbamazepine (CBZ), bisphenol A (BPA), and 2,4-dichlorophenol (DCP) at a concentration of 10 mg/L within a rapid reaction time of 30 min. Radical scavenging experiments and electron paramagnetic resonance spectra (EPR) confirm that the sulfate radical (•SO4−) is the dominant species responsible for organic contaminant degradation. The real-time conversion process between Fe3+ and Fe2+ was monitored by observing changes in iron species forms and concentrations within the reaction system. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy verify the formation of a complexation between Fe3+ and Bi2MoO6, facilitating anchoring of Fe3+ onto material surface. Based on these findings, we propose a reliable mechanism for the activation reaction. This work presents a promising heterogeneous PDS activation method based on Fe3+/Fe2+ cycle for water treatment.

Performance and mechanism of biochar@FeMg-LDH for efficient activation of persulfate for degradation of 2, 4-dichlorophenol in groundwater.

Groundwater environments are complex, and traditional advanced oxidation technologies mainly based on free radicals have limitations such as poor selectivity and low interference resistance, making it difficult to efficiently degrade target pollutants in groundwater. Therefore, we developed a sludge-based biochar-supported FeMg-layered double hydroxide catalyst (BC@FeMg-LDH) for the catalytic degradation of 2, 4-dichlorophenol (2, 4-DCP) using persulfate (PDS) as an oxidant. The removal efficiency of the catalyst exceeded 95%, showing high oxidation activity in a wide pH range while being almost unaffected by reducing substances and ions in the environment. Meanwhile, under neutral conditions, the leaching of metal ions from BC@FeMg-LDH was minimal, thereby eliminating the risk of secondary pollution. According to quenching experiments and electron paramagnetic resonance spectroscopy, the main active species during BC@FeMg-LDH/PDS degradation of 2, 4-DCP is 1O2, indicating a non-radical reaction mechanism dominated by 1O2. Characterization techniques, including X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, revealed that the carbonyl (C = O) and metal hydroxyl (M-OH) groups on the material surface were the main reactive sites mediating 1O2 generation. The 1O2 generation mechanism during the reaction involved ketone-like activation of carbonyl groups on the biochar surface and complexation of hydroxyl groups on the material surface with PDS, resulting in the formation of O2·- and further generation of 1O2. 1O2 exhibited high selectivity toward electron-rich organic compounds such as 2, 4-DCP and demonstrated strong interference resistance in complex groundwater environments. Therefore, BC@FeMg-LDH holds promising applications for the remediation of organic-contaminated groundwater.

Magnetic nickel ferrite for efficient persulfate activation to remove aqueous refractory organics: Synthesis, advantages, mechanism, and environmental implications

Magnetic spinel ferrites are promising catalysts for activating persulfate for aqueous organics removal. Herein, a high-efficiency ferrite NiFe2O4 was synthesized and comprehensively investigated for persulfate activation. The optimal preparation conditions and their interactions were successfully determined by response surface methodology. The resultant catalyst was characterized with favorable properties for persulfate activation, e.g., porous morphology, excellent magnetism, and good redox activity. The study of operating parameters showed good adaptability of the NiFe2O4 +PS system to pH variation (3–9), and 100 % diclofenac removal was achieved. Mineralization and PS consumption tests showed high TOC removal (65.6 %) and a low PS demand (PS:diclofenac = 6.7:1), which were clear advantages of NiFe2O4, indicating its excellent activity towards PS decomposition. Additionally, the catalyst could be recovered quickly and completely during reuse (> 90 % recovery within 10 s). In addition, persulfate was considered to bind to the catalyst via electrostatic and chemical bonding, followed by the generation of surface-bound SO4•−. A potential mechanism of persulfate activation by NiFe2O4 and three possible degradation routes of diclofenac were proposed. Finally, the environmental implications of the NiFe2O4 +persulfate system for treating actual waters and multiple pollutants were revealed. This work supplemented ferrite for persulfate activation and provided an effective oxidative system for decontamination.

A self-synthesised non-homogeneous MoS2/Fe–Co–N–BC composite catalyst as an activator for peroxomonosulfate activation for efficient degradation of perfluorooctanoic acid

In this study, in order to achieve efficient activation of persulfate, we added MoS2 as a co-catalyst to the iron, cobalt and nitrogen modified biochar (Fe–Co–N–BC) catalytic system.

Z-scheme g-C3N4/α-FOD heterojunction-assisted persulfate activation for degradation of tetracycline hydrochloride under visible light: Insights into mechanism

Tetracycline hydrochloride (TCH) as an emerging pollutant poses challenges for removal using traditional treatment methods. A new and high-efficient photocatalyst graphitic carbon nitride/α-ferrous oxalate dihydrate (g-C3N4/α-FOD) was synthesized to solve this issue, which acted as a Z-scheme heterojunction for efficient activation of persulfate (PS) degradation TCH under visible (Vis) light irradiation. A comprehensive characterization of the g-C3N4/α-FOD photocatalyst was performed to analyze the structural, morphological, optical, and electrochemical properties. The Z-scheme heterojunction enabled broader visible-light absorption and enhanced charge transfer. In g-C3N4/α-FOD/PS/Vis system, SO4−, OH, and O2− were identified as the main reactive species and contributed to the efficient degradation of TCH. The initial 100 mg/L TCH concentration can be degraded to 11.3 mg/L within 120 min, reaching a high mineralization rate of 83 %. Density functional theory calculation successfully predicted that the sites on TCH molecules with high Fukui index were preferable to be attacked by the reactive species. The ring contraction and elimination reaction were found to be two major degradation pathways of TCH. The cycling experiments confirmed the good stability and reusability of the g-C3N4/α-FOD photocatalyst. This study successfully confirms that heterojunction materials can enhance the activation potential of PS, which provides a reference for realizing the harmless degradation of environmental pollutants under visible light.

Cobalt in ZIF-8-ZIF-67 as dual catalyst for ZnO–Co3O4/C formation and Bisphenol A degradation with persulfate

Composited zeolitic imidazolate framework-8-67 (ZIF-8-ZIF-67 and ZIF-8/ZIF-67) solids were synthesized via two processes, which resulted in different cobalt content in the solids. The experimental results suggested that the cobalt content in the solids had a significant influence on the transformation from ZIF to the corresponded composited oxides and catalytic performances. It was revealed from the composition and structure analysis that the cage-like cobalt oxide-zinc oxide/carbon composite (Co3O4–ZnO/C) derived from the ZIF-8/ZIF-67 with 9 wt% of cobalt via a two-step synthesis displayed an efficient activation of persulfate to decompose the Bisphenol A (BPA) as well as a robust reusability compared with the solid obtained by one-step synthesized ZIF-8-ZIF-67 with a cobalt content of 0.8 wt%, which displayed no catalytic activity. It was proposed that the Co3O4–ZnO/C facilitated the electrons transfer in the reaction system and a possible radical oxidation process occurred. Thus, the present could provide new insight for the design of composited organic framework and their functional materials for catalytic applications.

Efficient Activation of Persulfate by TiO2/g-C3N4 Composite for Degradation of Acetaminophen Under Visible Light

Efficient Activation of Persulfate by TiO2/g-C3N4 Composite for Degradation of Acetaminophen Under Visible Light

Efficient activation of persulfate by metallic sulfide mineral for the efficient removal of pesticides: Performance, radical generation and mechanism

In current years, the harm of pesticide residual pollution to environmental ecology and human health has obtained increasing attention. Hydroxylamine (HA) promoted activation of persulfate (PS) by the natural metallic sulfide mineral chalcopyrite (CuFeS2) for the removal of pesticide chlorpyrifos (CPF) and imidacloprid (IMP) in water had been systematically investigated in this study. Experimental results showed that HA could greatly accelerate the regeneration of Cu2+ and Fe3+ in solutions for PS decomposition. Nearly 99% of CPF removal by CuFeS2/PS/HA process was achieved within 80 min under optimal conditions. The decomposition of PS in the CuFeS2/PS/HA process was higher than that in the CuFeS2/PS process. Several coexisting cations (ie., Ca2+, Mg2+ and Al3+) and anions (ie., HCO3− and HPO42−) presented different levels of negative effects on CPF removal. Both HO• and SO4•− were generated in the CuFeS2/PS/HA process, and HO• might be the main reactive species responsible for the removal of CPF. The synchronized removal of CPF and IMP by CuFeS2/PS/HA process had been successfully achieved under certain conditions. The possible pathways of CPF degradation and enhanced mechanism for both CPF and IMP removal by CuFeS2/PS/HA process were thereby proposed. This study highlights the applications of CuFeS2/PS/HA process for the remediation of multiple pesticides-polluted wastewaters.

Identifying the Role of Surface Hydroxyl on FeOCl in Bridging Electron Transfer toward Efficient Persulfate Activation.

FeOCl is a highly effective candidate material for advanced oxidation process (AOP) catalysts, but there remain enormous uncertainties about the essence of its outstanding activity. Herein, we clearly elucidate the mechanism involved in the FeOCl-catalyzed perdisulfate (PDS) activation, and the role of surface hydroxyls in bridging the electron transfer between Fe sites and PDS onto the FeOCl/H2O interface is highlighted. ATR-FTIR and Raman analyses reveal that phosphate could suppress the activity of FeOCl via substituting its surface hydroxyls, demonstrating the essential role of hydroxyl in PDS activation. By the use of X-ray absorption fine structure and density functional theory calculations, we found that the polar surface of FeOCl experienced prominent hydrolyzation, which enriched abundant electrons within the microarea around the Fe site, leading to a stronger attraction between FeOCl and PDS. As a result, PDS adsorption onto the FeOCl/H2O interface was obviously enhanced, the bond length of O-O in adsorbed PDS was lengthened, and the electron transfer from Fe atoms to O-O was also promoted. This work proposed a new strategy for PDS-based AOP development and a hint of building efficient heterogeneous AOP catalysts via regulating the hydroxylation of active sites.

Modi-Red Mud Loaded CoCatalyst Activated Persulfate Degradation of Ofloxacin

As an abundant potentially dangerous waste, red mud (RM) requires a straightforward method of resource management. In this paper, an RM catalyst loaded with cobalt (Co-RM) was prepared by the coprecipitation method for the efficient activation of persulfate (PS). Its degradation performance and mechanism of ofloxacin (OFL) were investigated. The characterization results of scanning electron microscopy, X-ray diffractometer, and energy dispersive spectrometer showed cobalt was successfully loaded onto the surface of RM, and the catalyst produced could effectively activate PS. Under the conditions of 15 mg/L OFL, 0.4 g/L Co-RM, 4 g/L PDS, 3.0 pH, and 40 °C temperature, the maximum removal rate of OFL by the Co-RM/PDS system was 80.06%. Free radical scavenging experiments confirmed sulfate radicals were the main active substances in the reaction system. The intermediates in OFL degradation were further identified by gas chromatography-mass spectrometry, and a possible degradation pathway was proposed. Finally, the relationship between defluorination rate and time in the Co-RM/PDS degradation OFL system was described by the first-order kinetic equation. This work reports an economical, environmental solution to the use of waste RM and provides a research basis for the further exploration of RM-based catalysts.

Efficient persulfate activation by photo-excited organic dyes: Mechanism and application for actual dyeing wastewater self-purification

Sulfate Radical-Advanced Oxidation Processes are considered an efficient way for purifying dyeing wastewater, which commonly resists conventional treatment processes owing to the complex components, low biodegradability and high toxicity. However, this emerging technique is associated with issues of secondary pollution and great energy consumption during peroxymonosulfate (PMS) or persulfate (PS) activation processes. Herein, a dye pollutant/PS/visible light self-catalytic system was constructed, based on the photosensitive property of organic dyes for PS activation without catalyst and energy input. In this system, the degradation ratio of 100 mL 10 mg L−1 basic fuchsin, rhodamine B and eosin Y significantly increased by 60%, 76% and 50%, compared with the process without light irradiation. Such improvements were attributable to an efficient photo-induced electron transfer from photo-excited dyes to PS, which has the precondition that the lowest unoccupied molecular orbital (LUMO) energy level of the dye is higher than that of PS, thereby generating oxidizing species like ·SO4−, ·OH and 1O2 for pollutants degradation. Due to the high performance of pollutants simultaneous removal, wide pH adaptability and anti-interference, the complex self-catalytic system consisted of nine dyes and bis-phenol A exhibited the possibility for practical application. Expectedly, the actual dyeing wastewater self-purification system featured a decolorization efficiency of 54% accompanied by the removal of co-existing aromatic proteins and tryptophan-like substances; moreover, the acute bio-toxicity of the raw wastewater greatly decreased by 61.6%. Owing to its high efficiency, eco-friendliness and low consumption, the constructed “using waste to treat waste” system provides a promising way for wastewater treatment.

Synthesis of lignin sphere-based carbon-coated nZVI nanocomposites for efficient activation of persulfate to degrade 2,4-dichlorophenol

In this study, taking advantage of the amphiphilic properties of alkali lignin, carbon shell-encapsulated nano-zero-valent iron particles (AL@nZVI) anchored in a porous carbon framework were firstly synthesized by a combination of antisolvent reaction and carbothermal reduction method. AL@nZVI exhibited efficient catalytic performance for the activation of persulfate for the complete removal of 2,4-dichlorophenol at 30 min. The formation of a porous carbon skeleton and carbon shell enhanced the dispersibility and antioxidation of Fe0 nanoparticles and enabled long-term storage of AL@nZVI in air for more than 60 days. Furthermore, oxidation was mainly responsible for the removal of 2,4-dichlorophenol. The adsorption was determined to be 26.9% by analyzing the 2,4-dichlorophenol content in the used material. The generation of O2·−, SO4·−, 1O2 and·OH, was confirmed by EPR and scavenging experiments, and O2·− and 1O2 played dominant roles in the AL@nZVI+ persulfate system. The O2·−-guided free radical pathway was induced by activation of persulfate by Fe0 nanoparticles, while O2·− acted as a precursor to induce the 1O2-guided non-radical pathway. It is worth noting that CO may be favourable for the generation of 1O2. Moreover, the graphitized carbon, micropores, and structural defects contained in AL@nZVI created an electron-rich environment to facilitate the interaction between 2,4-dichlorophenol and reactive oxygen species. Therefore, the free radical and non-radical pathways were coupled to work together to degrade 2,4-dichlorophenol. This work not only develops a new synthesis method for core-shell structured carbon-coated nZVI composites, but also open the way for the high-value utilization of industrial by-products and the advanced oxidation degradation of organic pollutants in environmental remediation.

Phytic acid-modulated iron phosphide/biochar catalyst activates persulfate for rapid sulfamethoxazole removal: Synergy between iron phosphides and biochar

The efficient activation of persulfate (PS) is essential for rapidly degrading refractory organic pollutants in water. Traditional metal-based catalysts are limited by defects such as the metal ion redox cycle and secondary pollution, resulting in insufficient catalytic performances. In this research, highly active micron-sized iron phosphides (FeP and Fe2P) are in-situ synthesized on biochar, and the primary crystal phase can be switched by adjusting the phytic acid (PA) amount. Under the conditions of 0.15 g/L catalyst, 0.5 mM PS, and pH 7, sulfamethoxazole (SMX) at concentrations of 0.25, 0.50, 1.00, and 10.00 mg/L can be completely oxidized within 3, 5, 15, and 180 min, respectively. The leached ferric ion amount is below 0.020 mg/L. Meanwhile, ideal SMX abatements are achieved in sodium humate solution and surface water matrices, demonstrating the potential of this catalytic system for drinking water and wastewater treatment. Moreover, SO4-•, •OH, and 1O2 are crucial reactive oxygen species for SMX removal. Based on density functional theory (DFT) calculations, it is found that the partially charged Fe ion (≡Feδ+) is the pivotal site for PS activation and ≡Fe2+ regeneration. FeP and Fe2P are typically semi-metallic. Biochar can enhance the catalytic efficacies of FeP and Fe2P by shifting d-band centers (spin up and down) towards fermi level and reducing band gaps (spin down). Besides, biochar may donate electrons to iron phosphides when activating PS. The enhancement of FeP by biochar is more significant, which is why FeP/biochar is superior to Fe2P/biochar in PS activation.

In-situ synthesis of magnetic iron-chitosan-derived biochar as an efficient persulfate activator for phenol degradation

Persulfate activation is a forceful method for eliminating organic pollutants from coal chemical wastewater. In this study, an in-situ synthesis method was used to fabricate an iron-chitosan-derived biochar (Fe-CS@BC) nanocomposite catalyst using chitosan as a template. Fe was successfully imprinted into the newly synthesized catalyst. The Fe-CS@BC can activate persulfate to effectively degrade phenol. This point was confirmed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The impact of various parameters on the removal rate was investigated in a single factor experiment. In Fe-CS@BC/PDS system, 95.96% of phenol (significantly higher than the original biochar of 34.33%) was removed within 45 min and 54.39% TOC within 2 h. The system showed superior efficiency over a broad pH value band from 3 to 9 and has a high degradation rate at ambient temperature. Free radical quenching experiment, EPR experiment and LSV experiment confirmed that multiple free radicals (including 1O2, SO4•-, O2•- and •OH) and electron transfer pathway combined to enhance phenol decomposition. Finally, the activation mechanism of persulfate by Fe-CS@BC was proposed to provide logical guidance on the treatment of organic pollutants in coal chemical wastewater.