In addition to the adsorption and immobilization capacities of iron-modified biochars,these materials produce persistent free radicals(PFRs)that can carry out metal[i.e.,Cr(VI)]redox transformations,but the primary fo...In addition to the adsorption and immobilization capacities of iron-modified biochars,these materials produce persistent free radicals(PFRs)that can carry out metal[i.e.,Cr(VI)]redox transformations,but the primary forms and active species of PFRs involved are not well understood.Here,we investigated the key species of PFRs ofα-Fe2O3-modified biochar(MBC)and their influence on Cr(VI)reduction under anaerobic conditions simulating paddy soil environments.MBC produced bulk phenoxyl PFRs that promoted Cr(VI)reduction due to the catalytic effect of the transition metal Fe.In addition,MBC was more efficient in reducing Cr(VI)under anaerobic conditions than under aerobic conditions due to the more active and accessible dissolved PFRs present in the dissolved organic matter(DOM).The electron transfer capacity of DOM was demonstrated by excitation-emission matrix(EEM)spectrophotometry combined with parallel factor analysis,which showed that the protein-like and humic-like components of DOM were involved in Cr(VI)reduction.Furthermore,Fourier transform ion cyclotron resonance mass spectrometry(FTICR-MS)analysis indicated that reduced-S compounds(O/S<4)and carboxylic acid(-COO)groups in the unsaturated aliphatic and lignin-like compounds are potentially the main active species accelerating Cr(VI)reduction under anaerobic conditions.Our results provide new insights into the role of dissolved PFRs from iron-modified biochar in promoting Cr(VI)reduction under anaerobic conditions such as flooded soils.展开更多
Generation of hydroxyl radicals(·OH)is the basis of advanced oxidation process(AOP).This study investigates the catalytic activity of microporous carbonaceous structure for in-situ generation of·OH radicals....Generation of hydroxyl radicals(·OH)is the basis of advanced oxidation process(AOP).This study investigates the catalytic activity of microporous carbonaceous structure for in-situ generation of·OH radicals.Biochar(BC)was selected as a representative of carbon materials with a graphitic structure.The work aims at assessing the impact of BC structure on the activation of H2O_(2),the reinforcement of the persistent free radicals(PFRs)in BC using heavy metal complexes,and the subsequent AOP.Accordingly,three different biochars(raw,chemically-and physiochemically-activated BCs)were used for adsorption of two metal ions(nickel and lead)and the degradation of phenol(100 mg/L)through AOP.The results demonstrated four outcomes:(1)The structure of carbon material,the identity and the quantity of the metal complexes in the structure play the key roles in the AOP process.(2)the quantity of PFRs on BC significantly increased(by 200%)with structural activation and metal loading.(3)Though the Pb-loaded BC contained a larger quantity of PFRs,Ni-loaded BC exhibited a higher catalytic activity.(4)The degradation efficiency values for phenol by modified biochar in the presence of H2O_(2) was 80.3%,while the removal efficiency was found to be 17%and 22%in the two control tests,with H2O_(2)(no BC)and with BC(no H2O_(2)),respectively.Overall,the work proposes a new approach for dual applications of carbonaceous structures;adsorption of metal ions and treatment of organic contaminants through in-situ chemical oxidation(ISCO).展开更多
基金supported by the National Natural Science Foundation of China(42025705 and 42107046)the GDAS’Project of Science and Technology Development(2022GDASZH-2022010105 and 2020GDASYL-202001102019)the Guangdong Basic and Applied Basic Research Foundation(2021A1515011540).
文摘In addition to the adsorption and immobilization capacities of iron-modified biochars,these materials produce persistent free radicals(PFRs)that can carry out metal[i.e.,Cr(VI)]redox transformations,but the primary forms and active species of PFRs involved are not well understood.Here,we investigated the key species of PFRs ofα-Fe2O3-modified biochar(MBC)and their influence on Cr(VI)reduction under anaerobic conditions simulating paddy soil environments.MBC produced bulk phenoxyl PFRs that promoted Cr(VI)reduction due to the catalytic effect of the transition metal Fe.In addition,MBC was more efficient in reducing Cr(VI)under anaerobic conditions than under aerobic conditions due to the more active and accessible dissolved PFRs present in the dissolved organic matter(DOM).The electron transfer capacity of DOM was demonstrated by excitation-emission matrix(EEM)spectrophotometry combined with parallel factor analysis,which showed that the protein-like and humic-like components of DOM were involved in Cr(VI)reduction.Furthermore,Fourier transform ion cyclotron resonance mass spectrometry(FTICR-MS)analysis indicated that reduced-S compounds(O/S<4)and carboxylic acid(-COO)groups in the unsaturated aliphatic and lignin-like compounds are potentially the main active species accelerating Cr(VI)reduction under anaerobic conditions.Our results provide new insights into the role of dissolved PFRs from iron-modified biochar in promoting Cr(VI)reduction under anaerobic conditions such as flooded soils.
基金the financial support of the National Science Foundation(NSF EPSCoR RII Grant No.OIA-1632899)。
文摘Generation of hydroxyl radicals(·OH)is the basis of advanced oxidation process(AOP).This study investigates the catalytic activity of microporous carbonaceous structure for in-situ generation of·OH radicals.Biochar(BC)was selected as a representative of carbon materials with a graphitic structure.The work aims at assessing the impact of BC structure on the activation of H2O_(2),the reinforcement of the persistent free radicals(PFRs)in BC using heavy metal complexes,and the subsequent AOP.Accordingly,three different biochars(raw,chemically-and physiochemically-activated BCs)were used for adsorption of two metal ions(nickel and lead)and the degradation of phenol(100 mg/L)through AOP.The results demonstrated four outcomes:(1)The structure of carbon material,the identity and the quantity of the metal complexes in the structure play the key roles in the AOP process.(2)the quantity of PFRs on BC significantly increased(by 200%)with structural activation and metal loading.(3)Though the Pb-loaded BC contained a larger quantity of PFRs,Ni-loaded BC exhibited a higher catalytic activity.(4)The degradation efficiency values for phenol by modified biochar in the presence of H2O_(2) was 80.3%,while the removal efficiency was found to be 17%and 22%in the two control tests,with H2O_(2)(no BC)and with BC(no H2O_(2)),respectively.Overall,the work proposes a new approach for dual applications of carbonaceous structures;adsorption of metal ions and treatment of organic contaminants through in-situ chemical oxidation(ISCO).
