Photodegradation Of Sulfadiazine Research Articles

Enhanced solar driven photocatalytic removal of antibiotics from aquaculture effluents by TiO2/carbon quantum dot composites

Aquaculture exploitation is associated with the consumption of antibiotics, such as sulfadiazine (SDZ), sulfamethoxazole (SMX) and trimethoprim (TMP), the latter two being also vastly used to treat bacterial infections in humans. Consequently, and given that aquaculture wastewater treatments are not actually designed for the removal of antibiotics, they are ubiquitous in aquaculture effluents, which sets the risk of bacterial resistance. To face the need for an efficient and sustainable treatment to remove these antibiotics from the referred effluents, carbon quantum dots (CQDs) were produced, incorporated into titanium dioxide (TiO2), and evaluated for solar driven photodegradation of SDZ, SMX and TMP. Eleven different materials were synthesized and tested for their photocatalytic activity in phosphate buffer solution (PBS) and synthetic sea salts (SSS), used as synthetic matrices to simulate fresh and brackish water, respectively. Upon selection of the most efficient photocatalyst for each antibiotic and matrix, kinetic results demonstrated that its use allowed for remarkable reductions of SDZ, SMX and TMP half-life times (t1/2) in both matrices (between 19 and 68 times). Therefore, the application of the here synthesized photocatalysts for the advanced treatment of aquaculture effluents is promising, allowing for a green solar driven removal of antibiotics.

Periodic mesoporous organosilicas containing naphthalenediimides as organic sensitizers for sulfadiazine photodegradation.

In this work, periodic mesoporous organosilicas (PMO) functionalized with the organic sentisizer naphthalenediimide (NDI) were employed as heterogeneous catalysts for the photodegradation of the antibiotic sulfadiazine (SDZ), taken as a model for contaminants of emerging concern (CECs). The catalysts, designated as PMONDI, were prepared by surfactant-directed co-condensation of the precursor N,N'-bis(3-triethoxysilylpropyl)-1,4,5,8-naphthalenediimide with tetraethoxysilane. The synthesized PMONDI were characterized using transmission electron microscopy, nitrogen adsorption isotherms and small and large angle x-ray scattering. The performance of PMONDI catalysts in the photodegradation of SDZ was compared to that of TiO2 nanoparticles impregnated into SBA-15 mesoporous silica (TiO2/SBA-15), under irradiation with a Hg lamp with a bandpass filter of 320-500nm. Under optimal conditions, PMONDI degraded 100% of the SDZ in 45min, while the total degradation of SDZ was achieved only after 150min with TiO2/SBA-15. PMONDI also performed better than TiO2/SBA-15 in reuse tests. The mechanism of photodegradation with PMONDI involves the formation of excited triplet states of NDI (3NDI*) upon irradiation, which can then react with molecular oxygen to form reactive oxygen species, which degrade SDZ. Analysis of the SDZ degradation products indicated two main pathways: (1) hydroxylation of the aniline ring and (2) SO2 extrusion and rearrangement, followed by oxidation of the aniline ring to nitrobenzene. In conclusion, the great potential of the PMONDI materials as photocatalysts for CECs degradation was demonstrated in this work, encouraging further research on these materials for the degradation of pollutants.

G-C3N4/polyvinyl alcohol-sodium alginate aerogel for removal of typical heterocyclic drugs from water

Heterocyclic drugs (HCDs) detected at high frequencies in wastewater have raised great concerns and their advanced removal has been the hotspot for safe water reuse in recent years. Two-dimensional graphitic carbon nitride (g-C3N4) and its photocatalytic systems are increasingly emerging, however, there are inevitable drawbacks of stacking and difficulty in recycling, resulting in decreased pollutant removal and limited application. Herein, for the first time, this paper reported a three-dimensional g-C3N4/polyvinyl alcohol-sodium alginate aerogel (g-C3N4/PVA-SA aerogel) photocatalyst synthesized by ultrasonic exfoliation and in-situ polymerization for typical HCDs (sulfadiazine (SDZ), sulfamethoxazole (SMX), and carbamazepine (CBZ)) removal in water. The reduced stacking of g-C3N4 dispersed in PVA-SA aerogel was achieved as revealed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD) analysis, and g-C3N4/PVA-SA aerogel was observed to possess encouraging degradation efficiencies and rates for SDZ (100%, 0.0249 min−1), SMX (100%, 0.1762 min−1) and CBZ (69.8%, 0.0056 min−1), which were improved by 50%–60% and 133%–216% compared to those of g-C3N4, respectively. Meanwhile, environmental impact factors such as pH and coexisting ions had less impact on the degradation of SDZ and SMX by g-C3N4/PVA-SA aerogel. The novel aerogel also had a good recyclability, with less than 5% reduction in degradation efficiency after five cycles observed. The photodegradation of SDZ, SMX and CBZ was confirmed to be driven by ⋅O2− and h+ through scavenger-quenching experiments. The new low carbon and recyclable g-C3N4/PVA-SA aerogel reported in this study indicated a good potential for efficient removal of HCDs from water, which provides an alternative strategy for advanced purification and safe reuse of wastewater.

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

In order to overcome the shortcomings in 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/S2O8 2-/hv system. The effect of Fe(III):EDDS molar ratio, the concentration of Fe(III)-EDDS and the concentration of S2O8 2- on SD degradation were explored. At neutral pH, when Fe(III):EDDS = 1:1, Fe(III)-EDDS = 0.1 mM, S2O8 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 CO3 2-, SO4 2-, while the degradation of SD almost unaffected when Cl- added. 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, SO4 ·− and O2 ·− were produced in the process. SO4 ·− and ·OH were identified as the main radicals while O2 ·− also played non-ignorable role. Eleven intermediate products of SD were analyzed. 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.

Enhanced photodegradation of antibiotics based on anoxygenic photosynthetic bacteria and bacterial metabolites: A sustainably green strategy for the removal of high-risk organics from secondary effluent

Antibiotic residues in effluents discharged from wastewater treatment plants (WWTPs) have been considered high-risk organics due to biorefractory property and potential toxicity. Secondary pollution and unsustainability existed in advanced treatment of secondary effluent are currently in urgent need of improvement. In this study, a sustainably green strategy based on Rhodopseudomonas palustris (R.palustris) by regulating the structure of extracellular polymeric substances (EPS) was proposed for the first time to achieve efficiently removal of sulfadiazine (SDZ). Results showed that 0.2 V was the optimal external potential for R.palustris to efficiently remove SDZ, where the biodegradation rate constant obtained at this potential was 4.87-folds higher than that in open-circuit mode and a complete removal was achieved within 58 h in the presence of EPS extracted at this potential. Three-dimensional excitation-emission matrix (3D-EEM) spectra analysis suggested that tryptophan protein-like, tyrosine protein-like, humic acid-like and fulvic acid-like substances present in EPS were the main effective components which was responsible for the indirect photodegradation of SDZ. The quenching experiments showed that 3EPS* was the dominant reactive species which accounted for 90% of SDZ removal. This study provides new implications for the advanced treatment of secondary effluent organic matters by developing eco-friendly bioaugmentation technology and biomaterials.

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 (t1/2) from 14.5 ± 0.7 h (in absence of photocatalyst) to 0.38 ± 0.04 h. Concerning OXA in SSS, the t1/2 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.

Functionalized mesoporous silicas SBA-15 for heterogeneous photocatalysis towards CECs removal from secondary urban wastewater

The photocatalytic activity of TiO2 nanoparticles (NPs) supported on mesoporous silica SBA-15 (TiO2/SBA-15) was evaluated for the photodegradation of sulfadiazine (SDZ), as target contaminant of emerging concern (CEC), using either pure water solutions (PW) or a real secondary urban wastewater (UWW) spiked with SDZ. For this purpose, TiO2/SBA-15 samples with 10, 20 and 30% TiO2 (w/w) were prepared by the sol-gel post synthetic method on pre-formed SBA-15, using titanium (IV) isopropoxide as a precursor. The TiO2/SBA-15 materials were characterized by HRTEM, SAXS and XRD, nitrogen adsorption isotherms and UV–vis diffuse reflectance spectroscopy. TiO2 NPs were shown to be attached onto the external surface, decorating the SBA-15 particles. The TiO2/SBA-15 catalysts were active in SDZ photodegradation using the annular FluHelik photoreactor, when irradiated with UVA light. The 30% TiO2/SBA-15 sample presented the best performance in optimization tests performed using PW, and it was further used for the tests with UWW. The photocatalytic activity of 30% TiO2/SBA-15 was higher (56% SDZ degradation) than that of standard TiO2–P25 (32% SDZ degradation) in the removal of SDZ spiked in the UWW ([SDZ] = 2 mg L−1). The photodegradation of SDZ with 30% TiO2/SBA-15 eached 90% for UWW spiked with a lower SDZ concentration ([SDZ] = 40 μg L−1). Aside of SDZ, a suit of 65 other CECs were also identified in the UWW sample using LC-MS spectrometry. A fast-screening test showed the heterogeneous photocatalytic system was able to remove most of the detected CECs from UWW, by either adsorption and/or photocatalysis.

Synthesis and properties of photocatalysts for the high degradation of sulfadiazine

In this study, it was discovered for the first time that the BiOBr/Bi3.84W0.16O6.24 catalyst can efficiently degrade sulfadiazine (SDZ). Multiple techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis diffuse reflection spectroscopy (DRS) were applied to research the structures, morphology and photocatalytic properties of as-prepared samples. In addition, the effect of different synthesis pH environment and initial SDZ solution pH on the catalyst degradation efficiency were discussed. The BiOBr/Bi3.84W0.16O6.24 catalyst synthesized under the condition of pH = 7 exhibited excellent photocatalytic activity for photodegradation of SDZ of 91% within 120 min under simulated solar light irradiation. Also, the roles of the radical species have been studied, and the ·O2- and h+ were proved to dominate the photocatalytic process. Based on the experimental results, the photocatalytic mechanism was proposed.

Photodegradation of sulfadiazine in different aquatic environments – Evaluation of influencing factors

The presence of antibiotics, such as sulfadiazine (SDZ), in the aquatic environment contributes to the generation of antimicrobial resistance, which is a matter of great concern. Photolysis is known to be a major degradation pathway for SDZ in surface waters. Therefore, influencing factors affecting SDZ photodegradation in different aquatic environments were here evaluated in order to have a better knowledge about its persistence in the environment. Photodegradation of SDZ was found to be more efficient at higher pH (t1/2 = 6.76 h, at pH = 7.3; t1/2 = 12.2 h, at pH = 6.3), in the presence of humic substances (HS) (t1/2 between 1.76 and 2.42 h), as well as in the presence of NaCl (t1/2 = 1.00 h) or synthetic sea salts (t1/2 = 0.78 h). Using ˙OH and 1O2 scavengers, it was possible to infer that direct photolysis was the main pathway for SDZ photodegradation in ultrapure water. Furthermore, results under N2 purging confirmed that 1O2 was not relevant in the phototransformation of SDZ. Then, the referred observations were used for the interpretation of results obtained in environmental matrices, namely the final effluent of a sewage treatment plant (STPF), fresh and brackish water (t1/2 between 2.3 and 3.48 h), in which SDZ photodegradation was found to be much faster than in ultrapure water (t1/2 = 6.76 h).

Molecular iodine enhancing sulfadiazine photodegradation in water under UVA irradiation

Photodegradation of sulfadiazine (SD), a typical sulfonamide antibiotic (SA) frequently detected in the aquatic environment, under UVA irradiation enhanced by molecular iodine was investigated. Herein, molecular iodine I2 and coexisting I3− were provided by hydrogen peroxide and potassium iodide in acidic solution. During the treatment, highly reactive iodine radicals (I·, I2−), produced by UVA photolytic activation of both I2 and I3−, were verified as the dominated oxidant species against the decomposition of SD in aqueous solution. Besides, SD removal was found to be affected by the initial pH value, KI and H2O2 added concentrations.

Modelled phototransformation kinetics of the antibiotic sulfadiazine in organic matter-rich lakes

Xenobiotic compounds are commonly detected in inland waters. Sunlight-induced photochemical reactions contribute to xenobiotic degradation, but the role of different photoreactions on large geographic scales remains poorly understood. Here, we used a combination of photochemical modelling and large-scale field data from 1020 lakes across Sweden to elucidate the photodegradation kinetics of the commonly used antibiotic sulfadiazine (SDZ) in organic matter-rich lakes. SDZ occurs in two forms, namely acidic HSDZ (pKa = 6.5) and basic/deprotonated SDZ−. Both species are oxidised fast by the photogenerated triplet states of natural organic matter (3NOM*). However, they also undergo efficient back reactions because the partially oxidised HSDZ (and SDZ− to a larger extent) can be reduced back to the initial compounds by the phenolic moieties contained in NOM. Typical lakes in Sweden are rich in NOM and have low pH, with the consequence that SDZ photochemistry would be dominated by HSDZ. Our simulation results showed that SDZ photodegradation kinetics in Swedish lakes would become significantly slower with increasing water depth and pH, while it depended little on latitude, which affects irradiance, or on organic matter content. As a consequence, SDZ would be particularly persistent in lakewater in some densely populated areas with relatively deep and high-pH lakes such as, most notably, the Stockholm region. Here the surface waters could be more heavily contaminated by pharmaceuticals compared to the scarcely populated regions in the centre-north of the country, where lakewater could otherwise promote an efficient photodegradation of SDZ.

Photodegradation of Sulfadiazine in Aqueous Solution and the Affecting Factors

Knowledge about photochemical behavior of sulfonamides under UV light is limited. In this study, photodegradation of sulfadiazine in water by ultraviolet (UV) light was studied using a 300 W, 365 nm UV lamp. The degradation process followed well the first-order kinetics, with a half-life of 9.76 min in water with air saturation. The photodegradation was slower at acidic pH 4.52 than at pH 6.98 and pH 8.90. Addition of H2O2and nitrate enhanced the photodegradation rate, while addition of ethanol, nitrite, sulfate, and bicarbonate depressed the reaction rate. This study suggested that sulfadiazine photodegradation under UV light is generally favored by the attack of hydroxyl radicals.

Composites of Silica and Molecularly Imprinted Polymers for Degradation of Sulfadiazine

We report on the fabrication of silica/zinc oxide/zinc sulfide nanoparticles (SiO2/ZnO/ZnS NPs) wrapped with thermoresponsive molecularly imprinted polymers (TMIPs) for photocatalysis (PC) applications. TMIPs were prepared via surface-initiated reversible addition–fragmentation chain transfer (SI-RAFT) polymerization of N-isopropylacrylamide (NIPAm) and ethylene glycol dimethacrylate (EGDMA), rendering the material solution accessible and temperature sensitive. Photodegradation of sulfadiazine (SD) was used as a probe to evaluate the effect of coated TMIPs on the PC performance of SiO2/ZnO/ZnS NPs. The results showed that TMIPs made SiO2/ZnO/ZnS NPs have an outstanding specific affinity PC activity toward template SD. Modification of SiO2/ZnO/ZnS NPs with Ag2S resulted in a tunable PC ability of the prepared material. For SI-RAFT conducted in a controlled manner, a thin layer of polymers (∼100 nm) formed around NPs was measured by a transmission electron microscopy (TEM). Also the polymers were characteri...

Photodegradation of Sulfadiazine by Goethite−Oxalate Suspension under UV Light Irradiation

Sulfadiazine, a potent antibacterial agent belonging to the group of antibiotics called sulfonamides, has been reported to be present in surface and groundwater. This study investigated the degradation of sulfadiazine in a goethite (α-FeOOH)−oxalate Fenton-like system under UV irradiation. The results showed that sulfadiazine could be effectively photodegraded by the goethite−oxalate Fenton-like system as a result of the formation of the highly oxidizing hydroxyl radicals, •OH. Among the iron oxides tested (α-FeOOH, γ-Fe2O3, γ-FeOOH, and α-Fe2O3), α-FeOOH was found to be the most effective. Degradation of sulfadiazine depended significantly on the pH and initial concentration of oxalic acid in the system, with optimal values of 3.5 and 4.0 mM, respectively, under UV irradiation. Five intermediate products of sulfadiazine degradation were identified using high-performance liquid chromatography−mass spectrometry (HPLC−MS), gas chromatography−mass spectrometry (GC−MS), and ion chromatography (IC), and a poss...

Photolysis of 14C-sulfadiazine in water and manure

Photolysis of 14C-sulfadiazine in aqueous solution under simulated sunlight followed first-order kinetics. The impact of H 2O 2, humic acid, fulvic acid and acetone to enhance the photodegradation of sulfadiazine (SDZ) was studied. Six photoproducts, 4-OH-SDZ, 5-OH-SDZ, N-formyl-SDZ, 4-[2-iminopyrimidine-1(2H)-yl] aniline, 2-aminopyrimidine, and aniline were identified. Extrusion of SO 2 was found to be the main degradation process during irradiation. These photoproducts can occur in water and soil upon sunlight exposure, when soil is treated with SDZ contained in manure. Due to photodegradation the experimental half-life of the SDZ in water was 32 h and in the presence of photosensitizers the half-life values were 19.3–31.4 h, 17.2–31.4 h, 12.6–29.8 h, and 3.8–30.7 h for H 2O 2, humic acid, fulvic acid, and acetone, respectively depending on the concentration of the photosensitizers. The presence of photosensitizers markedly reduced SDZ persistence, indicating that indirect photolytic processes are important factors governing the photodegradation of SDZ in aqueous environments. Investigation revealed further persistence behavior of SDZ in manure. The half-life value of SDZ in manure was 158 h.