Study of solar photocatalytic degradation of Acesulfame K to limit the outpouring of artificial sweeteners

Acesulfame degradation by thermally activated persulfate: Kinetics, transformation products and estimated toxicity

The existence of the artificial sweetener acesulfame (ACE) in quantities of significance can negatively impact water quality, and its consumption has been associated with deleterious health effects. The present investigation explores the efficacy of heat-activated sodium persulfate (SPS) for eliminating ACE. The complete degradation of 0.50 mg L-1 of ACE was achieved within 45 min under a reaction temperature of 50 °C and 100 mg L-1 of SPS. The impact of thermal decomposition on ACE at a temperature of 60 °C was negligible. This study considers several factors, such as the SPS and ACE loading, the reaction temperature, the initial pH, and the water matrix of the reactor. The results indicate that the method's efficiency is positively correlated with higher initial concentrations of SPS, whereas it is inversely associated with the initial concentration of ACE. Furthermore, higher reaction temperatures and acidic initial pH levels promote the degradation of acesulfame. At the same time, certain constituents of the water matrix, such as humic acid, chlorides, and bicarbonates, can hinder the degradation process. Additionally, the data from LC-QToF-MS analysis of the samples were used to investigate transformation through suspect and non-target screening approaches. Overall, ACE's eight transformation products (TPs) were detected, and a potential ACE decomposition pathway was proposed. The concentration of TPs followed a volcano curve, decreasing in long treatment times. The ecotoxicity of ACE and its identified TPs was predicted using the ECOSAR software. The majority of TPs exhibited not harmful values.

Oxidative treatment of micropollutants present in wastewater: A special emphasis on transformation products, their toxicity, detection, and field-scale investigations

Micropollutants have become ubiquitous in aqueous environments due to the increased use of pharmaceuticals, personal care products, pesticides, and other compounds. In this review, the removal of micropollutants from aqueous matrices using various advanced oxidation processes (AOPs), such as photocatalysis, electrocatalysis, sulfate radical-based AOPs, ozonation, and Fenton-based processes has been comprehensively discussed. Most of the compounds were successfully degraded with an efficiency of more than 90%, resulting in the formation of transformation products (TPs). In this respect, degradation pathways with multiple mechanisms, including decarboxylation, hydroxylation, and halogenation, have been illustrated. Various techniques for the analysis of micropollutants and their TPs have been discussed. Additionally, the ecotoxicity posed by these TPs was determined using the toxicity estimation software tool (T.E.S.T.). Finally, the performance and cost-effectiveness of the AOPs at the pilot scale have been reviewed. The current review will help in understanding the treatment efficacy of different AOPs, degradation pathways, and ecotoxicity of TPs so formed.

Acesulfame K Photodegradation over Nitrogen-Doped TiO2

Acesulfame K is a zero-calorie alternative to sugar used worldwide. There is contradictory information on the toxicity of the compound, but its accumulation in the aquatic environment is undeniable. In this study, one-pot sol-gel synthesis was used to obtain nitrogen-doped TiO2 photocatalysts. Doping up to 6.29 wt % of nitrogen caused an increase in the surface area of the catalysts (48.55–58.23 m2∙g−1) and a reduction of the pHPZC value (5.72–5.05). Acesulfame K photodegradation was tested at the initial concentration of 20–100 ppm and the catalyst concentration at the level of 1 g∙L−1. Compared to the pure anatase, 4.83–6.29 wt % nitrogen-doped TiO2 showed an effective photodegradation of Acesulfame K. Ninety percent molecule removal was obtained after ~100 min, ~90 min, and ~80 min for initial concentrations of 20 ppm, 50 ppm, and 100 ppm, respectively. The increased activity of the catalysts is due to the modification of the TiO2 lattice structure and probably the limitation of the photogenerated electron/hole charge carrier recombination. It was shown that the electrostatic interactions between Acesulfame K and the catalyst surface play an important role in the photodegradation efficiency.

Performance of ultraviolet/persulfate process in degrading artificial sweetener acesulfame

The degradation of the artificial sweetener acesulfame (ACE) was investigated using an ultraviolet (UV)₃₆₅-activated peroxydisulfate (PDS) process. The results demonstrated that the ACE reaction rate with the UV/PDS process followed pseudo first-order kinetics (R² > 0.9) under various conditions. A high dosage of PDS, alkaline condition, and the existence of NO₃^- and Cl^- enhanced ACE degradation; however, a high dosage of ACE, the existence of HCO₃^-, humic acid, and fulvic acid, and a real water matrix did not facilitate the degradation of ACE. Four types of transformation products were detected in the degradation of ACE by UV/PDS, and the primary degradation pathways were oxidation, hydroxyl substitution, hydrolysis, and hydration. The hydroxyl radicals played a predominant role (71.31%) in the degradation of ACE by the UV/PDS process, followed by sulfate radicals (14.57%) and UV photolysis (8.83%). Both the degradation and mineralization rates of ACE using the UV/PDS process had significant advantages over that of the UV/H₂O₂ process regarding ACE degradation, indicating that the UV/PDS process is more promising for treating water containing ACE.

Photocatalytic Activity of Aeroxide TiO2 Sensitized by Natural Dye Extracted from Mangosteen Peel

Natural dye sensitizers are environment-friendly and inexpensive substances that could be used for photocatalytic decontamination of organic pollutants. In this study, a natural dye extracted from mangosteen peel, containing a significant amount of anthocyanin dye, has been successfully employed to sensitize aeroxide TiO2 to lower its bandgap, thereby making the process visible sunlight-driven. We have demonstrated the photocatalytic activity of mangosteen dye-sensitized-TiO2 (MS-TiO2) under visible solar light by studying the degradation of methylene blue (MB), a well-studied model compound. A multivariate parametric study was performed using factorial design methodology with three factors—pH, MS-TiO2 dosage, and visible light intensity. The study indicated that pH and MS-TiO2 dosage are the two most dominant factors for MB degradation under visible solar light. The kinetic rate constant and adsorption equilibrium constant were determined, and a Langmuir-Hinshelwood-type equation was proposed to describe MB degradation on MS-TiO2 under visible solar light. Apparent quantum yield was also reported for the MS-TiO2 photocatalyst at optimum experimental conditions.

Hazardous waste treatment technologies

This is a review of the literature published in 2018 on topics related to hazardous waste management in water, soils, sediments, and air. The review covers treatment technologies applying physical, chemical, and biological principles for contaminated water, soils, sediments, and air. PRACTITIONER POINTS: The management of waters, wastewaters, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) was reviewed according to the technology applied, namely, physical, chemical and biological methods. Physical methods for the management of hazardous wastes including adsorption, coagulation (conventional and electrochemical), sand filtration, electrosorption (or CDI), electrodialysis, electrokinetics, membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non-thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed. Chemical methods including ozone-based, hydrogen peroxide-based, persulfate-based, Fenton and Fenton-like, and potassium permanganate processes for the management of hazardous were reviewed. Biological methods such as aerobic, anaerobic, bioreactor, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed.

Rapid removal of acesulfame potassium by acid-activated ferrate(VI) under mild alkaline conditions

Acesulfame potassium (ACE) is a widely used artificial sweetener that has consistently been detected in wastewater and surface waters. The high-valent iron-based green oxidant known as ferrate(VI) (potassium ferrate(VI); Fe(VI)) had low reactivity with ACE (i.e. 4 h (or 240 min) contact time removed only ∼ 67% ACE) at a molar ratio of 6.0 ([Fe(VI)]:[ACE]). Comparatively, it took 60 s (or 1 min) to remove ∼94% ACE when HCl (786 μM) was added to a mixture of Fe(VI)-ACE at the same molar ratio of 6.0 (or acid-activated Fe(VI)). Significantly, the final pH (i.e. 7.6-8.1) was similar for Fe(VI) and acid-activated Fe(VI). An empirical model using response surface methodology was developed that could describe reasonably well the removal efficiency of ACE. Inorganic constituents of wastewater (Cl^-, Na⁺, Ca²⁺, and Mg²⁺) had no significant effect on the oxidation of ACE by acid-activated Fe(VI). The degradation efficiency of ACE decreased in the presence of 10 mg/L of natural organic matter (NOM) but remained unchanged at 5 mg NOM/L. Sulfamic acid as the oxidized product of ACE was identified by liquid chromatography high resolution mass spectrometry method. Reaction pathways include ring opening of ACE through hydrolytic transformation. Acid-activated Fe(VI) has advantage of rapid removal of ACE under mild alkaline conditions of wastewater treatment plants compared to other oxidation processes such as chlorination, ozonation, and light-based processes.

Review on the determination and distribution patterns of a widespread contaminant artificial sweetener in the environment

The accurate determination of widespread artificial sweeteners (ASs) and the information of their distributions in environments are of significance to investigate the environmental behaviors. This paper firstly reviews the typical analytic methodologies for ASs and the main influencing factors during the analytic processes. Solid-phase extraction (SPE) with LC-ESI-MS is currently the leading-edge method. However, the efficiency and accuracy for ASs analysis in environmental samples are also dependent on the SPE cartridges, buffers and pH, matrix effects, and sample stability. A basic procedure for ASs determination in different environmental samples is proposed. The current occurrences of ASs in environments are then evaluated. The ASs, especially the acesulfame and sucralose, are widely detected in various environmental medium. The concentrations of investigated ASs are generally in the order of wastewater treatment plants (WWTPs) influent > WWTPs effluent > surface water > groundwater > drinking water; and atmosphere > soil. The ASs levels in the environment exhibit significant differences among different regions. Further analysis indicates that the phenomenon is highly correlated with the consumption patterns and the removal efficiency of WWTPs in a specific country.

Ecotoxicity and environmental fates of newly recognized contaminants-artificial sweeteners: A review

Artificial sweeteners (ASs) are used in countless application in daily life. ASs are newly recognized as pollutants due to their high detection frequency in various environmental media, which has aroused great concern. This review presents the current knowledge of AS ecotoxicity and possible elimination routes in the environment. The obtained results indicate that the negative impacts of ASs are more severe than previously expected. More attention should be paid to the chronic and metabolite toxicities of ASs. Moreover, numerous processes (physical, chemical and biological) have been reported to be able to degrade ASs. However, the elimination efficiency varies greatly depending on the specific AS and the particular experimental conditions. Cyclamate and saccharin are easily removed, while sucralose and acesulfame are generally persistent. Additionally, there is a large gap in the ASs removal efficiency between bench tests and full-scale studies. The potential for microbial degradation of persistent ASs was reported in some regions, but clarification of the underlying mechanisms is necessary to increase the likelihood of using this approach in wide applications with a satisfactory performance.