Transformation Of Acetaminophen Research Articles

Singlet oxygen and hydroxyl radical in the transformation of acetaminophen in surface water: The mechanism on the degradation pathways based on DFT calculations

Pharmaceuticals compounds are continuously released into the aquatic environment due to the widely used therapeutically in livestock and humans. These pharmaceuticals and their degradation products accumulate in fish and have potential impacts on human and ecosystems. In this study, acetaminophen (ACE), a pharmaceutical widely used in COVID-19 epidemic, was selected as the research object to study its microscopic transformation mechanism and ecotoxicity using density functional theory and computational toxicology. The research demonstrated that ACE could be degraded by 1O2 in three pathways (2,2-cycloaddition, Ene reaction and 2,4-cycloaddition). The 2,4-cycloaddition mechanism at para-site plays a dominant role in the 1O2 oxidation of ACE. The total rate constant of ACE for •OH-initiated reaction was 1.78×109 M−1s−1 at 298 K. Furthermore, the half-life of ACE was determined as 143 and 3.5 days at ambient temperatures, given the concentration of •OH and 1O2 as 10−16.5 and 10−13 M, respectively. Although the aquatic toxicity of most degradation by-products appears to be not harmful level, some products were identified as very toxic and have developmental toxicity, especially hydroquinone and 1,4-benzoquinone. The systematic mechanism study provides a pathway to understand the transformation and environmental impact of pharmaceutical pollutants containing paracetamol in natural water environment at the molecular level.

Peanut-shell-derived biochar mediated peracetic acid activation for the elimination of acetaminophen via an electron-transfer regime

Biochar-based heterogeneous activation of disinfectant peracetic acid (PAA) is an attractive and promising route for micropollutant elimination in water, yet the underlying activation mechanism is still scarce. In this study, PAA was first catalyzed by peanut shell-derived biochar (PSBC) to degrade acetaminophen (ACP). The enhancement of ACP removal was triggered by PAA activation, while the coexisted H2O2 was unexpected to be an adverse factor owing to its occupation of active sites. Higher dosages of PSBC (0–0.30 g/L) and PAA (0–4.0 mM) favored the destruction of ACP, and the activation energy (41.8 kJ/mol) of PSBC/PAA system is lower than that of the thermal or microwave activated PAA system. The experimental results demonstrate that the metastable complex PSBC-PAA* dominated ACP elimination through an electron transfer mechanism. The surface –OH group was validated to be the key active site for PAA activation. Surprisingly, the actual water matrices present a negligible effect and the promotion of HCO3− ion on ACP removal was even observed. Based on the identified intermediates, the transformation of ACP was further proposed with the formation of polymeric products via oxidative coupling reactions. The findings not only shed light on the mechanism of PAA activated by the biochar-based catalyst but also contribute to a novel perspective on future PAA studies in contamination remediation.

Transformation of acetaminophen in solution containing both peroxymonosulfate and chlorine: Performance, mechanism, and disinfection by-product formation

With the fast development of peroxymonosulfate (PMS)-dominating processes in drinking water and wastewater treatment, residual PMS is easy to come across chlorine as these processes are usually followed by secondary chlorine disinfection. The synergistic effect of PMS and chlorine on the degradation of micro-organic pollutants is investigated by selecting acetaminophen (ACT) as a reference compound for the first time in this study. Unlike conventional PMS or chlorine activation which generates reactive species such as hydroxyl radical (HO•), sulfate radical (SO4•−), chlorine radical (Cl•), and singlet oxygen (1O2), the efficient ACT removal is attributed to the direct catalytic chlorination by PMS due to the significantly enhanced consumption of chlorine along with negligible change of PMS concentration at neutral condition, and the same reaction pathways in both PMS/chlorine and chlorine processes. The kinetic study demonstrates that ACT oxidation by PMS/chlorine follows second order reaction, and the degradation efficiency can be promoted at alkaline conditions with peak rate constants at pH 9.0−10.0. The presence of chloride can enhance the removal of ACT, while ammonium and humic acid significantly retard ACT degradation. Higher formation of selected disinfection by-products (DBPs) is observed in the PMS/chlorine process than in the sole chlorination. This study highlights the important role of PMS in organic pollutants degradation and DBPs formation during the chlorination process.

Transformation of acetaminophen in natural surface water and the change of aquatic microbes

The kinetics and transformation pathway of acetaminophen (APAP) in natural surface water (one sample from the Yangtze River and three others from different lakes), and the changes of aquatic microbes in surface water were revealed in this study. Both photochemical and microbial reactions contributed to the transformation of APAP under irradiance of 1.0–250 mW/cm2. Microbial compositions were significantly different among surface water, and same microbial transformation product (1,4-bezoquinone) was detected as the predominant biotransformation intermediate in four studied surface water, but the lag phase (12−50-h) for the transformation was highly dependent on the aquatic microbial abundance and composition. The lag phase no longer existed with irradiance increased to 5.9 mW/cm2. Aquatic microbial abundance and composition were influenced by the presence of APAP and radiation, and the influence extent was dependent on microbial species. The findings demonstrated that the individual contribution of biotic and abiotic process to the overall transformation of APAP and maybe other phenol in surface water varied as the background composition of surface water and the external environment changed, and biotransformation dominated (>73%) the overall transformation of APAP in surface water.

Bicarbonate-activated persulfate oxidation of acetaminophen

Persulfate (PS) is widely used as an oxidant for in situ chemical remediation of contaminated groundwater. In this study we demonstrated for the first time that PS could be activated by bicarbonate. Acetaminophen was used as the probe compound to examine the reactivity of PS/bicarbonate system. It was found that acetaminophen could be effectively transformed and the reaction rate appeared pseudo-first-order to the concentrations of both acetaminophen and PS. Radical scavenger tests indicated that neither free radicals (SO4- and HO) nor superoxide (O2-) was responsible for acetaminophen transformation. Generation of singlet oxygen (1O2) was verified using furfuryl alcohol (FFA) as a probe. Formation of 1O2 was further quantified in D2O fortified solution based on kinetic solvent isotopic effect (KSIE) but it was found that 1O2 contributed only 51.4% of the total FFA transformation. The other 48.6% was presumed to be ascribed to the reaction with peroxymonocarbonate (HCO4−). However, the transformation of acetaminophen was mostly due to the reaction with HCO4− but not 1O2. Instead of degradation, HCO4− oxidized acetaminophen via a one-electron abstraction mechanism resulting in the generation of acetaminophen radicals which coupled to each other to form dimers and trimers. HCO4− also hydrolyzed rapidly to form hydrogen peroxide (H2O2) which led to the formation of 1O2, during which O2- was a key intermediates. Because bicarbonate is ubiquitously presented in groundwater, the findings of this research provide important insights into the fundamental processes involved in PS oxidation in subsurface.

Transformation of acetaminophen during water chlorination treatment: kinetics and transformation products identification.

As a high-consumption drug in the world, acetaminophen (AAP) has been widely detected in natural waters and wastewaters. Its reactivity and the transformation products formed during chlorination may greatly threaten the safety of drinking water. The reaction kinetics of AAP during chlorination was investigated in this study. The results showed that the reaction kinetics could be well described with a kinetics model of -d[AAP]/dt = k app[AAP]t (0.63)[Cl2]t (1.37). The values of apparent rate constant (k app) were dependent on reaction temperature, ammonium, and pH. With the increase in reaction temperature from 5.0 ± 1.0 to 40.0 ± 1.0°C, the removal efficiency of AAP increased from 60 to 100%. When ammonium was present in the solution at 2.0mg/L, the transformation of AAP was inhibited due to the rapid formation of chloramines. The maximum of k app was 0.58 × 10(2)M(-1) · min(-1) at pH9.0, and the minimum was 0.27M(-1) · min(-1) at pH11.0. A low mineralization of AAP (about 7.2%) with chlorination was observed through TOC analysis, implying the formation of plenty of transformation products during chlorination. The main transformation products, hydroquinone and two kinds of chlorinated compounds, monochlorinated acetaminophen and dichlorinated acetaminophen, were detected in gas chromatography-mass spectrometry analysis.

Transformation of acetaminophen using manganese dioxide − mediated oxidative processes: Reaction rates and pathways

This study investigates the oxidative transformation kinetics of acetaminophen (APAP) by δ-MnO2 under different conditions. APAP was rapidly oxidized by δ-MnO2 with the generation of Mn2+. The measured APAP reaction rate considerably increased with an increase in initial δ-MnO2 and APAP concentration, but decreased as pH increased. The APAP reaction rate also increased with an increase in temperature. The addition of inorganic ions (Mn2+, Ca2+, and Fe3+) and substituted phenols (guaiacol, caffeic acid, and p-coumaric acid) as co-solutes remarkably decreased the transformation rate of APAP. The UV–Vis absorption spectra exhibited the π→π* transition, typical for aromatic rings. In addition, the intensity of the absorption peak gradually improved with increasing reaction time, suggesting that APAP can polymerize to form oligomers. Moreover, the secondary mass spectra of the dimers elucidated that the dimers were formed by the covalent bonding of phenol aromatic rings. Moreover, the higher-degree oligomers were formed by the coupling polymerization of phenolic and anilidic groups of dimers. These results are useful in understanding the fate of APAP in natural systems.

Transformation of Acetaminophen by Dichromate Oxidation Produces the Toxicants 1,4-Benzoquinone and Ammonium Ions

The reaction of the common pain reliever acetaminophen (paracetamol, 4-acetamidophenol) with dichromate was investigated over time under conditions that simulate wastewater disinfection. The occurrence of the acetaminophen in the water bodies, especially in drinking water resources, has received considerable attentions. In situ chemical oxidation is a promising cost-effective treatment method to remove acetaminophen from water body as it degrades the drug to large extent. Experimental results indicate that the reaction is second order overall and first order with respect to both dichromate and acetaminophen, and has activation energy of 14.1 kJ/mol. The second-order rate constant ranges from 1.56 × 10−3 to 13.4 × 10−3 min−1 at temperature from 35 to 65°C. The acetaminophen degradation rates can be accelerated through increasing reaction temperature and oxidant concentration. The reaction under acid conditions was slightly faster than under alkaline or neutral conditions. Two of the products were unequivocally identified as the toxic compounds 1,4-benzoquinone and ammonium ions. These results demonstrate that acetaminophen is likely to be transformed significantly into toxic product if dichromate is used as an oxidizing agent during wastewater treatment.

Removal of Acetaminophen Using Enzyme-Mediated Oxidative Coupling Processes: II. Cross-Coupling with Natural Organic Matter

The influence of natural organic matter (NOM) on the transformation of acetaminophen in laccase-mediated oxidative coupling systems was investigated in this study. It was found that the removal of acetaminophen was enhanced while the self-coupling of acetaminophen was suppressed in the presence of dissolved NOM, likely resulting from cross-coupling between dissolved NOM and acetaminophen. In additionto cross-coupling with acetaminophen, NOM moieties could couple to each other upon reaction with laccase. This was evidenced by the development of a characteristic absorbance band centered at 472 nm. According to the rate of the absorbance change at 472 nm, the NOM coupling reactions in four different NOM solutions were evaluated. Apparently, the tendency of NOM coupling reactions correlates with the tendency of acetaminophen cross coupling with NOM in these solutions. Possible reaction pathways of cross-coupling were explored using guaiacol as a model NOM proxy, and the products were extracted and analyzed with mass spectrometry (MS). The results suggested that acetaminophen and guaiacol molecules were cross-coupled via the formation of C-O-C bonds.