Due to its high efficiency,Fe(Ⅱ)-based catalytic oxidation has been one of the most popular types of technology for treating growing organic pollutants.A lot of chemical Fe sludge alongwith various refractory polluta...Due to its high efficiency,Fe(Ⅱ)-based catalytic oxidation has been one of the most popular types of technology for treating growing organic pollutants.A lot of chemical Fe sludge alongwith various refractory pollutantswas concomitantly produced,whichmay cause secondary environmental problemswithout proper disposal.We here innovatively proposed an effective method of achieving zero Fe sludge,reusing Fe resources(Fe recovery=100%)and advancing organics removal(final TOC removal>70%)simultaneously,based on the in situ formation of magnetic Ca-Fe layered double hydroxide(Fe_(3)O_(4)@CaFe-LDH)nano-material.Cations(Ca^(2+)and Fe^(3+))concentration(≥30 mmol/L)and their molar ratio(Ca:Fe≥1.75)were crucial to the success of the method.Extrinsic nano Fe_(3)O_(4)was designed to be involved in the Fe(Ⅱ)-catalytic wastewater treatment process,and was modified by oxidation intermediates/products(especially those with COO-structure),which promoted the co-precipitation of Ca^(2+)(originated from Ca(OH)_(2)added after oxidation process)and byproduced Fe^(3+)cations on its surface to in situ generate core-shell Fe_(3)O_(4)@CaFe-LDH.The oxidation products were further removed during Fe_(3)O_(4)@CaFe-LDH material formation via intercalation and adsorption.Thismethodwas applicable to many kinds of organicwastewater,such as bisphenol A,methyl orange,humics,and biogas slurry.The prepared magnetic and hierarchical CaFe-LDH nanocomposite material showed comparable application performance to the recently reported CaFe-LDHs.This work provides a new strategy for efficiently enhancing the efficiency and economy of Fe(Ⅱ)-catalyzed oxidative wastewater treatment by producing high value-added LDHs materials.展开更多
Hydroxyl radical(·OH)formation from Fe(Ⅱ)-bearing clay mineral oxygenation in the shallow subsurface has been well documented under moderate environmental conditions.However,the impact of freezing processes on t...Hydroxyl radical(·OH)formation from Fe(Ⅱ)-bearing clay mineral oxygenation in the shallow subsurface has been well documented under moderate environmental conditions.However,the impact of freezing processes on the·OH production capability of Fe(Ⅱ)-bearing clay minerals for organic contaminant degradation,particularly in seasonally frozen soils,remains unclear.In this study,we investigated the influence of pre-freezing durations on the mineral proprieties,·OH production,and phenol degradation during the oxygenation of reduced Fe-rich nontronite(rNAu-2)and Fe-poor montmorillonite(rSWy-3).During the freezing process of reduced clay minerals(1 mM Fe(Ⅱ)),the content of edge surface Fe and Fe(Ⅱ)decreased by up to 46%and 58%,respectively,followed by a slight increased as clay mineral particles aggregated and subsequently partially disaggregated.As the edge surface Fe(Ⅱ)is effective in O_(2) activation but less effective in the transformation of H_(2)O_(2) to·OH,the redistribution of edge surface Fe(Ⅱ)leads to that·OH production and phenol degradation increased initially and then decreased with pre-freezing durations ranging from 0 to 20 days.Moreover,the rate constants of phenol degradation for both the rapid and slow reaction phases also first increase and then decrease with freezing time.However,pre-freezing significantly influenced the rapid phase of phenol degradation by rNAu-2 but affected the slow phase by rSWy-3 due to the much higher edge-surface Fe(Ⅱ)content in rNAu-2.Overall,these findings provide novel insights into the mechanism of·OH production and contaminant degradation during the freeze-thaw processes in clay-rich soils.展开更多
Monotonic pore size and particles inseparability of metal-organic frameworks(MOFs)caused serious effects on its light absorption ability and charge separation,restricting its application for antibiotic such as levoflo...Monotonic pore size and particles inseparability of metal-organic frameworks(MOFs)caused serious effects on its light absorption ability and charge separation,restricting its application for antibiotic such as levofloxacin(LEV)degradation in water.In this study,a magnetically detachable nano-photocatalyst(ZnFe_(2)O_(4)@MIL-88A(Fe))was synthesized using a simple two-step hydrothermal technique.The morphology and microstructure analyses showed that n-type ZnFe_(2)O_(4)catalyst particleswere efficiently assembled onto the surface of MIL-88A(Fe)crystal.Photocatalytic activity studies indicated that the ZnFe_(2)O_(4)@MIL-88A(Fe)plus H_(2)O_(2)exhibiting a significantly boosted photo-Fenton activity toward LEV at visible light irradiation,compared to the pure ZnFe_(2)O_(4)and MIL-88A(Fe),the degradation efficiency accordingly reached up to nearly 82%and 25%within 60 min.This excellent photocatalytic performance was ascribed to the synergistic effects of the heterogeneous structure of ZnFe_(2)O_(4)and MIL-88A(Fe),whereby the efficient separation of charge carriers in the catalytic system is mutually reinforced with the efficient reduction of Fe^(3+)and Fe^(2+).Meanwhile,the degradationmechanism and intermediates of LEV during the photo-Fenton reaction process were also studied in depth through free radical burst,electron paramagnetic resonance,and mass spectrometry analyses,etc.Additionally,the ZnFe_(2)O_(4)@MIL-88A(Fe)composite catalyst displayed significant stability and ease of separation,indicating potential for the photooxidative degradation of organic pollutants.展开更多
基金supported by the Chinese Agriculture Research System(No.CARS-35-06B)111 Project(No.B17030)the Sichuan Science and Technology Program(No.2021ZDZX0012).
文摘Due to its high efficiency,Fe(Ⅱ)-based catalytic oxidation has been one of the most popular types of technology for treating growing organic pollutants.A lot of chemical Fe sludge alongwith various refractory pollutantswas concomitantly produced,whichmay cause secondary environmental problemswithout proper disposal.We here innovatively proposed an effective method of achieving zero Fe sludge,reusing Fe resources(Fe recovery=100%)and advancing organics removal(final TOC removal>70%)simultaneously,based on the in situ formation of magnetic Ca-Fe layered double hydroxide(Fe_(3)O_(4)@CaFe-LDH)nano-material.Cations(Ca^(2+)and Fe^(3+))concentration(≥30 mmol/L)and their molar ratio(Ca:Fe≥1.75)were crucial to the success of the method.Extrinsic nano Fe_(3)O_(4)was designed to be involved in the Fe(Ⅱ)-catalytic wastewater treatment process,and was modified by oxidation intermediates/products(especially those with COO-structure),which promoted the co-precipitation of Ca^(2+)(originated from Ca(OH)_(2)added after oxidation process)and byproduced Fe^(3+)cations on its surface to in situ generate core-shell Fe_(3)O_(4)@CaFe-LDH.The oxidation products were further removed during Fe_(3)O_(4)@CaFe-LDH material formation via intercalation and adsorption.Thismethodwas applicable to many kinds of organicwastewater,such as bisphenol A,methyl orange,humics,and biogas slurry.The prepared magnetic and hierarchical CaFe-LDH nanocomposite material showed comparable application performance to the recently reported CaFe-LDHs.This work provides a new strategy for efficiently enhancing the efficiency and economy of Fe(Ⅱ)-catalyzed oxidative wastewater treatment by producing high value-added LDHs materials.
基金supported by the National Natural Science Foundation of China(Nos.U22A20591,42077185,42107217)the Sichuan Province Science and Technology Program for Distinguished Young Scholars(No.2022JDJQ0010)+1 种基金the Sichuan Science and Technology Program(No.2024NSFSC0842)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(No.SKLGP2020Z002)。
文摘Hydroxyl radical(·OH)formation from Fe(Ⅱ)-bearing clay mineral oxygenation in the shallow subsurface has been well documented under moderate environmental conditions.However,the impact of freezing processes on the·OH production capability of Fe(Ⅱ)-bearing clay minerals for organic contaminant degradation,particularly in seasonally frozen soils,remains unclear.In this study,we investigated the influence of pre-freezing durations on the mineral proprieties,·OH production,and phenol degradation during the oxygenation of reduced Fe-rich nontronite(rNAu-2)and Fe-poor montmorillonite(rSWy-3).During the freezing process of reduced clay minerals(1 mM Fe(Ⅱ)),the content of edge surface Fe and Fe(Ⅱ)decreased by up to 46%and 58%,respectively,followed by a slight increased as clay mineral particles aggregated and subsequently partially disaggregated.As the edge surface Fe(Ⅱ)is effective in O_(2) activation but less effective in the transformation of H_(2)O_(2) to·OH,the redistribution of edge surface Fe(Ⅱ)leads to that·OH production and phenol degradation increased initially and then decreased with pre-freezing durations ranging from 0 to 20 days.Moreover,the rate constants of phenol degradation for both the rapid and slow reaction phases also first increase and then decrease with freezing time.However,pre-freezing significantly influenced the rapid phase of phenol degradation by rNAu-2 but affected the slow phase by rSWy-3 due to the much higher edge-surface Fe(Ⅱ)content in rNAu-2.Overall,these findings provide novel insights into the mechanism of·OH production and contaminant degradation during the freeze-thaw processes in clay-rich soils.
基金supported by the National Natural Science Foundation of China(No.22178325)Jinhua Science and Technology Plan Project.
文摘Monotonic pore size and particles inseparability of metal-organic frameworks(MOFs)caused serious effects on its light absorption ability and charge separation,restricting its application for antibiotic such as levofloxacin(LEV)degradation in water.In this study,a magnetically detachable nano-photocatalyst(ZnFe_(2)O_(4)@MIL-88A(Fe))was synthesized using a simple two-step hydrothermal technique.The morphology and microstructure analyses showed that n-type ZnFe_(2)O_(4)catalyst particleswere efficiently assembled onto the surface of MIL-88A(Fe)crystal.Photocatalytic activity studies indicated that the ZnFe_(2)O_(4)@MIL-88A(Fe)plus H_(2)O_(2)exhibiting a significantly boosted photo-Fenton activity toward LEV at visible light irradiation,compared to the pure ZnFe_(2)O_(4)and MIL-88A(Fe),the degradation efficiency accordingly reached up to nearly 82%and 25%within 60 min.This excellent photocatalytic performance was ascribed to the synergistic effects of the heterogeneous structure of ZnFe_(2)O_(4)and MIL-88A(Fe),whereby the efficient separation of charge carriers in the catalytic system is mutually reinforced with the efficient reduction of Fe^(3+)and Fe^(2+).Meanwhile,the degradationmechanism and intermediates of LEV during the photo-Fenton reaction process were also studied in depth through free radical burst,electron paramagnetic resonance,and mass spectrometry analyses,etc.Additionally,the ZnFe_(2)O_(4)@MIL-88A(Fe)composite catalyst displayed significant stability and ease of separation,indicating potential for the photooxidative degradation of organic pollutants.
