Degradation Of Trimethoprim Research Articles

Comparison of TiO2 and ZnO for Heterogeneous Photocatalytic Activation of the Peroxydisulfate Ion in Trimethoprim Degradation.

The persulfate-based advanced oxidation process is a promising method for degrading organic pollutants. Herein, TiO2 and ZnO photocatalysts were combined with the peroxydisulfate ion (PDS) to enhance the efficiency. ZnO was significantly more efficient in PDS conversion and SO4•- generation than TiO2. For ZnO, the PDS increased the transformation rate of the trimethoprim antibiotic from 1.58 × 10-7 M s-1 to 6.83 × 10-7 M s-1. However, in the case of TiO2, the moderated positive effect was manifested mainly in O2-free suspensions. The impact of dissolved O2 and trimethoprim on PDS transformation was also studied. The results reflected that the interaction of O2, PDS, and TRIM with the surface of the photocatalyst and their competition for photogenerated charges must be considered. The effect of radical scavengers confirmed that in addition to SO4•-, •OH plays an essential role even in O2-free suspensions, and the contribution of SO4•- to the transformation is much more significant for ZnO than for TiO2. The negative impact of biologically treated domestic wastewater as a matrix was manifested, most probably because of the radical scavenging capacity of Cl- and HCO3-. Nevertheless, in the case of ZnO, the positive effect of PDS successfully overcompensates that, due to the efficient SO4•- generation. Reusability tests were performed in Milli-Q water and biologically treated domestic wastewater, and only a slight decrease in the reactivity of ZnO photocatalysts was observed.

Fabrication of novel 3D urchin-like mixed-phase TiO2 for efficient degradation of trimethoprim

Herein, we reported a novel sub-micron 3D urchin-like mixed-phase TiO2 with a desirable photocatalytic degradation performance. Scanning electron microscopy (SEM) shows that the urchin-like TiO2 is synthesized by a large number of one-dimensional conical monomers. X-ray diffraction (XRD) and Raman spectra revealed the formation of the anatase/rutile mixed-phase. Moreover, the 3D Urchin-like mixed-phase TiO2 can effectively photocatalytic degrade 95% trimethoprim within 90 min at a concentration of 15 mg/L, which is superior to commercial 25 nm grade rutile TiO2.

Efficient biodegradation of trimethoprim and transformation mechanism using the photoelectrocatalytic system

In this study, the coupling of a three-electrode photocatalytic microbial fuel cell system (PMFC) was established for trimethoprim (TMP) degradation, to achieve efficient degradation and electrical energy production simultaneously. The photocatalytic bioanode, degradation performance, electrochemical characteristics and microbial structure were analyzed to explore the degradation of TMP in PMFC. The results showed that rapid degradation and enhanced mineralization of TMP were obtained in the PMFC, which were 1.7 and 1.4 times higher than those of traditional microbial fuel cells (MFCs), respectively. Intermediates in the degradation process were identified in both systems, and three degradation pathways were inferred in the PMFC. The electricity characteristics were investigated and superior electrical production and higher electron transfer efficiency were observed in the PMFC, resulting in a maximum power density of 75.1 mW/m2 and a maximum voltage of 0.225 V. Additionally, the cyclic voltammetry test and electrochemical impedance spectra were used for electrochemical performance characterization, and the results showed the stronger oxidation ability of PMFC with half the charge transfer resistance of MFCs. The microbial community structure demonstrated that the dominant species were enriched and coexisted, involving degradation bacteria, exoelectrogens, and hydrocarbon removal bacterial. Furthermore, canonical correspondence analysis (CCA) revealed a mutual promotion of TMP degradation and electricity production with the involvement of these active genera. In conclusion, this novel technology is an excellent alternative in practical applications for the treatment of wastewater containing antibiotics.

Wastewater sludge recycling: An efficient catalyst for photo-Fenton degradation of antibiotics and effluent disinfection

An environmentally friendly strategy for recycling sewage sludge is proposed based on the thermal generation of a magnetic material for use as a catalyst in the photo-Fenton process. The main elements present in the catalyst were silicon, aluminum, oxygen, carbon, phosphorus, and iron, and the specific area was 35.53 m2 g−1. X-ray photoelectron spectroscopy and scanning electron microscopy analyses showed that there was no apparent alteration of the catalyst surface after the photo-Fenton process. Photo-Fenton experiments performed under UV irradiation revealed complete degradation of trimethoprim (TMP) and sulfamethoxazole (SMZ) in purified water after 180 min, with the catalytic activity maintained for at least 4 cycles. A comparison was made of the degradation of pollutants in sewage treatment plant effluents under artificial UV and solar irradiation. Under solar irradiation, at pH 3.5, total degradation of TMP and SMZ was achieved, together with TOC removal of up to 21%, showing SLC-600 as a potential low-cost catalyst to be used in photo-Fenton process.

Photocatalytic Degradation of Pharmaceutical Trimethoprim in Aqueous Solution over Nanostructured TiO2 Film Irradiated with Simulated Solar Radiation

Pharmaceuticals are characterized by a wide range of physical, chemical, and biological properties and functionalities that contribute to their inherent complexity as compounds. Unfortunately, human carelessness during the production, use, and disposal of these compounds results in their presence in the environment. This study utilized a nanostructured TiO2 film on a glass ring at the bottom of a reactor and simulated a solar radiation lamp as the radiation source for both photocatalytic and photolytic experiments, with the aim of unraveling the mechanism behind the degradation of trimethoprim (TMP), a pharmaceutical compound. This approach provides a novel perspective on the role of TiO2 in the degradation of pharmaceuticals and could pave the way for more efficient and sustainable wastewater treatment methods. Scavenger studies were carried out using isopropanol, ammonium oxalate, and triethanolamine to examine the photocatalytic mechanism. Isopropanol and triethanolamine were found to impede the photocatalytic degradation of TMP, highlighting the significance of hydroxyl radicals and positive holes in the degradation process, while no inhibition was observed in the presence of ammonium oxalate. The complete degradation of TMP through photocatalysis under simulated solar radiation was observed in ultra-pure water in fewer than 3 h, as indicated by the results. Our findings suggest that utilizing natural solar radiation as a source of UV-A radiation in reactor configurations based on this approach holds promise for cost-effective pharmaceutical degradation treatment in wastewater treatment plants. The practical potential of this approach is supported by the results obtained under simulated solar radiation with an irradiation intensity in the UV-A region of 33 ± 2 W/m2.

Quantifying the Relative Roles of Different Microorganisms on Trimethoprim Degradation by Nitrifying Activated Sludge

AbstractThe cometabolism of ammonia‐oxidizing bacteria (AOB) in nitrifying activated sludge can effectively degrade antibiotics. However, the roles of other microorganisms in antibiotic removal processes remain uncharacterized. In this study, the effects of AOB, nitrite oxidizing bacteria (NOB), and heterotrophs on the removal of the antibiotic trimethoprim (TMP) at environmentally relevant concentrations in an enriched nitrifying activated sludge are quantified. AOB is found to be the most efficient for TMP removal, which is related with ammonium concentration. TMP removal is increased from 48.0% to 64.0% as the ammonium concentration increased from 50 to 150 mg L−1. However, with a further increase in ammonium concentration to 250 mg L−1, TMP removal is decreased to 45.6%. The percentages of TMP removed by AOB, NOB, and heterotrophs are quantified by batch experiments, and are 78.7%, 18.6%, and 2.7%, respectively. The results demonstrate that in nitrifying activated sludge system, the contribution of NOB and heterotrophs on TMP removal should also be considered.

Performance evaluation of the UV activated chlorite process on trimethoprim: Degradation efficiency, energy consumption and disinfection by-products formation

As the primary inorganic by-product species of ClO2, chlorite is believed to have negative toxicological effects on human health and therefrom greatly limits the wide application of ClO2 in water treatment. The synergistic trimethoprim (TMP) removal concerning degradation efficiency, energy consumption and disinfection by-products (DBPs) formation in the UV activated chlorite process accompanied by the simultaneously elimination of chlorite was comprehensively evaluated. UV/chlorite integrated process removed TMP far more rapidly than UV (1.52%) or chlorite (3.20%) alone due to the endogenous radicals (Cl•, ClO• and •OH), the contributing proportions of which were 31.96%, 19.20% and 44.12%. The second-order rate constants of TMP reaction with Cl•, ClO• and •OH were determined to be 1.75 × 1010, 1.30 × 109 and 8.66 × 109 M−1 s−1. The effects of main water parameters including chlorite dosage, UV intensity, pH as well as water matrixes (nature organic matter, Cl− and HCO3−) were examined. kobs obeyed the order as UV/Cl2>UV/H2O2≈UV/chlorite>UV, and the cost ranking via electrical energy per order (EE/O, kWh m−3 order−1) parameter was UV/chlorite (3.7034) > UV/H2O2 (1.1625) >UV/Cl2 (0.1631). The operational scenarios can be optimized to achieve the maximum removal efficiencies and the minimum energy costs. The destruction mechanisms of TMP were proposed by LC-ESI-MS analysis. The overall weighted toxicity in subsequent disinfection was assessed as UV/Cl2>UV/chlorite > UV, the values of which in post-chlorination were 6.2947, 2.5806 and 1.6267, respectively. Owing to the vital roles of reactive chlorine species (RCS), UV/chlorite displayed far higher TMP degradation efficiency than UV, and concurrently presented much less toxicity than UV/Cl2. In an effort to determine the viability of the promising combination technology, this study was devoted to reduce and reuse chlorite and synchronously realize the contaminants degradation efficiently.

Synergistic degradation of trimethoprim and its phytotoxicity via the UV/chlorine process: Influencing factors on removal and kinetic

Occurrence of trimethoprim (TMP), recalcitrant antibiotic, and its adverse effect on ecosystem have been reported in several countries. The study aims to remove the TMP and its phytotoxicity via a UV/chlorine process, compared with chlorination and UV irradiation alone. Various treatment conditions including chlorine doses, pHs, and TMP concentrations was conducted with synthetic waters and effluent waters. The UV/chlorine process exhibited a synergistic effect on the TMP removal, compared with chlorination and UV irradiation alone. The UV/chlorine process was the most effective in removing TMP, followed by chlorination. The UV irradiation slightly affected the TMP removal (less than 5%). The UV/chlorine process completely removed TMP by 15 min contact time, while chlorination for 60 min could achieve 71% of TMP removal. The TMP removal fitted well with the pseudo first-order kinetics, and the rate constant (k′) increased with higher chlorine doses, lower TMP concentrations and low pH. HO• was the major oxidant affecting the TMP removal and its degradation rate, compared with other reactive chlorine species (e.g., Cl•, OCl•). The TMP exposure increased the phytotoxicity by decreasing a germination rate of Lactuca sativa and Vigna radiata seeds. The use of UV/chlorine process could effectively detoxify the TMP, resulting in the phytotoxicity level of treated waters equivalent or lower than those of TMP-free effluent water. The detoxification level depended on the TMP removal, and it was about 0.43–0.56 times of TMP removal. The findings indicated the potential use of UV/chlorine process in removing TMP residual and its phytotoxicity.

A hybrid nanocomposite based on CuFe layered double hydroxide coated graphene oxide for photocatalytic degradation of trimethoprim

Photocatalytic activation of persulfate (PS) has recently been considered an effective and environmentally friendly approach for antibiotic decomposition due to its high treatment efficiency, low energy consumption, and high reliability. The development of safe and high-performance catalysts is important for PS-based advanced oxidation processes. In this study, a CuFe-layered double hydroxide (LDH) coated graphene oxide (CuFe-LDH/GO) composite was constructed as a photocatalyst for trimethoprim (TMP) decomposition. The CuFe-LDH/GO catalyst was prepared via the co-precipitation method and characterized through Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and X-ray electron microscopy (XPS) techniques. Characterization results revealed that GO was entirely covered by LDH platelets which also kept its hydrotalcite structure in the as-prepared nanocomposite. The average crystallite size of CuFe-LDH/GO was 28.22 nm. The results confirmed that CuFe-LDH/GO exhibited excellent performance for the PS activation with a TMP removal efficiency of 90.8% under UV-light irradiation. Compared with pristine CuFe-LDH, the rate constant of TMP degradation of CuFe-LDH/GO was doubled. The results also indicated that acidic and alkaline conditions were not favorable for TMP degradation, and the catalytic activity of the used photocatalyst has not decreased significantly after 720 h of continuous recycling. Overall, CuFe-LDH/GO could be a promising photocatalyst for the treatment of wastewater containing antibiotics.

Flow-through heterogeneous electro-Fenton system using a bifunctional FeOCl/carbon cloth/activated carbon fiber cathode for efficient degradation of trimethoprim at neutral pH

The synthesis of multifunctional cathode with high-efficiency and stable catalytic activity for simultaneously producing and activating H2O2 is an effective way for promoting the performance of heterogeneous electro-Fenton process (HEF). In addition, accelerating mass transfer by adopting a flow-through reactor is also great importance because of its better utilization of catalysts and adequate contact of the contaminant with the oxidants generated on the electrode surface. Herein, a novel flow-through HEF (FHEF) system was designed for the degradation of trimethoprim (TMP) using bifunctional cathode with a sandwich structure FeOCl nanosheets loaded onto carbon cloth (CC) and activated carbon fiber (ACF) (FeOCl/CC/ACF). The cathode exhibited excellent performance in activating H2O2 for the in-situ generation of hydroxyl radicals (•OH). The electron spin resonance (ESR) measurements and radical quenching tests proved that the high production of •OH in the FHEF process was favorable to the high catalytic efficiency. 25 mg L−1 TMP was entirely degraded after 60 min, with the TOC removal of 62.6% (180 min) at pH 6.8, 9.0 mA cm−2, and flux rate 210 mL min−1. Moreover, the degradation rate still could reach 83% (60 min) after 10 cycles without obvious valence and crystal phase changes. Simultaneously, the current utilization rate has also been greatly enhanced, with an average current efficiency of 69.9% and a low energy consumption of 0.28 kWh kg−1. The reasonable degradation pathways for TMP were proposed based on the UPLC-QTOF-MS/MS results. Finally, the results of toxicological simulation showed a declining trend in the toxicity of the samples during TMP degradation. These results claim that the FeOCl/CC/ACF-FHEF system is an efficient and economical technology for the treatment of organic contaminants in effluents.

Electrochemically assisted photocatalytic degradation of contaminants of emerging concern in simulated wastewater using WO3 – Elucidation of mechanisms

In this work, the performance of a photoelectrochemical cell to degrade a mixture of contaminants of emerging concern (CECs) in distilled water and simulated wastewater effluents (SWWE) was assessed. The CECs mixture included trimethoprim (TMP), diclofenac (DFC), sulfamethoxazole (SMX) and carbamazepine (CBZ) (100 μg·L−1 each). WO3 nanoplate-like structures synthesized on fluorine tin oxide coated glass (FTO) were used as the photoanode with Pt or carbon gas diffusion electrodes (GDE) as the counter electrode. The most efficient degradation of the CECs was obtained with the WO3-GDE combination. Significant degradation of the CECs was observed under visible only radiation. Even under visible radiation, reasonable rate constants 5.67·10-3, 5.35·10-3, 2.9·10-3 and 4.35·10-3 min−1 were obtained for TMP, SMX, CBZ and DFC degradation. The degradation mechanism at the cathode and the photoanode was elucidated using a two-compartment cell, which allowed the identification of reactive species generated at each electrode. Photogenerated holes were the main responsible for CEC degradation in SWWE. With the carbon GDE, a high Faradaic efficiency (55 %) for H2O2 production was observed.

Unveiling the influence of Fe2O3 nanoparticles on CuxO–TiO2(B) nanofibers for dual Z-scheme electron transfer visible light photocatalysts: investigation on local atomic structures and electronic properties

We have investigated the local atomic structures and electronic properties of CFTNF (CuxO/Fe2O3/TiO2(B)) towards photocatalytic H2 production and trimethoprim degradation.

Promising MoS2 – ZnO hybrid nanocomposite photocatalyst for antibiotics, and dyes remediation in wastewater applications

In this work, a heterojunction system of ZnO nanorods (NRs) coupling with ultrathin MoS2 nanosheets (NSs) is designed through a facile and green microwave-assisted hydrothermal method. The purpose of this research is to investigate the use of a MoS2-ZnO hybrid nanocomposite as a photocatalyst for the degradation of sulfamethoxazole (SMX), trimethoprim (TMP), and meloxicam (MX) antibiotics, as well as Methylene blue (MB), malachite green (MG), and crystal violet (CV) dyes under simulating sunlight. The structural, morphological, optical, and textural properties of pristine ZnO NRs, MoS2 NSs, and their hybrid nanocomposite (MoS2-ZnO) are compared using XRD, TEM, SEM-EDX, UV-DRS, PL, and BET techniques. The MoS2-ZnO hybrid nanocomposite exhibited ZnO characteristic peaks with a very small MoS2 characteristic diffraction peak, indicating the heterojunction formation, as confirmed by TEM results. Furthermore, the MoS2-ZnO hybrid nanocomposite showed enhanced visible light absorption and surface area. The hybrid nanocomposite photocatalytic efficiency is higher than that of pristine ZnO NRs in all photocatalytic experiments. the Formation of heterojunction is the reason for improved performance due to increased charge carrier generation, separation, and transport, as confirmed by the PL technique. Moreover, The MoS2-ZnO revealed 100 % photocatalytic degradation efficiency after 30 min against SMX, MX, and MB pollutants respectively. Furthermore, complete photocatalytic degradation (100 %) is achieved after 90 min in the case of TMP, MG, and CV pollutants. Moreover, the possible photocatalytic mechanism has been clearly described, emphasizing the significance of OH. radicals and singlet oxygen (1O 2) in the degradation process. MoS2-ZnO hybrid nanocomposites can be considered promising photoactive materials for wastewater decontamination.

Ultra-uniform MIL-88B(Fe)/Fe3S4 hybrids engineered by partial sulfidation to boost catalysis in electro-Fenton treatment of micropollutants: Experimental and mechanistic insights

Fe-based metal–organic frameworks are promising catalysts for water treatment, although their viability is hampered by the slow regeneration of active Fe(II) sites. A facile sulfidation strategy is proposed to boost the catalytic activity of MIL-88B(Fe) in heterogeneous electro-Fenton (HEF) treatment of organic micropollutants at mild pH. The synthesized MIL-88B(Fe)/Fe3S4 hybrids possessed numerous and durable unsaturated iron sites, acting the S2− atoms as electron donors that enhanced the Fe(II) recycling. The sulfidated catalyst outperformed the MIL-88B(Fe), as evidenced by the 7-fold faster degradation of antibiotic trimethoprim by HEF and the fast destruction of micropollutants in urban wastewater. The hybrid catalyst was reused, obtaining >90% drug removal after four runs and, additionally, its inherent magnetism facilitated the post-treatment recovery. Electrochemical tests and DFT calculations provided mechanistic insights to explain the enhanced catalysis, suggesting that the accelerated Fe(III)/Fe(II) cycling and the enhanced mass transport and electron transfer accounted for the efficient trimethoprim degradation.

Oxygen doping facilitated N-vacancies in g-C3N4 regulates electronic band gap structure for trimethoprim and Cr (VI) mitigation: Simulation studies and photocatalytic degradation pathways

The strategic designing of graphitic carbon nitride (CN)by elemental doping is likely to generate nitrogen vacancies which benefit by serving as electron trapping sites or by introducing additional energy levels (mid-gap states). In this work, uracil-assisted oxygen doped graphitic carbon nitride (OCNv-Ux) was synthesized by the hydrothermal method. The OCNv-U40 exhibited vigorous photocatalytic efficiency for 98% trimethoprim (TMP) antibiotic degradation and 90.8% Cr (VI) reduction under visible light irradiations. A combined inference from experimental results and simulation studies indicates band gap reduction from 2.7 to 2.34 eV for extended visible light absorption up to 620 nm. In particular, the density of states comprehends band structure regulation by the electron redistribution resulting in valence band up shifting and downshift of the conduction band, as validated by Mott-Schottky spectra. The synergistic outcomes of nitrogen vacancies and oxygen doping sites restrain the recombination of electron-hole pairs by mid-gap state formation and also promote high oxygen molecule adsorption on the nitrogen vacancies. The pioneering advantage of highly adsorbed oxygen molecule leads to the generation of plentiful superoxide anion radicals along with indirect production of hydroxyl radicals via in-situ produced H2O2, evident by radical scavenging and electron paramagnetic resonance experiments. The effect of chloride and nitrate anions showed inhibitory effect on the TMP degradation efficiency. The identification of formed intermediates and TMP degradation mechanism involving oxidation, hydroxylation, and cleavage was proposed, as investigated by TMP DFT studies. This research accomplishes significant enhancement in pristine CN photocatalytic activity by the virtue of increased specific surface area, fully exposed N-vacancies active sites, optimized electronic, structure and visible light active band gap.

Neutral (Fe3+-NTA) and acidic (Fe2+) pH solar photo-Fenton Vs chlorination: Effective urban wastewater disinfection does not mean control of antibiotic resistance

Solar photo-Fenton (SPF) process in raceway pond reactors was investigated at neutral pH by Fe3+-NTA complex and at acidic pH by Fe2+and compared with chlorination process in E. coli inactivation, antibiotic Trimethoprim (TMP) and antibiotic resistance genes (ARGs) removal from secondary treated urban wastewater. E. coli inactivation below the detection limit (DL) was achieved in less than 15 min under acidic pH. At neutral pH, the DL was reached in 60 min treatment with 0.2 mM of Fe3+-NTA and 4.41 mM of H2O2. In contrast, the removal of TMP (50 µg/L) by SPF was higher at neutral pH (95%) compared to the acidic pH condition (80%). Although chlorination (10 mg/L chlorine dose) inactivated E. coli below the DL between 2.5 and 5 min, no degradation of TMP was observed. Target ARGs (quinolone, sulphonamides, β-lactams, cephalosporins and tetracycline classes), class 1 integron integrase (intI1) and the 16 S rRNA gene, were only slightly removed under realistic conditions (32% and 23% as max removals of intl1 by chlorination and SPF at acidic pH, respectively) and may not effectively control the potential of antibiotic resistant spread under the mild oxidation conditions investigated in this study.

Co-doped Fe3O4/α-FeOOH for highly efficient peroxymonosulfate activation to degrade trimethoprim: Occurrence of hybrid non-radical and radical pathways

Trimethoprim (TMP), as a widely used chemotherapeutic antibiotic agent, has caused potential risks to the aquatic environment. In this study, magnetic Co-doped Fe3O4/α-FeOOH was fabricated by a facile one-step ageing method and used for activation of peroxymonosulfate (PMS) in TMP degradation. It was found that low catalyst (0.5 g/L) and PMS addition (0.2 mM) led to the high degradation efficiency of TMP (97.2%, kobs = 0.11211 min−1) over a wide range of pH. The oxidation of active radical (SO4·−) and non-radical singlet oxygen (1O2) co-acted on TMP degradation. Besides, PMS was activated through the cycles between Co(II)/Co(III) and Fe(II)/Fe(III). Fifteen degradation intermediates of TMP were identified by LC-MS, and three possible degradation pathways including hydroxylation, demethylation, and cleavage were proposed. The recovered catalysts exhibited high stability and reusability, maintaining 80% TMP removal efficiency with inappreciable metal leaching (0.012 mg/L of Co, 0.113 mg/L of Fe) after six cycles. Besides, the Co–Fe3O4/α-FeOOH/PMS system was highly tolerant to inorganic anions and actual water bodies (river water, lake water, tap water, and sewage plant effluent). Overall, this work provided a promising way to the potential application of Fe-based binary metal oxide for PMS activation.

Hierarchical porous TiO2 with a uniform distribution of anchored gold nanoparticles for enhanced photocatalytic efficiency and accelerated charge separation for the degradation of antibiotics.

A novel approach to synthesize porous Au/TiO2 nanocomposites has been achieved through a pyrolytic strategy by employing NH2-MIL-125(Ti) as a TiO2 precursor, and photo-deposition of Au nanoparticles (NPs) onto porous nanocrystalline TiO2 with varying Au contents (0.05-0.5%). TEM images of Au/TiO2 nanocomposites showed that TiO2 particles were spherical structures, highly dispersed, and homogeneous with diameters of 10-15nm, and Au NPs (20-30nm) were anchored onto porous TiO2 matrices with a uniform distribution. The synthesized Au/TiO2 nanocomposites were assessed through the degradation of two antibiotic models, metronidazole (MNZ), and trimethoprim (TMP), under visible light and compared with undoped TiO2 and commercial TiO2 (P-25). The synthesized Au/TiO2 photocatalyst revealed enhanced photocatalytic performance in the mineralization (80%) and degradation (100%) of MNZ and TMP in both water matrices compared to undoped TiO2 (60%, 76%) and commercial P-25 (48%, 65%). The obtained 0.1% Au/TiO2 nanocomposite could complete the mineralization of TMP and MNZ with rate constant values (4.47 × 10-3min-1 and 5.23 × 10-1min-1) owing to the large well-developed porosity and high surface area of TiO2 and the small size of Au NPs with high dispersity, surface plasmon resonance, and stability. The recyclability of the 0.1% Au/TiO2 nanocomposite exhibited high durability without the leaching or loss of photocatalytic performance after four cycles. Complete degradation was achieved within 100min in the water matrix from real wastewater, indicating promising results for the degradation of pharmaceuticals in the different water matrices. The present work opens a new route to synthesize low-cost, effective, and high photocatalytic performance nanocomposites with a small Au content as a cocatalyst onto semiconductor materials.

Porphyrin@Lignin nanoparticles: Reusable photocatalysts for effective aqueous degradation of antibiotics

The aqueous photocatalyzed degradation of trimethoprim (TMP) and sulfamethoxazole (SMX), highly prescribed antibiotics, often found in hospital wastewaters and/or surface/ground waters in high concentrations, is described, using a 400 W medium pressure mercury lamp as irradiation source, air as oxidant and a porphyrin based photocatalyst. The new photocatalyst was prepared by encapsulation of stable meso-tetra(2,6-dichlorophenyl)porphyrin photosensitizer into acetylated lignin nanoparticles, which are derived from a bio-based cellulose industry byproduct. This is a reusable stable catalyst (after at least 7 cycles, no loss of activity or degradation/leaching, was observed) capable of promoting the nearly complete degradation of TMP and SMX antibiotics, with unprecedented total organic carbon (TOC) removal, namely 75 % and 85 %, respectively. Mechanistic studies of these reactions, using singlet oxygen and radical scavengers, followed by HPLC-MS analysis allowed the identification of only two residual TMP photoproducts.

S-scheme N-doped carbon dots anchored g-C3N4/Fe2O3 shell/core composite for photoelectrocatalytic trimethoprim degradation and water splitting

Photoelectrocatalysis is a promising technique for energy conversion and environmental treatment. This study describes the photoelectrochemical (PEC) degradation of trimethoprim and hydrogen evolution using a photoanode prepared by N-doped carbon dots (NCD) incorporated g-C3N4/α-Fe2O3 (CNFO) shell/core nanocomposite. The electrochemical analysis reveals that the photocurrent density of NCD@CNFO photoanode reached 3.07 mA cm−2 at 1.6 V vs. NHE, which is 4 and 15 times greater than that of CNFO and intact α-Fe2O3, respectively. In the presence of peroxymonosulfate (PMS), the NCD@CNFO photoanode enabled 95 % and 90 % of trimethoprim (TMP) degradation in aqueous solution and lake water, respectively. Hydrogen generation coupled with TMP degradation was also observed in the PEC system, where the H2 generation rate was 550 µmol cm−2 h−1. Both superoxide (•O2−) and hydroxyl (•OH) radicals played a significant role in the degradation of TMP. The achievements could be assigned to the excellent photoabsorption and electron transfer properties of NCD, which enhanced the PEC activity of CNFO by enabling the S-scheme heterojunction to reduce electron-hole recombination. Moreover, PMS served as a cathodic electron acceptor to improve the catalytic properties of NCD@CNFO photoanode, demonstrating its contribution to both water treatment and hydrogen production. Such superior efficiency offers great potential to develop a PEC system using carbon dots/semiconductor hybrid catalysts for antibiotic degradation and synchronous photocatalytic H2 evolution from wastewater, providing an alternative solution to environmental pollution and energy crisis issues.