Degradation Of Aqueous Organic Pollutants Research Articles

Fabrication of NiFe2O4 nanoparticles loaded on activated carbon as novel composites for high efficient ultra violet-light photocatalysis for degradation of aqueous organic pollutants

The study used nickel ferrite NiFe2O4/activated carbon (NiFe2O4/AC) as a means to remove organic dyes (methylene blue and Reactive red 120) from water-based solutions. The produced photocatalysts were characterized based on their morphological, structural, particle size, and surface charge characteristics. The transmission electron microscopy (TEM) pictures indicated that the NiFe2O4 particles, with an average diameter of around 2–2.5 μm, were evenly distributed and adhered to the outermost layer of the AC nanosheets. The BET analysis revealed that the 10-NiFe2O4/AC material had a surface area of 176 m2/g, a pore volume of 0.354 cm3/g, and an average pore diameter of 0.805 nm. The nanocomposite, as opposed to pure NiFe2O4 and clean AC, demonstrates a notably enhanced photocatalytic degradation efficiency for methylene blue (MB) and Reactive red 120 dye under visible light conditions. The findings indicate that the AC loaded with 10 % NiFe2O4 is the most effective photocatalyst, exhibiting a maximum degradation efficiency of 100 % towards MB dye. Additionally, it displays a high mechanical constant, excellent stability, and ease of recycling. The nanocomposite exhibits increased photocatalytic activity owing to the significant reduction in charge carriers recombination, improved capacity to absorb visible light, and the synergistic impact resulting from the heterojunction with NiFe2O4 and AC. The radical entrapment research revealed that the primary active compounds responsible for the photocatalytic degradation process are superoxide (O2−) and hydroxyl (OH*).

Efficient photocatalytic degradation of aqueous organic pollutants by using an advanced TiO2/Ti3C2/montmorillonite composites

In recent times, a substantial volume of effluents containing diverse organic contaminants, encompassing organic dyes and agrochemicals, has been discharged into aquatic ecosystems, precipitating pronounced ecological perturbations, thus manifesting as a critical concern. Photocatalytic degradation technology has emerged as a robust and efficacious approach for the remediation of aqueous contaminants. Herein, the TiO2/Ti3C2/MMT composites were synthesized via typical hydrothermal and calcination procedures and applied to the degradation of hazardous dye methylene blue (MB). The TiO2/Ti3C2/MMT hybrid demonstrated a pronounced photocatalytic degradation efficiency of 87.2% for the hazardous methylene blue (MB) when exposed to visible-light for 120-minutes timeframe. This efficiency was approximately 3.69 times greater than the degradation rate observed with pristine TiO2. This substantial enhancement is attributed to the synergistic interplay between the TiO2/Ti3C2 Schottky junction and montmorillonite-induced charge repulsion, which, in concert, bolster the charge transfer capabilities of the photocatalyst while simultaneously suppressing the recombination of photogenerated electron-hole pairs. This study not only presents an alternative material for the effective degradation of organic dyes but also holds promise for advanced applications in wastewater treatment.

Metal-free catalysts with local fluorination regulation for peroxymonosulfate activation: Nearly 100 % singlet oxygen production for selective degradation of aqueous organic pollutants

Generating singlet oxygen (1O2) via activating peroxymonosulfate (PMS) is crucial for the selective removal of organic pollutants in aquatic environments. However, achieving efficient and selective conversion of PMS into 1O2 without consuming energy or metals remains a significant challenge. In this study, graphite phase carbon nitride (g-C3N4) was locally fluorinated via a simple polymerization method. The local fluorinated g-C3N4 (FCN) was used as a metal-free catalyst to activate PMS, enabling highly efficient degradation of 4-chlorophenol (100 %) and detoxification. The FCN/PMS system demonstrates exceptional selectivity for electron-rich pollutants, functions effectively across a broad pH range (2–10), and exhibits remarkable interference resistances to background scavenging ions and natural organic compounds. Furthermore, quenching experiments, probe tests, electron paramagnetic spin resonance measurements, electrochemical characterizations, and theoretical calculations demonstrated that 1O2 was the only reactive species in the catalytic process. Local fluorination regulated the electronic structure of g-C3N4, juxtaposing electron-rich fluorine with electron-deficient carbon dual active sites. This modification alters the electron transfer direction between PMS and g-C3N4, allowing for nearly 100 % selective generation of 1O2via dual electron transfer channels without the need for energy or metals. This study provides a new strategy for designing metal-free heterogeneous catalysts to selectively generate 1O2 in a green way and can facilitate the wider applications of advanced oxidation processes for water purification.

Activation of periodate by ABTS as an electron shuttle for degradation of aqueous organic pollutants and enhancement effect of phosphate

Periodate (PI) based advanced oxidation processes (AOPs) have recently attracted much attention due to their high application potential in water purification through production of reactive species. In the study, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was used as a representative electron shuttle, and its reaction with PI was investigated in detail. It was found that PI can be activated by ABTS via one-electron transfer to produce ABTS•+ and IO3•, cooperatively promoting oxidation of organic contaminants such as bisphenol A (BPA). Their contribution in BPA oxidation at pH 7 was estimated as 81.9% and 18.1%, respectively. With phosphate, BPA oxidation rate in the PI/ABTS process increased linearly with raised phosphate concentrations from 0 to 10 mM. The enhancement effect of phosphate is attributed to formation of PI-phosphate complexes, which facilitate PI activation by ABTS, and production of more ABTS•+ and IO3•, and additional phosphate radicals. Accordingly, the contribution of IO3• and phosphate radicals in BPA oxidation raised to 57.7% in the process with 4 mM phosphate, while that of ABTS•+ decreased to 42.3%. The reaction stoichiometry ratio of ABTS to PI was measured as 1.1 at pH 7, suggesting the little involvement of IO3• and phosphate radicals in production of ABTS•+ due to their high self-quenching. The PI/ABTS process exhibited excellent anti-interference capacity towards water matrix components (e.g. Cl−, HCO3− and natural organic matters). Moreover, an immobilized ABTS (ABTS/ZnAl-LDH) was successfully developed as a heterogeneous electron shuttle for PI oxidation, which resultantly exhibited the good catalytic activity and stability in degradation of BPA, further improving feasibility of the process in treatment of actual water. This work advances understanding on reaction of PI with ABTS from stoichiometric and kinetic aspects, and provides a high performance AOP for selective oxidation of trace organic contaminants.

Enhanced electron-transfer for peroxymonosulfate activation by Ni single sites adjacent to Ni nanoparticles

Oriented generation of specific reactive oxygen species (ROS) has been challenging in peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs). In this work, we constructed a multifunctional catalyst composed of Ni NPs embedded in N-doped carbon nanotubes (NCNTs) with exposed Ni single-atom sites (Ni-NCNTs). The Ni-N4 single sites adjacent to the Ni NPs are more efficient for PMS adsorption and activation, resulting in enhanced production of singlet oxygen (1O2). More interesting, we demonstrated that the superoxide anion radical (O2•–) was generated from 1O2 reduction via the electron transfer from the graphitic-N sites of Ni-NCNTs rather than from O2 reduction or PMS decomposition as reported in previous studies. Thus, Ni-NCNTs can act as both electron acceptor and donor to trigger the cascade production of 1O2 and O2•–, respectively, leading to fast and selective degradation of aqueous organic pollutants. The graphitic-N adjacent to the aromatic π-conjugation of NCNTs facilitated chemisorption of 1O2 onto NCNTs via the strong π*–π interactions, and more importantly, donated the lone pair electrons to trigger the reduction of 1O2 to O2•–. This study unravels the mechanisms for enhanced production of ROS in the nanoconfined Fenton-like systems and shed new light on the application of multifunctional nanocatalyst for rapid wastewater decontamination.

Ru(III)-Periodate for High Performance and Selective Degradation of Aqueous Organic Pollutants: Important Role of Ru(V) and Ru(IV).

In this study, Ru(III) ions were utilized to activate periodate (PI) for oxidation of trace organic pollutants (TOPs, e.g., carbamazepine (CBZ)). The Ru(III)/PI system can significantly promote the oxidation of CBZ in a wide initial pH range (3.0-11.0) at 1 μM Ru(III), showing much higher performance than transition metal ions (i.e., Fe(II), Co(II), Zn(II), Fe(III), Cu(II), Ni(II), Mn(II), and Ce(III)) and noble metal ion (i.e., Ag(I), Pd(II), Pt(II), and Ir(III)) activated PI systems. Probe experiments, UV-vis spectra, and X-ray absorption near-edge structure (XANES) spectra confirmed high-valent Ru-oxo species (Ru(V)=O) as the dominant oxidant in the process. Because of the dominant role of Ru(V)=O, the Ru(III)/PI process exhibited a remarkable selectivity and strong anti-interference in the oxidation of TOPs in complex water matrices. The Ru(V)=O species can undertake 1-e- and 2-e- transfer reactions via the catalytic cycles of Ru(V)=O → Ru(IV) → Ru(III) and Ru(V)=O → Ru(III), respectively. The utilization efficiency of PI in the Ru(III)/PI process for the oxidation of TOPs can approach 100% under optimal conditions. PI stoichiometrically transformed into IO3- without production of undesired iodine species (e.g., HOI and I2). This study developed an efficient and environmentally benign advanced oxidation process for rapid removal of TOPs and enriched understandings on reactivity of Ru(V)=O and Ru catalytic cycles.

Nearly zero peroxydisulfate consumption for persistent aqueous organic pollutants degradation via nonradical processes supported by in-situ sulfate radical regeneration in defective MIL-88B(Fe)

The porous defective MIL-88B(Fe) with abundant oxygen vacancies and Fe-N sites was fabricated to accomplish nearly zero peroxydisulfate (PDS) consumption for persistent bisphenol A (BPA) degradation via electron-transfer pathway (ETP). Interestingly, the generated sulfates during ETP were oxidized to yield the confined sulfate radicals and to accomplish the peroxydisulfate regeneration in the fine-tuned MIL-88B(Fe), which was verified by series experiments and DFT calculations. Further studies suggested that the optimal De-MIL-88B(Fe)-1.25 catalyst achieved the persistent nonradical reactions for BPA decomposition under visible light irradiation with both low input and low consumption of PDS. It was the first case to achieve nearly zero PDS consumption for emerging pollutants elimination, which provided new strategy to design and tune defective metal-organic frameworks for the purpose of reducing the stoichiometry between PDS and contaminants for nearly zero PDS consumption.

Insights into the Photoelectrocatalytic Behavior of gCN-Based Anode Materials Supported on Ni Foams.

Graphitic carbon nitride (gCN) is a promising n-type semiconductor widely investigated for photo-assisted water splitting, but less studied for the (photo)electrochemical degradation of aqueous organic pollutants. In these fields, attractive perspectives for advancements are offered by a proper engineering of the material properties, e.g., by depositing gCN onto conductive and porous scaffolds, tailoring its nanoscale morphology, and functionalizing it with suitable cocatalysts. The present study reports on a simple and easily controllable synthesis of gCN flakes on Ni foam substrates by electrophoretic deposition (EPD), and on their eventual decoration with Co-based cocatalysts [CoO, CoFe2O4, cobalt phosphate (CoPi)] via radio frequency (RF)-sputtering or electrodeposition. After examining the influence of processing conditions on the material characteristics, the developed systems are comparatively investigated as (photo)anodes for water splitting and photoelectrocatalysts for the degradation of a recalcitrant water pollutant [potassium hydrogen phthalate (KHP)]. The obtained results highlight that while gCN decoration with Co-based cocatalysts boosts water splitting performances, bare gCN as such is more efficient in KHP abatement, due to the occurrence of a different reaction mechanism. The related insights, provided by a multi-technique characterization, may provide valuable guidelines for the implementation of active nanomaterials in environmental remediation and sustainable solar-to-chemical energy conversion.

Synthesis of a biomimetically formed core–shell SiO2@Ag photocatalyst for the degradation of aqueous organic pollutants

In this paper, a novel photocatalyst is prepared, characterized and tested. This material comprises a biomimetically formed silica core and silver based nanospheres, strongly attached to the substrate. The synthesis of the silica substrate is achieved by employing a silica precursor, tetraethyl-orthosilicate, and a dendritic polymer, poly(ethylene)imine. The latter enables the formation of silica cores through biosilification by regulating the pH with phosphate buffer solutions. These cores with a mean diameter of 200 nm, allow the formation of silver-based photocatalysts (10 nm) on their surface with the addition of silver nitrate and sodium hydrogen carbonate. Silver, silver carbonate and silver phosphate act synergistically regarding their photocatalytic performance. Furthermore, their immobilization on silica substrates enhances their photostability while silica prevents the formation of silver agglomerates. The structure of the catalyst was examined through Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction analysis and Fourier Transform Infrared Spectroscopy. Moreover, the photocatalytic properties were assessed by a model reaction, the reduction of 4-nitrophenol to 4-aminophenol using Ultraviolet–visible spectroscopy. Finally, the reusability of the photocatalyst was also examined. In conclusion, a viable photocatalyst, suitable for the degradation of 4-nitrophenol, is presented (100 % during the first and second cycle and 98 % during the third cycle).

Effect of activation time on sulfur-doped porous carbon for efficient degradation of organic pollutants with persulfate

Metal-free catalysis by using carbonaceous materials has propelled to the forefront in investigation of persulfate (PS) activation for green degradation of aqueous organic pollutants. Herein, sulfur-doped porous carbons (S-AC) were feasibly produced by chemical activation of Poly (phenylene sulphide) with KOH as activator. The influences of activation time on the porous structure, sulfur doping level, and chemical functionality of the as-prepared carbons were investigated by various characterization means. The S-AC samples were employed as metal-free catalysts to activate PS for phenol removal. Experiments results demonstrated that sulfur doping enhanced the catalytic activity of S-AC, and the S-AC-2 sample prepared by carbonization activation of 2 h was demonstrated to be a promising alternative to common metal oxides and other advanced carbon-based materials. Moreover, the S-AC-2/PS system could efficiently degrade various organics, which can be a green material for wastewater treatment and environmental remediation. In addition, the effects of various reaction parameters on phenol removal were discussed. It was found that S-AC-2 still presented an outstanding performance in a wide pH range. Furthermore, the PS activation mechanism over S-AC-2 was investigated by a series of classical radical quenching tests, EPR and Linear Sweep Voltammetry.

Interfacial coupling effects in α-Fe2O3/g-C3N4 composite magnetically separable heterojunction with upgraded Z-scheme photocatalytic performance of mixed organic pollutant degradation

Photocatalysis has fascinated wide consideration due to its promising advantage in wastewater treatment. And the metal-oxides and g-C3N4 that possess Z-scheme heterojunctions have become the energetic photocatalysts (PCs) in degrading the organic impurities. In this work, a novel magnetic separable g-C3N4/α-Fe2O3 (GFE) nanocomposites (NCs) were fabricated by a facile hydrothermal strategy. Structural, morphological, optical, surface area and magnetic belongings of GFE composites were effectively explored using XRD, FT-IR, XPS, FESEM, HRTEM with EDX mapping, BET, UV-DRS and PL spectra. The (g-C3N4/20 wt % α-Fe2O3) GFE2 composite PCs were verified robust with significantly upgraded the photocatalytic efficiency for (anionic) RhB (97.2%) and (cationic) MB (90.6%) mixed aqueous organic pollutants degradation in 150 min under visible-light exposure, which was favourably higher than to GCN (65.2%) and α-Fe2O3 (16.6%) PCs. Moreover, the as-obtained GFE composite PCs also exposed great stability after five successive recyclabilities. The enhanced photo-degradation activity was largely ascribed to the extended visible-light fascination ability, high surface area, augmented active sites and strong redox ability relatively. Also, the energetic formation of α-Fe2O3 coupled g-C3N4 heterojunction that skilled the probable recombination rate and beneficial for the separation of photo-excited electron and hole (e−/h+) pairs based on active “Z-scheme” mechanism was liable for eliminating organic mixed pollutants.

Magnetically sensitive TiO2 hollow sphere/Fe3O4 core-shell hybrid catalyst for high-performance sunlight-assisted photocatalytic degradation of aqueous antibiotic pollutants

Owing to the ease of catalyst separation and recycling, magnetically sensitive catalysts are essential for developing a cost-effective method for the photocatalytic degradation of aqueous organic pollutants. This study demonstrates the efficacy of a magnetically sensitive TiO2 hollow sphere/Fe3O4 (THS/FO) core-shell hybrid catalyst for the sunlight-assisted degradation of aqueous antibiotic pollutants, namely amoxicillin (AMC) and levofloxacin (LVF). To fabricate this core-shell hybrid catalyst, THS was first synthesized via a wrap–bake–peel approach using SiO2 templates and FO nanoparticles were then carefully deposited on the THS surface via an in situ growth method. The THS/FO core-shell hybrid catalyst exhibited significantly higher activity for degrading AMC and LVF than THS under simulated sunlight. Moreover, the activity results indicate that the proposed hybrid catalyst outperforms numerous reported photocatalysts owing to its strong optical response properties and the synergistic effect of THS and FO due to the core-shell configuration of the hybrid catalyst, which facilitates charge separation. Additionally, due to the strong magnetic properties of the hybrid catalyst, the catalyst can be magnetically recovered and reused in the AMC and LVF degradation processes without exhibiting a significant loss in its activity even after five consecutive test cycles. Thus, the hybrid catalyst designed herein promotes the use of practical photocatalytic techniques for treating aqueous antibiotic pollutants.

Contribution of photocatalytic and Fenton-based processes in nanotwin structured anodic TiO2 nanotube layers modified by Ce and V.

In the present work, nanotwin structured TiO2 nanotube (TNT) layers are prepared by the electrochemical anodization technique to form the anatase phase and by surface modification via spin-coating of Ce and V precursors to form Ce-TNT and V-TNT, respectively. The surface and cross-sectional images by SEM revealed that the nanotubes have an average diameter of ∼130 nm and a length of ∼14 μm. In addition, the TEM images revealed the nanotwin structures of the nanotubes, especially the anatase (001) and (112) twin surfaces, that increase the transport of photogenerated charges. The photoinduced degradation of caffeine (CAF) by TNT, Ce-TNT, and V-TNT led to a degradation extent of 16%, 26% and 33%, respectively, whereas it increased to 26%, 38%, and 46% in the presence of H2O2, owing to the involvement of Fenton-based processes (in addition to photocatalysis). The effect of the Fenton-based processes accounts for about 10% of the total degradation extent of CAF. Finally, the mechanism of the photoinduced degradation of CAF was investigated. The main oxidative species were the hydroxyl radicals, and the better efficiency of V-TNT over Ce-TNT and TNT was ascribed to its negative surface, thus improving the interactions with CAF.

Role of oxygen vacancies and Sr sites in SrCo0.8Fe0.2O3 perovskite on efficient activation of peroxymonosulfate towards the degradation of aqueous organic pollutants

Metal-based perovskite oxides have contributed significantly to the advanced oxidation processes (AOPs) due to their diverse active sites and excellent compositional/structural flexibility. In this study, we specially designed a perovskite oxide with abundant oxygen vacancies, SrCo 0.8 Fe 0.2 O 3 (SCF), and firstly applied it as a catalyst in peroxymonosulfate (PMS) activation towards organic pollutants degradation. The result revealed that the prepared SCF catalyst exhibited excellent performance on organic compounds degradation. Besides, SCF showed much better activity than La 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3 (LSCF) in terms of reaction rate and stability for the degradation of the organic compounds. Based on the analysis of scanning electron microscope, transmission electron microscope, X-ray diffraction, N 2 adsorption–desorption, X-ray photoelectron spectroscopy and electron paramagnetic resonance, it was confirmed that the perovskite catalysts with high content of Sr doping at A-site could effectively create a defect-rich surface and optimize its physicochemical properties, which was responsible for the excellent heterogeneous catalytic activity of SCF. SCF can generate three highly active species: 1 O 2 , SO − 4 ∙ and ∙OH in PMS activation, revealing the degradation process of organic compounds was a coupled multiple active species in both radical and nonradical pathway. Moreover, it was mainly in a radical pathway in the degradation through PMS activation on SCF and SO − 4 ∙ radicals produced were the dominant species in SCF/PMS system. This study demonstrated that perovskite-type catalysts could enrich OVs efficiently by doping strategy and regulate the PMS activation towards sulfate radical-based AOPs.

Paracetamol degradation by photo-assisted activation of peroxymonosulfate over ZnxNi1−xFe2O4@BiOBr heterojunctions

Developing efficient and recyclable heterogeneous catalysts in advanced oxidation processes towards aqueous organic pollutants degradation on real samples remains challenging. Herein, semiconductor heterojunction photocatalysts with variable composition (ZnxNi1−xFe2O4@BiOBr; x = 0, 0.2, 0.5, 0.8 and 1) were synthesized through a two steps hydrothermal process. The influence of cation composition, microstructure heterojunction, catalyst and peroxymonosulfate (PMS) dosage and pH variation were investigated for the degradation of paracetamol (PAM) as target pollutant. Real degradation datasets from commercial tablet solutions were compared with pure paracetamol (p-PAM). Doping Ni into ZnFe2O4 significantly affect the catalytic performance as well as enable magnetic removal of catalyst. The ratio between ZnxNi1−xFe2O4 and BiOBr was also optimized to realize best catalytic degradation. Complete removal of PAM was achieved after 100 min at optima conditions (0.5 g/L Zn0.8Ni0.2Fe2O4@BiOBr, 2 mM PMS, 10 mg/L PAM, UV-A, pH 7) while 64% removal account in 100 min in darkness. A chemical method probe, through free radical scavengers, revealed that SO4•- is the main specie involved in the degradation reaction. A novel degradation mechanism was proposed by the identification of eight different intermediates. Reusability of the heterojunction photocatalysts was studied after five consecutive treatments. Zn0.8Ni0.2Fe2O4@BiOBr efficiently activate PMS under UV-A irradiation vanishing PAM, one contaminants of most emerging concern found in water. This study will shed light into the understanding of photo-assisted PMS activation for aqueous pollution abatement.

Degradation of aqueous organic pollutants using an Fe2O3/WO3 composite photocatalyst as a magnetically separable peroxymonosulfate activator

Developing a cost-effective method for the separation and recovery of nanomaterials for water treatment is challenging due to the significantly high recovery cost associated with nanomaterial-based water treatment processes. In this study, we synthesized magnetically separable iron oxide/tungsten oxide (Fe2O3/WO3) composites through a chemical co-precipitation method and employed them as peroxymonosulfate (PMS) activators for the degradation of organic pollutants under visible light. Electron spin resonance analysis, chemical quenching, and photoluminescence analysis suggested that hydroxyl radicals, sulfate radicals, and valence band holes contribute to the degradation processes in the Fe2O3/WO3/PMS system under visible light. The results of the degradation and recovery experiments based on the mass ratio of WO3 to Fe2O3 ([WO3]:[Fe2O3]) in the Fe2O3/WO3 composite indicated that the Fe2O3/WO3 composite with [WO3]:[Fe2O3] = 2:1, which can be completely recovered using a magnet (magnetic flux density = 2500 G), is the optimal photocatalyst for PMS activation. The effects of reaction parameters, such as the PMS concentration, Fe2O3/WO3 dosage, solution pH, and background anions (chloride, carbonate, nitrate, and phosphate)/humic acid, on the degradation kinetics were investigated and discussed. Under visible light irradiation, the Fe2O3/WO3/PMS system efficiently degraded various organic pollutants, including 4-chlorophenol, 2-chlorophenol, 4-bromophenol, 4-methylphenol, 2,4-dimethylphenol, bisphenol A, tryptophan, sulfamethoxazole, sulfisoxazole, and furfuryl alcohol. In addition, the complete degradation of 4-chlorophenol in the Fe2O3/WO3/PMS system under visible light was achieved for up to five degradation cycles when Fe2O3/WO3 was reused after recovery using a magnet.

Photocatalytic Activity of Cellulose Acetate Nanoceria/Pt Hybrid Mats Driven by Visible Light Irradiation.

A photocatalytic system for the degradation of aqueous organic pollutants under visible light irradiation is obtained by an innovative approach based on ceria/platinum (Pt) hybrid nanoclusters on cellulose acetate fibrous membranes. The catalytic materials are fabricated by supersonic beam deposition of Pt nanoclusters directly on the surface of electrospun cellulose acetate fibrous mats, pre-loaded with a cerium salt precursor that is transformed into ceria nanoparticles directly in the solid mats by a simple thermal treatment. The presence of Pt enhances the oxygen vacancies on the surface of the formed ceria nanoparticles and reduces their band gap, resulting in a significant improvement of the photocatalytic performance of the composite mats under visible light irradiation. Upon the appropriate pretreatment and visible light irradiation, we prove that the most efficient mats, with both ceria nanoparticles and Pt nanoclusters, present a degradation efficiency of methylene blue of 70% and a photodegradation rate improved by about five times compared to the ceria loaded samples, without Pt. The present results bring a significant improvement of the photocatalytic performance of polymeric nanocomposite fibrous systems under visible light irradiation, for efficient wastewater treatment applications.

Piezoelectric activation of peroxymonosulfate by MoS2 nanoflowers for the enhanced degradation of aqueous organic pollutants

MoS2 NFs have exhibited abundant active sites in odd-number layers to piezoelectrically activate PMS for producing ˙OH and SO4˙− in order to degrade organic pollutants.

A facial synthesis of nitrogen-doped reduced graphene oxide quantum dot and its application in aqueous organics degradation

N-doped reduced graphene oxide quantum dots (N-rGQDs) have attracted more and more attention in efficient catalytic degradation of aqueous organic pollutants. However, the synthesis of N-rGQDs is generally a complex and high energy required process for the reduction and N-doping steps. In this study, a facile and green fabrication approach of N-rGQDs is established, based on a metal-free Fenton reaction without additional energy-input. The N structures of N-rGQDs play a significant role in the promotion of their catalytic performance. The N-rGQDs with relatively high percentage of aromatic nitrogen (NAr-rGQDs) perform excellent catalytic activities, with which the degradation efficiency of pollutant is enhanced by 25 times. Density functional theory (DFT) calculation also indicates aromatic nitrogen structures with electron-rich sites are prone to transfer electron, presenting a key role in the catalytic reaction. This metal-free Fenton process provides a green and cost-effective strategy for one-step fabrication of N-rGQDs with controllable features and potential environmental catalytic applications.

Rational design of ZnFe2O4/g-C3N4 heterostructures composites for high efficient visible-light photocatalysis for degradation of aqueous organic pollutants

A novel ZnFe2O4/g-C3N4 hybrid photocatalyst with different ratio was prepared by a facile and one step microwave irradiation method for the first time. Characterization results of XRD SEM, and TEM demonstrated that FCC spinel structural of ZnFe2O4 with monodispersed individual spherical shaped nanoparticles (sizes in the range of 35–45 nm) are wrapped on the surface of g-C3N4 nanosheets. The extent of absorption in the visible light region and effective prevent the electron-hole pair recombination was identified through UV–Vis-DRS and PL analysis. The visible light active ZnFe2O4/g-C3N4 heterostructure was used for the decomposition of methyl orange (MO) and rhodamine B (RhB) under stimulated visible light irradiation. ZnFe2O4/g-C3N4 composition, 15 wt.% (ZnFe2O4 loaded g-C3N4) composition has the highest rate of the degradation such as high removal efficiency (98%) and huge apparent constant (0.1955 min−1) and long term stability towards RhB. The kinetic constant over ZnFe2O4/g-C3N4 heterostructure photocatalyst was more than 15 times larger than that over pure ZnFe2O4 (0.0085 min−1). The photogenerated electrons from g-C3N4 surfaces could easily migrate to ZnFe2O4, leading to efficient separation of electron–hole pairs. The possible photocatalytic mechanism and photocatalytic activity enhanced mechanism has been proposed, taking into account the photosensitization effect and synergetic effect of ZnFe2O4 with g-C3N4.