Photocatalytic-oxidation and photo-persulfate-oxidation of sulfadiazine in a laboratory-scale reactor: Analysis of catalyst support, oxidant dosage, removal-rate and degradation pathway

Transformation of antibiotics to non-toxic and non-bactericidal products by laccases ensure the safety of Stropharia rugosoannulata

The substantial use of antibiotics contributes to the spread and evolution of antibiotic resistance, posing potential risks to food production systems, including mushroom production. In this study, the potential risk of antibiotics to Stropharia rugosoannulata, the third most productive straw-rotting mushroom in China, was assessed, and the underlying mechanisms were investigated. Tetracycline exposure at environmentally relevant concentrations (<500 μg/L) did not influence the growth of S. rugosoannulata mycelia, while high concentrations of tetracycline (>500 mg/L) slightly inhibited its growth. Biodegradation was identified as the main antibiotic removal mechanism in S. rugosoannulata, with a degradation rate reaching 98.31 % at 200 mg/L tetracycline. High antibiotic removal efficiency was observed with secreted proteins of S. rugosoannulata, showing removal efficiency in the order of tetracyclines > sulfadiazines > quinolones. Antibiotic degradation products lost the ability to inhibit the growth of Escherichia coli, and tetracycline degradation products could not confer a growth advantage to antibiotic-resistant strains. Two laccases, SrLAC1 and SrLAC9, responsible for antibiotic degradation were identified based on proteomic analysis. Eleven antibiotics from tetracyclines, sulfonamides, and quinolones families could be transformed by these two laccases with degradation rates of 95.54-99.95 %, 54.43-100 %, and 5.68-57.12 %, respectively. The biosafety of the antibiotic degradation products was evaluated using the Toxicity Estimation Software Tool (TEST), revealing a decreased toxicity or no toxic effect. None of the S. rugosoannulata fruiting bodies from seven provinces in China contained detectable antibiotic-resistance genes (ARGs). This study demonstrated that S. rugosoannulata can degrade antibiotics into non-toxic and non-bactericidal products that do not accelerate the spread of antibiotic resistance, ensuring the safety of S. rugosoannulata production.

Azadirachta indica leaf extract based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon for pharmaceuticals and personal care products removal

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants in aqueous systems, posing threat to both human health and environment. In prior research, predominant focus has been on examining various adsorbents for removing PPCPs from single-pollutant systems. However, no study has delved into simultaneous adsorption of PPCPs multi-pollutant mixture. This study evaluates performance of Azadirachta indica leaf extract-based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon (ZTAC) for removing sulfadiazine (SZN) and acetaminophen (ACN). Adsorption investigations were conducted in single-component (ACN/SZN) and binary-component (ACN + SZN) systems. The synthesized ZTAC was characterized using SEM, XRD, FTIR, EDX, porosimetry and pHpzc analysis. The study examines impact of time (1-60 min), dose (0.2-4 g/L), pH (2-12) and PPCPs concentration (1-100 mg/L) on ACN and SZN removal. Various kinetic and isotherm models were employed to elucidate mechanisms involved in sorption of PPCPs. Furthermore, synergistic and antagonistic aspects of sorption process in multi-component system were investigated. ZTAC, characterized by its crystalline nature and surface area of 980.85 m2/g, exhibited maximum adsorption capacity of 47.39 mg/g for ACN and 34.01 mg/g for SZN under optimal conditions of 15 min, 3 g/L and pH 7. Langmuir isotherm and pseudo-second-order kinetic model best-fitted the experimental data indicating chemisorption mechanism. Removal of ACN and SZN on ZTAC demonstrated synergistic nature, signifying cooperative adsorption. Overall, valorization of ZTAC offers effective and efficient adsorbent for elimination of PPCPs from wastewater.

Degradation of amoxicillin applying photo-Fenton and acid hydrolysis processes with toxicity evaluation via antimicrobial susceptibility tests

ABSTARCTThe antibiotic amoxicillin (AMX) is a semisynthetic aminopenicillin, classified as an β-lactam antibiotic. This work aims to evaluate the AMX degradation (190 mg L-1), in aqueous medium, applying photo-Fenton ([TOC]0 = 100 mgC L-1; FH2O2 = 3.27 mmol min-1; [Fe2+] = 0.27 mmol L-1; pH = 3.0; T = 40°C) and acid hydrolysis processes. Along the experiments, samples were withdrawn and analyzed by a total organic carbon (TOC) analyzer and a liquid chromatography system coupled to diode array (HPLC-DAD) and mass spectrometry (HPLC-MS) detectors. The hydrolysis process proved to be less efficient, because AMX removals greater than 80% were observed only after 24 hours of reaction (pH 2). Conversely, the photo-Fenton process removed completely AMX in just 20 minutes, reaching 85% of TOC removal in 2 hours. Finally, the AMX aqueous solutions treated by the studied processes was also evaluated in respect of its toxicity to some microorganisms, applying two antimicrobial susceptibility tests: disk-diffusion and broth microdilution methods. It was observed that the AMX aqueous solutions, pretreated by the photo-Fenton process, for just 7.5 min of reaction time, did not inhibit the microorganisms growth. The obtained results show that the photo-Fenton process was able to degrade AMX, in a relatively short time, and that the generated degradation products did not inhibit the microorganisms growth, when compared to acid hydrolysis process. Thus, it was verified the potential application of the photo-Fenton system as a pretreatment step to conventional biological oxidation processes for the treatment of industrial wastewaters.

Research progress of MOF-based membrane reactor coupled with AOP technology for organic wastewater treatment

MOF-based catalytic membrane reactor (MCMR), which can simultaneously achieve membrane separation and chemical catalytic degradation in an integrated system, is a cutting-edge technology for effective treatment of organic pollutants in water. The coupling of MCMR and advanced oxidation process (AOP) not only significantly improves the pollutant removal efficiency but also inhibits the membrane pollution through self-cleaning effect, thus improving the stability of MCMR. This paper reviews different MCMR systems combined with photocatalysis, Fenton oxidation, and persulfate activation, elucidates the reaction mechanism, discusses key issues to improve system effectiveness, and suggests future challenges and research directions.

Toxicity evolution and control for the UV/H2O2 degradation of nitrogen-containing heterocyclic compounds: SDZ and PMM

This study aimed to achieve toxicity control of sulfadiazine (SDZ) and pirimiphos-methyl (PMM) via the UV/H2O2 process by optimizing the reaction parameters. The results show that both drugs had a good degradation effect under the following parameters: a H2O2 molar ratio of 1:200, and neutral conditions. SDZ and PMM could be degraded by more than 99% within 3 min, respectively. In the Daphnia magna acute toxicity assay and Vibrio fischeri inhibition assay, both SDZ and PMM exhibited a phenomenon of increasing toxicity. Additionally, through the use of density functional theory (DFT) calculation and HPLC-QTOF-MS, 21 transformation products (TPs) were identified, and the principal degradation pathways were proposed. The toxicity of the TPs was determined by comparing the QSAR prediction results with toxicity test data. As a result, under the higher UV light intensity (2300 μW/cm2) and neutral conditions, SDZ showed highest toxicity, whereas PMM showed lowest toxicity under the lowest UV light intensity (450 μW/cm2) and neutral conditions. Four main toxic TPs were identified, and their yields could be reduced by adjusting the reaction parameters. Therefore, the selection of appropriate reaction parameters could reduce the production of toxic TPs and ensure the safety of water environment.

Photodegradation performance and mechanism of sulfadiazine in Fe(III)-EDDS-activated persulfate system

In order to overcome the shortcomings in the traditional Fenton process, Fe(III)-EDDS-activated persulfate advanced oxidation process under irradiation is carried out as a promising technology. The photodegradation of sulfadiazine (SD) in Fe(III)-EDDS-activated persulfate system was investigated in this paper. The results showed that SD could be effectively degraded in Fe(III)-EDDS/S 2 O 8 2 - /hv system. The effects of Fe(III):EDDS molar ratio, the concentration of Fe(III)-EDDS, and the concentration of S 2 O 8 2 - on SD degradation were explored. At neutral pH, when Fe(III):EDDS = 1:1, Fe(III)-EDDS = 0.1 mM, S 2 O 8 2 -  = 1.5 mM, the best SD degradation was achieved. The experiment of external influence factors showed that the degradation of SD could be obviously inhibited by the presence of C O 3 2 - , S O 4 2 - , whereas the degradation of SD was almost unaffected by the addition ofCl-. The degradation of SD could be slightly inhibited by the presence of humic acid and NO3-. The effect of pH on SD degradation was investigated, and SD could be degraded effectively in the pH range of 3-9. ESR proved that 1O2, ·OH, S O 4 - , and O2- were produced in the process. S O 4 - and ·OH were identified as the main radicals while O2·- also played non-ignorable role. Eleven intermediate products of SD were analysed. The C = N, S-N, and S-C bonds of SD were attacked by radicals firstly, leading to a series of reactions that eventually resulted in the destruction of SD molecules and the formation of small organic molecules.

Merits and Limitations of Radical vs. Nonradical Pathways in Persulfate-Based Advanced Oxidation Processes

Urbanization and industrialization have exerted significant adverse effects on water quality, resulting in a growing need for reliable and eco-friendly treatment technologies. Persulfate (PS)-based advanced oxidation processes (AOPs) are emerging as viable technologies to treat challenging industrial wastewaters or remediate groundwater impacted by hazardous wastes. While the generated reactive species can degrade a variety of priority organic contaminants through radical and nonradical pathways, there is a lack of systematic and in-depth comparison of these pathways for practical implementation in different treatment scenarios. Our comparative analysis of reaction rate constants for radical vs. nonradical species indicates that radical-based AOPs may achieve high removal efficiency of organic contaminants with relatively short contact time. Nonradical AOPs feature advantages with minimal water matrix interference for complex wastewater treatments. Nonradical species (e.g., singlet oxygen, high-valent metals, and surface activated PS) preferentially react with contaminants bearing electron-donating groups, allowing enhancement of degradation efficiency of known target contaminants. For byproduct formation, analytical limitations and computational chemistry applications are also considered. Finally, we propose a holistically estimated electrical energy per order of reaction (EE/O) parameter and show significantly higher energy requirements for the nonradical pathways. Overall, these critical comparisons help prioritize basic research on PS-based AOPs and inform the merits and limitations of system-specific applications.

Advanced oxidation and a metrological strategy based on CLC-MS for the removal of pharmaceuticals from pore & surface water

In this work, it is studied the photolysis, electrolysis, and photo-electrolysis of a mixture of pharmaceutics (sulfadiazine, naproxen, diclofenac, ketoprofen and ibuprofen) contained in two very different types of real water matrices (obtained from surface and porewater reservoirs), trying to clarify the role of the matrix on the degradation of the pollutants. To do this, a new metrological approach was also developed for screening of pharmaceuticals in waters by capillary liquid chromatography mass spectrometry (CLC-MS). This allows the detection at concentrations lower than 10 ng mL^-1. Results obtained in the degradation tests demonstrate that inorganic composition of the water matrix directly influences on the efficiency of the drugs removal by the different EAOPs and better degradation results were obtained for experiments carried out with surface water. The most recalcitrant drug studied was ibuprofen for all processes evaluated, while diclofenac and ketoprofen were found to be the easiest drugs for being degraded. Photo-electrolysis was found to be more efficient than photolysis and electrolysis, and the increase in the current density was found to attain a slight improvement in the removal although with an associated huge increase in the energy consumption. The main reaction pathways for each drug and technology were also proposed.

Competitive adsorption analysis of antibiotics removal from multi-component systems using chemically activated spent tea waste: effect of operational parameters, kinetics, and equilibrium study

In this study, spent tea powder waste was chemically treated for the synthesis of adsorbent using two activating agents, i.e., sulfuric acid and phosphoric acid, to obtain sulfuric acid activated carbon (SAC) and phosphoric acid activated carbon (PAC). The performance of PAC and SAC for the sorption of tetracycline (TCY) and sulfadiazine (SDZ) antibiotics from mono-component (SDZ/TCY) and multi-component (SDZ + TCY) adsorption systems was investigated. Synergistic and antagonistic effects were studied in removing target pollutants in SDZ + TCY systems. Kinetic and equilibrium studies were modeled by different kinetic and isotherm models. The adsorption capacity was assessed using Langmuir's competitive model in a [Formula: see text]. Pseudo-first-order kinetic and Langmuir isotherm models best fit the experimental kinetic and equilibrium data to remove antibiotics. The Langmuir's maximum adsorption capacity (q_m) of PAC for the removal of SDZ and TCY in a [Formula: see text] was found to be 16.75 and 10.87 mg/g, and q_m of SAC for the removal of SDZ and TCY was found to be 24.69 and 23.20 mg/g, respectively. In SDZ + TCY multi-component system, adsorption of TCY was synergistic in nature for both PAC and SAC. Sorption of SDZ displayed an antagonistic effect in the SDZ + TCY system for both SAC and PAC. In conclusion, the activated carbons synthesized from spent tea waste could be effectively adopted for the simultaneous adsorption of SDZ and TCY from multi-component systems.

Enhanced photocatalytic activity of Fe-, S- and N-codoped TiO2 for sulfadiazine degradation

The composite material based on N-, S-, and Fe-doped TiO2 (NSFe-TiO2) synthesized by wet impregnation was used as a photocatalyst to rapidly degrade sulfadiazine. The photocatalytic degradation behavior and mechanism of sulfadiazine on NSFe-TiO2 were investigated for revealing the role of degradation under ultraviolet light. The results showed that compared with TiO2, NSFe-TiO2 markedly improved the efficiency in photocatalytic degradation of sulfadiazine: more than 90% of sulfadiazine could be removed within 120 min by NSFe-TiO2 dosage of 20 mg L-1. The process conformed to first-order reaction kinetics model. The parameters such as loaded amount of NSFe-TiO2, solution pH value, humic acid concentration and recycle numbers on removal efficiency were also studied. Compared to neutral and alkaline conditions, acidic condition was not conducive to the photocatalysis. HA, Ca2+, Cu2+ and Zn2+ in the actual water body had mild inhibition on sulfadiazine degradation in UV/NSFe-TiO2 system. Fragments screened by high-resolution mass spectrometry were conducted to explore the oxidation mechanism and pathways of sulfadiazine degradation. On the whole, UV/NSFe-TiO2 photocatalysis has a good effect on sulfadiazine removal.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13762-023-04771-6.

Degradation of Antibiotics via UV-Activated Peroxodisulfate or Peroxymonosulfate: A Review

The ultraviolet (UV)/H2O2, UV/O3, UV/peroxodisulfate (PDS) and UV/peroxymonosulfate (PMS) methods are called UV-based advanced oxidation processes. In the UV/H2O2 and UV/O3 processes, the free radicals generated are hydroxyl radicals (•OH), while in the UV/PDS and UV/PMS processes, sulfate radicals (SO4•−) predominate, accompanied by •OH. SO4•− are considered to be more advantageous than •OH in degrading organic substances, so the researches on activation of PDS and PMS have become a hot spot in recent years. Especially the utilization of UV-activated PDS and PMS in removing antibiotics in water has received much attention. Some influencing factors and mechanisms are constantly investigated and discussed in the UV/PDS and UV/PMS systems toward antibiotics degradation. However, a systematic review about UV/PDS and UV/PMS in eliminating antibiotics is lacking up to now. Therefore, this review is intended to present the properties of UV sources, antibiotics, and PDS (PMS), to discuss the application of UV/PDS (PMS) in degrading antibiotics from the aspects of effect, influencing factors and mechanism, and to analyze and propose future research directions.

Degradation of sulfadiazine by UV/Oxone: roles of reactive oxidative species and the formation of disinfection byproducts

Sulfadiazine (SDZ) is a typical persistent sulfonamide antibiotic, which has been widely detected in natural drinking water sources. The degradation of SDZ by UV/Oxone (potassium monopersulfate compound) was explored in this study. The results showed that Cl^- can effectively activate PMS to promote rapid degradation of SDZ in the Oxone process by forming chlorine in the system. Radical quenching tests suggested that radical oxidation, including HO^•, SO₄^•-, and reactive chlorine species (RCS), played an important role by UV/Oxone. It further verified that concentration and distribution of HO^•, SO₄^•-, and RCS were pH-dependent; RCS act as a major contributor at pH 6.0 and pH 7.0 to degrade SDZ in this process. The SDZ degradation rate was firstly increased and then decreased by Cl^- and HCO₃^- (0-10 mM); HA (0-10 mg L^-1) exhibited insignificant influence on SDZ degradation. The degradation pathways of SDZ during UV/Oxone and formation pathways of five disinfection byproducts during subsequent chlorination were proposed. The possible DBP precursors formed by SO₂ extrusion, hydroxylation, and chlorination of SDZ during UV/Oxone pre-oxidation.

Photocatalytic oxidation degradation of inhibitory fatty acids for aged Chlorella vulgaris cultivation medium recycling

The medium used for Chlorella vulgaris cultivation exerted obvious inhibitory effects on the growth of C. vulgaris after several culture-harvest cycles. The accumulated fatty acids secreted by C. vulgaris during their growth process were expected to be the cell inhibition components. In this work, the ultraviolet-driven photocatalytic oxidation technique was applied for the degradation of microalgae cell growth inhibition components in the aged cultivation medium, and the reaction parameters were optimized. The results indicated that the photocatalytic oxidation processes using 0.5 g/L [Formula: see text] NPs as the catalyst under the aeration condition showed as high as 74.61 ± 4.60% FA degradation efficiency after 20 min illumination, and the contents of -COOH, [Formula: see text] (α) and -COO-R functional groups in the aged C. vulgaris medium were significantly reduced. In addition, the modification of the photocatalyst further improved the ability of the degradation of FA. When the modified [Formula: see text]/AC and [Formula: see text]/Ag catalysts were applied, the FA degradation rates reached as high as 92.46 ± 0.37% and 93.91 ± 1.37%, respectively. In the recycled medium treated with [Formula: see text]/AC, the cell density in the stable phase reached 96.33 ± 1.83% of that in the fresh medium as the control. In summary, the photocatalytic oxidation with the modified [Formula: see text]/AC catalyst was proposed as the efficient strategy to realize the recycling of the aged C. vulgaris cultivation medium via the degradation of the FA as the cell growth inhibitors.

Selenium nanoparticles with photocatalytic properties synthesized by residual activated sludge

The treatment and disposal of residual activated sludge is a worldwide problem and the research on its reuse is still only in the earliest stages. Selenite is a toxic pollutant, while selenium nanoparticles (SeNPs) are environmentally friendly and have promising application prospects. At present, the reduction mechanism of selenite under the complex system is still poorly understood. In order to explore the mechanism of SeNPs synthesis by activated sludge resource utilization, SeNPs were synthesized by activated sludge extracts of domestic sewage (DSeNPs) and coking sewage (CSeNPs), respectively. The synthesis process, zeta potential and morphology size of SeNPs were changed by pH value, extract concentration and extract composition. Under the same synthesis conditions, the morphologies of DSeNPs and CSeNPs were mainly spherical and pseudo-spherical, while CSeNPs also contained pseudo-rod shape particles. The sizes and crystal grains of CSeNPs were smaller than those of DSeNPs. Compared with DSeNPs, a specific protein (~35 kDa) was found on the surface of CSeNPs using SDS-PAGE. By analyzing the fluorescence images of the two SeNPs, it was found that the relative contents of proteins, α-d-glucopyranose polysaccharides, and β-d-glucopyranose polysaccharides on their surfaces were obviously different (P < 0.05). The present study demonstrated that proteins, polysaccharides, humic-like and fulvic acid-like substances cooperated in the formation and stabilization of SeNPs. Furthermore, CSeNPs (bandgap: 1.68 eV) had more desirable photocatalytic performance than DSeNPs (bandgap: 1.84 eV). Under the light condition, CSeNPs could degrade Rhodamine B faster without adding hydrogen peroxide. This experiment provided a new insight into the resource utilization of activated sludge and a reference for the synthesis of nanometer selenium with excellent performance.

Heterogeneous photo-Fenton degradation toward sulfonamide matrix over magnetic Fe3S4 derived from MIL-100(Fe)

Magnetic Fe₃S₄ was facilely derived from MIL-100(Fe) as the precursor and thioacetamide (TAA) as the sulfur source under hydrothermal condition. The as-prepared Fe₃S₄ was adopted as catalyst to promote the photo-Fenton process, in which sulfamethoxazole (SMX) was used as representative pollutant sample to test the oxidative degradation performance of Fe₃S₄. The results showed that Fe₃S₄ exhibited excellent photo-Fenton-like oxidation decomposition performances toward sulfamethoxazole (SMX) under both UV and visible light. A possible degradation mechanism over Fe₃S₄ in the photo-Fenton reaction is put forward based on quenching experiments and electron spin resonance (ESR). About 41% total organic carbon (TOC) removal efficiency of sulfamethoxazole (SMX) over the as-prepared Fe₃S₄ can be accomplished within 40 min. As well, different sulfonamide antibiotics (SAs) like sulfamethoxazole (SMX), sulfisoxazole (SIM) and sulfadiazine (SDZ) were selected to further investigate the oxidative degradation activity of Fe₃S₄ in this photo-Fenton-like reaction system, in which the possible degradation pathways of SMX, SIM and SDZ were put forward based on UHPLC-MS analysis. This work provided a new strategy to prepare magnetic Fe₃S₄ as catalyst for advanced oxidation process, which can be easily separated from the treated water samples to accomplish facile recovery and recyclability.

Photodegradation of Aquaculture Antibiotics Using Carbon Dots-TiO2 Nanocomposites

In this work, carbon dots (CD) were synthesized and coupled to titanium dioxide (TiO₂) to improve the photodegradation of antibiotics in aquaculture effluents under solar irradiation. Oxolinic acid (OXA) and sulfadiazine (SDZ), which are widely used in aquaculture, were used as target antibiotics. To prepare nanocomposites of CD containing TiO₂, two modes were used: in-situ (CD@TiO₂) and ex-situ (CD/TiO₂). For CD synthesis, citric acid and glycerol were used, while for TiO₂ synthesis, titanium butoxide was the precursor. In ultrapure water (UW), CD@TiO₂ and CD/TiO₂ showed the largest photocatalytic effect for SDZ and OXA, respectively. Compared with their absence, the presence of CD@TiO₂ increased the photodegradation of SDZ from 23 to 97% (after 4 h irradiation), whereas CD/TiO₂ increased the OXA photodegradation from 22 to 59% (after 1 h irradiation). Meanwhile, in synthetic sea salts (SSS, 30‰, simulating marine aquaculture effluents), CD@TiO₂ allowed for the reduction of SDZ’s half-life time (t_1/2) from 14.5 ± 0.7 h (in absence of photocatalyst) to 0.38 ± 0.04 h. Concerning OXA in SSS, the t_1/2 remained the same either in the absence of a photocatalyst or in the presence of CD/TiO₂ (3.5 ± 0.3 h and 3.9 ± 0.4 h, respectively). Overall, this study provided novel perspectives on the use of eco-friendly CD-TiO₂ nanocomposites for the removal of antibiotics from aquaculture effluents using solar radiation.

Biodegradation of sulfonamide antibiotics through the heterologous expression of laccases from bacteria and investigation of their potential degradation pathways

In this study, seven laccase genes from different bacteria were linked with the signal peptides PelB, Lpp or Ompa for heterologous expression in E. coli. The recombinant strains were applied for the removal of sulfadiazine (SDZ), sulfamethazine (SMZ), and sulfamethoxazole (SMX). The results obtained for different signal peptides did not provide insights into the removal mechanism. The removal ratios of SDZ, SMZ, and SMX obtained with the recombinant strain 6#P at 60 h were around 92.0%, 89.0%, and 88.0%, respectively. The degradation pathways of sulfonamides have been proposed, including SO₂ elimination, hydroxylation, oxidation, pyrimidine ring cleavage, and N-S bond cleavage. Different mediators participate in the degradation of antibiotics through different mechanisms, and different antibiotics have different responses to the same mediator. The addition of 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) slightly promoted the removal of sulfonamides by most recombinant strains with different signal peptides, especially for the recombinant strain 2#O. The removal of sulfonamides by 1-hydroxybenzotriazole (HBT) varied with the recombinant strains. Syringaldehyde (SA) had a slight inhibitory effect on the removal of sulfonamides, with the most significant effect on strains 7#L and 7#O.

A New Mechanism of the Selective Photodegradation of Antibiotics in the Catalytic System Containing TiO2 and the Inorganic Cations

The mechanism of sulfisoxazole (SFF) selective removal by photocatalysis in the presence of titanium (IV) oxide (TiO2) and iron (III) chloride (FeCl3) was explained and the kinetics and degradation pathways of SFF and other antibiotics were compared. The effects of selected inorganic ions, oxygen conditions, pH, sorption processes and formation of coordination compounds on the photocatalytic process in the presence of TiO2 were also determined. The Fe3+ compounds added to the irradiated sulfonamide (SN) solution underwent surface sorption on TiO2 particles and act as acceptors of excited electrons. Most likely, the SFF degradation is also intensified by organic radicals or cation organic radicals. These radicals can be initially generated by reaction with electron holes, hydroxyl radicals and as a result of electron transfer mediated by iron ions and then participate in propagation processes. The high sensitivity of SFF to decomposition caused by organic radicals is associated with the steric effect and the high bond polarity of the amide substituent.

Porous visible light-responsive Fe3+-doped carbon nitride for efficient degradation of sulfadiazine

The development of efficient solar driven catalyst for the degradation of antibiotics has become increasingly important in environmental protection. However, the reported efficient photocatalysts for antibiotic degradation are limited. In this work, porous Fe³⁺-doped graphitic carbon nitride (g-C₃N₄) with outstanding photocatalytic ability is synthesized and then used as the photocatalyst for the efficient degradation of sulfadiazine (SDZ) under visible light. A series of characterization results indicate that Fe³⁺ is successfully doped into the interlayer of g-C₃N₄ and is stabilized in g-C₃N₄ by Fe-N coordination bond. The SEM, DRS and ESI and transient photocurrent results demonstrated that Fe³⁺-doped g-C₃N₄ has a porous structure, a low band gap, improved separation efficiency of photogenerated electron and holes as well as a wider light absorption range. Such improved physical and chemical properties greatly enhanced the photocatalytic ability. Using Fe³⁺-doped g-C₃N₄ for photocatalytic degradation of SDZ under white light, almost complete degradation of SDZ was achieved with a degradation efficiency as high as 99.8% (whereas only 52.1% for bulk g-C₃N₄) within 90 min. The degradation was mainly ascribe to ¹O₂ during the irradiation, and also a small amount of •O₂^-, OH• and h⁺ are involved in the degradation process. The Fe³⁺-doped g-C₃N₄ was applicable for the degradation of a wide range of antibiotic pollutants.

Enhanced degradation of antibiotics by photo-fenton reactive membrane filtration

Micropollution such as pharmaceutical residuals potentially compromises water quality and jeopardizes human health. This study evaluated the photo-Fenton ceramic membrane filtration toward the removal of sulfadiazine (SDZ) as a common antibiotic chemical. The batch experiments verified that the photo-Fenton reactions with as Goethite (α-FeOOH) as the photo-Fenton catalyst achieved the degradation rates of 100% within 60 min with an initial SDZ concentration of 12 mg·L^-1. Meanwhile, a mineralization rate of over 80% was obtained. In continuous filtration, a negligible removal rate (e.g., 4%) of SDZ was obtained when only filtering the feed solution with uncoated or catalyst-coated membranes. However, under Ultraviolet (UV) irradiation, both the removal rates of SDZ were significantly increased to 70% (no H₂O₂) and 99% (with H₂O₂), respectively, confirming the active degradation by the photo-Fenton reactions. The highest apparent quantum yield (AQY) reached up to approximately 25% when the UV₂₅₄ intensity was 100 μW·cm^-2 and H₂O₂ was 10 mmol·L^-1. Moreover, the photo-Fenton reaction was shown to effectively mitigate fouling and prevent flux decline. This study demonstrated synchronization of photo-Fenton reactions and membrane filtration to enhance micropollutant degradation. The findings are also important for rationale design and operation of photo-Fenton or photocatalytic membrane filtration systems.

Kinetics and mechanisms of oxytetracycline degradation in an electro-Fenton system with a modified graphite felt cathode

The removal of trace antibiotics from the aquatic environment has received great interest. In this investigation, NaOH activated graphite felt (NaOH-GF) was characterized by multiple-methods, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle, linear sweep voltammetry (LSV) and electron paramagnetic resonance (EPR). The NaOH-GF was then used as the cathode in the electro-Fenton process for oxytetracycline (OTC) degradation, the experiment was carried out in an undivided and light-proof beaker with a Pt anode and a NaOH-GF cathode at pH 3. The results showed that the modification with NaOH enhanced the antibiotics degradation efficiency of graphite felt by increasing the oxygen reduction capacity and hydroxyl radicals yielding rate. Complete OTC removal was achieved at 5.17 mA cm^-2 after 40, 60 and 90 s with initial OTC concentration of 22, 44, and 66 μM, respectively. With an initial OTC concentration of 44 μM, after 30 min the removal rates of chemical oxygen demand (COD) by Raw-GF and NaOH-GF were 59.18% and 83.75%, respectively. The proposed degradation mechanism of OTC was an EF process, which consisted of hydroxylation, secondary alcohol oxidation, demethylation, decarbonylation, dehydration and deamination. This study demonstrates that NaOH activated GF cathode possesses high degradation capacity and good stability. It provides insight into the removal of non-biodegradable antibiotics and may shed light on future to its practical application.

Enhanced Degradation of Sulfamethoxazole (SMX) in Toilet Wastewater by Photo-Fenton Reactive Membrane Filtration

Pharmaceutical residuals are increasingly detected in natural waters, which made great threat to the health of the public. This study evaluated the utility of the photo-Fenton ceramic membrane filtration toward the removal and degradation of sulfamethoxazole (SMX) as a model recalcitrant micropollutant. The photo-Fenton catalyst Goethite (α-FeOOH) was coated on planar ceramic membranes as we reported previously. The removal of SMX in both simulated and real toilet wastewater were assessed by filtering the feed solutions with/without H₂O₂ and UV irradiation. The SMX degradation rate reached 87% and 92% respectively in the presence of UV/H₂O₂ for the original toilet wastewater (0.8 ± 0.05 ppb) and toilet wastewater with a spiked SMX concentration of 100 ppb. The mineralization and degradation by-products were both assessed under different degradation conditions to achieve deeper insight into the degradation mechanisms during this photo-Fenton reactive membrane filtration. Results showed that a negligible removal rate (e.g., 3%) of SMX was obtained when only filtering the feed solution through uncoated or catalyst-coated membranes. However, the removal rates of SMX were significantly increased to 67% (no H₂O₂) and 90% (with H₂O₂) under UV irradiation, respectively, confirming that photo-Fenton reactions played the key role in the degradation/mineralization process. The highest apparent quantum yield (AQY) reached up to approximately 27% when the H₂O₂ was 10 mmol·L⁻¹ and UV254 intensity was 100 μW·cm⁻². This study lays the groundwork for reactive membrane filtration to tackle the issues from micropollution.

Investigating the biodegradation of sulfadiazine in soil using Enterobacter cloacae T2 immobilized on bagasse

The application of the antibiotic sulfadiazine (SD) in veterinary medicine has created serious environmental issues due to its high mobility and non-degradability. A novel immobilized cell system has been developed and showed significant SD biodegradation potential in soil.

A catalyst selection method for hydrogen production through Water-Gas Shift Reaction using artificial neural networks

Hydrogen (H₂) is considered a clean valuable energy source and its worldwide demand has increased in recent years. The Water-Gas Shift (WGS) Reaction is one of the major routes for hydrogen production and uses different catalysts depending on the operating process conditions. A catalyst is usually composed of an active phase and a support for its dispersion. There are currently an increasing number of researches on catalytic field focusing on transition metals nanoparticles supported on different compounds. In order to predict optimal catalyst compositions for the WGS reaction, Artificial Neural Networks (ANNs) were used to build a model from the literature catalytic data. A three-layer feedforward neural network was employed with active phase composition and support type as some of the input variables, and Carbon Monoxide (CO) conversion as output variable. The insertion of properties such as surface area, calcination temperature and time allowed predicting the reaction performance based on intrinsic catalyst variables not commonly used in phenomenological kinetic models. Also, unlike previous studies, a detailed sensitivity analysis was carried out to observe useful trends. An important outcome of this work is the proposition of ceria-supported catalysts for the WGS reaction that present larger surface areas, with Ru, Ni or Cu as active phases conducted at moderate temperatures (≈300 °C) and with reasonable space velocities (2000-6000 h^-1). In addition, it was possible to predict the most relevant variables for the process: the temperature and the surface area. Thus, the results show the power of ANNs for predicting better catalysts and conditions for this important process in the environmental field.

Sequential coagulation/flocculation and microwave-persulfate processes for landfill leachate treatment: Assessment of bio-toxicity, effect of pretreatment and cost-analysis

The possibility of landfill leachate treatment in a coupled microwave-persulfate (MW-PS) system with and without pretreatment, i.e. coagulation-flocculation (C-F) was investigated. The C-F pretreatment with alum and FeCl₃ has reduced the turbidity from 90 NTU to 43 NTU and 10 NTU, respectively, at the optimized coagulant dosage. Moreover, 73% COD and 86% color removal was observed in C-F pretreatment with FeCl₃. The application of MW-PS system (at 10 g/L of PS dosage) for pretreated leachate (FeCl₃ dosage 1 g/L and pH 5.5) has produced a final COD removal of 89%. Similarly, alum pretreatment (dosage 1.6 g/L, pH 8.2) coupled with MW-PS system has achieved a total COD removal of 62%. In MW-PS system, the ratio of initial PS dosage to initial COD ratio has shown significant effect on leachate treatment. However, slightly lesser ammonia removal was observed in MW-PS (93%) compared to MW alone (97%) owing to reduction in pH of the system. The comparison of bio-toxicity (i.e. inhibition to aliivibrio fischeri) of treated samples from MW-PS and MW alone after pretreatment, i.e. 12.1 mg/L and 6.8 mg/L of equivalent ZnSO₄ toxicity, indicated that MW-PS treated sample were found to be more toxic than MW alone treatment and raw leachate (7.6 mg/L and 7.2 mg/L of equivalent ZnSO₄ toxicity, respectively) due to sulfate ion. This indicates that C-F followed by MW alone would be an ideal option for leachate treatment. The cost and energy estimation of MW and MW coupled systems well supported the above findings.