Degradation of microplastic in water by advanced oxidation processes.

Plastic products have gained global popularity due to their lightweight, excellent ductility, high durability, and portability. However, out of the 8.3 billion tons of plastic waste generated by human activities, 80% of plastic waste is discarded due to improper disposal, and then transformed into microplastic pollution under the combined influence of environmental factors and microorganisms. In this comprehensive study, we present a thorough review of recent advancements in research on the source, distribution, and effect of microplastics. More importantly, we conducted deep research on the catalytic degradation technologies of microplastics in water, including advanced oxidation and photocatalytic technologies, and elaborated on the mechanisms of microplastics degradation in water. Besides, various strategies for mitigating microplastic pollution in aquatic ecosystems are discussed, ranging from policy interventions, the initiative for plastic recycling, the development of efficient catalytic materials, and the integration of multiple technological approaches. This review serves as a valuable resource for addressing the challenge of removing microplastic contaminants from water bodies, offering insights into effective and sustainable solutions.

Facet-dependent activation of oxalic acid over hematite nanocrystals under the irradiation of visible light for efficient degradation of pollutants.

Naturally occurring hematite has been widely studied in the Fenton-like system for water pollutant remediation due to its abundance and non-toxicity. However, its inadequate catalytic activity results in difficulty in effectively degrading pollutants in the catalytic degradation system that it constitutes. Thus, we constructed a photochemical system composed of hematite with {001} facet of high activity facet and low-cost and non-toxic oxalic acid (OA) for the removal of various types of pollutants. The removal rate for the degradation of metronidazole, tetracycline hydrochloride, Rhodamine B, and hexavalent chromium by hematite nanoplate with the exposed {001} facet activating OA under visible light irradiation was 4.75, 2.25, 2.33, and 2.74 times than that by the exposed {110} facet, respectively. Density functional theory (DFT) calculation proved that the OA molecule was more easily adsorbed on the {001} facet of hematite than that on the {110} facet, which would favor the formation of the more Fe(III)-OA complex and reactive species. In addition, the reactive site of metronidazole for the attraction of radicals was identified on the basis of the DFT calculation on the molecular occupied orbitals, and the possible degradation pathway for metronidazole included carbon chain fracture, hydroxyethyl-cleavage, denitrogenation, and hydroxylation. Thus, this finding may offer a valuable direction in designing an efficient iron-based catalyst based on facet engineering for the improved activity of Fenton-like systems such as OA activation.

Study on the Effect of Foam Stability on the Properties of Foamed Lightweight Soils.

The properties of prepared foamed lightweight soils (FLSs) using prefabricated foam requires high foam stability. This paper investigates the geometrical characteristics of different foam densities, different types of foaming agents in the air, and the presence of slurry. Then, it studies their effects on the pore structure and mechanical properties of FLS. Results show that with the increase in foam density the bleeding rate of foam in the air for 1 h increases and the foam with a foam density of 50 kg/m3 is the most stable in the air. The stability of foam in slurry is not directly related to the property of foam in the air. The FLS prepared with the same foaming agent had the best performance with the FLS designed with a foam density of 50 kg/m3, which had the smallest average pore size and the most minor pore size distribution, and had the highest compressive strength. Among the three different foaming agents, Type-S was the best, and the slurry had the lowest rate of increase in wet density after the defoaming test, indicating that the foam had the best stability in the cement slurry. The FLS prepared with the density of 50 kg/m3 using the Type-S foaming agent and mixed with the slurry of cement, fly ash:slag:water = 105:105:140:227.5, was hardened to a mean pore size of 299 µm, and the 7 days, 28 days, and 56 days compressive strengths were 0.92 MPa, 2.04 MPa, and 2.48 MPa, respectively, which had the smallest average pore size and the highest compressive strength among the FLSs prepared using the three foaming agents.

Long-range hydrophobic force enhanced interfacial photocatalysis for the submerged surface anti-biofouling.

Developing anti-biofouling and anti-biofilm techniques is of great importance for protecting water-contact surfaces. In this study, we developed a novel double-layer system consisting of a bottom immobilized TiO2 nanoflower arrays (TNFs) unit and an upper superhydrophobic (SHB) coating along with the assistance of nanobubbles (NBs), which can significantly elevate the interfacial oxygen level by establishing the long-range hydrophobic force between NBs and SHB and effectively maximize the photocatalytic reaction brought by the bottom TNFs. The developed NBs-SHB/TNFs system demonstrated the highest bulk chemical oxygen demand (COD) reduction efficiency at approximately 80% and achieved significant E. coli and Chlorella sp. inhibition efficiencies of 5.38 and 1.99 logs. Meanwhile, the system showed a sevenfold higher resistance to biofilm formation when testing in a wastewater matrix using a wildly collected biofilm seeding solution. These findings provide insights for implementing nanobubble-integrated techniques for submerged surface protection.

Preparation and Properties of Low-Carbon Foamed Lightweight Soil with High Resistance to Sulphate Erosion Environments.

Foamed lightweight soil (FLS) is a lightweight cementitious material containing a large number of tiny closed pores and has been widely used as a filler in places such as railways, roads and airports. However, there has been little research into the resistance of FLS to sulphate attack in practical engineering applications. The performance of FLS against different sulphate erosion concentrations was studied to elucidate the engineering characteristics of using large volumes of FLS as fill material for the road base in the construction of intelligent networked vehicle test sites. The results showed that the compressive strength of FLS prepared using 30% Portland cement (C), 30% granulated blast furnace slag (GBFS), 40% fly ash (FA) and a small amount of a concrete antiseptic agent (CA) as cementitious materials reached 0.8 and 1.9 MPa at 7 and 28 d, respectively, when the wet density was about 600 kg/m3, which met the design requirements. The FLS prepared via the above-mentioned cementitious system had a low carbon emission, with a CO2 emission reduction rate of up to 70%. It also had excellent sulphate attack resistance: the corrosion resistance coefficient of the cementitious material system reached 0.97, which was considerably better than that of C (0.83). For an erosion medium environment with SO42- concentrations of less than 1000 mg/L (moderate), 40% GBFS or FA can be used to prepare FLS. When the concentration of SO42- is less than 4000 mg/L (severe), 30% C, 30% GBFS and 40% FA can be used as cementitious materials, preferably in combination with an appropriate amount of CA, to prepare FLS.

Novel Z-scheme AgI/Sb2WO6 heterostructure for efficient photocatalytic degradation of organic pollutants under visible light: Interfacial electron transfer pathway, DFT calculation and mechanism unveiling.

Developing highly efficient heterostructured photocatalysts with robust redox ability is of great significance to wastewater purification. Herein, a novel Z-scheme AgI/Sb2WO6 heterojunction was successfully constructed via a chemical-precipitation method. The Z-scheme system can serve as a highly efficient photocatalyst for degradation of organic pollutants in water. Under visible light illumination, the degradation efficiency of rhodamine B and tetracycline over the optimal Z-scheme heterojunction can achieve 95% in 12 min and 80% in 8 min, which is 10.8 and 11.4 times higher than that over single Sb2WO6, respectively. Interestingly, low amounts of Ag0 can be generated and attached on the surface of Sb2WO6 during the photocatalytic process, further enhancing the photocatalytic activity of the Z-scheme heterojunction. Based on theoretical calculations, the interfacial internal electric field (IEF) can facilitate the photoexcited electrons at the conduction band (CB) of AgI to consume the photoexcited holes at the valence band (VB) of Sb2WO6, which greatly promotes the Z-scheme charge transfer path. Quenching experiments and electron spin resonance analyses demonstrate superoxide radicals play a major role in the photocatalytic reactions. The concept of constructing a Z-scheme heterojunction photocatalyst with efficient interfacial charge transfer shall provide a design guide for wastewater purification.

Facet-Dependent Activation of Oxalic Acid over Magnetic Recyclable Fe3S4 for Efficient Pollutant Removal under Visible Light Irradiation: Enhanced Catalytic Activity, DFT Calculations, and Mechanism Insight.

Photo-Fenton-like reaction based on oxalic acid (OA) activation is a promising method for the fast degradation of pollutants due to the low cost and safety. Hence, the magnetic recyclable greigite (Fe3S4) with the exposed {011} facet (FS-011) was prepared using a facile one-pot hydrothermal method and activated OA under visible light irradiation for pollutant removal, in which the removal efficiency values of FS-011 for metronidazole (MNZ) and hexavalent chromium were 2.02 and 1.88 times higher than that of Fe3S4 with the exposed {112} facet, respectively. Density functional theory calculations revealed that OA was more easily adsorbed by the {011} facet of Fe3S4 than by the {112} facet, and the in situ-generated H2O2 preferred to diffuse away from the active sites of the {011} facet of Fe3S4 than from that of the {112} facet, which was conducive to the continuous adsorption and efficient activation of OA. Moreover, the analyses of Fukui index and dual descriptor confirmed the degradation mechanism that the imidazole ring of MNZ was easy to be attacked by electrophilic species, while the amino group of MNZ was easy to be attacked by nucleophilic species. These findings deeply analyzed the mechanism of enhanced OA activation by facet engineering and consolidated the theoretical basis for practical application of Fenton-like reactions.

Enhanced visible-light-driven photocatalysis of in-situ reduced of bismuth on BiOCl nanosheets and montmorillonite loading: Synergistic effect and mechanism insight.

Various improvement strategies have been developed to enhance the visible light photocatalytic properties of materials. In these enhancement strategies, bismuth, a non-noble metal-based plasma metal, is deposited on the surface of the photocatalyst, which can improve the visible light response and photocatalytic performance of the photocatalyst. Herein, we constructed montmorillonite loaded BiOCl nanosheets with in situ reduced bismuth by one-step hydrothermal method. As for the results of TEM analysis, the in-situ reduced bismuth nanoparticles with diameters of 5-20 nm were evenly distributed on the surface of BiOCl nanosheets. Due to the surface plasmon resonance (SPR) effect of semi metallic bismuth nanoparticles on the BiOCl nanosheets, the light absorption range of the modified photocatalyst was expanded and its absorption band gap (Eg) was reduced from 3.16 eV (pure BiOCl) to 2.26 eV. Besides, the results of dark adsorption experiments confirmed that the montmorillonite supporter greatly enhanced the adsorption capacity of the modified photocatalyst for pollutants. Moreover, the radical species trapping tests revealed that •O2- and h+ were the pivotal active agents in the pollutant degradation process. The visible light driven photocatalytic degradation rate of TCs and RhB by the modified photocatalyst was 3 and 4 times higher than that of pure BiOCl because of the synergistic effect of montmorillonite supporter and bismuth nanoparticles. The present work provides an innovative strategy for the great feasibility of fabricating low-cost clay and effective bismuth nanoparticles as a substitute for noble metal in environmental pollutants degradation.

Efficient degradation of organic pollutants by activated peroxymonosulfate over TiO2@C decorated Mg-Fe layered double oxides: Degradation pathways and mechanism.

To activate peroxymonosulfate (PMS) is an efficient way for decomposition of non-biodegradable organic pollutants. Herein, Mg-Fe layered double oxides decorated with Ti3C2 MXene-derived TiO2@C (T/LDOs) were fabricated to efficiently activate PMS for the degradation of Rhodamine B (RhB), acid red 1 (AR1), methylene blue (MB), and tetracycline hydrochloride (TC). The T/LDOs catalyst could decompose 95.8% of RhB, 94.8% of AR1, 84.9% of MB within 10 min, and 82.4% of TC within 60 min. The degradation rate constant of RhB in the optimal T/LDOs/PMS system was approximately 2.5 and 15.7 times higher than that in the Mg-Fe LDOs/PMS system and Mg-Fe LDH/PMS system, respectively. Importantly, the T/LDOs exhibited a wide working pH range (3.1-11.0) and high stability with low metal ions leaching, indicating its potential practical applications. Quenching experiments and electronic spin resonance results confirmed that both •O2- and 1O2 were the dominant active species in the T/LDOs/PMS system. In addition, the possible degradation pathway of RhB in the 5%-T/LDOs/PMS system was proposed. Finally, the catalytic mechanism study revealed that the T/LDOs with abundant surface hydroxyl groups and a certain amount of TiO2@C facilitated the electron transfer between ≡Fe(Ⅲ)‒OH complex and HSO5-, boosting the generation of •O2- and 1O2. This study provides an insight into exploiting highly efficient catalysts for PMS activation towards the degradation of organic pollutants.

2D WO3-x Nanosheet with Rich Oxygen Vacancies for Efficient Visible-Light-Driven Photocatalytic Nitrogen Fixation.

Oxygen vacancy modulation holds great promise for enhancing the photocatalytic activity for efficient nitrogen fixation under mild conditions. In this work, the two-dimensional WO3-x nanosheets with rich oxygen vacancies were prepared using solvothermal synthesis. The WO3-x nanosheets (rich oxygen vacancies) display nice photocatalytic activity for N2 reduction to ammonia with a high yield rate of 82.41 µmol·gcat-1·h-1 under irradiation of visible light (420 nm), which is 3.59 times higher than that of the WO3-x nanoparticles (poor oxygen vacancies). Electron spin resonance (ESR), N2 adsorption-desorption isotherms, and transient photocurrent responses in the N2 or Ar atmosphere experiments proved that the rich oxygen vacancies, which are induced by the nanosheet structure, could serve as active sites for the chemisorption of N2 and facilitate the electron transfer from unsaturated sites to activated N2. Moreover, based on the analysis of banding energy, the oxygen vacancies not only boosted the ability of visible light harvesting but also elevated the defect energy level to the Fermi level, further inhibiting the defect relaxation effect. The findings offer an insight into the design of the efficient photocatalysts via structure engineering and defect engineering for photocatalytic N2 fixation.

Advances in single-atom catalysts: Design, synthesis and environmental applications.

Over the past few years, single-atom catalysts (SACs) on the horizon have driven rapid and extensive scientific advances in heterogeneous catalysis. Nevertheless, large-scale applications of SACs in the environment have been hindered by the problematic synthesis of catalysts, because the atomic-scale materials with high activation energy are easy to form nanoclusters and nanoparticles in the synthesis stage. The catalytic stability and catalytic activity of SACs in the treatment of complex environmental pollutants also need to be further researched. Herein, the review is built on a comprehensive discussion of the design and synthesis strategies of SACs. The shortcomings of traditional methods and the improvement from different angles like defect regulation are analyzed. Furthermore, the reaction mechanism of SACs in different reactions was summarized, and the environmental applications of SACs, such as wastewater treatment, carbon dioxide reduction, nitrogen reduction, hydrogen evolution, NOx reduction and oxidation, volatile organic compounds removing and environmental monitoring are exemplified to deeply evaluate the prospects and challenges of SACs in the field of environmental protection.

Self-assembled ultrathin closely bonded 2D/2D heterojunction for enhanced visible-light-induced photocatalytic oxidation and reaction mechanism insights.

Two-dimensional (2D) layered heterojunctions with a staggered band structure and unique interface properties exhibit promising application prospects in photocatalytic pollutant removal, water splitting, and CO2 reduction. Ultrathin 2D/2D heterojunctions with a large specific surface area and a short migration path of the photogenerated charge always illustrate a better photocatalytic performance than non-ultrathin 2D heterojunction photocatalysts. In this study, a novel ultrathin 2D/2D heterojunction of the Bi2O2(OH)(NO3)/BiOBr nanosheet composite (ultrathin BION/BiOBr) was in situ self-assembled though a cetyltrimethylammonium bromide assisted one-step hydrothermal method. Benefiting from the advantage of the unique ultrathin heterojunction structure, the ultrathin 2D/2D BION/BiOBr heterojunctions exhibit a greatly improved photocatalytic removal effect for multiple pollutants compared to the nanocrystal BION/BiOBr, pure BION. As a representative, the ultrathin 2D/2D Br-modified BION/BiOBr heterojunction shows an enhanced tetracycline degradation rate of 76%, which corresponded to a higher photodegradation rate constant of 0.01116 min-1 when compared to pure BION (17%, 0.00161 min-1) and nanocrystal BION/BiOBr (24%, 0.00223 min-1) under visible-light irradiation for 2 h. A series of characterization and density functional theory calculations demonstrate the enhanced separation and migration efficiency of the photogenerated electrons and holes over the ultrathin heterojunction, facilitating the formation of oxidizing groups for the organic pollutant removal. The possible mechanism of the TC photodegradation and the possible photodegradation pathway are also investigated in detail. This work provides a feasible method for constructing ultrathin 2D/2D heterojunction materials for environmental purification.

Visible-NIR light-responsive 0D/2D CQDs/Sb2WO6 nanosheets with enhanced photocatalytic degradation performance of RhB: Unveiling the dual roles of CQDs and mechanism study.

Environmental pollution caused by dye wastewater discharge has attracted much attention in the past decades. Developing photocatalysts with high solar energy utilization efficiency for the treatment of dye wastewater is one of the most promising methods to address afore-mentioned environmental problem. Herein, novel Vis-NIR (visible to near-infrared) light-responsive carbon quantum dots modified Sb2WO6 (CQDs/Sb2WO6) nanosheets with remarkably enhanced photocatalytic degradation performance of Rhodamine B (RhB) aqueous solution were successfully synthesized. Under the irradiation of Vis light, the photocatalytic degradation efficiency reaches 83% over the optimal composite, which is nearly seven times higher than that of pristine Sb2WO6. Meanwhile, under NIR light irradiation, the optimal composite also keeps a stable degradation performance, while pristine Sb2WO6 exhibits sluggish performance. Besides, a detailed photocatalytic degradation pathway was proposed via the analyses of corresponding intermediates in the photocatalytic degradation process. On the basis of electron spin resonance spectrometry, quenching experiment and density functional theory (DFT) calculation, hydroxyl radicals (•OH) play a dominating role in the photocatalytic reactions and a possible photocatalytic degradation mechanism was unearthed. This work provides new insights for constructing novel Vis-NIR responsive photocatalysts to purify dye wastewater for environmental remediation.

Fabrication of 1D/2D BiPO4/g-C3N4 heterostructured photocatalyst with enhanced photocatalytic efficiency for NO removal.

The visible light photocatalytic removal of NO in air is a promising way. BiPO4 is restricted by its wide band gap and can only be responded to ultraviolet light. Herein, 1D BiPO4 nanorod/2D g-C3N4 heterostructured photocatalyst was successfully synthesized via a facile one-step hydrothermal process for efficient visible light photocatalytic removal of NO. With simulated sunlight irradiation, the photocatalytic NO removal activity of the BiPO4/g-C3N4 (64%) is much higher than that of the pure BiPO4 (7.2%) and g-C3N4 (50%). Its excellent photocatalytic performance was ascribed to broadening the light response range to visible light and boosting the separation and transfer of photogenerated electrons and holes. The NO photocatalytic removal mechanism was proposed by the free radical trapping experiment and in situ DRIFTS research. The present study might induce a new means to design BiPO4-based heterostructured photocatalysts for the removal of NO from air pollution under simulated solar light irradiation.

Enhanced degradation of tetracycline in water over Cu-doped hematite nanoplates by peroxymonosulfate activation under visible light irradiation.

Herein, Cu-doped hematite nanoplates (named as CuHNPs) with abundant oxygen-vacancies were prepared through a facile one-pot solvothermal method and used for efficient peroxymonosulfate (PMS) activation to degrade tetracycline (TC) in water. The catalytic activity of optimal CuHNPs-7.5 catalyst to activate PMS for the degradation of TC in water under visible light irradiation is 7.74 and 2.93 times higher than that of pure one without and with visible light irradiation. CuHNPs-7.5 exhibited excellent degradation for TC in the broad pH range from 2.14 to 10.75, and the removal of TC was barely inhibited by co-anions. The combination of free radicals and non-radical pathway, including sulfate radicals (SO4·-), hydroxide radicals (·OH), superoxide radical (·O2-) and single oxygen (1O2), contributed to TC oxidation. The introduction of Cu2+ not only accelerated the transformation of Fe(III)/Fe(II) redox cycle but also induced rich oxygen defects in the structure of hematite, boosting more generation of reactive oxygen species (ROSs) for TC degradation. Density functional theory (DFT) calculation and electrochemical impedance spectroscopy (EIS) tests confirmed the accelerated electrons transfer of CuHNPs-7.5 in PMS activation. This study provides a strategy to construct effective catalysts of PMS activation combining radicals and non-radical pathways for environmental remediation.

The fabrication of two-dimensional g-C3N4/NaBiO3·2H2O heterojunction for improved photocatalytic CO2 reduction: DFT study and mechanism unveiling.

Photocatalytic CO2 reduction is typically limited by the separation efficiency of photogenerated carriers for a single semiconductor. Thus, fabricating a two-dimensional/two-dimensional (2D/2D) heterojunction photocatalyst with high separation efficiency of photogenerated carriers has become a research priority. Here, a 2D/2D g-C3N4/NaBiO3·2H2O (CN/NBO) heterojunction photocatalyst was successfully synthesized for CO2 photoreduction. With the assistance of the nature of CN, the 10CN/NBO composite showed the best performance with the production yield rates of 110.2 and 43.8 µmol g-1 for CO and CH4, respectively. Our experiments showed that the introduction of CN in CN/NBO composites, which is under the step-scheme (S-step) transfer direction of photogenerated carriers, could greatly inhibit the recombination of photogenerated e--h+ pairs to prolong the carriers' lifetime, which was further confirmed by analysis of photoluminescence and photochemical characterization. As we expected, the CN/NBO composites show improved photocatalytic CO2 reduction activity. The in situ infrared spectroscopy was also performed to study the intermediate products of the photocatalytic CO2 reduction process. This study provides a way to design CN-based heterojunction photocatalysts for CO2 photoreduction.

Acid-activated ROS generator with folic acid targeting for bacterial biofilm elimination.

Many medical and chemical applications require the precise supply of antimicrobial components in a controlled manner at the location of mature biofilm deposits. This work reports a facile strategy to fabricate nanoscale metal-organic frameworks (NMOFs) coencapsulating the antibacterial ligand (lysine carbon dots, Lys-CDs) and targeted drug (folic acid, FA) in one pot to improve antibiofilm efficiency against established biofilms. The resulting products are characterized by transmission electron microscopy, field-emission scanning electron microscopy, powder x-ray diffraction, and ultraviolet-visible spectroscopy. The results show that Lys-CDs could coordinate with Zn2+ and the adding of FA inhibits the coordination of Lys-CDs with central ions of Zn. The Lys-CDs and FA are successfully exposed with the NMOFs disintegrating in the acid environment of bacterial metabolites. We are surprised to find a sharp increase of reactive oxygen species (ROS) inside the bacterial cells by FA functionalizing NMOFs, which undoubtedly enhance the antibacterial and antibiofilm activity. The as-synthesized ZIF-8-based nanocomposites also show the peroxidase-like activity in an acid environment, and produce extremely active hydroxyl radicals resulting in the improved antibacterial and antibiofilm activity. The possible mechanisms of antibacterial activities indicate that the presence of FA is significant in the sense of targeting bacteria. This study shows a novel approach to construct acid stimulation supply system which may be helpful for the research of antibiofilms.

Facile fabrication of AgI/Sb2O3 heterojunction photocatalyst with enhanced visible-light driven photocatalytic performance for efficient degradation of organic pollutants in water.

The construction of heterojunction is considered as a promising approach to designing highly effective visible-light driven photocatalysts. In this research, the AgI/Sb2O3 heterojunction photocatalyst was synthesized by a simple in situ deposition-precipitation procedure, which was supported by XPS results. Among the prepared samples, the 60% AgI/Sb2O3 samples exhibited the best ARG degradation ratio (98.3%) in 1 h under visible light irradiation, while the pure Sb2O3 and AgI exhibited almost none photocatalytic performance. The trapping experiments and EPR proved that the photo-generated ·O2- and ·OH made major contributions to the photocatalytic degradation of ARG by the 60% AgI/Sb2O3 samples. The enhanced photocatalytic performance of AgI/Sb2O3 heterojunction photocatalysts was ascribed to that the e- produced in the CB of AgI would be transferred to the empty CB of Sb2O3, which could effectively promote separation of photo-induced carries. More importantly, the transfer of electrons from AgI to Sb2O3 would be in favor of restraining the reduction of Ag+ to Ag0 resulting in the good stability of heterojunction photocatalysts. The heterojunction photocatalyst provided in this work might be a prospective candidate for decontamination of water.

Novel AgI/BiSbO4 heterojunction for efficient photocatalytic degradation of organic pollutants under visible light: Interfacial electron transfer pathway, DFT calculation and degradation mechanism study.

Herein, we constructed a novel AgI/BiSbO4 heterojunction via a hydrothermal-precipitation method. The heterojunction structure boosts the generation of hydroxyl and superoxide radicals for efficient degradation of organic pollutants. The photocatalytic activities of the optimal sample for ARG and TC degradation are 10 and 1.6 times higher than those of bare AgI, respectively. Characterizations and theoretical calculations together confirm a strong interfacial charge transfer exists between the interlayer in AgI and BiSbO4 by the formation of Ag‒O bond, making O atoms obtain rich free electrons from Ag atoms of AgI, thus forming an ultrahigh electron transfer tunnel, and ultimately accelerating the separation of photoinduced electrons. More interestingly, low amounts of Ag0 NPs formed during the photocatalytic process, enhancing the visible light absorption because of its SPR (surface plasmon resonance) effect and further promoting the separation of photoinduced carriers. Furthermore, photocatalytic degradation pathways were proposed in detail by analyzing intermediates and a reasonable photocatalytic mechanism was unearthed. This work extends the development of AgI-based heterojunction photocatalysts.

Efficient activation of persulfate by a magnetic recyclable rape straw biochar catalyst for the degradation of tetracycline hydrochloride in water.

A recyclable magnetic rape straw biochar (MRSB) catalyst was synthesized by a high value-added and energy-saving method using abandoned rape straw as the raw material. The MRSB catalyst showed high catalytic activity and recyclability for activating persulfate (PS) to degrade tetracycline hydrochloride (TC) in water. The Fe3O4 in the MRSB greatly promoted the activation of PS. More importantly, the MRSB catalyst exhibited high catalytic performance over a wide pH range (2.99-11.01) for activating PS to degrade TC in water. Moreover, MRSB still had good catalytic activity for TC degradation after 8 recycling cycles and was easily separated by an external magnetic field for reuse. The electron spin resonance (ESR) analysis indicated that the generation of the sulfate radicals (SO4-), hydroxyl radicals (OH) and superoxide radicals (O2-) was greatly promoted in the MRSB/PS system. As a result, MRSB exhibited 13.24-fold higher reaction rate for activating PS than those of rape straw biochar (RSB). Both radical mechanism and non-radical mechanism existed in the MRSB/PS system, and SO4- and singlet oxygen (1O2) played a determinative role. This study might give a new way to reuse abandoned rape straw and synthesize new recyclable catalysts for activating PS to degrade organic pollutants in water.