Photo-assisted catalytic degradation of acetaminophen using peroxymonosulfate decomposed by magnetic carbon heterojunction catalyst

Enhanced tetracycline degradation by novel Mn-FeOOH/CNNS photocatalysts in a visible-light-driven photocatalysis coupled peroxydisulfate system

Recently, photocatalysis combined peroxydisulfate activation under visible light (PC-PDS/Vis) was developed as a promising technology for removing antibiotics in water. Herein, Mn doped FeOOH (Mn-FeOOH) nanoclusters were grown in-situ on the surface of graphitic carbon nitride nanosheets (CNNS) using a wet chemical method, which served as a visible-light-driven photocatalyst for peroxydisulfate (PDS) activation. Photovoltaic property characterizations revealed that Mn-FeOOH/CNNS owned superior light capture ability and carrier separation efficiency. According to DFT calculations, the synergistic effect between Mn and Fe species was proved to enhance the adsorption and activation of PDS. 99.7% of tetracycline (TC) was rapidly removed in 50 min in the PC-PDS/Vis system. In addition, Mn-FeOOH/CNNS exhibited high recycling stability with low iron leaching, attributed to the interaction between Mn-FeOOH clusters and carbon species. Quenching experiments and electron spin resonance (ESR) tests unveiled that •O2- played a significant role in TC removal, while •OH and SO4•- acted as additional roles contributing to the overall process. These findings given a new strategy for antibiotics degradation by photocatalysis, offering deeper insights for the advancement of sustainable and cutting-edge wastewater treatment technologies.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite derived from lignin: an efficient peroxymonosulfate activator for naphthalene degradation

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite (Fe-Cu-N-PC) was prepared via direct pyrolysis by employing black liquor lignin as a main precursor, and it was utilized as a novel catalyst for PMS activation in degrading naphthalene. Under the optimum experimental conditions, the naphthalene degradation rate was up to 93.2% within 60 min in the Fe-Cu-N-PC/PMS system. The porous carbon framework of Fe-Cu-N-PC could facilitate the quick molecule diffusion of reactants towards the inner bimetallic nanoparticles and enriched naphthalene molecules from the solution by a specific adsorption, which increased the odds of contact between naphthalene and reactive oxygen species and improved the reaction efficiency. The quenching reaction proved that the non-free radical pathway dominated by 1O2 was the main way in naphthalene degradation, while the free radical pathway involving SO4·- and ·OH only played a secondary role. Moreover, owing to its high magnetization performance, Fe-Cu-N-PC could be magnetically recovered and maintained excellent naphthalene degradation rate after four degradation cycles. This research will offer a theoretical basis for the construction of facile, efficient, and green technologies to remediate persistent organic pollutants in the environment.

Advances in the Removal of Organic Pollutants from Water by Photocatalytic Activation of Persulfate: Photocatalyst Modification Strategy and Reaction Mechanism

Environmental pollution caused by persistent organic pollutants has imposed big threats to the health of human and ecological systems. The development of efficient methods to effectively degrade and remove these persistent organic pollutants is therefore of paramount importance. Photocatalytic persulfate-based advanced oxidation technologies (PS-AOTs), which depend on the highly reactive SO4 - radicals generated by the activation of PS to degrade persistent organic pollutants, have shown great promise. This work discusses the application and modification strategies of common photocatalysts in photocatalytic PS-AOTs, and compares the degradation performance of different catalysts for pollutants. Furthermore, essential elements impacting photocatalytic PS-AOTs are discussed, including the water matrix, reaction process mechanism, pollutant degradation pathway, singlet oxygen generation, and potential PS hazards. Finally, the existing issues and future challenges of photocatalytic PS-AOTs are summarized and prospected to encourage their practical application. In particular, by providing new insights into the PS-AOTs, this review sheds light on the opportunities and challenges for the development of photocatalysts with advanced features for the PS-AOTs, which will be of great interests to promote better fundamental understanding of the PS-AOTs and their practical applications.

Hybrid approaches based on hydrodynamic cavitation, peroxymonosulfate and UVC irradiation for treatment of organic pollutants: fractal like kinetics, modeling and process optimization

Hydrodynamic cavitation (HC) was emerged as one of the most potential technologies for industrial-scale wastewater or water treatment. In this work, a combined system of HC, peroxymonosulfate (PMS) and UVC irradiation (HC - PMS - UVC) was constructed for effective degradation of carbamazepine. The effect of several experimental parameters and conditions on the carbamazepine degradation was considered. The results show that the degradation and mineralization rates increases with an increase in the inlet pressure from 1.3 to 4.3 bars. The rates of carbamazepine degradation with the combined processes of HC - PMS - UVC, HC - PMS, HC - UVC, and UVC - PMS were 73%, 67%, 40% and 31%, respectively. Under the optimal conditions of reactor, the carbamazepine degradation and mineralization rates were 73% with 59%, respectively. The kinetics of carbamazepine degradation was studied applying a fractal-like approach. So, a new model was proposed by combining first order kinetics model and fractal-like concept. The obtained results show that the proposed fractal-like model gives a better performance compared with traditional first order kinetics model. It has been demonstrated that the HC - PMS - UVC process is a potential treatment method to destroy pharmaceutical pollutants from water and wastewater sources.

A newly-designed free-standing NiCo2O4 nanosheet array as effective mediator to activate peroxymonosulfate for rapid degradation of emerging organic pollutant with high concentration

Nowadays effective treatment of high concentration organic wastewater is still a formidable task facing human beings. Herein, for the first time, a well-defined ZIF-67-derived NiCo₂O₄ nanosheet array was successfully prepared by a feasible method. In comparison with ordinary NiCo₂O₄ nanosphere, the formation of nanosheet structure could offer more opportunities to exposure internal active sites of NiCo₂O₄, thereby resulting in smaller interface resistance and higher charge transfer efficiency. As expected, ZIF-67-derived NiCo₂O₄ nanosheet array displayed great performance in peroxymonosulfate (PMS) activation. More importantly, recyclable redox couples of Co³⁺/Co²⁺ and Ni³⁺/Ni²⁺ endowed the stable catalytic activity of NiCo₂O₄ nanosheet. Interestingly, developed NiCo₂O₄-1/PMS oxidation system could achieve the effective degradation of antibiotics with high concentration in a short time. Both radical and nonradical pathways were involved into PMS activation, wherein SO₄^-, OH, O₂^- and ¹O₂ were major reactive oxygen species. The formation paths of reactive oxygen species and effects of inorganic anions were also investigated. Electrochemical analyses revealed that NiCo₂O₄-1 with nanosheet structure mediated the electron transfer between PMS and tetracycline (TC), which played a vital role in TC degradation. Furthermore, developed NiCo₂O₄-1/PMS oxidation system displayed great removal ability towards TC in actual water samples, and degradation products were low toxicity or no toxicity. In short, current work not only developed an effective oxidation system for completing the rapid degradation of antibiotic with high concentration, but also shared some novel insights into the activation mechanism of SR-AOPs.

Rice husk biochar modified-CuCo2O4 as an efficient peroxymonosulfate activator for non-radical degradation of organic pollutants from aqueous environment

A series of rice husk biochar (RHBC) modified bimetallic oxides were prepared using a simple pyrolysis method to activate peroxymonosulfate (PMS) for the degradation of acid orange G (OG). The results demonstrated that 50 mg L⁻¹ OG was completely decomposed by 1 mM PMS activated with 100 mg L⁻¹ RHBC–CuCo₂O₄ within 15 min at initial pH 3.4. The OG degradation rate constant k of RHBC–CuCo₂O₄/PMS (0.95 × 10⁻¹ min⁻¹) was five times greater than that of CuCo₂O₄/PMS (0.19 × 10⁻¹ min⁻¹), suggesting that the introduction of RHBC significantly improved the activity of bimetallic oxides. The effects of the initial pH, catalyst dosage, PMS concentration and reaction temperature on OG removal were also studied. The degradation products of OG were analysed using a gas chromatography-mass spectrometer (GC-MS). Electron paramagnetic resonance (EPR) and quenching experiments showed that singlet oxygen (¹O₂) was the main active species. The RHBC–CuCo₂O₄/PMS oxidation system is not only unaffected by inorganic anions (Cl⁻, NO₃⁻, HCO₃⁻) and humic acid (HA), but also could remove other typical pollutants of acetaminophen (ACT), sulfathiazole (STZ), rhodamine B (RhB), and bisphenol A (BPA). These findings show that RHBC–CuCo₂O₄ has great potential for practical applications in the removal of typical organic pollutants.

A series of rice husk biochar (RHBC) modified bimetallic oxides were prepared using a simple pyrolysis method to activate peroxymonosulfate (PMS) for the degradation of acid orange G (OG).

Peracids - New oxidants in advanced oxidation processes: The use of peracetic acid, peroxymonosulfate, and persulfate salts in the removal of organic micropollutants of emerging concern - A review

In recent years, there has been increasing interest in using of advanced oxidation processes in water and wastewater decontamination. As a new oxidants peracids, mainly peracetic acid (PAA) and peracid salts, i.e. peroxymonosulfate (PMS) and persulfate (PS) are used. The degradation process of organic compounds takes place with the participation of radicals, including hydroxyl (^•OH) and sulfate (SO₄^•-) radicals derived from the peracids activation processes. Peracids can be activated in homogeneous systems (UV radiation, d-electron metal ions, e.g. Fe²⁺, Co²⁺, Mn²⁺, base, ozonolysis, thermolysis, radiolysis), or using heterogeneous activation (metals with zero oxidation state, metal oxides, quinones, activated carbon, semiconductors). As a result of oxidation, products of a lower mass than the parent compounds, less toxic, and more susceptible to biodegradation are formed. An important task is to investigate the effect of the peracid activation method and matrix composition on the efficiency of contamination removal. The article presents the latest information about the application of peracids in the removal of organic micropollutants of emerging concern (mainly focuses on endocrine disrupted compounds). The most important information on peracetic acid, peroxymonosulfate and persulfate salts, and methods of their activation are presented. Current uses of these oxidants in organic micropollutants removal are also described. Information was collected on the factors influencing the oxidation process and the effectiveness of pollutant removal. This paper compares PAA, PMS and PS-based processes for the first time in terms of kinetics and efficiency.

Fabrication of Co3O4-Bi2O3-Ti catalytic membrane for efficient degradation of organic pollutants in water by peroxymonosulfate activation

In this study, a functionalized Co₃O₄-Bi₂O₃-Ti catalytic membrane (CBO-Ti-M) was prepared and applied for removing organic pollutants via activating peroxymonosulfate (PMS) in the dead-end filtration mode. Characterizations including scanning electron microcopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the Co₃O₄-Bi₂O₃ catalyst was successfully supported on the Ti membrane. The CBO-Ti-M /PMS system could efficiently remove various organic pollutants such as sulfamethoxazole, methyl orange, bisphenol A and methylene blue, achieving removal efficiencies of 98.0%-99.5%. The effects of PMS concentration, flow rate and solution environment on degradation efficiency were investigated in detail. Furthermore, quenching experiments, electron spin resonance (ESR) and in-situ open circuit potential (OCP) tests collectively demonstrated that singlet oxygen as well as the non-radical electron transfer pathway mainly contributed in the reaction mechanism. The synergistic effect of Co and Bi was illustrated according to XPS results, and the possible degradation pathway of MB was proposed based on LC-MS analysis. Reusability test showed that pollutant removal efficiency with the CBO-Ti-M /PMS system remained stable in four runs and limited metal leaching was observed.

N-Doped Biochar as a New Metal-Free Activator of Peroxymonosulfate for Singlet Oxygen-Dominated Catalytic Degradation of Acid Orange 7

In this paper, using rice straw as a raw material and urea as a nitrogen precursor, a composite catalyst (a nitrogen-doped rice straw biochar at the pyrolysis temperature of 800 °C, recorded as NRSBC800) was synthesized by one-step pyrolysis. NRSBC800 was then characterized using XPS, BET, TEM and other technologies, and its catalytic performance as an activator for permonosulfate (PMS) to degrade acid orange 7 (AO7) was studied. The results show that the introduction of N-doping significantly improved the catalytic performance of NRSBC800. The NRSBC800/PMS oxidation system could fully degrade AO7 within 30 min, with the reaction rate constant (2.1 × 10 ^-1 min^-1) being 38 times that of RSBC800 (5.5 × 10^-3 min^-1). Moreover, NRSBC800 not only had better catalytic performance than traditional metal oxides (Co₃O₄ and Fe₃O₄) and carbon nanomaterial (CNT) but also received less impact from environmental water factors (such as anions and humic acids) during the catalytic degradation process. In addition, a quenching test and electron paramagnetic resonance (EPR) research both indicated that AO7 degradation relied mainly on non-free radical oxidation (primarily singlet oxygen (¹O₂)). A recycling experiment further demonstrated NRSBC800's high stability after recycling three times.

N-doped graphitic C3N4 nanosheets decorated with CoP nanoparticles: A highly efficient activator in singlet oxygen dominated visible-light-driven peroxymonosulfate activation for degradation of pharmaceuticals and personal care products

CoP nanoparticle-loaded N-doped graphitic C₃N₄ nanosheets (CoP/N-g-C₃N₄) were fabricated via a facile three-step method to degrade pharmaceuticals and personal care products (PPCPs) via a visible-light-driven (VLD) peroxymonosulfate (PMS) activation system. 2 ppm carbamazepine (CBZ) can be removed completely within 10 min by the VLD-PMS system with a kinetic constant of k = 0.29128 min^-1, as 25.8 times compared to that under dark conditions (k = 0.01128 min^-1). The experimental and theoretical results showed that the doped graphitic N atoms could modulate the electronic properties of the g-C₃N₄ nanosheets. Subsequently, the Density Functional Theory (DFT) explained that CoP showed preference to bonding with the nitrogen atoms involved in the newly formed N˭N bond, and the Co‒N bond dramatically enhanced the transfer of photo-generated electrons from the N-g-C₃N₄ nanosheets. Electron paramagnetic resonance (EPR) tests show that singlet oxygen (¹O₂) plays a leading role in this case. Moreover, PMS molecules are also tended to be absorbed onto the electron-deficient carbon atoms near the newly formed N˭N bonds for PMS reduction, synergistically enhancing the degradation efficiency for CBZ and benzophenone-3 (BZP). The newly established VLD-PMS activation system was shown to treat the actual sewage in Hong Kong sewage treatment plants (STPs) very well. This work supplements the fundamental theory of radical and non-radical pathways in the sulfate radical (SO₄^•-)-based advanced oxidation process (SR-AOP) for environmental cleanup purposes.

Photocatalytic activation of peroxymonosulfate (PMS) by novel mesoporous Ag/ZnO@NiFe2O4 nanorods, inducing radical-mediated acetaminophen degradation under UVA irradiation

A new mesoporous Ag/ZnO@NiFe₂O₄ nanorod was prepared by a facile, low-cost, and environmentally friendly strategy from a bimetallic Fe₂Ni-MIL-88 metal organic framework (MOF), as an effective catalyst and peroxymonosulfate (PMS) photo-activator. The structural, morphological, optical, and magnetic properties, as well as the material composition were investigated by XRD, FE-SEM, EDX, HR-TEM, XPS, DRS, PL, EIS, VSM, N₂ adsorption-desorption and ICP-AES analysis. 1.0% w/w loading of Ag nanoparticles on ZnO_0.04@NiFe₂O₄ led to the best catalytic activity for PMS activation under UVA in acetaminophen (ACT) degradation. The maximum degradation efficiency for ACT was 100% within 15 min (at pH = 7.0), with a first-order rate constant of 0.368 min^-1. The calculated quantum yield (1.3 × 10^-3 molecule/photon) of the optimum catalyst was 2.05, and 5.63 times higher than its simple constituents, ZnO_0.04@NiFe₂O₄ and NiFe₂O₄, respectively. Among the various inorganic ions, Cl^- and HCO₃^- showed significant inhibition effect in 1.0%w/w Ag/ZnO_0.04@NiFe₂O₄/PMS/UVA system, due to radical quenching effects. Based on scavenger experiments, HO^• and SO₄^•- were the dominant reactive species in photocatalytic process coupled with PMS. Due to presence of the Fe³⁺/Fe²⁺, and Ni²⁺/Ni³⁺ reaction cycles in the as-made catalyst, the reaction rate of PMS activation was greatly enhanced. Moreover, the formation of a hetero-junction structure with NiFe₂O₄ and ZnO promoted the charge separation of the photo-generated electron/hole pairs. Finally, the major intermediates produced during the reaction were detected by LC-MS analysis, and a plausible mechanism for the photocatalytic degradation of ACT was proposed and discussed in detail.

Preparation and application of Fe/biochar (Fe-BC) catalysts in wastewater treatment: A review

The removal of organic pollutants from water environments is a challenging problem. Fe-based BC (Fe-BC) composites are promising catalysts for generating reactive oxygen species (ROS) for environmental remediation considering their low costs and excellent physicochemical surface characteristics. The synthesis methods, properties, applications, and the mechanism of Fe-BC for removing pollutants are reviewed. Various methods have been used to prepare Fe-BC composites, and the synthetic methods and conditions used affect the properties of the Fe-BC material, thereby influencing its pollutant removal performance. The mechanisms of pollutant removal by Fe-BC are intricate and include adsorption, degradation and reduction. Fe loading on BC could improve the performance of BC by affecting its surface area, surface functional groups and electron transfer rate. Moreover, research gaps and uncertainties that exist in the use of Fe-BC were identified. Finally, the problems that need to be solved to make Fe-BC suitable for future applications are described.

Efficient activation of peroxymonosulfate and degradation of Orange G in iron phosphide prepared by pickling waste liquor

In this study, the low-cost preparation of iron phosphide by using pickling waste liquor as the initial material was performed through a two-step reaction. The degradation of Orange G was evaluated using iron phosphide coupled with peroxymonosulfate to construct a catalytic system. The removal efficiencies of Orange G and total organic carbon reached 97.4 and 58.4% at 60 min, respectively. Iron phosphide has dual-catalysis centers for the activation of PMS. Multiple free radicals (e.g., SO₄^•-, HO^•, SO₅^•-, and O₂^•-) and singlet oxygen were involved in the pollutant degradation, of which sulfate radicals played the main role. The iron phosphide catalyst exhibited excellent recycling stability, and its catalytic efficiency reached 95% after five cycles. In summary, the Fe₂P/PMS system-as a Fenton-like catalytic system-has certain advantages, including low cost, high efficiency, sufficient reusability, and good stability, all of which are favorable for its practical application.

Life time enhanced Fenton-like catalyst by dispersing iron oxides in activated carbon: Preparation and reactivation through carbothermal reaction

Heterogeneous Fenton-like catalyst prepared by dispersing iron oxides in activated carbon (FeOx@AC) has frequently been assembled for advanced oxidation processes (AOPs). An intriguing but barely emphasized property of FeOx@AC is that it can be easily reactivated through a simple carbothermal reaction. Importantly, by this manner the life time of FeOx@AC could be effectively enhanced. We herein reported the synthesis of FeOx@ACs hydrothermally with assistance of several commercially available surfactants and their performance in degrading real dye wastewater were evaluated. In general, as-synthesized FeOx@ACs were noted to equip high Fe content. Deposited FeOx reduced the fraction of micropores but simultaneously introduced additional mesopores and macropores. Elevated magnetite content was observed in FeOx@AC equipped with high fraction of micropore and mesopore and macropore but fast dye degradation occurred at FeOx@AC possessing low fraction of micropore along with low mesopores and macropores. Reactivation via carbothermal reaction redistributed the deposited FeOx by increasing micropores while decreasing mesopores and macropores. Importantly, well dispersed FeOx synthesized with the assistance of surfactants exhibited high resistance to the corrosion in the degradation process. For the perspective of circular economy, deep understanding the material chemistry of FeOx@AC would be of particularly interest for further enhancing its life time.

Magnetic Fe3O4-N-doped carbon sphere composite for tetracycline degradation by enhancing catalytic activity for peroxymonosulfate: A dominant non-radical mechanism

The design of sustainable, effective and recyclable hybrid catalysts for advanced oxidation processes is highly significant for remediation of the water environment. In this study, we synthesized magnetic Fe₃O₄-N-doped carbon sphere composite catalysts (Fe₃O₄-NCS-x) for efficient removal of tetracycline by activating peroxymonosulfate (PMS). The Fe₃O₄-NCS-x composite was obtained by facile hydrothermal treatment of chitosan-iron complexes followed by pyrolysis. The unique structure of N-doped carbon spheres embedded in Fe₃O₄ nanoparticles intensified the electron transport, consequently improving the catalytic activity via a synergistic effect. Factors influencing the catalytic activity of the Fe₃O₄-NCS-2 were systematically investigated. High degradation efficiency of TC-97.1% within 1 h-was achieved in this Fe₃O₄-NCS-2/PMS system under the optimum conditions (C₀ = 20 mg L^-1, catalyst dosage 0.2 g L^-1, PMS concentration 2.4 mM, native pH and 25 °C). The inhibitory effect of anions in the water matrix decreased in the order Cl^- > NO₃^- > SO₄^2- > CH₃COO^- > HCO₃^-. The obtained results from the competitive quenching tests and electron paramagnetic resonance measurements demonstrated that singlet oxygen (¹O₂), a non-radical species, plays a major role in TC degradation. It is estimated that ¹O₂ and hydroxyl radicals (·OH) contributed ∼65.2% and ∼24.2% to TC degradation in the Fe₃O₄-NCS-2/PMS system, respectively. The M-H hysteresis loop of Fe₃O₄-NCS-2 revealed that its saturation moment is 56 emu g^-1. Magnetic responsive behavior and consecutive runs confirmed that Fe₃O₄-NCS-2 possesses remarkable separation performance and desirable reusability. This novel magnetic Fe₃O₄-NCS-2 composite activator for PMS promises great potential in TC degradation.

Acetaminophen degradation by a synergistic peracetic acid/UVC-LED/Fe(II) advanced oxidation process: Kinetic assessment, process feasibility and mechanistic considerations

Application of peracetic acid (PAA) in Advanced Oxidation Processes (AOPs) has seen an increase in the last few years. In this study, PAA/UVC-LED/transition metal was used to degrade acetaminophen (ACT) in an aqueous solution. Amongst tested transition metals (Fe, Cu, Co, Mn, Ag), Fe(II) demonstrated the highest efficiency. The effect of pH, PAA dosage, initial concentration of ACT and Fe(II) concentration was investigated on ACT removal. More than 95% removal efficiency was obtained in 30 min employing pH = 5.0, PAA 4 mM and 0.5 mM Fe(II) (k_app = 0.0993 min^-1). Scavenging experiments highlighted the contribution of oxygen-centered radicals; however, the dominant mechanism is hydroxyl radical-induced, while the superoxide radicals had a negligible role. The effect of anions in water showed that carbonate, (dihydrogen) phosphate and nitrite ions had a strong inhibitory effect, while a neutral effect was observed by sulfate, nitrate and chloride ions. Seven intermediates of ACT oxidation were determined and the ACT degradation pathway by the PAA/UVC-LED/Fe(II) is presented. The efficacy of the PAA/UVC-LED/Fe(II) process was also verified for the degradation of other contaminants of emerging concern and disinfection of fecal indicator microorganisms in real matrix (secondary WW). In conclusion, the studied PAA/UVC-LED/Fe(II) process opens a new perspective as a promising application of advanced oxidation for the degradation of organic pollutants.

Efficient activation of peroxymonosulfate by composites containing iron mining waste and graphitic carbon nitride for the degradation of acetaminophen

In this work, the potential to use an iron mining waste (IW), rich in α-Fe₂O₃ and α-FeOOH, for the development of composites based on graphitic carbon nitride (CN) is demonstrated. These materials were synthesized through a simple thermal treatment at 550 °C of a mixture containing melamine and different IW mass percentages, giving rise to the catalysts xIWCN (where x is related to the initial mass percentage of IW). The iron phases of the precursor were partially transformed throughout the formation of the composites, in such a way that a mixture of α-Fe₂O₃ and γ-Fe₂O₃ was observed in their final composition. Furthermore, structural defects were produced in the carbonaceous matrix of the materials, causing the fragmentation of g-C₃N₄ and an increase of surface area. The catalytic activities of these composites were evaluated in reactions of peroxymonosulfate activation for the degradation of paracetamol. Among these materials, the composite 20IWCN showed the best catalytic activity, being able to degrade almost 90 % of the total paracetamol in only 20 min of reaction. This catalyst also demonstrated high chemical stability, being successfully utilized in five consecutive reaction cycles, with negligible iron leaching.

Degradation of Acetaminophen via UVA-induced advanced oxidation processes (AOPs). Involvement of different radical species: HO, SO4- and HO2/O2. CHEMOSPHERE 2020;258:127268. [PMID: 32569955 DOI: 10.1016/j.chemosphere.2020.127268]

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO₄^- and HO₂/O₂^-) are generated through activation of hydrogen peroxide (H₂O₂), sodium persulfate (Na₂S₂O₈) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/H₂O₂ and UVA/Na₂S₂O₈ systems whatever the solution's pH. To explain these results, second order reaction rate constant (k_{radical, ACTP}) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO₂/O₂^- radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and Na₂S₂O₈ exhibits synergistic effects rather than antagonism effects with H₂O₂. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.

Nanomaterials application in greenhouse structures, crop processing machinery, packaging materials and agro-biomass conversion

The discovery of nanomaterials has flagged off crucial research and innovations in science and engineering. Its unique properties and diverse applications present it as the material for the future. The aim of this study is to presents the relative applications of nanomaterial in some aspects of agriculture production. The study discussed nanotechnology applicability in climate control and photosynthesis in the greenhouse farming, hydroponic systems, solar drying, fabrication of crop processing machine components, oxygen scavengers in crop packaging, and micro-organism stimulant in anaerobic digestion for agro biomass conversion. Some highlights from the review revealed that Nanotechnology can be applied to increase water surface area to volume ratio and heat transfer in the air moving into a greenhouse farming. Water cluster can be changed when treated with nanoparticles through ultraviolet absorption spectrum and nuclear magnetic resonance (NMR) spectroscopy resulting in lower micelles to manipulate water delivery in green house farming. Nano-fluids or Nano-composites can be used to recombine the reactive parts of thermal storage materials after broken at elevated temperature to recover the stored heat for drying purpose during the off-sunshine periods in solar drying of crops. Nanomaterials can be a source of electroluminescence light in hydroponic system and act as coatings and surface hardener in crop processing machinery for post-harvest machines. The reviewed work showed that nanotechnologies has good prospect in adding value in agricultural production in the aspects discussed.

Enhanced activation of peroxymonosulfate by nitrogen-doped graphene/TiO2 under photo-assistance for organic pollutants degradation: Insight into N doping mechanism

Production of sulfate radical from peroxymonosulfate (PMS) activation by carbon-based catalysts is a promising strategy to degrade pollutants. However, the electron-transfer ability of carbon catalysts, which is critical in PMS activation, still needs to be improved. In this study, a novel photo-assisted PMS activation system (PPAS) was constructed on a nitrogen-doped graphene/TiO₂ (NG/TiO₂), in which the photogenerated electrons excited from TiO₂ could be utilized by NG for enhanced PMS activation on it. Moreover, the N content was varied to firstly investigate the role of N doping on PPAS. Under photo-assistance, the NG/TiO₂ displayed significantly enhanced PMS activation for removal of organic pollutants. 100% bisphenol A (BPA) can be removed within 1 h. The results show that the degradation kinetic constant of BPA by the NG/TiO₂ PPAS was 24 times higher than that under PMS alone, and was 1.4 times higher than that of rGO/TiO₂ PPAS. The singlet oxygen (¹O₂) and sulfate radical (SO₄^-) were the main reactive species in PPAS. The outstanding performance of NG/TiO₂ system was ascribed to the two main reasons: on one hand, the N doping decreased the schottky barrier formed between NG and TiO₂, which favored the electron transfer from TiO₂ to NG. On the other hand, the N doping enhanced the adsorption and electron-transfer ability of NG towards PMS.

Mo0 and Mo4+ bimetallic reactive sites accelerating Fe2+/Fe3+ cycling for the activation of peroxymonosulfate with significantly improved remediation of aromatic pollutants

In Fe²⁺/peroxymonosulfate (PMS) activation system, the slow cycle rate of Fe³⁺/Fe²⁺ has been considered to be the limiting step in the remediation of organic contaminants. In this paper, commercial molybdenum (Mo) powder is employed as the cocatalyst in Fe²⁺/PMS system, which can significantly accelerate the Fe³⁺/Fe²⁺ cycling efficiency by the exposed bimetallic active sites of Mo⁴⁺ and Mo⁰, and the process is accelerated as the amount of Mo powder increased. The Mo cocatalytic Fe²⁺/PMS system exhibits an enhanced performance for the activation of PMS and the removal of different aromatic pollutants including dyes, phenolic pollutants and antibiotics, in a wide pH range of 4.0-9.0. Importantly, Mo powder exhibits excellent cycle performance in the PMS activation system, and rhodamine B (RhB) can be removed within 10 min even after 5 cycles. Electron paramagnetic resonance (EPR) prove that the sulfate radicals (SO₄^-) is the major reactive oxides species in the PMS activation, the increase of Fe²⁺ content induced by the cocatalytic effect of Mo powder can effectively promote the production of SO₄^- and increase the utilization of PMS. In addition, to observe the process of pollutant removal more intuitively, HPLC-MS is used to analyze the decomposing pathway of RhB and sulfadiazine in Mo+FeSO₄+PMS system. It is believed that this research provides a new idea for the efficient activation of PMS by iron ions in a wide initial pH range, which is expected to be applied to the treatment of large-scale industrial wastewater.

Magnetite-based catalysts for wastewater treatment

The increasing number and concentration of organic pollutants in water stream could become a serious threat in the near future. Magnetite has the potential to degrade pollutants via photocatalysis with a convenient separation process. This study discusses in detail the control size and morphology of magnetite nanoparticles, and their composites with co-precipitation, hydrothermal, sol-gel, and electrochemical route. Further photocatalytic enhancement with the addition of metal and porous support was proposed. This paper also discussed the technology to extend the lifetime of recombination through an in-depth explanation of charge transfer. The possibility to use waste materials as catalyst support was also elucidated. However, magnetite-based photocatalysts still require many improvements to meet commercialization criteria.

Synergistic activation of peroxymonosulfate and persulfate by ferrous ion and molybdenum disulfide for pollutant degradation: Theoretical and experimental studies

Activation of peroxymonosulfate (PMS) and persulfate (PS) by Fe²⁺ is widely used for oxidizing organic pollutants. However, their application is limited by the slow conversion rate of Fe³⁺ to Fe²⁺ and the accumulation of Fe³⁺. Here, we introduce commercial molybdenum disulfide (MoS₂) to promote the activation of PMS and PS by Fe²⁺, and explore the mechanism of this promotion using experimental and theoretical methods. The Fe²⁺/PMS/MoS₂ and Fe²⁺/PS/MoS₂ systems achieved faster rate of PMS and PS conversion and also higher degradation efficiency toward pollutants. About 94.7% and 87.6% of rhodamine B (RhB) could be degraded in Fe²⁺/PMS/MoS₂ (54 μM Fe²⁺, 1 mM PMS) and Fe²⁺/PS/MoS₂ (54 μM Fe²⁺, 0.25 mM PS) system, respectively. MoS₂ addition simultaneously promoted the Fe³⁺/Fe²⁺ cycle, the PMS and PS conversion, and the RhB mineralization. As a co-catalyst, MoS₂ exhibited excellent stability for eight successive cycles of use. The predominant oxidant was identified as SO₄^- in Fe²⁺/PMS/MoS₂ and Fe²⁺/PS/MoS₂ systems. Theoretical calculations and a kinetic model were employed to evaluate the catalytic performance of the systems. These novel findings indicate that the combination of a commercially available MoS₂ catalyst with a low dosage of Fe²⁺ is a promising and effective approach for efficient activation of PMS and PS to produce SO₄^- and OH.

Efficient clean-up of waters contaminated with diazinon pesticide using photo-decomposition of peroxymonosulfate by ZnO decorated on a magnetic core/shell structure

In the present study, ZnO nanoparticles were anchored on a magnetic core/shell structure (SiO₂@Fe₃O₄) to perpetrate ZnO@SiO₂@Fe₃O₄ and then coupled with UV light as a heterogeneous nanocatalyst for activating peroxymonosulfate (PMS) into diazinon (DZ) degradation. Several techniques like XRD (X-ray diffraction), BET (Brunaeur, Emmett and Teller), TEM (Transmission electron microscope), FESEM (Field emission-scanning electron microscope) coupled with EDS (Energy Dispersive X-ray Spectrometer), PL (photoluminescence), VSM (Vibrating Sample Magnetometer) and UV-vis diffuse reflectance spectroscopy (DRS) were applied for identification of catalyst features. A possible mechanism for PMS activation and DZ degradation was proposed in details. The effect of solution pH, various concentrations of catalyst, PMS and DZ, quenching agents, different chemical oxidants and co-existing anions was assessed as operating factors to determine the optimum conditions. PMS decomposed effectively in coupling with ZnO@SiO₂@Fe₃O₄ and UV. At optimal conditions, over 95 and 56% of DZ and TOC were removed during 60 min reaction, respectively. The complete degradation of DZ was confirmed using its absorption peak in UV-vis spectra analysis over 60 min treatment. A wide variety of free radicals was identified during quenching tests. HO^• and h⁺ played a pivotal role in the degradation process of DZ. Decreasing the degradation efficiency in the presence of anions was as Cl^- > CO₃^2- > NO₃^- > PO₄^3- > SO₄^2- > HCO₃^-. A negligible amount of leaching Fe (<0.2 mg/L) was found for ZnO@SiO₂@Fe₃O₄, indicating that the catalyst possesses a high stability in oxidation systems. In addition, a significant potential was achieved in reusing of catalyst within five consecutive runs. In conclusion, ZnO@SiO₂@Fe₃O₄/PMS/UV hybrid system can be utilized as a promising advanced oxidation process into efficient degradation of pesticides, thanks to easy recovery, high catalytic activity, co-production of different reactive species and high durability and recyclability potential.