Degradation Of Diclofenac Research Articles

Ultraviolet Light (UV)-Induced Photocatalytic Degradation of Diclofenac Using Naturally Derived TiO2@rGO Composite

Ultraviolet Light (UV)-Induced Photocatalytic Degradation of Diclofenac Using Naturally Derived TiO2@rGO Composite

Degradation of diclofenac and 4-chlorobenzoic acid in aqueous solution by cold atmospheric plasma source

In this study, cold atmospheric plasma (CAP) was explored as a novel advanced oxidation process (AOP) for water decontamination. Samples with high concentration aqueous solutions of Diclofenac sodium (DCF) and 4-Chlorobenzoic acid (pCBA) were treated by plasma systems. Atmospheric pressure plasma jets (APPJs) with a 1 pin-electrode and multi-needle electrodes (3 pins) configurations were used. The plasma generated using argon as working gas was touching a stationary liquid surface in the case of pin electrode-APPJ while for multi-needle electrodes-APPJ the liquid sample was flowing during treatment. In both configurations, a commercial RF power supply was used for plasma ignition. Measurement of electrical signals enabled precise determination of power delivered from the plasma to the sample. The optical emission spectroscopy (OES) of plasma confirmed the appearance of excited reactive species in the plasma, such as hydroxyl radicals and atomic oxygen which are considered to be key reactive species in AOPs for the degradation of organic pollutants. Treatments were conducted with two different volumes (5 mL and 250 mL) of contaminated water samples. The data acquired allowed calculation of degradation efficiency and energy yield for both plasma sources. When treated with pin-APPJ, almost complete degradation of 5 mL DCF occurred in 1 min with the initial concentration of 25 mg/L and 50 mg/L, whereas 5 mL pCBA almost degraded in 10 min at the initial concentration of 25 mg/L and 40 mg/L. The treatment results with multi-needle electrodes system confirmed that DCF almost completely degraded in 30 min and pCBA degraded about 24 % in 50 min. The maximum calculated energy yield for 50 % removal was 6465 mg/kWh after treatment of 250 mL of DCF aqueous solution utilizing the plasma recirculation technique. The measurements also provided an insight to the kinetics of DCF and pCBA degradation. Degradation products and pathways for DCF were determined using LC-MS measurements.

Catalytic activation of formic acid using Pd nanocluster decorated graphitic carbon nitride for diclofenac reductive hydrodechlorination

Halogenated pharmaceuticals exhibit high toxicity if released to natural environment, and dehalogenation is a key process for their degradation. In this study, a reductive and directional dehalogenation technique, heterogenous formic acid (HCOOH) catalytic activation system, was proposed for diclofenac (DCF) dechlorination and detoxification. A functional material of Pd nanocluster decorated graphitic carbon nitride (Pd/g-C3N4) was developed for HCOOH activation. Although the optimized material (Pd1/g-C3N4) showed lower HCOOH decomposition rate (k1 = 0.287 ± 0.017 min−1) than the pristine Pd particles (k1 = 0.401 ± 0.031 min−1), it processed higher DCF degradation efficiency (97.9% within 30 min) than Pd particles. The enhancement mechanism was revealed by both experiments and theoretical calculations. Firstly, the six-fold cavities of g-C3N4 acted as anchor sites, which offered strong coordination environment for Pd nanoclusters. Secondly, the strong coordination environment of Pd led to upshifted d-band center of Pd 4d with enhanced bonding state, and then promoted HCOOH adsorption on Pd/g-C3N4, thus facilitating HCOOH decomposition through formate pathway rather than carboxyl pathway. Thirdly, Pd/g-C3N4 ensured HCOOH selectively decomposed as dehydrogenation reaction, which generated more H* (adsorbed H on Pd) than the dehydration reaction. The H* was proved to be the dominant reductive species for DCF hydrodechlorination. Moreover, the toxicities of DCF dechlorination products were greatly reduced.

Non-radical degradation of organic pharmaceuticals by g-C3N4 under visible light irradiation: The overlooked role of excitonic energy transfer

In this work, an excitonic energy transfer (EET) based non-radical mechanism was proposed for the degradation of organic pharmaceuticals by graphitic carbon nitride (g-C3N4) under visible light irradiation. Using diclofenac (DCF) as a model molecule, the competition between single electron transfer (SET) and EET was studied through modulating the exciton binding energy of g-C3N4. The different mechanisms of SET and EET for DCF degradation were predicted by DFT calculation, and further confirmed by their different degradation pathways. When EET played an important role, the rationality of some very popular radical scavengers, such as p-BQ, TEMPOL and furfuryl alcohol must be reconsidered. In addition, humic acid (HA) had a distinct effect on EET and SET. Specifically, HA enhanced the EET process through photosensitization, but suppressed SET through radical quenching effect. The effect of HA on DCF degradation depended on the contribution ratio of SET and ET.

Enhanced Permanganate Activation under UVA-LED Irradiation: Unraveled Mechanism Involving Manganese Species and Hydroxyl Radical.

Permanganate [Mn(VII)] has gained broad attention in water treatment. However, its limited reactivity toward some refractory micropollutants hinders its application for micropollutant degradation. Herein, we introduced UVA-LED photolysis of Mn(VII) (UVA-LED/Mn(VII)) to degrade micropollutants (diclofenac (DCF), 4-chlorophenol (4-CP), atrazine, and nitrobenzene) by selecting DCF and 4-CP as target micropollutants. The effects of operating conditions (e.g., light intensity, radiation wavelengths, pH, and water constituents) on DCF and 4-CP degradation as well as the underlying mechanisms were systematically studied. The degradation rates of DCF and 4-CP linearly decreased with increasing radiation wavelengths (from 365 to 405 nm), likely due to the decreased molar absorption coefficients and quantum yields of Mn(VII). Reactive manganese species (RMnS), including Mn(V), Mn(III), and HO•, were generated in the UVA-LED/Mn(VII) process. Mn(V) and HO• were responsible for DCF degradation, while Mn(III), HO•, and likely Mn(V) accounted for 4-CP degradation. Competitive kinetic results revealed that contributions of RMnS and HO• decreased with increasing radiation wavelengths, wherein RMnS played the dominant role. Increasing pH displayed opposite effects on DCF and 4-CP degradation with higher degradation efficiency obtained at acidic pH for the former one but alkaline pH for the latter one. The presence of water background ions (e.g., Cl-, HCO3-, and Ca2+) barely influenced DCF and 4-CP degradation. Finally, in comparison with Mn(VII) alone, enhanced degradation of DCF and 4-CP by UVA-LED/Mn(VII) was observed in real waters. This work advances the understanding of the photochemistry of manganese species in micropollutant degradation and facilitates Mn(VII) oxidation in practical application.

Degradation of diclofenac under irradiation of UV lamp and solar light using ZnO photo catalyst

Diclofenac sodium (DCF) is a non-steroidal anti-inflammatory drug mainly used as an analgesic, arthritic and anti-rheumatic. This study deals with the degradation of diclofenac by photo catalytic-based advanced oxidation processes. The solar reactor system is comprised of quartz and borosilicate tubes for the absorption of the solar rays and transmission to the pollutant sample. Artificial UV lamp and solar rays have been applied to activate the ZnO catalyst, thereby generating highly oxidizing species. These species initiate the degradation process of the drug, which results in intermediates that finally dissociate into carbon dioxide and water. The degradation rate has been analyzed by composition analysis using high performance liquid chromatography. TOC and COD tests have also been conducted for degraded samples. ZnO catalyst loading was tested from 0.1 gm/L to 1 gm/L and the degradation rate showed a rising trend up to 0.250 gm/L, but further increase in loading resulted in a drop in degradation. Similarly, degradation is higher in acidic condition as compared to neutral or basic pH condition. The results showed a higher degradation rate for UV lamp irradiation as compared to the solar system. Moreover, TOC and COD reduction results were also found to be higher for UV lamp photo catalysis.

Kinetic Model of Diclofenac Degradation Developed Using Multivariate Curve Resolution Method.

This study presents the kinetic modeling of the natural long-term aging of the pharmaceutical substance as well as the intact tablets of Diclofenac. Datasets are collections of near-infrared spectra acquired from the intact tablets packed in plastic blisters and the spectra of the pure substance. Fresh samples and samples at different stages of degradation are analyzed. No methods of accelerated aging were applied. Multi-step application of MCR-ALS in its soft version followed by the kinetic modeling of the results helps to propose a generic degradation mechanism; which includes: a global kinetic model; approximations of the NIR spectra of the intermediate and product; rough estimates of rate constants. We study tablets in blister packs; exactly as they are presented in pharmacies; and this is important from a practical point of view.

Rapid Microwave-Assisted Synthesis of N/TiO2/rGO Nanoparticles for the Photocatalytic Degradation of Pharmaceuticals.

Nanocomposites comprising nitrogen-doped TiO2 and reduced graphene oxide (N/TiO2/rGO), with different rGO loading qualities, were prepared by a cost-effective microwave-assisted synthesis method. The synthesized materials were broadly characterized by Raman spectroscopy, X-ray diffraction (XRD), infrared spectroscopy (FTIR), photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), electron microscopy (SEM-EDS), and nitrogen adsorption/desorption isotherms. Anatase was the only crystalline phase observed for all synthesized materials. The rGO loading did not affect the morphological properties, but it positively influenced the photocatalytic activity of the nanocomposite materials, especially at low rGO loading. Photocatalysts were evaluated via the degradation of specific organic micropollutant (OMP) pharmaceuticals: ciprofloxacin (CIP), diclofenac (DCF), and salicylic acid (SA), under different radiation sources: ultraviolet A (UVA), solar light simulator (SLS), blue visible light (BVL) and cold visible light (CVL). CIP and SA were removed effectively via the synergy of adsorption and photocatalysis, while DCF degradation was achieved solely by photocatalysis. After implementing scavenger agents, photocatalytic degradation processes mainly depended on the specific pollutant type, while irradiation sources barely defined the photocatalytic mechanism. On the other hand, changes in irradiation intensity significantly influenced the photolysis process, while photocatalysis was slightly affected, indicating that irradiation spectra are more relevant than intensity.

Comparison of the degradation mechanisms of diclofenac in the presence of iron octacarboxyphthalocyanine and myeloperoxidase

The degradation process of diclofenac (DCF) by hematoprotein myeloperoxidase (MPO) and iron octacarboxyphthalocyanine (FePcOC) in the presence of hydrogen peroxide was compared. During the oxidation of diclofenac, in the presence of iron octacarboxyphthalocyanine (FePcOC) and hydroxyl radicals (HO•) (from H2O2), an intermediate product (dimer with an m/z value of 587) with the characteristic yellow colouration and an intense band at λmax = 451 nm is formed. Iron octacarboxyphthalocyanine oxidises in the presence of hydrogen peroxide, following the first-order reaction kinetics for FePcOC and H2O2. The concentration of diclofenac does not affect the initial reaction rate. For comparison, the oxidation of DCF in the presence of myeloperoxidase and hydrogen peroxide also provided yellow-coloured solutions with an absorption maximum at λmax = 451 nm. However, LC-MS/MS analysis indicates the presence of at least seven main products of the diclofenac oxidation process in the final reaction mixture, including two dimers with the ion mass [M−H]¯ = 587.01. The mechanism of the diclofenac degradation with hematoprotein myeloperoxidase is more complex than with iron octacarboxyphthalocyanine. Furthermore, the biological activity of diclofenac and DCF dimer (iron octacarboxyphthalocyanine and hydroxyl radicals degradation product) was tested. In this case, the long-term assayed in vitro against E. coli, colorectal HCT116 and melanoma Me45 cancer cells were performed.

Photocatalytic degradation of diclofenac using hybrid MIL‐53(Al)@TiO2 and MIL‐53(Al)@ZnO catalysts

AbstractIn this work, TiO2 and ZnO were incorporated successfully into a MIL‐53(Al) metal–organic framework (MOF) to form nanocomposites via a facile post‐modification technique. The hybrid MIL‐53(Al)@TiO2 and MIL‐53(Al)@ZnO were characterized by several characterization tests. The X‐ray diffraction (XRD), Fourier‐transform infrared (FTIR), and field‐emission scanning electron microscopy (FE‐SEM) analyses showed evidence of the successful incorporation of TiO2 and ZnO within the MIL‐53(Al) framework. The thermal gravimetric analysis (TGA) analysis demonstrated the excellent thermal stability of MIL‐53(Al)@TiO2 and MIL‐53(Al)@ZnO, while diffuse reflectance spectroscopy (DRS) determined the direct optical band gaps of MIL‐53(Al)@ZnO and MIL‐53(Al)@TiO2 to be 3.24 and 3.34 eV, respectively. The composites were also tested for the photocatalytic degradation of diclofenac (DCF) as a micropollutant. The DCF degradation efficiency of the photocatalysts was ranked in the following order: MIL‐53(Al)@TiO2 > MIL‐53(Al) > TiO2 > ZnO > MIL‐53(Al)@ZnO. The incorporation of TiO2 enhanced the optical properties of MIL‐53 (Al), which was confirmed with the superior photodegradation efficiency of MIL‐53(Al)@TiO2 (>85% in 2 h) as compared to the pristine MIL‐53(Al) (around 80% in 2 h). The improvement in the photodegradation of the hybrid‐MOF is mostly associated with the possible dual function of the adsorption and photodegradation mechanisms. The reusability of MIL‐53(Al) and its composites was inspected over 3 cycles of photodegradation experiments with DCF. The photocatalytic activity of MIL‐53(Al)@TiO2 remained unchanged (>90%), while for MIL‐53(Al) and MIL‐53(Al)@ZnO a slight drop was observed over three cyclic degradation experiments. Fluorescence measurements revealed that the hydroxyl radical is an important reactive oxygen species produced by all the photocatalysts that aid in the photodegradation of DCF. Furthermore, the kinetic modelling of the photoreaction identified a second‐order kinetics for all catalysts. Experiments with scavengers showed that hydroxyl radicals played a major role in the photocatalytic process, and it was found that only 2 h of treatment was sufficient to obtain a considerable chemical oxygen demand (COD) reduction of 58%.

Synthesis of novel LaCoO3/graphene catalysts as highly efficient peroxymonosulfate activator for the degradation of organic pollutants

Metal leaching in perovskite-based catalysts during peroxymonosulfate activation processes can severely restrict their application in wastewater treatment. Therefore, enhancing the stability of perovskite nanostructures is crucial to improve catalytic performance and broaden applications but has been rarely achieved so far. We developed a scalable method to synthesize novel stable and environmentally-friendly nanocomposites of LaCoO3 and few-layer graphene (consisting of roughly-nine layers) for the removal of organic pollutants from wastewater. With abundant oxygen vacancies and synergistic effects between LaCoO3 and few-layer graphene, the novel LaCoO3/graphene catalyst exhibits outstanding catalytic degradation (>99 %) of diclofenac, metoprolol, carbamazepine, and bisphenol A at a high concentration (40 mg/l) in less than 10 min in the peroxymonosulfate activation system, with mineralization of 57, 55, 61, and 62 %, respectively. The LaCoO3/graphene catalyst exhibited excellent reusability and high catalytic performance within a wide pH range (3–11). The formation of LaCoO3/graphene composites prevents cobalt leaching (0.004 mg/l), stabilizes sub-stoichiometric LaCoO3 and thus increases the content of Co2+ in the structure, leading to much higher catalytic activity than that of pure LaCoO3. Electron paramagnetic resonance and radical quenching experiments revealed that both radical pathways (SO4−, OH, and O2−) and non-radical pathways (1O2) contribute to bisphenol A degradation and the relative contributions of OH, SO4−, and 1O2/O2− were determined to 13.4, 32.6, and 54 % for bisphenol A removal, respectively. Overall, our results indicate that LaCoO3/graphene is a promising material towards peroxymonosulfate activation for environmental remediation.

ABTS as Both Activator and Electron Shuttle to Activate Persulfate for Diclofenac Degradation: Formation and Contributions of ABTS•+, SO4•-, and •OH.

The activation of peroxydisulfate (PDS) by organic compounds has attracted increasing attention. However, some inherent drawbacks including quick activator decomposition and poor anti-interference capacity limited the application of organic compound-activated PDS. It was interestingly found that 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) could act as both activator and electron shuttle for PDS activation to enhance diclofenac (DCF) degradation over a pH range of 2.0-11.0. Multiple reactive species of ABTS•+, •OH, and SO4•- were generated in the PDS/ABTS system, while only ABTS•+ and •OH directly contributed to DCF degradation. ABTS•+, generated via the reactions of ABTS with PDS, SO4•-, and •OH, was the dominant reactive species of DCF degradation. No significant decomposition of ABTS was observed in the PDS/ABTS system, and ABTS acted as both activator and electron shuttle. Four possible degradation pathways of DCF were proposed, and the toxicity of DCF decreased after treatment with the PDS/ABTS system. The PDS/ABTS system had good anti-interference capacity to common natural water constituents. Additionally, ABTS was encapsulated into cellulose to obtain ABTS@Ce beads, and the PDS/ABTS@Ce system possessed excellent performance on DCF degradation. This study proposes a new perspective to reconsider the mechanism of activating PDS with organic compounds and highlights the considerable contribution of organic radicals on contaminant removal.

Fate, transformation and toxicological implications of environmental diclofenac: Role of mineralogy and solar flux

Diclofenac is an emerging surface water contaminant, yet the environmental impact of its degradation products remains elusive. The current study focuses on mineralogy-controlled diclofenac photo-degradation and its potential health impacts. Under irradiated conditions, we studied the effects of kaolinite, hematite, and anatase on diclofenac degradation. Our results showed that kaolinite doubled the diclofenac degradation rate, which can be attributed to the high catalytic effect, mediated via increased surface area and pore size of mineral surface in the low pH. Conversely, anatase, a crystal phase of titanium dioxide (TiO2), diminished the diclofenac degradation compared to treatments without TiO2. Hematite, on the other hand, showed no effect on diclofenac degradation. Photo-degradation products also varied with the mineral surface. We further assessed in vitro toxicological effects of photo-degraded products on two human cell lines, HEK293T and HepG2. Biological assays confirmed that photo-degraded compound 6 (1-(2,6-dichlorophenyl)indolin-2-one) decreased HEK293T cell survival significantly (p < 0.05) when compared to diclofenac in all concentrations. At lower concentrations, inhibition of HEK293T cells caused by compounds 4 (2-(8-chloro-9H-carbazol-1-yl)acetic acid), and 5 (2-(9H-carbazol-1-yl)acetic acid) was greater than diclofenac. Compound 7 (1-phenylindolin-2-one) was toxic only at 250 µM. Additionally, compound 6 decreased HepG2 cell viability significantly when compared to diclofenac. Overall, our data highlighted that mineralogy plays a vital role in environmental diclofenac transformation and its photo-degraded products. Some photo-degraded compounds can be more cytotoxic than the parent compound, diclofenac.

Synergistic effect of humic substances and bicarbonate on diclofenac degradation by Cu(Ⅱ)/peracetic acid

Bicarbonate (HCO3-) and humic substances (HS), two common water matrix components, were found to exhibit synergistic effect on diclofenac (DCF) degradation by Cu(Ⅱ)/peracetic acid (PAA) process in this work. The mechanism of their impacts on the performance of Cu(Ⅱ)/PAA system was systematically investigated and the reactive species generated in this system was identified. The results revealed that organic radicals (CH3C(O)OO• and CH3C(O)O•) and Cu(Ⅲ) were both generated in HCO3--Cu(Ⅱ)-fulvic acid (FA)/PAA system, and the presence of FA induced Cu(Ⅲ) to become the dominant reactive species for DCF degradation. In comparison with humic acid (HA), FA showed a stronger enhancement effect on DCF removal in HCO3--Cu(Ⅱ)/PAA system, which might be due to its stronger electron transfer capability. However, DCF degradation in HCO3--Cu(Ⅱ)-HS/PAA system with HA-FA mixture was similar to that with HA alone, because Cu(Ⅱ) was prior to be coordinated with HA in HA-FA mixture. The operating parameters (i.e., HCO3-, Cu(Ⅱ) and PAA concentrations) were optimized for DCF degradation. Finally, the efficient DCF degradation in real waters proved that the presence of HS and HCO3- in real waters also strongly enhanced DCF elimination by Cu(Ⅱ)/PAA process. The findings of this work suggested that HCO3- and HS, which are extensively distributed in aquatic environment, can significantly improve the performance of Cu(Ⅱ)/PAA system and this system may be an efficient technology for the removal of refractory pollutants in real waters.

Fabrication and characterization of pectin-graphene oxide-magnesium ferrite-zinc oxide nanocomposite for photocatalytic degradation of diclofenac in an aqueous solution under visible light irradiation

Wastewater containing pharmaceutical contaminants has become a critical environmental concern due to rising population and drug consumption caused by increased life expectancy. Diclofenac (DCF) is one of the most applicable drugs for veterinary and human health purposes, polluting surface waters in different ways. This work aims to synthesize a novel pectin-graphene oxide (GO)-magnesium ferrite (MgFe2O4)-zinc oxide (ZnO) nanocomposite (PGMZ) for photocatalytic degradation of DCF in an aquatic environment under visible light irradiation. The single and synthesized nanocomposites were characterized by several analyses, confirming the successful synthesis of the nanocomposite. Effects of four operation conditions, including nanocomposite dosage (1–1.25 g/L), nanocomposite type, initial contaminant concentration (35–55 mg/L), and solution pH (3–11), were investigated on the degradation performance. From the kinetic study, the effect of mixing two composites, i.e., synergy percentage, was 38.7% when ZnO–MgFe2O4 particles were added to the GO-pectin structure. By examining the effect of different free radical enhancers and scavenging compounds on the DCF photodegradation, the most influential scavenging components were in the following order; NaCl > Na2CO3 > Na2SO4, while K2S2O8 was a better enhancer than H2O2 at their optimal concentration. Finally, the PGMZ photocatalyst was reused six times with a reduction of about 20% in its removal efficiency, indicating excellent reusability and stability.

Mechanistic study of cobalt and iron based Prussian blue analogues to activate peroxymonosulfate for efficient diclofenac degradation

Cobalt and iron-based Prussian blue analogues (PBAs) have been assumed as highly efficient peroxymonosulfate (PMS) activators. Herein, four PBAs using iron and/or cobalt as the coordination metals were synthesized by coprecipitation method to investigate the degradation of diclofenac (DCF). Results showed that Co3[Fe(CN)6]2 (CoFe) and Co3[Co(CN)6]2 (CoCo) exhibited much better PMS activating capabilities than Fe3[Co(CN)6]2 (FeCo) and Fe3[Fe(CN)6]2 (FeFe). The optimum performance achieved by CoCo/PMS resulted in a complete degradation of 0.1 mM (30 mg/L) DCF within 2 min under a broad pH range of 4–10. The leaching of Co2+ of both CoFe and CoCo was more significant than that of FeCo, but the leaching of iron species was very low in all FeContaining PBAs. However, both homogeneous and heterogeneous mechanisms were assumed to contribute to DCF degradation, and the high spin state cobalt existing in CoFe and CoCo that was linked to nitrogen was considered as main active site. Moreover, based on principal component analysis the most influential parameter was the initial pH. Electron spin resonance (ESR) and quenching experiments exhibited that SO4•−, 1O2 and O2•− all led to DCF degradation. The high-valent cobalt-oxo species [Co(IV)] was for the first time proposed in both CoFe/PMS and CoCo/PMS processes, also contributing to DCF degradation. Additionally, CoCo exhibited better reusability and DCF mineralization performance than CoFe.

Z-scheme S, B co-doped g-C3N4 nanotube@MnO2 heterojunction with visible-light-responsive for enhanced photodegradation of diclofenac by peroxymonosulfate activation

In this study, the manganese dioxide (MnO2) nanosheets were successfully embedded onto boron and sulfur co-doped g-C3N4 (CNBS) nanotubes to construct the flower-like core–shell CNBS@MnO2 heterojunction with Z-scheme structure for the enhanced photodegradation of diclofenac (DCF) in the presence of peroxymonosulfate (PMS) and 460-nm visible light. The CNBS@MnO2 provides large specific surface area and reduced interfacial resistance for rapid electron transport. Moreover, the redox cycling of Mn species effectively activates PMS to produce sulfate radicals for DCF photodegradation. The PMS-based photodegradation of DCF over CNBS@MnO2 displays the excellentphotodegradation performance after 15 min of irradiation, and the efficiency is highly dependent on initial pH, ion species, and concentrations of PMS and DCF. The CNBS@MnO2 also shows its excellent stability and reusability over ten cycles. Besides, h+, O2●− and SO4●− are the dominantly reactive species for the enhanced degradation of DCF over Z-scheme CNBS@MnO2 heterojunction. The possible reaction mechanism as well as the degradation pathway of DCF over CNBS@MnO2 in the presence of PMS is also proposed. Results clearly highlight the superior photoactivity of Z-scheme CNBS@MnO2 toward micropollutant degradation by PMS activation, which can open an avenue to fabricate the g-C3N4 nanotube@metal oxide structure as an effective activator for water and wastewater purification.

The efficient degradation of diclofenac by ferrate and peroxymonosulfate: performances, mechanisms, and toxicity assessment.

In this study, the degradation efficiency and reaction mechanisms of diclofenac (DCF), a nonsteroidal anti-inflammatory drug, by the combination of ferrate (Fe(VI) and peroxymonosulfate (PMS) (Fe(VI)/PMS) were systematically investigated. The higher degradation efficiency of DCF in Fe(VI)/PMS system can be obtained than that in alone persulfate (PS), Fe(VI), PMS, or the Fe(VI)/PS process at pH 6.0. DCF was efficiently removed in Fe(VI)/PMS process within a wide range of pH values from 4.0 to 8.0, with higher degradation efficiency in acidic conditions. The increasing reaction temperature (10 to 30 ℃), Fe(VI) dose (6.25 to 100µM), or PMS concentration (50 to 1000µM) significantly enhanced the DCF degradation. The existences of HCO3¯, Cl¯, and humic acid (HA) obviously inhibited the DCF removal. Electron paramagnetic resonance (EPR), free radical quenching, and probing experiments confirmed the existence of sulfate radicals (SO4•¯), hydroxyl radicals (•OH), and Fe(V)/ Fe(IV), which are responsible for DCF degradation in Fe(VI)/PMS system. The variations of TOC removal ratio reveal that the adsorption of organics with ferric particles, formed in the reduction of Fe(VI), also were functioned in the removal process. Sixteen DCF transformation byproducts were identified by UPLC-QTOF/MS, and the toxicity variation was evaluated. Consequently, eight reaction pathways for DCF degradation were proposed. This study provides theoretical basis for the utilization of Fe(VI)/PMS process.

Pyrolysis of hydrothermally dewatering sewage sludge: Highly efficient peroxydisulfate activation of derived biochar to degrade diclofenac

The resource utilization of sewage sludge can solve its disposal issue essentially. Meanwhile the removal of diclofenac (DCF) in wastewater is an emerging environmental problem. In this study, a novel strategy of sludge utilizing via hydrothermal - peroxydisulfate (PDS) dewatering coupled pyrolysis process was proposed. The obtained sludge-derived biochar (HSC) could be as candidate to activate PDS to degrade DCF. Results indicated that exceed 90% of DCF was eliminated within 30 min in HSC-PDS/DCF ternary system under the optimized condition (0.6 mmol/L PDS and 0.5 mg/L HSC, without temperature and pH pre-adjusting). The inner mechanism of HSC-PDS/DCF system was revealed as follows: (1) Major: CO in quinones and ketone structure in HSC accelerated the degradation of DCF via non-radical pathway (electron transfer and 1O2). (2) Minor: Graphitic N structure accelerated the electron transfer and O2•- originated from defective sites involved into the redox. Several by-products were identified and two tentative degradation pathways of DCF (eg. dechlorination and C–N cleavage) were proposed.

Efficient degradation of diclofenac by digestate-derived biochar catalyzed peroxymonosulfate oxidation: Performance, machine learning prediction, and mechanism

Diclofenac (DCF), a widely used drug, is frequently found in natural waters, and its removal has caused extensive concern. Sulfate radical-based advanced oxidation processes are efficient for the degradation of organic pollutants, but the self-decomposition of persulfates is always sluggish and restricted. Herein, self-N doped biochar derived from food waste digestate (FWDB) was evaluated as the activator of peroxylmonosulfate (PMS) in terms of DCF degradation. The effects of several key operating variables were examined, and the results indicated that ∼93% of DCF with an initial concentration of 20 mg/L was removed at FWDB dosage of 0.3 g/L and PMS concentration of 1.0 mM. Thereafter, the machine learning method was explored to simulate and predict the DCF removal process. The reactive oxygen species participated in the reaction was identified as 1O2, and the reaction sites on FWDB were determined as graphitized carbon, CO structure, doped-N, and defective edges. Moreover, based on the identification of intermediates and products, the possible DCF destruction pathways were proposed as hydroxylation, cleavage of N−C bond, and decarboxylation. This study provided an economical and convenient heterogeneous PMS activator for remediation of organic wastewater and confirmed the feasibility of optimizing the contaminant degradation process via data mining.