Degradation Of Acetaminophen Research Articles

Photocatalytic degradation and pollutant-oriented structure-activity analysis of carbamazepine, ibuprofen and acetaminophen over faceted TiO2

Photocatalytic degradation of carbamazepine, ibuprofen, acetaminophen and phenol was studied in the presence of anatase photocatalyst, exposing three different crystal facets in the majority of {0 0 1}, {1 0 0} or {1 0 1}. It was found that octahedral anatase particles exposing {1 0 1} facets allow to achieve the best degradation and mineralization of all persistent organic pollutants. This confirms that the previous findings, showing high {1 0 1} activity, are not limited to phenol and could be generalized for other water pollutants. Based on the obtained results, a correlation model including exposed TiO2 crystal facet and chemical hardness of the pollutant was developed to predict the degradation rate of pollutants with a possibly diverse electronic structure. The structure-activity analyses, based on the reactivity predictors obtained from the DFT calculations for all tested compounds, have shown that pollutants with higher chemical hardness react faster with the photocatalyst. Alternatively, a similar effect was observed for the higher HOMO-LUMO energy gap of the compound. This relation indicates that for compounds with a low energy position of LUMO orbital, e.g., carbamazepine, process efficiency is not strictly dependent on the stability of h+ generated organic radical, which is often pointed out as an initial reactive form. Based on these results, a correlation model was developed for the first time to quantitatively describe the effect of the facet-pollutant interactions based on their independent electronic properties. Finally, this was followed by the detailed degradation study of the pharmaceuticals mixture, showing the impact of the total concentration and role of active species on the degradation efficiency over facet-engineered TiO2 photocatalysts.

Novel isoreticular UiO-66-NH2 frameworks by N-cycloalkyl functionalization of the 2-aminoterephtalate linker with enhanced solar photocatalytic degradation of acetaminophen

This work reports for the first time the functionalization of the 2-aminoterephtalate linker of UiO-66-NH2 with cyclopentyl or cyclohexyl rings. The resulting materials displayed reduced bandgaps with enhanced separation of the photogenerated charges due to the inductive electron effect of the cycloalkyl substituent. These functionalized materials displayed higher photocatalytic performance towards the solar abatement of acetaminophen than UiO-66-NH2. The photocatalytic activation mechanism was proposed based on the band alignment and scavenger tests, suggesting the major contribution of holes and superoxide radicals. In particular, UiO-66-NH-C5 exhibited high stability under reaction with low activity loss after reusing. The acetaminophen degradation pathway was also studied indicating that the ACE molecules were coupled to dimers and trimers that were further oxidized. The small bandgap, the band structure, and the photocatalytic performance resulting from the cycloalkyl functionalization of UiO-66-NH2 make it a promising approach to designing novel photocatalysts for solar abatement of emerging contaminants.

Tungsten disulfide (WS2) is a highly active co-catalyst in Fe(III)/H2O2 Fenton-like reactions for efficient acetaminophen degradation

The most important factor that restricts the decomposition of H2O2 in the Fe3+/H2O2 reaction is the slow cycling efficiency of reducing Fe3+ to Fe2+. In this study, the addition of tungsten disulfide (WS2) as a co-catalyst achieved a rapid cycling of the reaction rate-limiting step and a significant enhancement of H2O2 decomposition, which resulted in the effective degradation of acetaminophen (APAP). Results show that 99.6% of APAP (5 mg L−1) could be degraded by H2O2/Fe3+/WS2 system within 2.5 min. The conversion of Fe3+ to Fe2+ occurred mainly on the surface of WS2 due to the redox reaction of the exposed W4+ active sites with Fe3+ after the unsaturated S atoms were bound to protons. Electron paramagnetic resonance (EPR) and radical quenching experiments evaluated the contribution of hydroxyl radical (•OH) and superoxide radical (O2•−) in the degradation of pollutants. WS2 showed good recoverability after four cycles of the reaction. This study provides a new perspective to improve the efficiency of Fe3+/H2O2 and provides a reference for the involvement of transition metal sulfides in advanced oxidation processes (AOPs).

N-Doped HNT/TiO2 Nanocomposite by Electrospinning for Acetaminophen Degradation.

In this study, we combined electrospinning of a large amount of halloysite (HNT, 95%) with nitriding to produce N-HNT-TiO2 composite nanofibers (N-H95T5 hereafter) to be used for acetaminophen (ACT) photodegradation. Investigation of the morphological and structural properties of the obtained materials did not highlight any significant difference in their morphological features and confirmed that nitrogen was evenly distributed in the samples. Photocatalytic tests under visible light showed that acetaminophen photodegraded faster in the presence of samples with nitrogen (N-H95T5) than without (H95T5 nanofibers). Moreover, the N-H95T5 nanocomposite photocatalytic activity did not change after repeated utilization (five cycles). The addition of scavengers during photocatalytic tests showed the key implication of OH•-, O2•- and h+ radicals in acetaminophen degradation. These results indicated that N-H95T5 composite nanofibers could be considered a cheap multifunctional material for photodegradation and could open new prospects for preparing tunable photocatalysts.

In situ generation of hydroxyl radicals by B-doped TiO2 for efficient photocatalytic degradation of acetaminophen in wastewater.

Acetaminophen (AP) is a widely used antipyretic analgesic belonging to the class of PPCPs, which is difficult to be effectively degraded by traditional water treatment processes. However, photocatalytic technology may be an effective approach. Herein, B-doped TiO2 photocatalytic materials were synthesized by sol-gel method, calcinated at 600℃ for 2h, investigated by XRD, TEM, XPS, and other characterization methods. The photocatalytic efficiency and factors affecting the photocatalytic activity were assessed by degradation of AP under 365nm UV light. Compared with undoped TiO2, 4%B-TiO2 nanopowder has smaller grain size, higher porosity, and lower bandgap energy of 3.11eV. Scavenging experiments and ESR results show that •OH is the principal active species. Hence, the degradation efficiency of AP is as high as 98.8% in 30min when adopting 10-mg/L AP initial concentration and 1-g/L 4%B-TiO2 loading, owing to efficient •OH generated by B-TiO2.

Heterojunction of (P, S) co-doped g-C3N4 and 2D TiO2 for improved carbamazepine and acetaminophen photocatalytic degradation

Novel photocatalysts of phosphorus and sulfur co-doped graphitic carbon nitride incorporated in 2D TiO2 structure were successfully fabricated and applied for solar-driven degradation of emerging pollutants from the group of pharmaceuticals not susceptible to biodegradation. The hybrid photocatalysts with different loadings of (P, S)-doped g-C3N4 were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (DR/UV–vis), photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). The optimum (P, S)-doped g-C3N4/TiO2 (5 %) composite revealed improved photocatalytic activity towards the degradation of carbamazepine and acetaminophen. For CBZ, about 100 % degradation was achieved in less than 30 min of photodegradation, whereas for ACT, the complete removal was observed in 60 min of irradiation under simulated solar light. The multi-anion doped g-C3N4/2D TiO2 composite demonstrated an excellent synergy towards the degradation of CBZ and ACT with a synergy index of 1.35 and 1.62. Moreover, the mineralization efficiency measured as TOC removal was 76 % and 40 % for CBZ and ACT, respectively. The reactive oxygen species responsible for the degradation of selected pharmaceuticals are superoxide (O2–) and hydroxyl radicals (HO), and the kinetics of reactions proved to fit the first-order kinetics with a rate constant of 0.21 min−1 for CBZ degradation and 0.074 min−1 for ACT degradation. Our results suggest that (P, S)-doped g-C3N4/ 2D TiO2 heterostructure is a Z-scheme heterojunction, which can effectively separate photogenerated charge carriers. The emissions and decay times analyzed for single components and the optimal (P, S)-doped g-C3N4/ 2D TiO2 (5 %) composite confirmed interfacial charge transfer between TiO2 nanosheets and (P, S)-g-C3N4 and more effective separation of electron-hole pairs. Identification of carbamazepine and acetaminophen intermediates was performed using LC-MS analysis in combination with additional DFT calculations of the possible by-products formation. Regarding reusability, the photocatalytic activity of (P, S)-doped g-C3N4/ 2D TiO2 (5 %) was stable after subsequent cycles of carbamazepine and acetaminophen degradation.

Role of superoxide radical and singlet oxygen in peroxymonosulfate activation by iron-doped bone char for efficient acetaminophen degradation

Bone char is a hydroxyapatite-rich product obtained by calcining animal bones. However, the role of inorganic hydroxyapatite is often overlooked in bone char-catalyzed persulfate systems. In this work, iron was doped into swine bone-derived biochar (Fe-BC) by simple impregnation, and the Fe-BC catalysts were used for the first time to activate peroxymonosulfate (PMS). The obtained Fe-BC/PMS system could rapidly degrade the target pollutants (0.0529 s−1, 90 s) employing singlet oxygen (1O2) as the dominant reactive oxygen species (ROS). The characterization results demonstrated that iron was mainly intercalated into the catalyst by substituting calcium sites in swine bone biochar, and the Fe-BC composition was significantly affected by annealing temperature. A comprehensive study including quenching experiments, electron paramagnetic resonance (EPR), chemical probes, and linear sweep voltammetry (LSV) revealed that 1O2 was the dominant ROS. According to the characterization results, 1O2 was generated from the conversion of superoxide radical (O2•−) and the self-dissociation of PMS. Iron was the main active site of Fe-BC catalysts, and the carbon defects and oxygen-containing groups also played roles in catalyzing PMS. The Fe-BC/PMS system exhibited outstanding oxidative capability over a wide pH range (3.0–9.0) and was resistant to interference from some high concentrations of anions (Cl−, NO3–, and SO42−). This work provides a new perspective on using animal bone-derived biochar catalysts in advanced oxidation processes.

A novel BN/TiO2/HNT nanocomposite for photocatalytic applications fabricated by electrospinning

Here, we fabricated non-toxic composite nanofibers by including controlled amounts of boron nitride (BN) nanosheets (5 %), titanium oxide (TiO2) nanofibers and halloysite nanotubes (HNT) with the aim of obtaining a good catalyst for acetaminophen (ACT) degradation. After annealing at 400 °C under air, we characterized the samples’ morphological, structural, and optical features by scanning and transmission electron microscopy, Brunauer-Emmet-Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Under visible light, BN/TiO2/HNT nanocomposite (5 % of BN nanosheets and 5 % of TiO2) degraded more than 98 % of acetaminophen after 3 h. Moreover, the BN/TiO2/HNT nanocomposite could be used for five cycles without significant changes in acetaminophen degradation rate. The acute toxicity and scavenging tests to monitor the formation of by-products and reactive species showed that OH•-, O2•-, and h+ played a major role in acetaminophen degradation. These results indicate that BN/TiO2/HNT composite nanofibers can be used for photodegradation and open new prospects for developing tunable photocatalysts.

Electrocatalytic ultrafiltration membrane reactors designed from dry-spun self-standing carbon nanotube sheets

The development of electrochemically active ultrafiltration membrane reactors offers promising perspectives to achieve simultaneous separation and degradation of persistent organic pollutants and support triggered self-cleaning of membrane materials upon surface fouling. Here, electro-responsive ultrafiltration membranes were synthesised from drawable carbon nanotubes (CNT) dry-spun as ultra-thin sheets onto preformed carbon nanofibre (CNF) supports to generate a unique class of electrically conductive and flexible ultrafiltration membranes. The pore size of the CNT-based membranes, on the order of ∼ 28 nm, was fine-tuned by controlling the dry layering and orientation of the CNT sheets to manage the membrane selectivity. The CNT-based membranes were used as effective conductive platforms to promote charge transfer during electrocatalytic degradation of acetaminophen, as a model contaminant. The CNT-based membranes, besides offering water permeance up to 2.77 × 103 L.m−2.h−1.bar−1, yielded electrocatalytic kinetic constant up to 46.5 × 10−3 min−1 during combined electrochemical reaction and ultrafiltration process, which is 1.4 to 39 times larger than previously reported values. Such high performance was maintained quite stable even after 8 reuse cycles. These results demonstrate the potential of CNT dry spinning technology for the scalable fabrication of highly permeable, but selective CNT-based membranes with remarkable electrochemical properties towards cost-effective water treatment at an exceptional reaction rate.

Schottky-like photo/electro-catalytic carbon nanotube composite ultrafiltration membrane reactors

Stimuli-responsive membrane reactors offer advanced strategies towards simultaneous separation and degradation of persistent organic contaminants, allowing for triggered response through photo or electro stimuli. However, the scalable fabrication of stimuli-responsive nanoporous membranes with high selectivity and catalytic reactivity is still challenging in practical application. Here, photo-electro responsive membranes were designed by assembling carbon nanotubes (CNT) scaffolds decorated with conformal nanoscale SnO2 coatings. The membranes, built from spinnable CNT materials supported the generation of a unique class of ultrathin and flexible ultrafiltration membranes with thicknesses down to 25 nm and pore size as narrow as ∼20 nm. The CNTs were used as effective conductive photosensitizers to promote charge transfer from the graphitic to the SnO2 layer, supporting synergistic effects arising from generated Schottky-like diodes to improve the photo/electro-catalytic activity of nanocomposite membranes. The SnO2-CNT membranes exhibited high water permeance of 2.24 × 103 L m−2 h−1.bar−1, and faster reaction kinetics of 77.6 × 10−3 for acetaminophen degradation, which was 2–10 times higher than the kinetics achieved by currently available catalytic membrane reactors. The structural stability and outstanding performance of SnO2-CNT membranes were maintained over 8 reuse cycles with ∼99% degradation efficiency against acetaminophen in 60 min. The unique solid-state fabrication method of uniformly coated catalytic metal oxide on well aligned CNTs provides a scalable feasible approach to produce high-performance ultrafiltration photo/electro-catalytic membrane reactors towards cost-effective water purification at a competent reaction rate.

Design and synthesis of TiO2/Ti3C2 composites for highly efficient photocatalytic removal of acetaminophen: The relationships between synthesis parameters, physicochemical properties, and photocatalytic activity

In this study, we report the potential of TiO2/Ti3C2 composite fabricated by oxidation of MXene for degradation of persistent organic pollutants. The effect of the synthesis conditions (time, temperature, and reaction environment) on the morphology, physicochemical properties, and photocatalytic activity was investigated. It was found that acetaminophen degradation was positively correlated with TiO2 content in the composite structure. Furthermore, the findings confirmed that the synthesis reaction environment strongly influenced the obtained materials photocatalytic activity. The TiO2/Ti3C2 composite obtained by solvothermal route in the presence of hydrochloric acid and ammonium fluoride exhibited the highest efficiency towards acetaminophen degradation than other composite materials, for which ACT removal reached 92 % within 60 min of irradiation under simulated solar light. The improved photocatalytic performance can be attributed to the presence of anatase-rutile polymorphs exposing highly active { 0 0 1} and { 1 0 1} facets coupled with MXene. Superoxide anion radicals and hydroxyl radicals played a major role in ACT degradation. Moreover, 3-hydroxyacetaminophen was detected as the first intermediate of ACT degradation, leading quickly to aromatic ring opening and production of aliphatic acids. Overall, this work provides an effective strategy for designing novel and efficient MXene-based photocatalysts for the degradation of emerging contaminants in water systems.

Fabricating metal-free Z-scheme heterostructures with nitrogen-deficient carbon nitride for fast photocatalytic removal of acetaminophen

Photocatalytic technology has been increasing explored for the elimination of pollutants from aquatic environments. However, constructing powerful photocatalyst to drive rapid decontamination remains challenging. Here, we assemble boron-doped nitrogen-deficient carbon nitride (BNCN) into metal-free Z-scheme heterojunction via a facile approach to boost photocatalytic degradation of acetaminophen. Incorporating boron dopants and nitrogen defects to C3N4 significantly increase the photoabsorption. Furthermore, the constructed heterojunction exhibited decreased band gap and remarkably enhanced separation efficiency of photogenerated carriers compared with individual BNCN. Owing to the modulation of band structures and the better separation of photogenerated carriers, acetaminophen conversion approaching 100 % was achieved in just 30 mins under simulated sunlight, outperforming equivalent quantities of bulk carbon nitride and commercial TiO2 by 3.1 and 2.7 times, respectively. Two possible photodegradation pathways were proposed with hydroxylation and ring-opening reactions as dominant degradation reactions. Our findings provide an instructive catalyst design strategy to boost photocatalytic degradation efficiency.

Ti–N coordination bonds boost Z-scheme interfacial charge transfer in TiO2/C-deficient g-C3N4 heterojunctions for enhanced photocatalytic phenolic pollutant degradation

Rational designing of chemical bond-bridged TiO2-based Z-scheme heterojunctions and deep understanding mechanism of significantly enhanced visible-light photocatalytic performance of the heterojunctions is a hotspot in photocatalysis. Herein, a defect-engineering strategy is developed to fabricate Ti–N coordination bond-bridged TiO2/C-deficient g-C3N4 heterojunctions (TiO2/VC-CN), and the preparation process includes formaldehyde-assisted preorganization of molten urea in the presence of titanium isopropoxide followed by thermal condensation. The detailed characterization results evidence the formation of a unique atomic-level heterojunction contact interface via Ti–N coordination bonds in TiO2/VC-CN, in which N atoms around the C vacancies of g-C3N4 donate electrons to unoccupied Ti 3d orbitals of TiO2. At the optimal TiO2 doping level, the TiO2/VC-CN heterojunctions exhibit remarkably high visible-light photocatalytic oxidation performance in the degradation of recalcitrant phenolic pollutants, methylparaben and acetaminophen, which outperforms commercially available P25 TiO2, as-prepared anatase TiO2 and bulk g-C3N4. The experimental results combined with theoretic calculations reveal that the outstanding interfacial Ti–N coordination bonding remarkably boosts the direct Z-scheme charge carrier transfer in the TiO2/VC-CN heterojunctions, which results in the generation of plentiful reactive oxidation species including O2−, OH and 1O2 for efficient removal of the target pollutants.

Green Synthesis of Silver-Doped Titanium Dioxide Nanostructures for Acetaminophen Degradation Under Solar Radiation

Objective: In this paper, the photocatalytic degradation of acetaminophen was evaluated using silver-doped titanium dioxide nanoparticles in a cylindrical-parabolic composed photoreactor. Materials and methods: Titanium dioxide was synthesized via green synthesis using Cymbopogon citratus leaf extract and doped by silver photodeposition. Results and discussion: Morphological information shows that large agglomerates of approximately 49 nm can be attributed to the strong interaction between nanoparticles and their polycrystalline nature. The photodeposition of metallic silver reduces the surface effects, allowing a decrease in the electrostatic interaction and diameter size of the titanium dioxide, as well as the optical properties due to surface poising during the reduction of silver ions to metallic silver. The photocatalytic activity was performed to degrade acetaminophen as the drug model under visible-light radiation. The results are promising, with superior photodegradation of acetaminophen of approximately 37% and 11% for unmodified titanium dioxide and silver-doped titanium dioxide (0.75 at%) nanostructures compared to the commercial photocatalyst, respectively. Conclusions: Accordingly, the potential photocatalytic application of silver-doped titanium dioxide nanostructures is highlighted and represents a promising alternative for the photodegradation of organic compounds from wastewater eluents.

Influence of water matrix components on the UV/chlorine process and its reactions mechanism

The UV/chlorine system has become an attractive alternative Advanced Oxidation Process (AOP) for the removal of recalcitrant pollutants in the last decade due to the simultaneous formation of chlorine and hydroxyl radicals. However, there is no consensus regarding the results and trends obtained in previous micropollutant removal studies by AOPs, highlighting the complexity of the UV/chlorine process and the need for further research. This study investigates the degradation of acetaminophen (ACTP) by UV/chlorine and the effects of the water matrix in the reaction kinetics. In particular, the effects of natural organic matter (NOM), alkalinity and mineral salts on the kinetics and reactive species were elucidated. The complexity of the system was revealed by the analysis of the radical generation and transformation in different water matrices, applying the kinetic modelling approach to complement the scavenger tests.The higher kinetic rates of ACTP at alkaline pH provided new insights into the chlorine reactions under UV radiation, where secondary and tertiary reactive oxygen species including ozone were proven to play the major role in degradation. On the contrary, at acidic pH, reaction kinetic modelling demonstrated that ClO• radical occurs at high concentrations in the order of 10−10 M, being therefore the main oxidant, followed by other chlorine radicals. It is noteworthy that at alkaline pH the presence of typical inorganic ions such as carbonate had little impact on ACTP degradation, contrary to the observed reduction of degradation rates at acidic pH. The expected detrimental effect of the NOM in AOPs was also evidenced, although the use of chlorine as radical source reduces the relevance of the inner filter effect in comparison to UV/H2O2.

Degradation of acetaminophen using persulfate activated with P-doped biochar and thiosulfate

• Acetaminophen was rapidly degraded in persulfate/P-doped biochar/thiosulfate system. • A synergistic effect existed among persulfate, p-doped biochar and thiosulfate. • Electron transfer could be responsible for the degradation of acetaminophen. • The system maintained high removal efficiency in the water from difference sources. In the study, p-doped biochar (PBC) was prepared by the pyrolysis of H 3 PO 4 -impregnated cyanobacteria and used together with thiosulfate (TS) to activate persulfate (PS) for the degradation of acetaminophen (ACP). The biochar was characterized and the results showed that H 3 PO 4 treatment had a pronounced effect on the surface structure and chemical composition of biochar. ACP (0.05 mmol/L) could be completely removed within 90 min under the optimal conditions: 2.0 mmo/L of PS, 0.1 g/L of PBC and 2.0 mmol/L of TS. A synergistic effect existed among PS, PBC and TS. The PS/PBC/TS system maintained high removal efficiency for ACP in the water from difference sources and Cl - (< 2.0 mmol/L) had little effect on it. Quenching experiments, electron paramagnetic resonance measurements and ion analysis revealed that free radicals (SO 4 • − and •OH) and singlet oxygen were not the main reactive species and biochar-mediated electron transfer could be responsible for the degradation of ACP. This work provides a novel method for the degradation of pharmaceutical and personal care products through non-radical pathway and will be benefit for the development of efficient persulfate-based advanced oxidation processes.

Cyano group modified graphitic carbon nitride with K intercalation for sustainable photodegradation of pharmaceutical waste

BackgroundPharmaceutical and personal care product (PPCP) pollutants in the aquatic environment are worrying as the conventional treatment processes are challenging due to the low molecular weight and strong hydrophilicity of PPCPs. The nontoxic g-C3N4 is highly promising for sustainable environmental remediation but suffers from key bottlenecks of rapid charge recombination and poor light absorption capacity. MethodsPotassium-intercalated g-C3N4 (K-CN) was prepared by a facile alkali and heat treatment with varying KOH concentrations. Significant findingsThe photocatalytic performance of g-C3N4 was significantly improved where the best acetaminophen degradation efficiency and the corresponding pseudo-first-order rate constant over 1.2K-CN were 2.51-fold and 5.29-fold higher relative to pristine g-C3N4. This is ascribed to the formation of cyano group and intercalation of K atoms in g-C3N4, which were corroborated through various characterization techniques to reveal the greater light absorbance, narrowed band gap, effective charge transfer, and suppressed electron-hole recombination. Furthermore, superoxide anions (•O2−) were verified to be the leading reactive species for acetaminophen photodegradation, followed by photoinduced holes (h+) and hydroxyl (•OH) radicals. Overall, this work provides a simple yet effective approach to boost the performance of g-C3N4 and is anticipated to initiate further research in sustainable pharmaceutical wastewater degradation.

Synthesis, Characterization, and Application of Pt/PtO2-TiO2/SiO2 Materials on a Continuous Flow Packed Bed Microreactor for Enhanced Photocatalytic Activity under Sunlight

The present work aimed at the development of Pt-TiO2/SiO2 materials applied to the degradation of a pharmaceutical pollutant in a fixed-bed microreactor in continuous mode. First, a wide investigation of the optimal platinum content in TiO2/SiO2 was carried out based on extensive characterization through XRD, DRS, SEM, TEM, and XPS techniques. For the content range studied, no significant changes were observed in the crystallinity of the material, with peaks related to the anatase phase and PtO2 in the diffractograms. SEM images combined with EDS spectra indicated the presence of platinum and a large heterogeneity in the particles. MET analyses showed PtO2 nanoparticles in close contact with TiO2, allowing the formation of a type II heterojunction. XPS showed platinum in the 0 and +4 oxidation states, suggesting that platinum metal and PtO2 are both present. Regarding the degradation experiments, the optimal catalyst achieved 81% degradation of acetaminophen for a residence time of 1 h, while the catalyst without platinum reached only 27% degradation. The catalyst activity dropped from 81 to 57% in 2 h and remained stable for six reuse cycles. Increasing the inlet flow rate and concentration reduced the pollutant degradation although there was an increase in the reaction rate. Finally, a photocatalytic mechanism was proposed in which a type II heterojunction was developed, with generation of hydroxyl radicals by the positive holes in the VB of TiO2 as well as superoxide radicals by the electrons in the CB of PtO2.

Investigation of CuCoFe-LDH as an efficient and stable catalyst for the degradation of acetaminophen in heterogeneous electro-Fenton system: Key operating parameters, mechanisms and pathways

Pharmaceuticals, as anthropogenic pollutants in a wide range of water sources, generally require specific treatment methods for degradation. A trimetallic layered double hydroxide (CuCoFe-LDH) was successfully fabricated by coprecipitation and applied as a novel heterogeneous electro-Fenton (EF) catalyst for the degradation of acetaminophen (ACT) from aqueous environments. The EF experiments showed that the CuCoFe-LDH/EF process achieved 100% of ACT degradation efficiency within 60 min at pH = 5, catalyst dosage of 0.50 g/L, current density of 10 mA/cm2 and initial ACT concentration of 20 mg/L. An impressive (>80%) mineralization of ACT was obtained over a wide pH range (pH 3–9) after 180 min. Meanwhile, the role of ·OH and O2.- were certified by radical quenching experiments and electron paramagnetic resonance (EPR) analysis. Through mechanism exploration, the coexistence of Cu and Co on Fe-based LDHs can accelerate the interfacial electron transfer and promote the formation of the reactive oxygen species (ROS), thus facilitating the EF process. Furthermore, the degradation by-products and possible degradation pathways of ACT in the CuCoFe-LDH/EF process were proposed. The reusability test and the treatment of various typical organic pollutants experiments indicated that the CuCoFe-LDH/EF process has excellent stability and broad application prospects. This work provides a valuable reference for the treatment of pharmaceuticals by the heterogeneous EF process in a wide range of pH.

Mechanistic study for enhanced photocatalytic degradation of acetaminophen by Fe(III) doped TiO2 hollow submicrospheres

The Fe (III) ions incorporated into TiO2 hollow submicrospheres are an excellent photocatalyst that could improve the catalyst activity by varying experimental parameters like controlling the flow rate, rotation speed, and contaminant concentration. Fe-TiO2 hollow submicrospheres with different Fe wt% in TiO2 were prepared. Our studies revealed that 2.5 wt% Fe-TiO2 has the best photocatalyst activity to generate strong oxidizing hydroxyl radicals during the photocatalytic degradation reaction. Ex-situ L and K-edge of Ti and Fe X-ray absorption near edge structure (XANES) spectra showed that Fe3+ ions in the 2.5 wt% sample produced more structural distortions in the TiO6 octahedral symmetry. Further, in-situ XANES Ti and Fe 3d spectral changes above the Fermi level (EF) revealed an increased electron charge transfer attributed to the Fe 3dz2- O 2pz orbital hybridization. Fe(III) doping not only increases the interaction between transition metal (Fe and Ti) 3d orbitals in TiO2, but also promotes the Fe(III)/Fe(II) redox kinetics and the associated photo-Fenton degradation of acetaminophen. Taking advantage of the magnetic property of the catalyst, the samples can be effectively recycled by applying a magnetic field.