Herein, Fe-g-C3N4/Bi2WO6 Z-scheme heterojunction is elaborately designed to build a photo-Fenton system for the degradation of tetracycline (TC). In this study, the H2O2 decomposition performance of the Z-scheme heterojunction has been improved due to the doping of iron, improve photogenerated electrons transportability and facilitate spread of radicals, according to the efficacy analyses, and trapping experiment, ESR analysis as well as degradation pathways of TC. Moreover, DFT theoretical results suggest that the Z-scheme transfer route coupled with the generated photo–Fenton process builds a Z-scheme-charge-transfer platform for remarkable degradation of emerging pollutants, and the formation of Fe-N4 sites induces a spin polarization of the material and also introduces a defect state in the original forbidden band, which leads to extremely activity for the removal of TC in the photo-Fenton system. The study shows that 1O2 and •O2− are the main active species participating in the degradation process. 

Photo-Fenton degradation of tetracycline over Z-scheme Fe-g-C3N4/Bi2WO6 heterojunctions: Mechanism insight, degradation pathways and DFT calculation

Effect of phosphate on pollutant removal was widely investigated in various peroxumonosulfate-based advanced oxidation processes (AOPs) but the role of phosphate was controversial. Many studies also used phosphate as buffer in PMS-based AOPs. This study shows that phosphate promoted PMS activation for pollutants removal. Therefore, PMS activation capacity of some strategies may be overestimated when conducted in the phosphate buffer. Importantly, the results of radical quenching tests, radical probes and reaction stoichiometries indicated that the yields of SO4 − was elevated by the presence of phosphate and linearly depended on phosphate concentration, while the yields of OH remained constant. Density Functional Theory (DFT) calculation confirmed that PO43− and HPO42− could efficiently break O O bond of PMS, promoting the generation of SO4 − for contaminants decomposition. These results illuminated the role of phosphate in AOPs utilizing PMS and uncovered the underlying mechanism of PMS activation by phosphate.

Effect of phosphate on peroxymonosulfate activation: Accelerating generation of sulfate radical and underlying mechanism

Exploitation of catalysts with multi-active sites is very important for enhancing catalytic performance. 0D/2D hybrids, especially quantum dots (QDs)/nanosheets (NSs), have attracted increasing attentions for advanced oxidation processes due to high charge mobility and more active sites. However, 0D/2D hybrids with multi-active sites still remain a great challenge. Herein, 0D Cu-Fe bi-metal oxide QDs/2D g-C3N4 (CNNSs) exhibiting superior advantages beyond single-metal 0D/2D counterparts was fabricated via a facile one-step synthesis strategy for photo-Fenton catalysis. The synergy of ultrafine Cu-Fe sites on CNNSs led to outstanding tetracycline removal efficiency over a wide pH range. Our experiments and DFT calculations clearly demonstrated that except for the fast charge separation and transfer, this synergy could achieve the optimal H2O2 adsorption-activation trade-off on Cu-Fe sites, while also modify tetracycline absorption, leading to multiple synergies of adsorption-catalytic degradation and photocatalysis-Fenton oxidation. This work provides new insights in developing multi-functional 0D/2D hybrids for environment and energy applications.

Novel Cu-Fe bi-metal oxide quantum dots coupled g-C3N4 nanosheets with H2O2 adsorption-activation trade-off for efficient photo-Fenton catalysis

Oxygen doped graphitic carbon nitride with regulatable local electron density and band structure for improved photocatalytic degradation of bisphenol A

Exploitation of catalysts with multi-active sites is very important for enhancing catalytic performance. 0D/2D hybrids, especially quantum dots (QDs)/nanosheets (NSs), have attracted increasing attentions for advanced oxidation processes due to high charge mobility and more active sites. However, 0D/2D hybrids with multi-active sites still remain a great challenge. Herein, 0D Cu-Fe bi-metal oxide QDs/2D g-C3N4 (CNNSs) exhibiting superior advantages beyond single-metal 0D/2D counterparts was fabricated via a facile one-step synthesis strategy for photo-Fenton catalysis. The synergy of ultrafine Cu-Fe sites on CNNSs led to outstanding tetracycline removal efficiency over a wide pH range. Our experiments and DFT calculations clearly demonstrated that except for the fast charge separation and transfer, this synergy could achieve the optimal H2O2 adsorption-activation trade-off on Cu-Fe sites, while also modify tetracycline absorption, leading to multiple synergies of adsorption-catalytic degradation and photocatalysis-Fenton oxidation. This work provides new insights in developing multi-functional 0D/2D hybrids for environment and energy applications. 

Nitrogen was usually doped into carbon matrix to boost its catalytic activity owing to its electronic adjusting activity toward the topological carbon structure. Herein, an overlooked role of nitrogen dopant was unraveled. The nitrogen dopant was firstly incorporated into the carbon matrix and then partially evaporated, leaving the newly generated topological intrinsic defects under high temperature. It was confirmed that peroxymonosulfate (PMS) could be activated by topological defects-rich carbon catalysts. Surface-activated PMS complex was found to be the dominant reactive oxidation species for organic degradation through electron-transfer mechanism. The distinct current density attenuation revealed that N-rich carbon catalysts possessed more effective stoichiometric reaction between the surface-activated PMS and adsorbed organic than topological defects-rich carbon. Findings from this work confirmed the roles of topological defects and extrinsic defects in PMS activation and provided new insight into the synthesis of defects-rich carbon catalysts.

Overlooked role of nitrogen dopant in carbon catalysts for peroxymonosulfate activation: Intrinsic defects or extrinsic defects?

Galvanic corrosion of zero-valent iron to intensify Fe2+ generation for peroxymonosulfate activation

Low glycemic index (GI) diet has been considered as a strategy for type II diabetes patients. In the present study, the phenolics profile, α-amylase inhibitor activities, starch composition as well as the glycemic index of seven varieties of kidney beans were studied. An enzymatic inhibitory reaction model was employed to determine the α-amylase inhibitor activity, and the in vitro digestion model coupled with the 3, 5-dinitrosalicylic acid colorimetry method was adopted to evaluate the starch composition and glycemic index. The results showed that gallic acid was dominant in kidney beans, and the colored beans contained more phenolics than the white ones. In addition, the α-amylase inhibitor activities of kidney beans ranged from 1.659 ± 0.050 to 4.162 ± 0.049 U/g DW, among which the Y2 variety was the top-ranked. Furthermore, kidney beans starch demonstrated brilliant resistance to digestion with the contribution of resistant starch to total starch between 70.90 ± 0.39% and 83.12 ± 0.42%. Eventually, these kidney beans were categorized as low GI foods, which ranged from 32.47 ± 0.13 to 52.99 ± 0.56, the resistant starch makes dominant contribution to the low GI. These results indicate that kidney beans can be served as ingredients in functional low GI foods.

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Functional components profile and glycemic index of kidney beans

Heteroatom doping into the carbon matrix has been widely accepted to overcome the electronic inertness of carbonaceous material. In this study, N was doped into carbonaceous material within S to evaluate the peroxymonosulfate (PMS) activation performance of the obtained carbocatalyst for the degradation of acetaminophen (ACE). The results demonstrated that individually N or S doped carbocatalysts could activate PMS, but only N doping exhibit significant PMS activation performance. More interestingly, simultaneously co-existed of N and S exhibited obviously lower PMS activation performance than individual N doping. Density functional theory (DFT) calculation exhibited that N doped carbon matrix possessed more positive surface electrostatic potential than N and S co-doped carbocatalyst, amongst S exhibited opposite electronic structure regulation compared with N. Therefore, the PMS activation performance of N doped carbon was significantly higher than that by N and S co-existed carbon. SO4∙-, HO∙,1O2 and O2∙- was involved in the reaction, the result shown that singlet oxygen amplified the non-radical mechanism and the electron transfer from adsorbed organic pollutant to adsorbed PMS was the another dominated pathway to the ACE degradation. Further experiments unraveled that higher PMS concentration, catalysts dosage, and lower initial solution pH would facilitate the PMS activation process. 

Shengshuo Xu

Papers

Overlooked role of nitrogen dopant in carbon catalysts for peroxymonosulfate activation: Intrinsic defects or extrinsic defects?

Galvanic corrosion of zero-valent iron to intensify Fe2+ generation for peroxymonosulfate activation

Functional components profile and glycemic index of kidney beans

Insights into nitrogen doped sulfur-existed carbonaceous material toward acetaminophen removal by peroxymonosulfate activation

Precursor-Driven Structural Tailoring of Iron Oxychloride for Enhanced Heterogeneous Fenton Activity