Heterogeneous photo-Fenton System Research Articles

Amino-functionalized iron-based MOFs for Rhodamine B degradation in heterogeneous photo-Fenton system

Amino-functionalized iron-based MOFs were successfully synthesized and used for the photo-Fenton-catalyzed degradation of Rhodamine B (RhB). The degradation efficiency of NH2-MIL-53(Fe) towards RhB (95.0%) exceeded that of NH2-MIL-88B(Fe) (87.0%) and NH2-MIL-101(Fe) (88.0%), which might be mainly because that NH2-MIL-53(Fe) had the most suitable specific surface area and pore volume, and the best light absorption properties. Additionally, NH2-MIL-53(Fe) exhibited higher degradation efficiency than MIL-53(Fe) (84.0%), possibly owing to the incorporation of amino functional groups that inhibited the recombination of photogenerated electron-hole pairs and enhanced visible light responsiveness. Remarkably, NH2-MIL-53(Fe) had a good degradation effect on RhB in a wide range of pH (3.0–7.0), and the degradation rate was still as high as 90.0% after 5 consecutive degradation experiments. The degradation process was predominantly influenced by the involvement of ·OH and 1O2, as evidenced by the outcomes of free radical capture experiments. Possible degradation pathways of RhB were proposed by mass spectrometry.

Long-lived nanoparticle-embedded superhydrophobic membranes with rapid photocatalytic properties and continuous oil–water separation

Superhydrophobic oil–water separation membranes have aroused widespread research interest as ideal candidates for treating oily wastewater. However, this type of membrane has difficulty simultaneously balancing the removal of organic matter in complex oily wastewater and achieving large-scale continuous oil–water separation. Herein, FeOOH/polydopamine/cotton (FPC) membranes with significant photocatalytic properties were prepared via the deposition of a complex formed by mineralizing polydopamine and Fe3+ on a cotton-based surface. Further modification with long-chain hexadecyltrimethoxysilane constructed multipurpose superhydrophobic hexadecyltrimethoxysilane/FeOOH/polydopamine/cotton (HFPC) membranes. The heterogeneous photo-Fenton system built from clipped FPC membranes rapidly degrades methyl blue pollutants with a 99.5 % degradation rate. Notably, HFPC membranes maintain exceptional superhydrophobicity even after enduring various severe damages, including 1000 sandpaper abrasions/hammer blows, 5 min running water impact, 12 h chemical immersion, 24 h UV aging, and 5 months of outdoor weathering. Additionally, HFPC membranes have separation efficiencies up to 99.5 % and continuous separation as long as 15 min, making them especially suitable for large-scale oil absorption. Long-lived nanoparticle-embedded membranes offer fast photocatalysis, long-lasting robustness, high separation efficiency and flux. Meanwhile, it has the advantages of large-scale continuous oil absorption, repeatability, low cost, and sustainability. This work merges rapid photocatalysis and efficient oil–water separation technologies, bringing a new breakthrough in expanding the multifunctional membrane field and opening a new door for the future development of related fields.

In-situ production and activation of H2O2 over hydroxyapatite modified CuFeO2 for self-sufficient heterogeneous photo-Fenton degradation of doxycycline hydrochloride

The self-sufficient heterogeneous photo-Fenton (SH-PF) system was constructed for doxycycline hydrochloride (DOH) degradation with hydroxyapatite (Hap) modified CuFeO2 (Hap/CuFeO2) composites through H2O2 in-situ production. The modification of Hap could improve the specific surface area, visible-light response, light conversion efficiency, photoelectron lifetime and oxygen vacancies (OVs) of CuFeO2, which was conducive to H2O2 production and DOH degradation in SH-PF system. Notably, Hap/CuFeO2 fabricated with 0.5 g Hap (Hap/CuFeO2-0.5) displayed more superior performance for DOH degradation compared to other synthesized catalysts. The Hap/CuFeO2-0.5 load and initial solution pH for DOH degradation in SH-PF system were optimized, and the Hap/CuFeO2-0.5 had good reusability and stability. The •OH was the main active species for DOH degradation, and the facilitation effect of •O2– and photoelectrons on DOH degradation was associated with the H2O2 production in the present work. In addition, the capture of photogenerated holes suppressed the recombination of photogenerated carriers, elevating the production of photoelectrons and thereby enhancing H2O2 production and DOH degradation. The degradation pathways for DOH were proposed and the comprehensive toxicities of DOH were relieved after degradation in SH-PF system.

High-Efficient Elimination of Spiramycin by Fe3O4/ZSM-5/Sch via Heterogeneous Photo-Fenton Oxidation at Neutral pH

Spiramycin (SPM), a widely employed antibiotic in both clinical therapy and the livestock industry, poses significant challenges in terms of safe and efficacious management. A heterogeneous photo-Fenton system, devised using Schwertmannite (Sch), can effectively degrade contaminants. However, it is accompanied by a relatively low conversion efficiency of ≡Fe3+/≡Fe2+ and a significant iron loss. In this study, a catalyst featuring Fe3O4 and ZSM-5 molecular sieve-modified Sch (Fe3O4/ZSM-5/Sch) was devised to enhance the catalytic activity and stability. The findings revealed that Fe3O4/ZSM-5/Sch exhibited exceptional catalytic activity, with the reaction first-order kinetic exceeding that of pure Sch. The active species including ·OH, h+, e−, ·O2− and SO4·− were identified in the UV/Fe3O4/ZSM-5/Sch-H2O2 system. The enhanced catalytic activity of Fe3O4/ZSM-5/Sch could be ascribed to the effective conversion of ≡Fe3+/≡Fe2+. The photogenerated electrons within Fe3O4 were transported to Sch via ZSM-5, which effectually reduced ≡Fe3+/≡Fe2. Moreover, Fe3O4/ZSM-5/Sch demonstrated outstanding stability; even after six cycles, the degradation efficiency of SPM remained above 86.50%, and the leaching quantity of Fe remained below 0.24 mg/L. This research not only develops an excellent catalyst for the safe treatment of SPM but also proffers innovative perspectives for the future design of efficient iron-based catalysts.

Deep degradation of sulfamethoxazole by the Fe-Co/γ-Al2O3-catalysed photo-Fenton system

ABSTRACT The heterogeneous photo-Fenton system using Fe-Co/γ-Al2O3 as a catalyst was applied in the study of sulfamethoxazole(SMX) degradation. The morphology, structure, elemental composition and metal valence distribution of Fe-Co/γ-Al2O3 were found to be relatively stable before and after the reaction. The highest SMX degradation efficiency and mineralization (The ratio of organic matter being oxidized to carbon dioxide and water) were obtained under the conditions of 15% Fe-Co loading rate, 1:1 mass ratio of Fe and Co, 1 g/L catalyst dosage, 1.5 mL 30% H2O2 dosage, 18 W UV lamp power and 60 min reaction time, which were 98% and 66%, respectively. Radical quenching experiments and electronic paramagnetic resonance (EPR) characterization revealed that ·OH played an important role in the degradation and mineralization SMX in the Fe-Co/γ-Al2O3 heterogeneous photo-Fenton system. Combined with the analysis of N, S and intermediate products, there may be three degradation pathways of SMX in the heterogeneous photo-Fenton system. This work provides a technical reference for realizing the efficient degradation and mineralization of SMX in a heterogeneous photo-Fenton reaction system.

Degradation of diclofenac sodium with low concentration from aqueous milieu through polydopamine-chitosan modified magnetic adsorbent-assisted photo-Fenton process

Given the widespread occurrence of low-concentration diclofenac sodium (DCFS) in the aquatic milieu, the development of an efficient and economical purification method is essential. Magnetic polydopamine-chitosan modified adsorbent (MPDA-CS) was successfully prepared by coating polydopamine-chitosan onto Fe3O4 nanoparticles in this study. The favorable adsorption performance towards DCFS was well demonstrated by regulating the solution to various pH values and initial concentrations of DCFS. Furthermore, the convincing fitting of pseudo-second-order model and intraparticle diffusion model suggested that the dominance of chemical processes and intraparticle diffusion. The specific adsorption mechanism was presumed to be the interaction between MPDA-CS and DCFS molecules, including electrostatic attraction, hydrogen bonding and aromatic stacking. Through regulating standing time in acidic solution, the integrated homogeneous and heterogeneous photo-Fenton system was employed to degrade adsorbed DCFS through dissolved and surfaced Fe(II)/Fe(III) of MPDA-CS, which achieved the waste utilization of dissolved iron ions with excellent degradation efficiency of 96.38% in 40 min. The adsorption-degradation efficiency of DCFS decreased slightly by 2.2% during the initial three cycles. This work presents an energy-efficient method for removing low-concentration DCFS by drawing on the strengths of adsorption and degradation.

Degradation of organophosphorus flame retardants in heterogeneous photo-Fenton system driven by Fe(III)-based metal organic framework: Intermediates and their potential interference on bacterial metabolism

Organophosphorus flame retardants (OPFRs) have been regarded as one of the most rebarbative classes of emerging contaminants due to their persistence and toxicity. In the current study, Fe-based metal organic framework (MIL-88A) was synthesized and employed as photo-Fenton catalyst for the degradation of tris-(2-chloroisopropyl) phosphate (TCPP), a typical representative of OPFRs. The observations indicated that visible light could boost the reduction of ≡FeIII to ≡FeII in Fe–O clusters of MIL-88A during the photo-Fenton system and consequently induce the transformation of H2O2 to OH, which realized efficient degradation of TCPP. Due to the excellent function of MIL-88A, the effective pH application range of photo-Fenton system was extended in comparison with traditional Fenton system. The degradation efficiency of TCPP was visibly influenced in presence of humic acid (HA). MIL-88A exhibited a commendable reusability and stability after 3 times cycle. As the photo-Fenton reaction proceeded, TCPP was disintegrated to several kinds of carboxylated, dechlorinated and hydroxylated products. The observations of metabolomics endorsed that the interference of intermediate products mixture on E. coli weakened to a certain extent. In conclusion, carboxylation, dechlorination, hydroxylation and oxidation of TCPP were likewise effective for its detoxification, revealing that heterogeneous photo-Fenton system driven by Fe-based metal organic framework will be an attractive and safe treatment technique for OPFRs control.

Heterogeneous photo-fenton oxidation degradation of methyl orange using Alg-m, Alg-HAp, and Alg-mHAp catalysts

ABSTRACT Removal of methyl orange (MO) anionic dye was investigated by composite beads of sodium alginate-magnetic hydroxyapatite (Alg-mHAp), sodium alginate-magnetite (Alg-m), and sodium alginate-hydroxyapatite (Alg-HAp) as catalysts of heterogeneous photo-Fenton process. Evaluation of XRD and FT-IR analysis proved the presence of magnetite and hydroxyapatite nanoparticles in the structure of synthesised catalysts. SEM analyses showed that the surface of the Alg-mHAp catalyst is rougher than the other two catalysts. The results demonstrated the effluent discoloration of 79.41%, 71.42, and 84.28% for Alg-m, Alg-Hap, and Alg-mHAp, respectively, at an optimum pH = 3. By increasing the pH to more than 3, the removal rate decreased. In addition, it was found that by increasing the hydrogen peroxide concentration from 0.5 to 3 , photo-Fenton activity can be further enhanced to effectively degrade MO. However, with increasing the concentration of H2O2 from 3 to 20 , the removal percentage of Alg-m, Alg-HAp, and Alg-mHAp catalysts decreased to 92.70%, 86.20%, and 95.62, respectively. The results revealed with increasing initial dye concentration, the removal percentage decreased for all three catalysts. Also, by increasing the catalyst dosage from 0.5 to 2 , the removal percentage for Alg-m, Alg-HAp, and Alg-mHAp catalysts increased 16, 21, and 12%, respectively. Furthermore, it was determined that as the UV intensity increased, the removal percentage increased by an average of 26%. The first-order kinetic equation was most consistent with the experimental results of MO degradation in all three catalysts. This study confirmed the feasibility of a heterogeneous photo-Fenton system of Alg-mHAp for the highly efficient degradation of MO in wastewater.

Highly efficient removal of tetracycline hydrochloride under neutral conditions by visible photo-Fenton process using novel MnFe2O4/diatomite composite

A simple solvothermal method was used to prepare poly-porous MnFe2O4/diatomite (MFD) with excellent catalytic performance. The characteristics of the prepared catalysts were examined by XRD, SEM, BET, XPS, UV-DRS, PL and NH3-TPD. BET analysis indicated that introduction of diatomite could increase the specific surface and porosity of the MFD. NH3-TPD studies clearly revealed that loading onto diatomite increased the availability of acid sites and surface hydroxyl groups in the composite materials. Under the combination of visible light and H2O2, the degradation effect of 80 mg/L 100 mL tetracycline hydrochloride (TC-HCl) reached 96.7% within 60 min at 0.1 g/L MFD and initial pH value, according to the experimental results. The proposed heterogeneous photo-Fenton system with MnFe2O4/diatomite showed an extremely wide pH range of 3–11 for TC-HCl degradation. At pH = 7, 91.8% of the TC-HCl (80 mg/L 100 mL) could be degraded within 60 min. In addition, the removal rate remained close to 90% after 60 min of irradiation at pH = 9 and 11. Free radical capture experiment showed that superoxide radicals (•O2−) and holes (h+) play a crucial role in the removal of TC-HCl. Moreover, the synergistic activation of H2O2 by Fe and Mn was confirmed to promote the degradation, leading to higher TC-HCl removal efficiency.

A comparative study among catalytic wet air oxidation, Fenton, and Photo-Fenton technologies for the on-site treatment of hospital wastewater

The feasibility of catalytic wet air oxidation, intensified homogeneous Fenton and heterogeneous Photo-Fenton systems for the treatment of real hospital wastewater has been investigated. Wastewater samples were collected from a hospital sewer, during a weekly monitoring program, and fully characterized. Up to seventy-nine pharmaceuticals, including mostly parent compounds and some of their transformation products, were analyzed. Catalytic wet air oxidation allowed the complete removal of several pharmaceutical groups, but it did not allow to eliminate analgesics/anti-inflammatories and antibiotics, whose average removal was around 85%. Intensified Fenton oxidation was the most efficient process for all the drugs removal with an almost complete reduction of the initial pharmaceutical load (99.8%). The heterogeneous Photo-Fenton system reached a 94.5% reduction of the initial pharmaceutical load. The environmental risk of the treated samples by the hazard quotient (HQ) method was also evaluated. Fenton oxidation was the most effective system with a final ∑HQ of 5.4. Catalytic wet air oxidation and Photo-Fenton systems achieved total ∑HQ values of 895 and 88, respectively. This fact was related to the presence of refractory antibiotics in the treated catalytic wet air oxidation samples. On the opposite, the Photo-Fenton system provided the elimination of most pharmaceutical pollutants that pose a high environmental risk such as antibiotics. Simplified cost estimation was finally performed as a preliminary approach of the economy of the three oxidation processes for the hospital wastewater treatment.

Coaxial Fe2O3/TiO2 nanotubes for enhanced photo-Fenton degradation of electron-deficient organic contaminant

Coaxial Fe2O3/TiO2 nanotubes (Fe2O3/TiO2 NTs) were prepared by two anodic oxidation processes. The synthesized Fe2O3/TiO2 NTs catalysts showed high photocatalytic activity in heterogeneous photo-Fenton system. With the help of Fe2O3/TiO2 NTs, 4-nitrophenol (10 mg·L−1, 50 ml), a typical electron-deficient organic contaminant, can be completely removed by adding only 0.4 mmol·L−1 of H2O2 under irradiation. Investigation results clarify that the calculated position of Fe2O3/TiO2 NTs valence band is at 2.944 eV, its potential is higher than the potential of OH−/·OH (2.800 eV), thereby ensuring the generation of ·OH. Meanwhile, the transformation of photogenerated electrons from the conduction band of TiO2 to Fe2O3 accelerates the reduction of Fe3+ to Fe2+. The unstable Fe2+ can be oxidized by H2O2 to produce high yields of ·OH. Therefore, both the coaxial heterojunction and fast Fe2+/Fe3+ conversion provide abundant ·OH to effective attack the electron-deficient benzene ring passivated by the nitro group. Thus, surface-catalyzed degradation of 4-nitrophenol can be carried out step by step. This work contributes a detailed understanding of charge transfer in semiconductor composites and degradation of organic contaminants.

Comparing the Degradation Potential of Copper(II), Iron(II), Iron(III) Oxides, and Their Composite Nanoparticles in a Heterogeneous Photo-Fenton System.

Heterogeneous photo-Fenton systems offer efficient solutions for the treatment of wastewaters in the textile industry. This study investigated the fabrication and structural characterization of novel peculiar-shaped CuIIO, FeIII2O3, and FeIIO nanoparticles (NPs) compared to the properties of the iron(II)-doped copper ferrite CuII0.4FeII0.6FeIII2O4. The photocatalytic efficiencies of these NPs and the composite of the simple oxides (CuIIO/FeIIO/FeIII2O3) regarding the degradation of methylene blue (MB) and rhodamine B (RhB) as model dyes were also determined. The catalysts were synthesized via simple co-precipitation and calcination technique. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) were utilized for structural characterization. The structure of CuIIO was bead-like connected into threads, FeIII2O3 was rod-like, while FeIIO pallet-like, with average crystallite sizes of 18.9, 36.9, and 37.1 nm, respectively. The highest degradation efficiency was achieved by CuIIO for RhB and by CuII0.4FeII0.6FeIII2O4 for MB. The CuIIO/FeIIO/FeIII2O3 composite proved to be the second-best catalyst in both cases, with excellent reusability. Hence, these NPs can be successfully applied as heterogeneous photo-Fenton catalysts for the removal of hazardous pollutants. Moreover, the simple metal oxides and the iron(II)-doped copper ferrite displayed a sufficient antibacterial activity against Gram-negative Vibrio fischeri.

Heterogeneous photo-Fenton system of novel ternary Bi2WO6/BiFeO3/g-C3N4 heterojunctions for highly efficient degrading persistent organic pollutants in wastewater

In this study, novel ternary Bi2WO6/BiFeO3/g-C3N heterojunctions with enhanced photocatalytic activity were synthesized and its heterogeneous photo-Fenton system was construct for highly effectively degrading persistent organic wastes, namely rhodamine B (RhB) and tetracycline hydrochloride (TH). Furthermore, the mechanism of generated free radicals in this heterogeneous photo-Fenton system was explored. The characteristics of the as-prepared photocatalysts were investigated in detail by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectra (FT-IR), UV–vis diffuse reflectance spectra (UV-DRS), Photoluminescence spectra (PL), Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky curves. The results demonstrated that the heterojunction between Bi2WO6, BiFeO3 and g-C3N has formed, which can narrow the band gap to improve separation and migration of photogenerated electrons-hole pairs. In addition, it has been suggested that the recombination of photogenerated electron-holes can be inhibited due to the good conductivity of BiFeO3 and g-C3N4. Hence, Bi2WO6/BiFeO3/g-C3N possessed enhanced photocatalytic activity, which can further enhance photo-Fenton activity to effectively degrade RhB (99.85 % in 30 min) and TH (83.68 % in 45 min). In addition, it has been determined that Bi2WO6/BiFeO3/g-C3N mainly produce O2− and e+ played the main roles in the photo-Fenton activity, rather than OH−. This study not only confirmed the feasibility of heterogeneous photo-Fenton system of Bi2WO6/BiFeO3/g-C3N4 for highly efficient degradation of persistent organic pollutants in wastewater, but also provided a mothed to synthesized the novel heterojunction of Bi2WO6/BiFeO3/g-C3N4 with enhanced photocatalytic activity.

Synthesis, Characterization and Application of Iron(II) Doped Copper Ferrites (CuII(x)FeII(1-x)FeIII2O4) as Novel Heterogeneous Photo-Fenton Catalysts.

The heterogeneous photo-Fenton type system has huge fame in the field of wastewater treatment due to its reusability and appreciable photoactivity within a wide pH range. This research investigates the synthesis and characterization of iron(II) doped copper ferrite (CuII(x)FeII(1-x)FeIII2O4 nanoparticles (NPs) and their photocatalytic applications for the degradation of methylene blue (MB) as a model dye. The NPs were prepared via simple co-precipitation technique and calcination. The NPs were characterized by using Raman spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). SEM reveals the structural change from the spherical-like particles into needle-like fine particles as the consequence of the increasing ratio of copper(II) in the ferrites, accompanied by the decrease of the optical band-gap energies from 2.02 to 1.25 eV. The three major determinants of heterogeneous photo-Fenton system, namely NPs concentration, hydrogen peroxide concentration and pH, on the photocatalytic degradation of MB were studied. The reusability of NPs was found to be continuously increasing during 4 cycles. It was concluded that iron(II) doped copper ferrites, due to their favorable band-gap energies and peculiar structures, exhibit a strong potential for photocatalytic-degradation of dyes, for example, MB.

The degradation of BPA on enhanced heterogeneous photo-Fenton system using EDDS and different nanosized hematite.

Photo-Fenton processes have been widely studied in wastewater treatment. In this research, the degradation of bisphenol A (BPA) was carried out in a new heterogeneous photo-Fenton process. The ethylenediamine-N,N'-disuccinic acid (EDDS) was used as chelating agent in this system with two different kinds of commercially available nanosized hematite (30nm and 80nm) addition. The results showed that the present of EDDS could enhance the degradation efficiency. And can be concluded that the degradation efficiency is better in the system with 30nm hematite. The TEM, XRD, and specific surface area were conducted to understand the different characteristics of the two size hematite. The adsorption experiments of BPA and EDDS on hematite proved that there was little adsorption of BPA while the EDDS was adsorbed much more on hematite, which has confirmed Fe(III) and EDDS can form Fe(III)-EDDS complex. The effects of different parameters including hematite loading, H2O2, and EDDS concentrations on the degradation process were investigated. According to the results, the optimum condition for BPA degradation using 30nm (0.8gL-1 hematite, 0.1mmolL-1 H2O2, and 1.2mmolL-1 EDDS) and 80nm (0.6gL-1 hematite, 0.05mmolL-1 H2O2, and 1.2mmolL-1 EDDS) hematite were selected. It was confirmed that the ·OH plays an important role in the oxidation process through attacking the BPA molecule and produce hydroxyl addition derivative. In addition, O2 can react with electron (e-) and holes (h+) produced by iron oxide under UV irradiation to create 1O2, which could work as potential reactive species to oxidize BPA.

Application and mechanism of ferrihydrite in the EDDS improved heterogeneous photo-Fenton system: the role of different reactive species under different conditions

The application of carboxylic acid and natural iron oxide in heterogeneous AOP systems for the treatment of organic pollutants in water has attracted extensive attention.

Ag/AgCl/MIL-101(Fe) Catalyzed Degradation of Methylene Blue under Visible Light Irradation.

A novel photo-Fenton catalyst named Ag/AgCl/MIL-101(Fe) was synthesized by the method of precipitation and photo reduction and characterized by X-ray diffraction patterns (XRD), Brunauer-Emmett-Teller (BET) measurements, Fourier transform infrared spectra (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectra. Moreover, the catalytic activity of the synthesized catalyst was tested using methylene blue (MB) as the target pollutant. The obtained results illustrated that the plasmonic material Ag/AgCl was successfully loaded on MIL-101(Fe) and the obtained catalyst exhibited an excellent catalytic activity under visible light at the neutral pH. According to the analyses of Plackett-Burman and Box-Behnken design, the optimum conditions for MB degradation were obtained. Under these conditions, the MB decolorization and mineralization efficiencies could reach to 99.75% and 65.43%, respectively. The recycling experiments also showed that the as-prepared catalyst displayed good reusability. In addition, the possible reaction mechanisms for the heterogeneous photo-Fenton system catalyzed by Ag/AgCl/MIL-101(Fe) were derived. The synthesized catalyst provides a promising approach to degrade organic pollutants in waste water.

Effects of reaction conditions and liquid property on degradation of phenol by RGO/α-FeOOH supported on Al-MCM catalyst in heterogeneous photo-Fenton system

This study focused on investigating the effect of reaction conditions (catalyst and H2O2 dosage, light source under different pH) and liquid property on degradation of phenol over RGO/α-FeOOH supported on Al-MCM catalyst in heterogeneous photo-Fenton system. Batch experiments were conducted under specific operating conditions. It was found that with the increase of catalyst and H2O2 dosage, the phenol and COD removal efficiency went up to reach a maximum (at Cata/H2O2 mass ratio was 1.471) and then decreased. The reactions all fitted pseudo first order model. The phenol were degraded apparently by RGO/α-FeOOH-Al-MCM catalyst at different light source irradition or not when pHs ranged from 4.0 to 8.0. The solar irradiation not only dramatically accelerated the rate of Fenton-based reactions, but also extended the operating pH for the Fenton reaction (from 4.0 to 8.0). Higher initial phenol concentrations inhibited the rate of phenol degradation although actual phenol removal amount increased, which may be due to the fact that more intermediates produced at higher phenol concentration competed with phenol for the active sites. The addition of anions (Cl−, SO42−, NO3−, HCO3−, HPO42−), small molecule organic acids (CA, OA, TA) and natural organic matter (HA, FA) caused inhibition effect on phenol degradation.

Facile assembly of novel g-C3N4@expanded graphite and surface loading of nano zero-valent iron for enhanced synergistic degradation of tetracycline.

The two-stage removal process of tetracycline (TC) in aqueous solutions using a novel photocatalyst based on nano-zero-valent iron (NZVI), g-C3N4 and expanded graphite by carbon layer (EGC) is reported for the first time. The composite (NZVI/g-C3N4@EGC) exhibits remarkable adsorption, reduction ability and visible light activity over the reaction course. Compared with pristine g-C3N4 (25.9%) and pure NZVI (45.9%), NZVI/g-C3N4@EGC achieves high degradation efficiency of TC (98.5%) due to the formation of a heterogeneous photo-Fenton system. This study shows that synergistic effects are achieved in the reaction system, including maintaining the reduction ability of NZVI and enhancing the photocatalytic activity of g-C3N4 by facilitating the separation of photogenerated electrons (e−) and holes (h+). TC removal involved a two-stage process of adsorption–reduction and photo-degradation. The quencher experiments determined that holes (h+) and superoxide radicals (˙O2−) are the major reactive species in the degradation of TC. The degradation pathways of TC were proposed based on the analysis of the intermediates. In addition, NZVI/g-C3N4@EGC revealed a high stability in a five-cycle test and good magnetic properties for facile separation from aqueous solutions. From an application viewpoint, NZVI/g-C3N4@EGC has favorable prospects in the direction of the photocatalytic degradation of antibiotic wastewater.

Hollow-structured Fe2O3/Au/SiO2 nanorods with enhanced and recyclable photo-Fenton oxidation for the remediation of organic pollutants

A novel heterogeneous Fenton-like catalyst, hollow-structured Fe2O3/Au/SiO2 nanorods, was synthesized, characterized, and used for the degradation of methyl orange (MO) organic pollutant under visible light irradiation. with an oxide–To acquire an iron oxide-based catalyst separately loaded with stable Au nanoparticles, calcination was conducted with polyacrylic acid (PAA) decorated and thin SiO2 film coated to protect and form a hollow structure. The degradation results showed that Fe2O3/Au/SiO2 could effectively degrade MO, with almost 100% removal efficiency within 20 min. Moreover, the degradation rate still can reach up to 91.7% after five successive cycles. Combined with kinds of characterization, the enhanced catalytic activity can be ascribed to the incorporation of Au NPs and hollow-structured Fe2O3 via localized surface plasmon resonance effect. The possible catalytic mechanism of Fe2O3/Au/SiO2 was tentatively proposed. This research provides a new approach for the development of heterogeneous photo-Fenton system with a high stability.