Degradation Of Acetaminophen Research Articles

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.

Molten-salts assisted preparation of iron-nitrogen-carbon catalyst for efficient degradation of acetaminophen by periodate activation

Highly efficient and stable heterogeneous catalysts were desired to activate periodate (PI) for sustainable pollution control. Herein, iron-nitrogen-carbon catalyst was synthesized using a facile molten-salts mediated pyrolysis strategy (denoted as FeNC-MS) and employed to activate PI for the degradation of acetaminophen (ACE). Compared with iron-nitrogen-carbon catalyst prepared by direct pyrolysis method (marked as FeNC), FeNC-MS exhibited superior catalytic activity due to its large specific surface area (1600 m2 g−1) and the abundance of FeNx sites. The batch experiments revealed that FeNC/PI process achieved 37 % ACE removal within 20 min, while ACE removal in FeNC-MS/PI process was 98 % under the identical conditions. Integrated with electron paramagnetic resonance tests, quenching experiments, chemical probe identification, and electrochemical experiments, we demonstrated that FeNC-MS-PI complexes-mediated electron transfer was the predominant mechanism for the oxidation of ACE. Further analysis disclosed that FeNx sites in FeNC-MS were the main active sites for the activation of PI. Additionally, FeNC-MS/PI process exhibited significant resistance to humic acid and background electrolyte, and avoided the secondary pollution imposed by Fe leaching. The possible degradation pathways of ACE were proposed. The germination experiments of lettuce seeds showed that the ecotoxicity of ACE solution was significantly reduced after treatment with FeNC-MS/PI process. Overall, this study provided a facile strategy for the synthesis of efficient iron-nitrogen-carbon catalysts and gained fundamental insight into the mechanism of PI activation by iron-nitrogen-carbon catalysts for pollutants degradation.

Boosted Activity of g-C3N4/UiO-66-NH2 Heterostructures for the Photocatalytic Degradation of Contaminants in Water.

The combination of graphitic carbon nitride and the metal-organic framework UiO-66-NH2 has been developed with the aim to enhance the photocatalytic activity of pure semiconductors. Different proportions of g-C3N4 and UiO-66-NH2 were combined. Complete characterization analysis of the resulting photocatalytic materials was conducted, including N2 adsorption isotherms, XRD, FTIR, STEM-EDX microscopy, DRS-UV-visible, and photoluminescence. The photocatalytic activity was tested in an aqueous solution for the removal of acetaminophen as the target pollutant. From the obtained results, less than 50% of UiO-66-NH2 incorporated in the g-C3N4 structure enhanced the photocatalytic degradation rate of both bare semiconductors. Concretely, 75% of g-C3N4 in the final g-C3N4/UiO-66-NH2 heterostructure led to the best results, i.e., complete acetaminophen elimination initially at 5 mg·L-1 in 2 h with a pseudo-first order rate constant of ca. 2 h-1. The presence of UiO-66-NH2 in the g-C3N4 enhanced the optoelectronic properties, concretely, the separation of the photo-generated charges was improved according to photoluminescence characterization. The better photo-absorption uptake was also confirmed by the determination of the quantum efficiency values of the heterostructure if compared to either pure g-C3N4 or UiO-66-NH2. This photocatalyst with the best activity was further tested at different pH values, with the best degradation rate at a pH close to the pHpzc ~4.15 of the solid. Sequential recycling tests demonstrated that the heterostructure was stable after five cycles of use, i.e., 15 h. A high contribution of photo-generated holes in the process of the degradation of acetaminophen, followed marginally by superoxide radicals, was suggested by scavenger tests.

Heterogeneous Activation of Persulfate by Activated Carbon for Efficient Acetaminophen Degradation: Mechanism, Kinetics, Mineralization, and Density Functional Theory

AbstractPharmaceutical compounds attracted environmentalists according to their unknown impact on the ecosystem and the increase in their demand. Acetaminophen (ACT) or paracetamol has been detected more than the natural concentration value. To avoid the negative impact of the ACT accumulation into the environment, many treatment techniques have been applied. Among them, advanced oxidation process (AOP) techniques have shown high efficiency to remove ACT. In this study, the ability of AC to catalyze PS by its functional group was evaluated, and the degradation efficiency of ACT was determined by using an activated carbon (AC)/persulfate (PS) system. In addition, the mechanism, kinetics, mineralization, and the density functional theory were also investigated. HPLC was used to measure ACT concentration, and the optimum results in this work were 100 % degradation within 3 minutes at catalysts concentrations AC 8.25 mM/PS 1.65 mM at pH 7 and the mineralization were 24 % after 90 min of reaction. And the degradation pathway of ACT was built based on density functional theory. This study will contribute to clarifying the role of carbon catalysts in the PS oxidation of pollutants. The degradation of ACT by using an AC/PS system is recommended because of the high degradations efficiency, non‐toxic by‐products, and environmentally friendly.

Simultaneous degradation of amoxicillin, ciprofloxacin and acetaminophen in a mixture by ozonation: Kinetics and mechanisms pathway

The treatment of pharmaceutical wastewater is challenging as it contains multiple pollutants and complex in nature. The conventional treatment methods are insufficient and it is essential to adopt advanced techniques for effective treatment. This study investigates the simultaneous degradation of a mixture of pollutants -amoxicillin (AMX), acetaminophen (ACET), and ciprofloxacin (CIP) from an aqueous solution by ozonation. High-performance liquid chromatography and liquid chromatography-mass spectrometry equipped with electrospray ionization (LC-ESI-MS) were employed for analysis. The experiments were conducted by varying the operating conditions such as ozone dose (1–5 mg/L), pH (3–9) and time (0–25 min) respectively. The mixture of each pollutant (5 mg/L) was removed maximum at the optimum condition of ozone dose: 4 mg/L, pH-9 and reaction time was found to be within 5 min. The experimental results indicate that the ozonation has a higher degradation potential even though the aqueous solution contains multiple pollutants and the simultaneous degradation of AMX, ACET and CIP was found to be 98%, 98.5% and 99% respectively at 2 min. The mineralization of these compounds was observed at 89%. The degradation byproducts formed during the ozonation were identified using LC-ESI-MS. Further, the degradation mechanism and possible pathway of targeted pollutants were reported.

Effect of kinetics on the photocatalytic degradation of acetaminophen and the distribution of major intermediate with anatase-Ag synthesized by sol gel under visible irradiation

The degradation of acetaminophen (ACET) was studied with TiO2-Ag catalysts, whose predominant crystalline phase was anatase, synthesized by the sol–gel method and doped by photo-deposition under UV radiation with silver particles. The catalyst was characterized by energy dispersive X-ray fluorescence (EDXRF) and X-ray diffraction (DRX). The acetaminophen degradation was determined by high-performance liquid chromatography (HPLC) and total organic carbon (TOC). The reaction behavior was studied under the Langmuir–Hinshelwood (LH-HW) equation and in a TOC-based model. With the experimental data, mass balances were performed to introduce the constants (reaction and adsorption kinetics) to the LH-HW equation. With the analysis of the generation and consumption behavior of the organic intermediate compounds (OI), coupled differential equations were generated, which express the degradation and formation-consumption behavior. The kinetic constants were obtained by nonlinear regression using the Levenberg–Marquardt equation. The results show high removal percentages, and the behavior of the experimental data is assumed to fit the LH-HW equation. The analysis of the organic intermediates by solid phase micro-extraction (SPE), HPLC and gas chromatography (CG-MS), shows that the transformation is feasible under the formation of nitro-aromatic derivatives and hydroxylated species.

Electrocatalytic performance of oxygen-activated carbon fibre felt anodes mediating degradation mechanism of acetaminophen in aqueous environments.

Carbon felts are flexible and scalable, have high specific areas, and are highly conductive materials that fit the requirements for both anodes and cathodes in advanced electrocatalytic processes. Advanced oxidative modification processes (thermal, chemical, and plasma-chemical) were applied to carbon felt anodes to enhance their efficiency towards electro-oxidation. The modification of the porous anodes results in increased kinetics of acetaminophen degradation in aqueous environments. The utilised oxidation techniques deliver single-step, straightforward, eco-friendly, and stable physiochemical reformation of carbon felt surfaces. The modifications caused minor changes in both the specific surface area and total pore volume corresponding with the surface morphology. A pristine carbon felt electrode was capable of decomposing up to 70% of the acetaminophen in a 240min electrolysis process, while the oxygen-plasma treated electrode achieved a removal yield of 99.9% estimated utilising HPLC-UV-Vis. Here, the electro-induced incineration kinetics of acetaminophen resulted in a rate constant of 1.54 h-1, with the second-best result of 0.59 h-1 after oxidation in 30% H2O2. The kinetics of acetaminophen removal was synergistically studied by spectroscopic and electrochemical techniques, revealing various reaction pathways attributed to the formation of intermediate compounds such as p-aminophenol and others. The enhancement of the electrochemical oxidation rates towards acetaminophen was attributed to the appearance of surface carbonyl species. Our results indicate that the best-performing plasma-chemical treated CFE follows a heterogeneous mechanism with only approx. 40% removal due to direct electro-oxidation. The degradation mechanism of acetaminophen at the treated carbon felt anodes was proposed based on the detected intermediate products. Estimation of the cost-effectiveness of removal processes, in terms of energy consumption, was also elaborated. Although the study was focussed on acetaminophen, the achieved results could be adapted to also process emerging, hazardous pollutant groups such as anti-inflammatory pharmaceuticals.

N-doped TiO2 nanotubes synthesized by atomic layer deposition for acetaminophen degradation

Titanium dioxide (TiO2) is widely used in photocatalysis applications for wastewater treatment. Investigations demonstrated that titanium dioxide structure strongly contributes to increase micropollutant degradation efficiency. Indeed, pollutant degradation rates are enhanced when using photocatalysts with highly ordered structures and high specific surface area, such as TiO2 nanotubes (NTs) synthesized by atomic layer deposition (ALD). Here, TiO2 NTs, fabricated by ALD followed by nitrogen doping via thermal treatment, were compared with TiO2 nanofibers (NFs), prepared by electrospinning. Their morphology and structure were investigated by scanning and transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Photoluminescence measurements showed that TiO2 NT photoluminescence intensity was lower than that of TiO2 NFs, due to lower electron-hole pair recombination, and consequently their degradation efficiency was higher. As the surface to volume ratio was higher in TiO2 NTs than NFs, the rate of non-radiative surface recombination also was higher in TiO2 NTs. Comparison of their performance for photocatalytic degradation of acetaminophen showed higher degradation activity with TiO2 NTs than TiO2 NFs. TiO2 NT doping with nitrogen (N-TiO2 NTs) further enhanced their photocatalytic activity that was 5 times higher than that of TiO2 NFs (degradation rates: 0.05 and 0.01 mg.L−1.min−1, respectively). The N-TiO2 NT photocatalyst was stable after four cycles of acetaminophen degradation. Acute toxicity assays confirmed the release of harmful by-products during the first hours of acetaminophen degradation, but toxicity strongly decreased after 5 h.

Establishing a high-speed electron transfer channel via CuS/MIL-Fe heterojunction catalyst for photo-Fenton degradation of acetaminophen

Active pharmaceutical pollution has become “a new force” of water pollution, and a high-efficiency process is urgently required to remove it. Herein, the CuS/MIL-Fe heterojunction catalyst with high-speed electron transfer channel is designed by adjusting the energy band and regulating the direction of electron transfer, which exhibits excellent acetaminophen (APAP) removal ability in photo-Fenton reaction. The charge transfer pathway of heterojunction is identified by X-ray photoelectron spectroscopy analysis and density functional theory (DFT) calculation, which provides the evidence of electron transfer from CuS to MIL-101(Fe) at the heterointerface. Meanwhile, kelvin probe force microscopy measurement indicates that photogenerated electrons can be easily transported through the CuS/MIL-Fe interface. The close contact interface and high charge transfer conductivity realize the synergistic effect of photo and Fenton degradation by establishing high-speed electron transfer channel. This study will open up a new insight into the application of heterojunction photo-Fenton technology in environmental remediation.

Sodium tetraborate simultaneously enhances the degradation of acetaminophen and reduces the formation potential of chlorinated by-products with heat-activated peroxymonosulfate oxidation

In this study, sodium tetraborate (Na2B4O7) was introduced to enhance the degradation of acetaminophen (ACT) in heat-activated peroxymonosulfate (PMS) process. The elimination of ACT in Na2B4O7/heat/PMS process followed the pseudo-first order kinetics. The corresponding kobs value with 10 mM Na2B4O7 was 33.1 times higher than that in heat/PMS process. 1O2 and HO· were identified as primary reactive species via quenching experiments and electron paramagnetic resonance technology. B(OH)4−, the hydrolysis product of Na2B4O7, reacted with PMS to generate HOOB(OH)3−. 1O2 was generated by the self-decomposition of PMS using B(OH)4− as catalyst, while HO· was produced via the breakage of peroxide bond of PMS and HOOB(OH)3−under high temperature. ACT was degraded by reactive species via the pathways of -NH- bond breakage, -OH replacement, -NH2 oxidation and benzene ring cleavage. Nine transformation intermediates were detected by LC/Q-TOF/MS, and the toxicity of reaction solution decreased significantly with the elimination of ACT. Increasing Na2B4O7 dosage, PMS concentration, initial pH and reaction temperature were conducive to ACT elimination. Humic acid, Cl− and CO32− inhibited the degradation of ACT heavily, while SO42− and NO3− had the negligible effects. Moreover, B(OH)4− could react with free chlorine to the inert B(OH)3OCl− and further significantly suppress the formation of chlorinated by-products for the treatment of Cl−-containing water in Na2B4O7/heat/PMS process. This study provided an effective way to enhance the oxidation capacity of heat/PMS process and suppress the formation of chlorinated by-products in chloride-containing water, and the findings had important implications for using borate buffer in the studies of PMS-based advanced oxidation processes.

Novel composite of Zn/Ti-layered double hydroxide coupled with MXene for the efficient photocatalytic degradation of pharmaceuticals

In the present study, a hybrid photocatalyst of Zn/Ti layered double hydroxide (LDH) coupled with MXene – Ti3C2 was synthesized for the first time and applied in photocatalytic degradation of acetaminophen and ibuprofen, two commonly present in the natural environment and prone to accumulate in the aquatic ecosystem pharmaceuticals. The effect of MXene content (0.5 wt%, 2.5 wt%, and 5 wt%) on the photocatalytic activity of LDH/MXene composite was investigated. The composite of LDH/MXene containing 2.5 wt% of MXene revealed the highest photocatalytic activity in the degradation of acetaminophen (100% within 40 min) and ibuprofen (99.7% within 60 min). Furthermore, an improvement in acetaminophen and ibuprofen mineralization was observed for the composite material. Meanwhile, the introduction of interfering ions (Na+, Ca2+, Mg2+, Cl−, SO42−) in the model seawater did not affect the removal efficiency of both pharmaceuticals. The photocatalytic experiment performed in the four subsequent cycles, as well as FTIR, TEM, and XPS analyses after the photodegradation process confirmed the excellent stability and reusability of the prepared composite material. In order to evaluate the effect of various reactive oxidizing species (ROS) on the photocatalytic process, the trapping experiment was applied. It was noticed that •O2− had the main contribution in photocatalytic degradation of acetaminophen, while •OH and h+ mainly affected the degradation of ibuprofen. Finally, based on the results of Mott Schottky analysis, bandgap calculation, and ROS trapping experiment, the possible mechanism for pharmaceuticals degradation was proposed. This research illustrates the feasibility and novelty of the treatment of pharmaceuticals by LDH/MXene composites, implying that MXene plays a significant role in the electron-hole separation and thus high photocatalytic activity.

Synthesis of a reusable magnetic photocatalyst based on carbon xerogel/TiO2 composites and its application on acetaminophen degradation

This work describes the production photocatalyst in two steps, (1) production of N-CXTi nanocomposites by sol-gel polymerization of resorcinol-formaldehyde-melamine in the presence of K2TiF6 inorganic metallic salt with TiO2 as precursor; (2) Synthesis of the Fe3O4/N-CXTi and Fe3O4/SiO2/N-CXTi nanocomposites by mechanical mixing of N-CXTi and magnetic nanoparticles. The magnetic nanoparticles (Fe3O4 and Fe3O4/SiO2) were prepared by a chemical co-precipitation method and subsequent functionalization by silica (SiO2). The materials were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, X-ray diffractometry, and textural properties. The composites presented a morphology heterogeneous structure and the presence of two phases for the introduction of TiO2. The region was formed by amorphous carbon and carbon spheres, where Ti is detected only immersed in the amorphous carbon particles, in the anatase and rutile phase, and the presence of magnetic nanoparticles is located surrounded by the carbon structure. Results for the recovery and reuse of the photocatalyst Fe3O4/SiO2/N-CXTi presented the highest efficiency in the removal of the acetaminophen (APP) in the aqueous medium; the result of the reaction carried out in the presence of ultraviolet irradiation showed that the magnetic photocatalyst removed 99.2% of APP in an aqueous medium. Results for the recovery and reuse of the photocatalysts for nine consecutive reactions showed that they can be separated from the reaction medium in a simple and fast way, without significant losses of photocatalytic efficiency and excellent recovery of the photocatalyst.

Role of N-Doping and O-Groups in Unzipped N-Doped CNT Carbocatalyst for Peroxomonosulfate Activation: Quantitative Structure–Activity Relationship

We examined the relationship between the intrinsic structure of a carbocatalyst and catalytic activity of peroxomonosulfate (PMS) activation for acetaminophen degradation. A series of nitrogen-doped carbon nanotubes with different degrees of oxidation was synthesized by the unzipping method. The linear regression analysis proposes that pyridinic N and graphitic N played a key role in the catalytic oxidation, rather than pyrrolic N and oxidized N. Pyridinic N reinforce the electron population in the graphitic framework and initiate the non-radical pathway via the formation of surface-bound radicals. Furthermore, graphitic N forms activated complexes (carbocatalyst-PMS*), facilitating the electron-transfer oxidative pathway. The correlation also affirms that -C=O was dominantly involved as a main active site, rather than -C-OH and -COOH. This study can be viewed as the first attempt to demonstrate the relationship between the fraction of N-groups and activity, and the quantity of O-groups and activity by active species (quenching studies) was established to reveal the role of N-groups and O-groups in the radical and non-radical pathways.

The role of non-radical pathway in heterogeneous activation of persulfate and H2O2 by superparamagnetic magnetite-reduced graphene oxide nanocomposite

Superparamagnetic magnetite-reduced graphene oxide nanocomposite (Fe3O4-rGO) was synthesized by a one-pot solvothermal method and were characterized by XRD, TEM, FESEM, FTIR, XPS, and VSM analysis. The different systems such as PS/Fe3O4-rGO, H2O2/Fe3O4-rGO, and the combined system of PS + H2O2/Fe3O4-rGO were evaluated for acetaminophen (ACP) degradation under different pH conditions. The study showed the superior activity of PS/ Fe3O4-rGO over the other systems with >98% of ACP removal within 150 min in a wide pH range (3–10). The ACP removal and TOC reduction at acidic pH are as follows; PS/ Fe3O4-rGO > PS + H2O2/ Fe3O4-rGO > H2O2/ Fe3O4-rGO. The investigation of different reactive species involved in these systems showed the predominance of non-radical pathway over the radical pathway for the ACP degradation. The extensively reactive catalyst surface leads to further reactions of radicals to end up with less reactive species. Despite the lower reactivity, the abundance of O2•-, 1O2 are sufficient to carry out the ACP removal with good mineralization. The pathway of ACP degradation in the PS/Fe3O4-rGO system was proposed based on the HR-LC-MS/MS analysis. The applicability of PS/Fe3O4-rGO system was further confirmed by studying the removal of ACP from groundwater. In PS + H2O2/Fe3O4-rGO combined system, the addition of lower polar solvents such as ethanol and t-butanol acted as activity enhancer. Combining PS and H2O2 in the same system to gain more radicals is not a good strategy in terms of economical and reactivity aspects.

Deriving an ɑ-Fe2O3/g-C3N4 nanocomposite from a naturally hematite-rich soil, for dual photocatalytic and photo-Fenton degradation of Acetaminophen under visible light

In this study, a facile synthesis route was reported for the fabrication of an ɑ-Fe2O3@g-C3N4 (FeCN) photocatalyst, derived from a hematite-rich soil. Among the various as-made catalysts prepared using different weights of hematite, FeCN-0.5 showed the best catalytic performance in Acetaminophen (ACT) degradation under visible light irradiation with high mineralization efficiency. The superb activity of this photocatalyst results from a Z-scheme structure formation between ɑ-Fe2O3 and g-C3N4 that increased the light adsorption capacity, facilitated the generation of charge-carries, and increased the generated electrons that participated in Fe3+/Fe2+ cycles, thus enhancing the photo-Fenton reaction. UV–Vis diffuse reflection spectroscopy (DRS) and photoluminescence analysis (PL) confirmed the excellent separation of charge carriers in the as-made photocatalyst. The reaction rate of the FeCN-0.5/Vis/H2O2 process was around 3, and 7 times of that in the FeCN-0.5/Vis and FeCN-0.5/H2O2 processes respectively, which indicated the synergy effect of the involved processes in ACT degradation. Based on the radical trapping experiments, hydroxyl radical (HO∙) was the dominant reactive species in ACT degradation. The catalyst showed high stability in consecutive reuse cycles. Overall, this study provides new insights into the fabrication of novel materials derived from natural sources, suitable for their use in advanced oxidation processes.