Photodegradation of diclofenac in seawater by simulated sunlight irradiation: The comprehensive effect of nitrate, Fe(III) and chloride

Phototransformation of tetrabromobisphenol A in saline water under simulated sunlight irradiation

The widespread use of halogenated flame retardants in recent years has led to the accumulation of TBBPA in water, which may cause potential harm to living organisms. The phototransformation of the flame retardant TBBPA in alkaline saline water under simulated sunlight irradiation was investigated. The effects of abiotic factors such as the initial concentration of TBBPA, chloride ion concentration, solution pH, inorganic anions and cations, dissolved organic matter (DOM) were studied. The results showed that the phototransformation rate of TBBPA accelerated with the decrease of the initial concentration of TBBPA, the increase of chloride ion concentration and solution pH. The scavenging experiments showed that •OH, ¹O₂, O₂•^- and ³TBBPA* all participated in the phototransformation of TBBPA. The presence of NO₃^-, CO₃^2-, SO₄^2-, Mg²⁺, Ca²⁺, Fe³⁺ and fulvic acid (FA) all inhibited the phototransformation of TBBPA in the present study. The phototransformation products of TBBPA were detected by liquid chromatography-mass spectrometry (LC-MS), and the phototransformation pathways were proposed. This is the first report on the photo-induced generation of halogen exchange products from TBBPA in saline solutions, which will contribute to a better understanding of the environmental behavior and risks of BFRs in water.

Photodegradation of Anti-Inflammatory Drugs: Stability Tests and Lipid Nanocarriers for Their Photoprotection

The present paper provides an updated overview of the methodologies applied in photodegradation studies of non-steroidal anti-inflammatory drugs. Photostability tests, performed according to international standards, have clearly demonstrated the photolability of many drugs belonging to this class, observed during the preparation of commercial forms, administration or when dispersed in the environment. The photodegradation profile of these drugs is usually monitored by spectrophotometric or chromatographic techniques and in many studies the analytical data are processed by chemometric procedures. The application of multivariate analysis in the resolution of often-complex data sets makes it possible to estimate the pure spectra of the species involved in the degradation process and their concentration profiles. Given the wide use of these drugs, several pharmaceutical formulations have been investigated to improve their photostability in solution or gel, as well as the pharmacokinetic profile. The use of lipid nanocarriers as liposomes, niosomes or solid lipid nanoparticles has demonstrated to both minimize photodegradation and improve the controlled release of the entrapped drugs.

Effects of fertilization on the triafamone photodegradation in aqueous solution: Kinetic, identification of photoproducts and degradation pathway

Triafamone is a highly effective, low toxicity sulfonamide herbicide widely used for weeding paddy fields. The triafamone photodegradation in water environment must be explored for its ecological risk assessment. In this work, the effects of chemical fertilizer (urea, diammonium phosphate, potassium chloride, and potassium sulfate), urea metabolites (CO₃^2- and HCO₃^-), and organic fertilizers (unfermented organic fertilizer [UOF] and fermented organic fertilizer [FOF]) on the triafamone photodegradation in aqueous solution under simulated sunlight were evaluated. Results showed that the triafamone photodegradation rate was unaffected by urea. The half-life of triafamone decreased from 106.8 h to 68.4 h with increasing diammonium phosphate concentration. Potassium chloride, potassium sulfate, CO₃^2-, and HCO₃^- could accelerate the triafamone photodegradation at all concentrations, whereas the degradation rate of triafamone decreased when the concentration of potassium sulfate or CO₃^2- was 2000 mg/L. Triafamone photodegradation was promoted by 20-200 mg/L UOF and FOF but decreased to 236.6 and 142.3 h when the concentration reached 2000 mg/L. Twenty-three transformation products were isolated and identified from triafamone by using ultra-performance liquid chromatography with quadrupole time-of-flight mass spectrometry under simulated sunlight irradiation, and the kinetic evolution of these products was explored. Five possible degradation pathways were inferred, including the cleavage of C-N, C-C, and C-O bonds; CO bond hydrogenation; the cleavage of triazine ring; the cleavage of the sulfonamide bridge; hydroxylation; hydroxyl substitution; methylation; demethylation; amination; and rearrangement. In summary, these results are important for elucidating the environmental fate of triafamone in aquatic systems and further assessing environmental risks.

Effect of dissolved organic matters and inorganic ions on TiO2 photocatalysis of diclofenac: mechanistic study and degradation pathways

Diclofenac (DCF) exists extensively in sewage treatment plant effluent, and it is one of the most reported environmental pharmaceutical contaminants. In this work, the photocatalytic degradation of DCF by titanium dioxide (TiO₂) in pure water under visible light and the influence of humic acids (HA) (as a kind of dissolved organic matter (DOM), phosphate and ferrous ion (Fe²⁺)) were investigated. The results showed that the lower the pH was, the better the degradation effect of DCF under acidic conditions was. Different concentrations of DOM, phosphate ion, and Fe²⁺ could inhibit the degradation of DCF, and the higher the concentration was, the stronger the inhibition was. Different concentrations of chloride ions had little effect on the degradation. A slight elimination (8-12.9%) of total organic carbon (TOC) was observed during the mineralization of DCF with and without DOM and inorganic ions, indicating poor mineralization during the process of photocatalytic degradation, and DOM, phosphate, and Fe²⁺ had little effect on DCF mineralization. Furthermore, hydroxyl radicals, superoxide radicals, and singlet oxygen radicals were present during the photocatalytic degradation of DCF. DOM and inorganic ions could inhibit the intensity of hydroxyl radical and promote superoxide radicals (O₂^-) and singlet oxygen (¹O₂) to varying degrees. Finally, the degradation mechanism and main products were analyzed by liquid chromatography-mass spectrometry (LC-MS), and nine possible intermediates were detected. Hydroxylation, dechlorination, cyclization, and oxidation were the main degradation mechanisms. However, DOM, phosphate, and Fe²⁺ did not affect the type of intermediate products in terms of the mass-to-charge ratio. This paper mainly studied the mechanisms of different influencing factors in simulated environments to provide a theoretical basis for the degradation of DCF in wastewater treatment plants. Graphical abstract.

Intensification of the O3/TiO2/UV advanced oxidation process using a modified flotation cell

A novel approach for the ozone and TiO₂ intensification process for wastewater treatment is presented using a modified flotation cell.

The fate of prazosin and levonorgestrel after electrochemical degradation process: Monitoring by-products using LC-TOF/MS

Prazosin (PRZ) and levonorgestrel (LNG) are widely used as an anti-disease drugs due to their biological activity in the human body. The frequent detection of these compounds in water samples requires alternative technologies for the removal of both compounds. After electrochemical degradation of PRZ and LNG, the parent compounds could be completely removed after treatment, but the identification and characterization of by-products are necessary as well. In this study, the effects of NaCl concentration and applied voltage were investigated during the electrochemical degradation process. The results revealed that the increase of NaCl concentration and applied voltage could promote the generation of hypochlorite OCl^- and then enhance the degradation of PRZ and LNG. After initial study, 6V and 0.2g NaCl were selected for further experiments (96% and 99% removal of PRZ and LNG after 40min, respectively). Energy consumption was also evaluated and calculated for PRZ and LNG at 3, 6 and 8V. Solid phase extraction (SPE) method plays an important role in enhancing the detection limit of by-products. Furthermore, characterization and identification of chlorinated and non-chlorinated by-products were conducted using an accurate liquid chromatography-time of flight/mass spectrometry LC-TOF/MS instrument. The monitoring of products during the electrochemical degradation process was performed at 6V and 0.2g NaCl in a 50mL solution. The results indicated that two chlorinated products were formed during the electrochemical process. The toxicity of by-products toward E. coli bacteria was investigated at 37°C and 20hr incubation time.

Electrochemical degradation of diclofenac using three-dimensional electrode reactor with multi-walled carbon nanotubes

The electro-oxidation treatment of aqueous solution containing diclofenac (DCF) on a Ti/RuO₂-TiO₂ electrode in the presence of multi-walled carbon nanotubes (MWCNTs) was studied in a three-dimensional electrochemical (3DE) reactor. The response surface methodology (RSM) based on central composite design (CCD) was utilized to determine the influence of different factors. The results revealed that the obtained polynomial experimental model had a high coefficient of determination (R² = 0.9762) based on analysis of variance. The optimum condition for the removal of DCF by the 3DE process was obtained with the initial pH of 3.8, the initial DCF concentration of 4 mg/L, the current density of 20 mA/cm², the particle electrode concentration of 70 mg/L, and the electrolysis time of 85 min. The quadratic model developed for DCF removal and subsequently the analysis of the F value illustrated that the initial pH was the most important factor in the removal of DCF. The comparative experiments between electrochemical processes showed the high electrocatalytic activity and removal efficiency of the 3DE reactor with the MWCNT particle electrode. The results also showed that the Ti/RuO₂-TiO₂ electrode, in addition to its high stability, had a very good electrocatalytic activity in the 3D reactor. The stability and reusability test proved that MWCNTs, as a particle electrode, had a potential to improve the long-term electrocatalytic degradation of DCF in the aqueous solutions. Based on the identified intermediate compounds along with the results of other studies, a possible pathway for the electrochemical oxidation of DCF by the 3DE process catalyzed with MWCNTs was proposed.

Aquatic photodegradation of clofibric acid under simulated sunlight irradiation: kinetics and mechanism analysis

Clofibric acid is one of the most frequently detected pharmaceuticals in various aquatic environments.