Catalytic Degradation Mechanism Research Articles

Highly efficient degradation of sulfamethoxazole (SMX) by activating peroxymonosulfate (PMS) with CoFe2O4 in a wide pH range

The cobalt ferrite materials (CoxFe3−xO4) with different molar ratios of Co:Fe (1:16, 1:8, 1:4, 1:2, and 3:4) were synthesized by simple co-precipitation method, and used for catalyzing activation of peroxymonosulfate (PMS) to degrade sulfamethoxazole (SMX). The effects of catalyst dose, PMS dose, pH value, and inorganic ions on the degradation of SMX were investigated. Particularly, the degradation efficiency of SMX reached 91% within 10 min in CoFe2O4/PMS, and the removal rate of SMX achieved 81% at first 1 min. Meanwhile, the CoFe2O4/PMS reaction system exhibited excellent catalytic performance at a wide pH range from 3.00 to 11.00. The CoFe2O4 catalyst could be easily magnetically separated and exhibited high stability in cycle experiments. EPR and quenching experiments showed that 1O2, SO4−, and OH species were produced in the CoFe2O4/PMS system, especially OH and 1O2 played dominant roles during the degradation of SMX. The catalytic degradation mechanism of SMX in the CoFe2O4/SMX system was proposed, involving radical process and non-radical process. This work will provide a new way for the efficient treatment of wastewater especially those containing SMX compounds.

Porous carbon nanofibers loaded with copper-cobalt bimetallic particles for heterogeneously catalyzing peroxymonosulfate to degrade organic dyes

Countering the problem of expediting the peroxymonosulfate oxidation, porous carbon nanofibers loaded with copper-cobalt bimetallic particles (CuCo@ CNF) were synthesized by a three-step process, including electrospinning, solvothermal reaction and carbonization. The well-crystallized copper-cobalt nanoparticles with an average particle size of 322 nm, which were evenly decorated on the surface of the porous carbon nanofibers with a relatively high specific surface area (average value=161.281 m2 g−1), as examined by XRD, SEM, TEM, and BET. The saturation magnetization of CuCo@CNF measured by VSM is 26.5 emu g−1, suggesting its easy separation due to magnetic property. In CuCo@CNF-PMS system, the removal rate of Acid Red 1 (AR1) as a model pollutant can achieved 99.0% and 98.1% in the 1st and 7th run, respectively. Metal leaching after reaction were reduced for CuCo@CNF when compared with the respective CNF supported Co or Cu catalysts. In addition, the catalytic degradation mechanism of AR1 was elucidated by detecting reactive oxygen species (ROS: SO•4-, •OH and 1O2) alongside the reaction. AR1 can even be mineralized through CuCo@CNF-PMS, evidenced by TOC removal rate of 55.5% within 20 min. These results suggest that the as-synthesized catalyst is an attractive candidate for the treatment of wastewater with recalcitrant organic pollutants.

UV Stimulated Manganese Dioxide for the Persulfate Catalytic Degradation of Bisphenol A

One of the most commonly produced industrial chemicals worldwide, bisphenol A (BPA), is used as a precursor in plastics, resins, paints, and many other materials. It has been proved that BPA can cause long-term adverse effects on ecosystems and human health due to its toxicity as an endocrine disruptor. In this study, we developed an integrated MnO2/UV/persulfate (PS) process for use in BPA photocatalytic degradation from water and examined the reaction mechanisms, degradation pathways, and toxicity reduction. Comparative tests using MnO2, PS, UV, UV/MnO2, MnO2/PS, and UV/PS processes were conducted under the same conditions to investigate the mechanism of BPA catalytic degradation by the proposed MnO2/UV/PS process. The best performance was observed in the MnO2/UV/PS process in which BPA was completely removed in 30 min with a reduction rate of over 90% for total organic carbon after 2 h. This process also showed a stable removal efficiency with a large variation of pH levels (3.6 to 10.0). Kinetic analysis suggested that 1O2 and SO4•− played more critical roles than •OH for BPA degradation. Infrared spectra showed that UV irradiation could stimulate the generation of –OH groups on the MnO2 photocatalyst surface, facilitating the PS catalytic degradation of BPA in this process. The degradation pathways were further proposed in five steps, and thirteen intermediates were identified by gas chromatography-mass spectrometry. The acute toxicity was analyzed during the treatment, showing a slight increase (by 3.3%) in the first 30 min and then a decrease by four-fold over 2 h. These findings help elucidate the mechanism and pathways of BPA degradation and provide an effective PS catalytic strategy.

Insights into the mechanism of peroxydisulfate activated by magnetic spinel CuFe2O4/SBC as a heterogeneous catalyst for bisphenol S degradation

• CuFe 2 O 4 /SBC was synthesized via hydrothermal method assisted by PEG-20000. • The CuFe 2 O 4 /SBC/PDS system showed superior stability against metal ions leaching. • CuFe 2 O 4 /SBC could efficiently degrade 84.5% BPS in CuFe 2 O 4 /SBC/PDS system. • The adsorbed BPS on CuFe 2 O 4 /SBC could be further degraded. • The surface-bound radical pathways played a more crucial role. The CuFe 2 O 4 catalyst in advanced oxidation processes had received much attention, while the leaching metal ions and its agglomeration limited its application prospect. The conversion of waste activated sludge (WAS) into sludge-derived biochar (SBC) through pyrolysis could not only be the option of reducing the environmental burden but also converted to be the value-added environmental remediation materials. Hence, the present study prepared as a CuFe 2 O 4 /SBC heterogeneous catalyst to degrade new environmental pollutants (bisphenol S, BPS). To our best knowledge, CuFe 2 O 4 /SBC as a heterogeneous catalyst activating peroxydisulfate to degrade BPS in solution is rarely reported, and the catalytic performances and degradation mechanism of CuFe 2 O 4 /SBC need to be comprehensively investigated. The synergistic effect between CuFe 2 O 4 and SBC enhanced catalytic performances and alleviated agglomeration. The CuFe 2 O 4 /SBC was greatly ameliorated metal ions leaching, but the synthetic strategy could better optimize to further reducing Cu ion leaching. The dominant role of heterogeneous catalysis by CuFe 2 O 4 /SBC also have been elucidated. It was proposed that radical ( OH and SO 4 − ) and non-radical ( 1 O 2 ) oxidation processes worked together for BPS degradation, but surface-bound radical pathways played more crucial roles. Some intermediate products with higher toxicity may be produced due to the non-completely mineralized, thus future attention should be paid to their environmental risks. Hence, the detoxification efficiency of CuFe 2 O 4 /SBC needs to be further strengthened via improving the reaction conditions. Overall, this study provided a new strategy to simultaneously solve the problems of WAS disposal and leaching metal ions of CuFe 2 O 4 .

Biodegradation pathway of penicillins by β-lactamase encapsulated in metal-organic frameworks

The pollution caused by the abuse of antibiotics has posed a serious threat to the ecological environment and human health, so development of effective strategies for degradation and disposal of antibiotic residues is urgently needed. In this work, penicillinase, a kind of β-lactamase, was immobilized into zeolitic imidazolate framework-8 (ZIF-8) by self-assembly method and the catalytic performance of the β-lactamase@ZIF-8 porous materials for degradation of penicillins has been investigated by high performance liquid chromatography coupled with mass spectrometry. The results illustrated that the catalytic activity of the encapsulated enzyme was significantly enhanced comparing with that of free enzyme. Meanwhile, the β-lactamase@ZIF-8 exhibited excellent stability under denaturing conditions including high temperature, organic solvent and the enzyme inhibitor. The catalytic degradation mechanism of the β-lactamase@ZIF-8 for penicillins has been probed and verified, and it has been found that the Zn (II) ion on ZIF-8 frameworks could form the complex with the target molecule, which weakened the bond of the four-membered β-lactam ring in the penicillin molecule, and thus enhanced the degradation efficiency of the enzyme. This work provided a promising strategy for eliminating the penicillin residues in water environment.

Electrochemical/Peroxymonosulfate/NrGO-MnFe2O4 for Advanced Treatment of Landfill Leachate Nanofiltration Concentrate

A simple one-pot method was used to successfully embed manganese ferrite (MnFe2O4) nanoparticles on the nitrogen-doped reduced graphene oxide matrix (NrGO), which was used to activate peroxymonosulfate to treat the landfill leachate nanofiltration concentration (LLNC) with electrochemical enhancement. NrGO-MnFe2O4 and rGO-MnFe2O4 were characterized by various means. This indicates that nitrogen-doped could induce more graphene oxide (GO) spall and reduction to produce more active centers, and was favorable for uniformly loading MnFe2O4 particles. The comparison between electrochemical/peroxymonosulfate/NrGO-MnFe2O4 (EC/PMS/NrGO-MnFe2O4) system and different catalytic systems shows that electrochemical reaction, NrGO and MnFe2O4 can produce synergies, and the chemical oxygen demand (COD) removal rate of LLNC can reach 72.89% under the optimal conditions. The three-dimensional (3D-EEM) fluorescence spectrum shows that the system has a strong treatment effect on the macromolecules with intense fluorescence emission in LLNC, such as humic acid, and degrades into substances with weak or no fluorescence characteristics. Gas chromatography-mass spectrometry (GC-MS) indicates that the complex structure of refractory organic compounds can be simplified, while the simple small molecular organic compounds can be directly mineralized. The mechanism of catalytic degradation of the system was preliminarily discussed by the free radical quenching experiment. Therefore, the EC/PMS/NrGO-MnFe2O4 system has significant application potential in the treatment of refractory wastewater.

Efficient persulfate activation by hematite nanocrystals for degradation of organic pollutants under visible light irradiation: Facet-dependent catalytic performance and degradation mechanism

Hematite has been well studied in advanced oxidant processes (AOPs) due to its abundance and non-toxicity, but its precise mechanism in persulfate (PS) activation remains unclear. Here, we studied PS activation by hematite nanoplates (NPs) with dominant {001} facets, nanocubes (NCs) with dominant {012} facets, and nanorods (NRs) with dominant {110} facets, disclosing the facet-dependent PS activation for efficient degradation of organic pollutants over hematite crystals under visible light irradiation. Hematite NPs exhibited much higher oxidation degradation of organic pollutants than NCs and NRs. Density functional theory (DFT) calculation confirms that PS was more easily adsorbed by NPs than by NCs and NRs, which favored more PS-Fe(Ⅲ) complexes on the surface of hematite NPs. More reduced Fe(II) species from NPs than from others under visible light irradiation promoted PS activation, producing radicals for pollutants oxidation. These findings highlight the structure-performance relationship of irradiated hematite and the mechanisms in contaminant degradation.

Effective Removal of Tetracycline from Water by Catalytic Peroxymonosulfate Oxidation Over Co@Mos2: Catalytic Performance and Degradation Mechanism

Effective Removal of Tetracycline from Water by Catalytic Peroxymonosulfate Oxidation Over Co@Mos2: Catalytic Performance and Degradation Mechanism

Theoretical study on the adsorption and catalytic degradation mechanism of sulfacetamide on anatase TiO2(001) and (101) surfaces

In this paper, the adsorption of sulfacetamide on anatase titanium dioxide (001) and (101) was studied. The mechanism of six degradation pathways of sulfacetamide was discussed.

Catalytic degradation and mineralization mechanism of 4-chlorophenol oxidized by phosphomolybdic acid/H2O2

Adsorbable organic halogens (AOX) are used as a parameter to determine the total amount of organic halogens in the environment. 4-chlorophenol (4-CP), as a type of AOX, can persist in the environment for a long time and is not biodegradable. 4-CP has significant carcinogenic and teratogenic effects on humans and animals. In this study, a catalytic system employing phosphomolybdic acid (PMA) and hydrogen peroxide (H2O2) was developed for degrading 4-CP. The degradation and the mechanisms of 4-chlorophenol (4-CP) as an AOX simulant was investigated. The removal efficiency of 4-CP, the AOX content, and total organic carbon were used to evaluate its molecular structure. The results show that 4-CP was fully converted, 19.81% to other species of AOX and 44.52% to CO2 and H2O. Moreover, the intermediates were detected and analyzed, and the possible pathways of 4-CP degradation were drawn. 4-CP attached to PMA, there by leading to ring-opening or dichlorination, and the generation of some other chemical species, such as phenol, benzoquinone, cyclohexanone, 4-chlorohexa-2,4-dien-1-ol, and 3-chlorohexa-2,4-diene-1,6-diol. These species would then be mineralized under the effects of free radicals. PMA can promote the formation of free radicals and shows exceptional efficiency in the degradation of 4-CP.

Deposition of perovskite-type LaFeO3 particles on spherical commercial polystyrene resin: A new platform for enhanced photo-Fenton-catalyzed degradation and simultaneous wastewater purification

Abstract The application of nanosized photocatalytic materials in powder form bring some drawbacks like agglomeration and difficulty in separation in scale up processes. In this study, commercial polystyrene based resin was offered as a new platform for the deposition of catalyst nanoparticles. For this purpose, perovskite LaFeO3 nanoparticles were deposited on Diaion TM HP21 resin via a facile hydrothermal process and the heterostructured catalyst exhibited enhanced ultraviolet–visible light absorption efficiency, photocatalytic, Fenton and photo-Fenton catalytic activities towards tetracycline antibiotic. The effect of solution pH, stability and the degradation intermediates of tetracycline as well as environmental application in different water media under sunlight irradiation were also explored. Furthermore, the catalytic degradation mechanism was examined with reactive radical scavenger tests. Apart from tetracycline molecule, the photo-Fenton catalytic activities of the heterostructured catalyst with respect to different dye and antibiotic components were also investigated to establish the relationship between adsorption and photocatalysis. Exploring the possible utilization of the newly designed commercial resin not only solving the environmental issue but also highlighting its further usage with the concept of “photocatalysis”.

Efficient removal of antibiotic thiamphenicol by pulsed discharge plasma coupled with complex catalysis using graphene-WO3-Fe3O4 nanocomposites

Pulsed discharge plasma (PDP) induced complex catalysis for synergetic removal of thiamphenicol (TAP) was investigated using graphene-WO3-Fe3O4 nanocomposites. The prepared samples were characterized systematically in view of the structure and morphology, chemical bonding state, optical property, electrochemical property and magnetic property. Based on characterization and TAP degradation, the catalytic performance followed: graphene-WO3-Fe3O4>graphene-WO3>WO3, and the highest removal efficiency and kinetic constant could reached 99.3% and 0.070 min-1, respectively. With increase of catalyst dosage, the removal efficiency firstly enhanced and then declined. Lower pH value was beneficial for TAP degradation. The prepared graphene-WO3-Fe3O4 owed higher stability and lower dissolution rate of iron ion. The rGO-WO3-Fe3O4 could decompose O3 and H2O2 into more ·OH in PDP system. The degradation intermediates were characterized by fluorescence spectrograph, LC-MS and IC. Based on the detected intermediates and discrete Fourier transform (DFT) analysis, degradation pathway of TAP was proposed. Besides, the toxicity of intermediates was predicted. Finally, catalytic degradation mechanism of TAP by PDP with graphene-WO3-Fe3O4 was summarized.

Metal-organic framework modified pine needle-derived N, O-doped magnetic porous carbon embedded with Au nanoparticles for adsorption and catalytic degradation of tetracycline

Pine needles (PNs) were used as a biomass precursor to fabricate N, O-doped magnetic porous carbon frameworks (PN−MPC) after modification with metal-organic frameworks (MOFs) and carbonization. And PN−MPC catalysts embedded with Au nanoparticles (Au/PN−MPC) were fabricated by a facile two-step route involving impregnation and subsequent thermal reduction procedures. The crystal structures, morphologies, chemical component, and microstructure of the Au/PN−MPC catalysts were initially investigated through various physicochemical characterization. Au/PN−MPC900 exhibited outstanding catalytic activity toward tetracycline (TC) degradation in the presence of H2O2, with a degradation efficiency and degradation rate constant of 96% and 0.133 min−1 within initial 10 min, respectively. The effects of operating parameters, including initial pH, temperature, catalyst dosage, initial concentrations of TC, and H2O2 concentration on TC degradation were comprehensively investigated. The superior mineralization performance and pH tolerance abilities and catalytic stability of Au/PN−MPC900 were also discussed. After seven consecutive cycles, the removal efficiency of Au/PN−MPC900 for TC degradation was not only greater than 82%, but also exhibited excellent reusability performance. Furthermore, ·OH radicals were confirmed as the dominant reactive species roles for the degradation of antibiotic pollutants through EPR and ·OH−trapping fluorescence spectral tests, and a plausible catalytic degradation mechanism was proposed. Correspondingly, several possible degradation pathways of TC were tentatively proposed on the basis of the degradation intermediates identified by HPLC-MS measurements. Overall, this novel biomass-derived magnetic porous carbon material embedded with Au nanoparticles is highly promising for many applications, especially in the field of environmental remediation.

Density functional theory study on the catalytic degradation mechanism of polystyrene

The density functional theory method of B3LYP/6-311G(d) was used to study two catalytic degradation (acid-catalyzed and alkali-catalyzed) reaction mechanisms of polystyrene (PS). The geometric structure optimization and frequency calculations of all the molecules involved in the catalytic degradation were performed, and the standard thermodynamic parameters of each catalytic cracking path were obtained. The calculation results show that the energy barrier of the optimal reaction path’s rate control step to form styrene monomer is 68.2 kJ/mol in the alkali-catalyzed degradation reaction paths. In the acid-catalyzed cracking paths, the energy barrier of the optimal path’s rate control step to form styrene is 151.9 kJ/mol. The energy barriers of rate control steps for the formation of styrene monomer in both types of these catalytic cracking reactions are lower than those for other products, so the main degradation product in the two types of catalytic degradation is styrene monomer. Compared with pure thermal degradation, an obvious feature of acid-catalyzed degradation is the formation of benzene, indene, and derivatives of indene. The formation of benzene reduces the phenyl content of the PS main chain, which results in a reduction in the yield of styrene monomer. However, an alkali catalyst shows a positive catalytic effect, which increases the yield of styrene monomer.

Catalytic degradation mechanism of sulfamethazine via photosynergy of monoclinic BiVO4and microalgae under visible-light irradiation

To improve the efficiency of antibiotic degradation, the photosynergistic performance of bismuth vanadate (BiVO4) with a microalga, Dictyosphaerium sp., was demonstrated under visible-light irradiation for the first time. Sulfamethazine (SM2) was selected as a representative sulfanilamide antibiotic, and the photocatalytic degradation mechanism of SM2 was evaluated in media via the BiVO4–algae system. The hydrothermally synthesized sample was characterized using X-ray powder diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area, and Fourier transform infrared spectroscopy techniques. The results demonstrated that the prepared photocatalyst corresponded to phase-pure monoclinic scheelite BiVO4. The synthesized BiVO4 showed superior photocatalytic properties under irradiation with visible light, and more than 80% of photocatalytic degradation efficiency was obtained by the BiVO4–algae system. Based on quenching experiments, the photocatalytic degradation of SM2 in the BiVO4–algae system was primarily accomplished via the generation of triplet state dissolved organic matter, and hydroxyl radicals played a small role in the degradation process. The direct oxidation of holes made no contribution to the degradation. Metabolomics data showed that a total of 91 metabolites were significantly changed between the two comparison groups (algae–SM2 group vs algae group; algae–BiVO4–SM2 group vs algae–BiVO4 group). The glycometabolism pathways were increased and the tricarboxylic acid cycle was activated when BiVO4 was present. The study provides a distinctive approach to remove antibiotics using visible light in the aqueous environment.

Facile synthesis of MnO2 nanorods and ZnMn2O4 nanohexagons: a comparison of microwave-assisted catalytic activity against 4-nitrophenol degradation

The present preliminary research work reports the synthesis of MnO2 nanorods and ZnMn2O4 spinel via co-precipitation method. The synthesized nanomaterials were characterized via scanning electron microscopy coupled energy-dispersive X-ray spectroscopy (SEM-EDX) with elemental mapping, transmission electron microscopy(TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) techniques. The chemical composition and purity were established via XRD and XPS studies. Formation of MnO2 nanorods and hexagonal shaped ZnMn2O4 nanostructures was confirmed via SEM and TEM studies. The TGA studies confirmed high thermal stability of MnO2 as compared to ZnMn2O4. Microwave-assisted catalytic activity was assessed by degrading 50ppm of 4-nitrophenol solution in presence of MnO2 and ZnMn2O4 under microwave irradiation for 30min. almost 85% degradation within 30min was achieved using ZnMn2O4 as catalyst. The degradation followed first order kinetics in both cases and the rate constant (k) values were found to be 0.02075 in presence of MnO2 min−1 and 0.05912min−1 in presence of ZnMn2O4. The effect of addition of hydrogen peroxide was also investigated and the increase in catalyst dosage from 50mg to 250mg increased the degradation efficiency from 71% to 94% using ZnMn2O4 as catalyst. Likewise, upon increasing the microwave power from 200W to 1000W, the degradation efficiency increased from 71% to 94%. The radicals responsible for degradation were confirmed by the scavenging experiments using tert-butyl alcohol (TBA) and 1,4-Benzoquinone (BQ) as radical scavengers. The degradation efficiency decreased to almost 50% in presence of TBA as compared to BQ which revealed 75% degradation of 4-nitrophenol solution under microwave irradiation for 30min. A plausible mechanism of microwave-assisted catalytic degradation was proposed.

Biomimetic preparation of MoS2-Fe3O4 MNPs as heterogeneous catalysts for the degradation of methylene blue

In this work, we reported the preparation of MoS2-based Fe3O4 magnetic composites (MoS2-Fe3O4 MNPs) through the biomimetic strategy, which relied on the self-polymerization of dopamine under alkaline aqueous solution. The utilization of MoS2-Fe3O4 MNPs as catalysts for Fenton reaction to degrade organic dyes was also examined in details. A number of experimental parameters, including concentrations of H2O2, dosages of MoS2-Fe3O4 MNPs and pH values on the degradation efficiencies were evaluated. The mechanism for catalytic degradation of methylene blue through Fenton reaction was illustrated by electron spin resonance (ESR) measurement and results indicated that the generation of ·OH and ·O2− is the major reason for the degradation reaction. The results from recycle experiments suggest that catalysts possess good reusability. We demonstrated that Fe3O4 MNPs would be well dispersed on the surface of MoS2 sheets relied on the linkage by polydopamine (PDA), which prevented the aggregation of Fe3O4 MNPs and thus maintained high efficiency. Furthermore, we proved that the catalysts could also have high removal efficiency under low catalyst dosage and H2O2 concentration. In conclusion, we believed the MoS2-Fe3O4 MNPs could be successfully fabricated via the biomimetic strategy and should be promising candidates for environmental treatment. The biomimetic method should be also expanded for fabrication of other functional composites owing to the universal adhesion of PDA.

Fabrication of SnS/TiO2 NRs/NSs photoelectrode as photoactivator of peroxymonosulfate for organic pollutants elimination

In the study, SnS decorated TiO2 nanorods/nanosheets (SnS/TiO2 NRs/NSs) photoelectrode was successfully fabricated as photoactivator of peroxymonosulfate (PMS) for organic pollutants elimination via hydrothermal reaction, followed by successive ionic layer adsorption and reaction (SILAR) method. The result of scanning electron microscope suggested that SnS nanoparticles with sizes varying from 20 to 50 nm were uniformly decorated on the surface of TiO2 NRs/NSs to form a nano-heterojunction. Moreover, we also evaluated the catalytic degradation performance of SnS/TiO2 NRs/NSs photoactivator through PMS activation system for decomposition of rhodamine B (RhB), tartrazine (TTZ), 4-chlorophenol (4-CP), methylene blue (MB), sulfamethoxazole (SMZ), Ibuprofen (IBP), and ciprofloxacin (CIP). Results suggested that SnS/TiO2 NRs/NSs photoelectrode showed higher catalytic degradation efficiency compared with other reaction systems, which was mainly ascribed to intense light response, lower recombination rate of electron-hole pairs and synergistic effect of PMS. Moreover, the possible catalytic degradation mechanism of the constructed catalyst/light/PMS system was proposed and confirmed. Finally, the SnS/TiO2 NRs/NSs/Light/PMS system possessed well reusability and wide adaptability.

Low-temperature constructing N-doped graphite-like mesoporous structure biochar from furfural residue with urea for removal of chlortetracycline from wastewater and hydrothermal catalytic degradation mechanism

A novel N-doped graphite-like mesoporous structure biochar (NBC) was prepared from furfural residue with urea under mild low temperature, its performance in the removal of chlortetracycline (CTC) from aqueous solution and the hydrothermal catalytic degradation mechanism were investigated. This preparation strategy of the adsorbent demonstrated the properties of urea as a crosslinking agent and reactive reagent in the heat treatment process from room temperature to 300 °C. In addition, the pore structure, species and number of surface active adsorption sites of NBC were verified through SEM/EDS, FTIR, BET, XRD, TG and XPS analyses. The results showed that N atoms could be uniformly distributed on the surface of NBC, up to 17.7%, which was about ten times higher than that of direct pyrolysis of biomass (pristine BC) and NBC with graphite-like mesoporous structure had the abundant surface nitrogenous functional groups, such as pyrrolic-N and graphitic-N species besides the oxygen-containing functional groups. Batch adsorption studies indicated that NBC achieved equilibrium faster for CTC adsorption (200 min) than other reported adsorbents. The maximum adsorption capacity of CTC onto NBC was 44.3 mg/g, and the adsorption efficiency was still 26.7 mg/g after four recycling. The adsorption experimental data fitted well with the pseudo-second-order kinetic model and the Freundlich isotherm model. Besides, its catalytic degradation of CTC with hydrothermal treatment also exhibited a potential catalytic activity, and catalytic degradation pathway was proposed through the identification of intermediates using LC-MS. The furfural residue is industrially relevant to the furfural production process and hence NBC may be a promising new environment-friendly material.

Study on the efficacy and mechanism of Fe-TiO2 visible heterogeneous Fenton catalytic degradation of atrazine

In order to improve the catalytic activity and recycling performance of heterogeneous Fenton catalyst, a heterogeneous Fenton catalyst Fe/TiO2 based on TiO2 supported visible light response was prepared by a simple method using TiO2 synthesized by sol-gel method as carrier and ferric nitrate as Fe source. It was characterized by SEM, EDX, XRD, UV–vis instruments. The influencing factors of catalytic degradation of atrazine by visible light heterogeneous Fenton of Fe/TiO2 were studied and the reaction kinetics were fitted. The mineralization degree of atrazine was reflected by the removal rate of TOC. The intermediate products by the degradation of the catalytic system was analyzed and the reaction mechanism of Fe/TiO2–H2O2 visible light system was discussed. The XRD results showed that Fe was highly dispersed on the surface of TiO2 in the form of α-Fe2O3. The Fe/TiO2 catalyst with heterogeneous Fenton and visible light photocatalytic activity was successfully optimized, forbidden bandwidth of Fe/TiO2 after Fe supported was narrower, the scope of light absorption red-shifted, the electron-hole pairs were more generated, and there was a significant synergistic effect between the carrier TiO2 and the supported Fe, which exhibited good oxidation capacity for degradation of 10 mg L−1 atrazine in pH of 3, the concentration of H2O2 was 1.6 mM, and the catalyst was added at 1 g L−1, achieving over 95% removal efficiency within 30 min, and, in the range of pH 3–7, the degradation rate of the reaction for 30 min can be maintained above 75%, which greatly broadened the range of pH application and had good recycling performance. The degradation process conformed to the quasi-first-order kinetic model. Through LC-MS analyzed, 12 intermediate products were formed during the degradation of atrazine, the final products were all cyanuric acid, and then the triazine ring was mineralized into inorganic substances such as CO2, H2O and NO3− by oxidation of ·OH, and the possible degradation pathways were inferred.