In this study, a series of biochar were prepared via pyrolyzing cellulose-rich pakchoi (PBC) and lignin-rich corncob (CBC) to explore the photoreduction process of Cr(VI). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy confirmed higher oxygenated functional groups in PBC (48.9%-57.1%), whereas CBC exhibited more aromatization properties due to the stable aromatic network in lignin. For PBC, the valence bands decreased from 1.42 eV to 1.20 eV with the increase of pyrolysis temperature from 300 °C to 500 °C; however, an opposite trend was observed for CBC. The photoreduction of Cr(VI) clearly showed that both PBC and CBC had the best performance at the carbonization temperature of 300 °C (named PBC300 and CBC300). It is noted that PBC300 exhibited the most effective photoreduction of Cr(VI), which was about 1.3 times higher than that of CBC300. The maximum reduction capacities of Cr(VI) were 68.2 mg g on PBC300 and 66.1 mg g on CBC300 at pH∼2.0. Compared with the insoluble char substances, dissolved black carbons made more contributions for Cr(VI) photoreduction, ∼70% in PBC and almost 100% in CBC, which suggested that in the case of PBC, the insoluble char and the corresponding dissolved black carbons play an important role in the photoreduction of Cr(VI). However, only dissolved black carbons contributed to Cr(VI) photoreduction on CBC. As the key reaction pathway, the interfacial electron transport dominated Cr(VI) reduction on PBC and CBC. Moreover, the radical of •O had some contribution to the reduction of Cr(VI) only in the PBC system. Interestingly, •OH could promote the photoreduction of Cr(VI) in both PBC and CBC systems, which might be due to the fact that •OH facilitated the formation of small molecule fragments. These findings provide an essential basis for evaluating the environmental impact of photocatalytic behaviors of biochar.
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http://dx.doi.org/10.1016/j.envres.2023.116819 | DOI Listing |
J Hazard Mater
January 2025
CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei 230026, China.
The introduction of structural defects can improve the charge separation efficiency of metal-organic frameworks (MOFs)-based photocatalysts, which however come with suboptimal decontamination performance, due to steric hindrance and limited binding capacity of the involved modulators. In this work, hydroxyl group capturing the advantages of both worlds was utilized as new modulator to improve the photocatalytic performance of Fe-based defective MOFs. Benefited from its low steric effect and strong coordination bonding capability, hydroxyl-induced defects in Fe-MOF contributed to a nearly 8-fold increase of rate constant for the photocatalytic removal of hexavalent chromium (Cr(VI)) compared to that of pristine one, which also exceeded the defective one induced by acetic acid as modulator.
View Article and Find Full Text PDFInt J Mol Sci
December 2024
Yunnan Province Engineering Research Center of Photocatalytic Treatment of Industrial Wastewater, Yunnan University, Kunming 650091, China.
Heavy metal ion pollution poses a serious threat to the natural environment and human health. Photoreduction through Bi-based photocatalysts is regarded as an advanced green technology for solving environmental problems. However, their photocatalytic activity is limited by the rapid recombination of photogenerated e and h pairs and a low photo-quantum efficiency.
View Article and Find Full Text PDFChemosphere
December 2024
School of Environment, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Normal University, Xinxiang, Henan, 453007, China. Electronic address:
Chromium (VI) (Cr(VI)) generally coexists with organic dyes in industrial effluents, posing a formidable challenge in water purification. Herein, NH-MIL-125(Ti)/TiO Z-scheme heterojunction with intimate interfacial contact was synthesized for synchronous removal of pollutant in coexisting Cr(VI)/dyes system under simulated solar irradiation. Structural and optical investigations indicated that a well-defined interface was formed by establishing a Ti-N-C bond, facilitating the spatial separation of the photoexcited carriers of the Z-scheme heterojunction.
View Article and Find Full Text PDFACS Appl Mater Interfaces
November 2024
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130026, P.R. China.
The interface of substances at the photoexcited state is completely different from that at the ground state, which gives a chance to create some unprecedented physical and chemical properties. These interface-dominated properties can significantly improve carrier transport kinetics. Herein, we report a special photochemical strategy for constructing a heterogeneous interface.
View Article and Find Full Text PDFACS Appl Mater Interfaces
November 2024
Dipartimento di Chimica, Università Degli Studi di Milano, Via C. Golgi 19, 20133 Milano, Italy.
The interplay on anatase TiO photoactivity between particle morphology and gold nanoparticles (NPs) deposition, via either deposition-precipitation (DP) or photodeposition (P), is here investigated by evaluating the photoactivity of Au modified anatase (Au/TiO) nanocrystals with either a pseudospherical shape or a nanosheet structure in both reduction and oxidation test reactions. The presence of Au NPs on the anatase surface only slightly affects its photoactivity in Cr(VI) reduction, which is kinetically limited by the anodic half-reaction, whereas a larger exposure of highly oxidant {001} facets is beneficial for overcoming this rate-determining step. In the photocatalytic oxidation of both formic acid, proceeding through a direct mechanism, and rhodamine B (RhB) on surface fluorinated photocatalysts, occurring through a hydroxyl-radical-mediated mechanism, the presence of gold NPs produces a significant photoactivity increase only with spherically shaped photocatalysts, mainly exposing {101} facets.
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