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Nitrogen doped graphene oxide loaded CuFe2O4 nanoparticles (CuFe2O4-NG) catalyst was successfully synthesized by thermal annealing and hydrothermal reaction approaches for degrading organic pollutants by peroxymonosulfate (PMS) activation. CuFe2O4-NG exhibited superior degradation efficiency toward orange II among GO, NG, CuFe2O4 and CuFe2O4-NG. The obtained catalysts were systemically characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectrum analysis and X-ray photoelectron spectroscopy to understand the relationship between inner structure and catalytic activity. It can recognize the key reactive oxygen species including SO4•–, •OH, O2•– and 1O2 in CuFe2O4-NG/PMS degradation system by electron paramagnetic resonance and free radical quenching studies, indicating the existence of both radical pathway and non-radical pathway. Based on the valence state changes of Cu and Fe in XPS spectra, the redox cycles between Fe(III) and Fe(II), Cu(II) and Cu(I) mediated by HSO5– contributed to the production of SO4•–, •OH and O2•–. Carbonyl groups and ketonic groups on the catalyst could promote the self-decomposition of PMS, leading to the generation of 1O2. The synergistic effect between NG and CuFe2O4 can accelerate the activation of PMS and pose the new insight for organic pollutants removal. more...

Susceptibility weighted imaging (SWI) is a relatively new magnetic resonance imaging (MRI) technique that uses the difference in tissue magnetic susceptibility to image, and has unique value compared to traditionalmagnetic resonance imaging. This article summarizes its application inthe central nervous system and provides a reference for imaging diagnosisand clinical treatment. more...

Three novel graphitized hierarchical porous biochar (MX) and MnFe2O4 magnetic composites (MnFe2O4/MX) have been prepared for degrading organic pollutants by peroxymonosulfate (PMS) activation. MX including MS, ML, MC synthesized using corn stems (S), leaves (L) and cores (C) as raw materials, respectively, possesses hierarchical porous structure, graphitization domains and tremendous surface area. The orange II removal effects of MX and MnFe2O4/MX outperform the corresponding carbonization products, despite that adsorption probably undertakes the major removal efficiency for MX and degradation contributes the most for MnFe2O4/MX. A structure-dependent degradation efficiency is discovered for MX and MnFe2O4/MX, among of which both MS and MnFe2O4/MS present the best removal effect, by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The lowest EIS owning to its better balance between graphitization degree and specific surface area and micropore volume of MnFe2O4/MS among MnFe2O4/MX explains its best catalytic activity. The catalytic degradation occurs by the following three ways. First, the radical-induced oxidation is attained by surface-bound SO4− and OH on MnFe2O4 nanoclusters and hierarchical porous carbon nanosheets generated by one-electron reduction of PMS under the participating and coupling of Mn(III)/Mn(II), Fe(III)/Fe(II), O2/ O2−, and active sites on carbon surface. Second, non-radical pathway involves the contribution of 1O2, which is produced in a large quantity by promoted self-decomposition of PMS in presence of MnFe2O4/MS. Third, non-radical pathway is achieved through electron transfer from organic compounds as electron donator to PMS as electron acceptor mediated by graphitization structures. Taking into consideration the excellent degradation performance, easy magnetic separation, and bulk availability of MnFe2O4/MS, this work is expected to pave a new way for precision utilization of corn biomass-based biochar for environmental application. more...

A convenient and efficient method to fabricate isolated Fe single-atom catalysts deposited on Myriophyllum aquaticum-based biochar (ISA-Fe/MC) is reported for peroxymonosulfate-based organics degradation. Firstly, the Fe nanoparticles anchored on the hierarchical porous biochar (nano-Fe/MC) can be obtained by utilizing K2FeO4 as a synchronous activation and graphitization agent. Subsequently, ISA-Fe/MC was achieved by HCl etching of nano-Fe/MC to remove the excess Fe nanoparticles. Compared with nano-Fe/MC, ISA-Fe/MC demonstrated outperformed catalytic capacity towards PMS activation for phenol degradation. The combination of super high surface area, hierarchical porous structure, graphitization structure and atomically dispersed Fe species should be responsible for prominent catalytic oxidation ability and outstanding resistance to common anions and humic acid. Based on the chemical scavengers, EPR experiments and electrochemistry tests, the SO4•- dominated radical degradation pathway for nano-Fe/MC and electron transfer reigned non-radical degradation pathway for ISA-Fe/MC was revealed. In contrast to nano-Fe/MC, density functional theory calculations demonstrated the enhanced density of states around Fermi level in ISA-Fe/MC meaning the increased catalytic performance and more electron transfer between single-atom Fe to adjacent graphitic C and N which could serve as electron transfer channel for PMS activation. more...

Three types of hierarchically porous magnetic biochars (HMBs) were prepared by pyrolyzing low-cost wheat straw and potassium ferrate (K2FeO4) under a nitrogen atmosphere at 600, 700 and 800 °C, respectively, which could be used as amendments for cadmium (Cd) in water and soil. HMB fabricated at 700 °C (HMB700) had the best remediation performance for Cd in water and soil, which was mainly due to its largest specific surface area and micropore volume. Batch sorption experiments showed that Cd(II) sorption onto HMBs were well-described by a pseudo-second-order model and Sips (Freundlich-Langmuir) model, indicating that HMBs removed Cd(II) mainly through chemical adsorption. MINTEQ modeling evidenced that HMBs adsorbed Cd(II) mainly through precipitation rather than surface complexation. The adsorption behavior of HMB700 to Cd(II) could be explained by surface complexation (–OCd, –COOCd), precipitation (Cd(OH)2 and CdCO3), physical adsorption (rich pore structure) and ion exchange (K+, Ca2+, Mg2+). Furthermore, adding HMBs (1 wt%) (incubation 60 days) could also significantly increase soil pH and electrical conductivity (EC), and significantly reduce the available Cd content in soil (47.97%–61.38%). Adding HMBs could promote the conversion of bioavailable to less bioavailable Cd forms. These results provided a new idea for fabricating agricultural waste-based HMBs to remediate Cd in water and soil. more...

The biochar loaded with CoFe2O4 nanoparticles (CoFe2O4/HPC) fabricated by pyrolysis exhibited strong magnetic property, hierarchical porous and graphitized structure. CoFe2O4/HPC showed much better bisphenol A degradation than CoFe2O4 in presence of peroxymonosulfate. The graphitized structure and the synergistic effect between graphitized structure and CoFe2O4 were found to be responsible for the superiority of CoFe2O4/HPC among all the other catalysts. The prominent role including radical way mainly contributed by SO4 − and non-radical way achieved by 1O2, and the secondary role of electron transfer way proceeded by graphitized structure were uncovered. The processes such as redox between Co(III)/Co(II) and Fe(III)/Fe(II), the reduction of Fe(III) by O2 −, and the participation of C O in 1O2 production were significant to the excellent catalytic performance of CoFe2O4/HPC. Considering its excellent separation, stability, adaptability and reusability, CoFe2O4/HPC opened up a novel way to develop green catalyst to activate PMS for organic pollutants degradation. more...

In this work, porous defective g-C3N4 ultrathin nanosheets were prepared through thermal condensation of freeze-dried precursor. First-principles density functional theory (DFT) calculations well predicted the role of VN in modulating energy levels and photocatalytic properties. The optimally defective g-C3N4 manifested the better photocatalytic disinfection performance towards E. coli and S. aureus than pristine g-C3N4, respectively. The gradual damaged cell membrane for E. coli and the intimate mechanical constraint for S. aureus was imaged to further decipher the antibacterial behavior. The synergistic effect of enhanced visible light absorption ability, more exposed active sites and improved photogenerated charge separation was responsible for excellent photocatalytic disinfection activity. The photocatalytic disinfection mechanism towards E. coli was explored by electron spinning resonance (EPR), radical scavenger and spectral quantification technology, confirming the major role of h+ and O2 −. This study provides alternative strategy for rational design of effective g-C3N4-based photocatalysts by defective engineering for environmental remediation. more...

In this work, a novel AgInS2 nanosheets/TiO2 nanobelts photocatalyst was prepared by a facile hydrothermal method. The AgInS2/TiO2 with the optimal ration showed excellent photocatalytic performance in simultaneous Escherichia coli (E. coli) disinfection and Cr(VI) reduction or E. coli disinfection and bisphenol A (BPA) degradation. The superior photocatalytic effect were possibly attributed to formation of heterojunction between AgInS2 nanosheets and TiO2 nanobelts, which could increase the absorption of visible light, facilitate the separation of photo-induced carrier and held the redox of photo-generated e– and h+. The production of reactive species during the disinfection process was also investigated by employing chemical scavengers, electron spin resonance, and spectroscopy technique, revealing the paramount role of h+ and O2•–. This study paves a new way to rationally design the novel TiO2 nanobelts or AgInS2 nanosheets based photocatalysts for combined pollution remediation in water environment. more...

The novel Fe3O4 and porous biochar originated from Myriophyllum aquaticum composites (Fe3O4/MC) with graphitized structure, hierarchical porous and strong magnetism were used as efficient catalysts for degradation of organic pollutants in the presence of peroxymonosulfate (PMS). Three types of catalysts pyrolyzed at 600, 700, 800 °C manifested quit different PMS activation effect with the much better p-hydroxybenzoic acid (HBA) degradation efficiency at 700 and 800 °C than that of 600 °C, which was assigned to the high graphitization degree and mesopores ration of catalysts pyrolyzed at higher temperature. Based on radicals quenching experiments and electron paramagnetic resonance (EPR) analyses, the radical pathway dominated by surface-bound SO4 − was the prevailing way while the non-radical pathway performed as electro-transfer was the recessive way during the degradation process. The large amount of surface-bound SO4 − radicals were produced through the reduction of PMS by Fe(II), which was regenerated by participation of O2 −/O2. The non-radical pathway was achieved by the graphitized structure which acted as electron transfer bridges accepting electrons form organic pollutants and denoting electrons to PMS. Six HBA intermediates were detected and the possible HBA degradation pathway was proposed tentatively. Consequently, the conversion of Myriophyllum aquaticum to composite catalyst provides a brand-new idea for efficient utilization of waste biomass in a high value-added way and simultaneously achieving the contaminants elimination. more...