Degradation of paracetamol by advance oxidation processes using modified reticulated vitreous carbon electrodes with TiO(2) and CuO/TiO(2)/Al(2)O(3)

Electrocatalytic performance of oxygen-activated carbon fibre felt anodes mediating degradation mechanism of acetaminophen in aqueous environments

Carbon felts are flexible and scalable, have high specific areas, and are highly conductive materials that fit the requirements for both anodes and cathodes in advanced electrocatalytic processes. Advanced oxidative modification processes (thermal, chemical, and plasma-chemical) were applied to carbon felt anodes to enhance their efficiency towards electro-oxidation. The modification of the porous anodes results in increased kinetics of acetaminophen degradation in aqueous environments. The utilised oxidation techniques deliver single-step, straightforward, eco-friendly, and stable physiochemical reformation of carbon felt surfaces. The modifications caused minor changes in both the specific surface area and total pore volume corresponding with the surface morphology. A pristine carbon felt electrode was capable of decomposing up to 70% of the acetaminophen in a 240 min electrolysis process, while the oxygen-plasma treated electrode achieved a removal yield of 99.9% estimated utilising HPLC-UV-Vis. Here, the electro-induced incineration kinetics of acetaminophen resulted in a rate constant of 1.54 h^-1, with the second-best result of 0.59 h^-1 after oxidation in 30% H₂O₂. The kinetics of acetaminophen removal was synergistically studied by spectroscopic and electrochemical techniques, revealing various reaction pathways attributed to the formation of intermediate compounds such as p-aminophenol and others. The enhancement of the electrochemical oxidation rates towards acetaminophen was attributed to the appearance of surface carbonyl species. Our results indicate that the best-performing plasma-chemical treated CFE follows a heterogeneous mechanism with only approx. 40% removal due to direct electro-oxidation. The degradation mechanism of acetaminophen at the treated carbon felt anodes was proposed based on the detected intermediate products. Estimation of the cost-effectiveness of removal processes, in terms of energy consumption, was also elaborated. Although the study was focussed on acetaminophen, the achieved results could be adapted to also process emerging, hazardous pollutant groups such as anti-inflammatory pharmaceuticals.

In-situ fabrication of polypyrrole composite with MoO3: An effective interfacial charge transfers and electrode materials for degradation and determination of acetaminophen

Pharmaceutical wastes, acetaminophen (AP) widely used in medical fields, is often discharged into water, causing harm to human health. Hence, there is an urgent need to effectively remove AP from wastewater systems. In this paper, polypyrrole (PPy) composite with MoO₃ has been synthesized via an in-situ polymerization method. The as-prepared materials were thoroughly characterized by XRD, FT-IR, UV-DRS, SEM, TEM and mapping techniques. The as-prepared MoO₃@PPy composite was utilized to removal of AP via photocatalytic degradation and electrochemical determination. Under optimized composite, MoO₃@PPy (2) showed an excellent photocatalytic degradation and electrochemical determination of AP compared to pure MoO₃ and all other composites. The higher catalytic activity was ascribed to the effective interfacial charges transfer, reduce the recombination and enhance the active surface area of electrode via a synergistic effect. The photocatalytic degradation mechanism, rate and kinetic of the reaction were investigated and discussed. The major active degradation species and an effective charge transfer properties were confirmed by trapping experiments and photocurrent spectra. In addition, the MoO₃@PPy (2) modified GCE exhibit the AP determination activity by DPV with a linear range of 0.05-546 μM. The limit of detection and sensitivity of electrode were 0.0007 μM and 0.242 μM^-1 cm^-2 respectively. Moreover, the proposed electrode showed good selectivity, stability and reproducibility. This method was useful for the determination of AP in real samples.

Recent advances on modified reticulated vitreous carbon for water and wastewater treatment - A mini-review

Recently, modifications on reticulated vitreous carbon (RVC) have attracted attention as a promising strategy to produce low-cost, stable, and highly active electrodes leading to significant advances in the water/wastewater treatment field compared with raw RVC. Modified RVC materials have been used as cathode, anode, and membrane. Improvements on physical and electrocatalytic properties are achieved by RVC modification via diverse strategies, including the deposition of metal oxides, the introduction of surface functional groups, and the formation of composites, which were used to remove organic contaminants and pathogens from water matrices, as summarized in this mini-review. This mini-review mainly focused on papers published from 2015 to 2020 that reported modified RVC electrodes to eliminate pollutants and pathogens from water matrices by electrochemical advanced oxidation processes. Likewise, news challenges and opportunities are discussed, and perspectives for the ongoing and future studies in this research field are also given.

Determination of short-chain carboxylic acids and non-targeted analysis of water samples treated by wet air oxidation using gas chromatography-mass spectrometry

A method based on gas chromatography coupled with electron ionization mass spectrometry employing N,O-bis(trimethylsilyl)trifluoroacetamide with trimethylchlorosilane as derivatization agent was developed to quantify short-chain carboxylic acids (C₁-C₆) in hospital wastewater treated by wet air oxidation, an advanced oxidation process. Extraction from water and derivatization of volatile and semi-volatile short chain carboxylic acids were optimized and validated and limits of quantification (LOQ = 0.049 mg L^-1-4.15 mg L^-1), repeatability (RSD = 1.7-12.8%), recovery (31-119%) and trueness (relative bias = -19.0-3.4%) were acceptable. The validated method was successfully applied to monitor the concentration of organic acids formed after wet air oxidation of water samples. Results showed that the method described herein allowed to identify 38% and up to 46% of the final chemical oxygen demand's composition after wet air oxidation of acetaminophen spiked in deionised water and hospital wastewater samples, respectively. The developed method also allowed to perform qualitative non-targeted analysis in hospital wastewater samples after treatment. Results demonstrated that glycerol, methenamine, and benzoic acid were also present in the samples and their presence was confirmed with reference standards.

Novel Ti/RuO2IrO2 anode to reduce the dangerousness of antibiotic polluted urines by Fenton-based processes

The treatment of hospital wastewater is very complex, so treating polluted human urine is a significant challenge. Here, we tested a novel MMO-Ti/RuO₂IrO₂ electrode to reduce the ecotoxicity risk of hospital urines contaminated with antibiotics. This electrode was used as the anode in electro-Fenton (EF) and photoelectro-Fenton (PhEF) processes. The results were compared with those obtained using the boron-doped diamond (BDD) anode, as well as those obtained by a conventional Fenton oxidation. In order to analyze the performance of the processes, the treatments were evaluated on the subject of Penicilin G (PenG) removal, toxicity (using a standardized method with Vibrio Fisheri), and antibiotic activity (Enterococcus faecalis as the target bacterium). The results reveal that PenG degrades in the following order: Fenton < EF < PhEF. The best results are found for the MMO-PhEF, which completely removed PenG, decreased 96% of toxicity, and completely removed antibiotic activity. Besides, for comparison, tests were performed with BDD, and results point out the higher convenience of the new electrode in terms of acceptable use of energy because the effluents generated can be further degraded in an urban wastewater treatment plant. Because of that, MMO-RuO₂-IrO₂ emerges as a promising cost-effective material for the pre-treatment of hospital urine effluents.

Metal-Loaded Mesoporous MCM-41 for the Catalytic Wet Peroxide Oxidation (CWPO) of Acetaminophen

MCM-41 based catalysts (molar ratio Si/Al = 40) were prepared by a hydrothermal route, modified by ionic exchange with different metals (Cu, Cr, Fe and Zn) and finally calcined at 550 °C. The catalysts were fully characterized by different techniques that confirmed the formation of oxides of the different metals on the surfaces of all materials. Low-angle X-ray diffraction (XRD) analyses showed that calcination resulted in the incorporation of metallic Zn, Fe and Cr in the framework of MCM-41, while in the case of Cu, thin layers of CuO were formed on the surface of MCM-41. The solids obtained were tested in the catalytic wet peroxide oxidation (CWPO) of acetaminophen at different temperatures (25–55 °C). The activity followed the order: Cr/MCM-41 ≥ Fe/MCM-41 > Cu/MCM-41 > Zn/MCM-41. The increase of the reaction temperature improved the performance and activity of Cr/MCM-41 and Fe/MCM-41 catalysts, which achieved complete conversion of acetaminophen in short reaction times (15 min in the case of Cr/MCM-41). Fe/MCM-41 and Cr/MCM-41 were submitted to long-term experiments, being the Fe/MCM-41 catalyst the most stable with a very low metal leaching. The leaching results were better than those previously reported in the literature, confirming the high stability of Fe/MCM-41 catalysts synthesized in this study.

Paracetamol Degradation by Catalyst Enhanced Non-Thermal Plasma Process for a Drastic Increase in the Mineralization Rate

In order to remediate the very poor mineralization of paracetamol in water, even when well degraded by using a Non-Thermal Plasma (NTP) process at a very low dissipated power, a plasma-catalyst coupling process was tested and investigated. A homemade glass fiber supported Fe3+ catalyst was immersed in the liquid to be treated in a Dielectric Barrier Discharge plasma reactor. The plasma-catalysis process, at the same low dissipated power, achieved a mineralization rate of 54% with a full conversion rate of paracetamol at 25 mg L−1 in initial concentration after 60 min treatment, thanks to Fenton-like effects. The synergetic effects of the plasma-catalysis coupling process also improved the Energy Yield by a factor of two. The catalyst before and after use for treatment was characterized by Brunauer-Emmett-Teller and Thermogravimetric analysis. High-Performance Liquid Chromatography was used to measure the concentration of treated solution and to investigate the intermediates. Two of them, namely 1,4-hydroquinone and 1,4-benzoquinone, were formally identified. Some intermediates are presented in this paper as a function of treatment time and their UV absorbance spectra. NTP processes with and without catalyst coupling were compared in terms of acidity, conductivity, and nitrate concentrations in the treated solution.

A novel single-step hydrogenation of 2-imidazolecarboxaldehyde to 2-methylimidazole over Pd-impregnated Al–Ti mixed oxide and kinetics

A novel and clean route for the hydrogenation of 2-imidazolecarboxaldehyde to 2-methylimidazole with high yield and selectivity over a Pd/ATMO catalyst.

Acetaminophen micropollutant: Historical and current occurrences, toxicity, removal strategies and transformation pathways in different environments

Acetaminophen (ACT) is commonly used as a counter painkiller and nowadays, it is increasingly present in the natural water environment. Although its concentrations are usually at the ppt to ppm levels, ACT can transform into various intermediates depending on the environmental conditions. Due to the complexity of the ACT degradation products and the intermediates, it poses a major challenge for monitoring, detection and to propose adequate treatment technologies. The main objectives of this review study were to assess (i) the occurrences and toxicities, (2) the removal technologies and (3) the transformation pathways and intermediates of ACT in four environmental compartments namely wastewater, surface water, ground water, and soil/sediments. Based on the review, it was observed that the ACT concentrations in wastewater can reach up to several hundreds of ppb. Amongst the different countries, China and the USA showed the highest ACT concentration in wastewater (≤300 μg/L), with a very high detection frequency (81-100%). Concerning surface water, the ACT concentrations were found to be at the ppt level. Some regions in France, Spain, Germany, Korea, USA, and UK comply with the recommended ACT concentration for drinking water (71 ng/L). Notably, ACT can transform and degrade into various metabolites such as aromatic derivatives or organic acids. Some of them (e.g., hydroquinone and benzoquinone) are toxic to human and other life forms. Thus, in water and wastewater treatment plants, tertiary treatment systems such as advanced oxidation, membrane separation, and hybrid processes should be used to remove the toxic metabolites of ACT.

Bioinspired metal oxide particles as efficient wet air oxidation and photocatalytic oxidation catalysts for the degradation of acetaminophen in aqueous phase

The catalytic performances of the biomimetic metal oxides were tested in photo Fenton-like oxidation and catalytic wet air oxidation processes. Biomimetic copper oxide, iron oxide, and cobalt oxide catalysts were prepared by using pollen grains as biotemplate. The surface characteristics of the biomimetic metal oxides were characterized. SEM micrographs of the biomimetic catalysts demonstrated that pollen grains were successfully mimicked by metal oxide structures. The influences of UV light intensity, catalyst loading, and the initial hydrogen peroxide concentration on acetaminophen degradation were investigated in the photo Fenton-like oxidation process whereas the effects of reaction temperature and catalyst loading were investigated in catalytic wet air oxidation process. The biomimetic copper oxide was the most effective catalyst for the removal of acetaminophen in both of the advanced oxidation processes. The highest acetaminophen degradation efficiency was 86.9% in photo Fenton-like oxidation process when the initial acetaminophen concentration, catalyst loading, and the initial H₂O₂ concentrations were 10 mg/L, 0.1 g/L and 1 mM, respectively, at room temperature. In the catalytic wet air oxidation process, 98.3% degradation was achieved for the treatment of 100 mg/L acetaminophen solutions at 180 °C and 10 bar by using 1 g/L of catalyst loading at the same reaction time as photo Fenton-like oxidation. Mineralization analysis and the toxicity tests indicated that the biomimetic copper oxide catalysts were promising for the acetaminophen removal in catalytic wet air oxidation processes.

Carbon/FexOy magnetic composites obtained from PET and red mud residues: paracetamol and dye oxidation

Composite materials from PET and red mud (RM) wastes were used as catalysts for environmental application such as the wastewater treatment. The PET-RM catalysts were obtained by a mechanical mixture of the residues followed by thermal treatment under an N₂ atmosphere (300°C/1 h). An additional activation of the composites with CO₂ was investigated (at 800-900°C) to reduce the red mud basicity. The CO₂ activation affected the composites surface area and reduced their carbon content. XRD revealed that the haematite (α-Fe₂O₃) and maghemite/magnetite are the main iron oxides present in the composites. Mössbauer characterization indicated the formation of reduced iron species (Fe²⁺), highly reactive, after the composites heat treatment. The materials were very active catalysts for methylene blue (MB) and paracetamol (PRC) removal from aqueous solution. The catalytic activity revealed to be dependent on the surface area and mainly of the presence of reduced iron species in the catalysts. The MB removal reached 97% for both PET-RM 800/2 h and PET-RM 800/5 h, after 1 h of reaction. In the case of PRC, the highest removal was also obtained for PET-RM 800/2 h and PET-RM 800/5 h, of ≈25% and 40%, respectively. The contaminants removal mechanism likely occurred through combined adsorption and Fenton-like oxidation processes.

Photocatalytic Treatment of Paracetamol Using TiO2 Nanotubes: Effect of pH

Pharmaceuticals are considered among the group of emerging contaminants. Paracetamol is a moderate painkiller, which has been detected in ground and surface water. Photodegradation of paracetamol at a wavelength of radiation of 254 nm with TiO2 nanotubes was studied by UV-spectroscopy, HPLC and measurement of the potential zeta in dependence of the solution pH. The efficiency of the photodegradation of paracetamol (20 mg L−1) was 99% after 100 min exposure. Application of the Langmuir-Hinshelwood equation allowed the evaluation of the rate constant. Non-organic by-products were detected under the conditions of the chromatographic analysis. The photoreaction was faster at pH 6.5, a value at which adsorption was favored, leading to higher efficiency.

Removal of urea from dilute streams using RVC/nano-NiOx-modified electrode

Reticulated vitreous carbon (RVC), a high surface area electrode (40 cm²/cm³), has been modified with nickel oxide nanoparticles (nano-NiO_x) and used for electrochemical oxidation of urea from alkaline solution. For the cyclic voltammetry measurements, the used dimensions are 0.8 cm × 0.8 cm × 0.3 cm. The purpose was to offer high specific surface area using a porous open network structure to accelerate the electrochemical conversion. NiO_x nanoparticles have been synthesized via an electrochemical route at some experimental conditions. The morphological, structural, and electrochemical properties of the RVC/nano-NiO_x are characterized by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), and potentiostatic measurements. The fabricated electrode, RVC/nano-NiO_x, demonstrates high electrocatalytic activity towards urea oxidation in an alkaline electrolyte. The onset potential of the RVC/nano-NiO_x compared to that of the planar GC/NiO_x is shifted to more negative value with higher specific activity. The different loadings of the NiO_x have a substantial influence on the conversion of urea which has been evaluated from concentration-time curves. The urea concentration decreases with time to a limit dependent on the loading extent. Maximum conversion is obtained at 0.86 mg of NiO_x per cm³ of the RVC matrix.

Nano-TiO2, ultrasound and sequential nano-TiO2/ultrasonic degradation of N-acetyl-para-aminophenol from aqueous solution

The application of nano-TiO₂ as adsorbent combined with ultrasound for the degradation of N-acetyl-para-aminophenol (AAP) from aqueous solution was investigated. The nano-TiO₂ was characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). Experimental results revealed that the adsorption of AAP by nano-TiO₂ fitted the pseudo-second-order kinetic model, the equilibrium could be explained by the Freundlich isotherm and the treatment process is exothermic. The optimum removal efficiency of AAP (128.89 mg/g (77.33%)) was achieved at pH 4 when 0.03 g of nano-TiO₂ was mixed with 50 mL of 100 mg/L AAP aqueous solution at ambient temperature, 60 min contact time, and a stirring speed of 120 rpm. Ultrasound at 20 kHz and pH 3 was favorable and it resulted in 52.61% and 57.43% removal efficiency with and without the addition of nano-TiO₂, respectively. The degradation of AAP by ultrasound followed by nano-TiO₂ treatment resulted in approximately 99.50% removal efficiency. This study showed that a sequential ultrasound and nano-TiO₂ treatment process could be employed for the removal of AAP or other emerging water and wastewater contaminants.

Toxicity removal assessments related to degradation pathways of azo dyes: Toward an optimization of Electro-Fenton treatment

The degradation pathway of Acid Orange 7 (AO7) by Electro-Fenton process using carbon felt cathode was investigated via HPLC-UV and LC-MS, IC, TOC analysis and bioassays (Vibrio Fischeri 81.9% Microtox(®) screening tests). The TOC removal of AO7 reached 96.2% after 8 h treatment with the optimal applied current density at -8.3 mA cm(-2) and 0.2 mM catalyst concentration. The toxicity of treated solution increased rapidly to its highest value at the early stage of electrolysis (several minutes), corresponding to the formation of intermediate poisonous aromatic compounds such as 1,2-naphthaquinone (NAPQ) and 1,4-benzoquinone (BZQ). Then, the subsequent formation of aliphatic short-chain carboxylic acids like acetic acid, formic acid, before the complete mineralization, leaded to a non-toxic solution after 270 min for 500 mL of AO7 (1 mM). Moreover, a quantitative analysis of inorganic ions (i.e. ammonium, nitrate, sulfate) produced during the course of degradation could help to verify molar balance with regard to original nitrogen and sulfur elements. To conclude, a clear degradation pathway of AO7 was proposed, and could further be applied to other persistent pharmaceuticals in aquatic environment.

Fenton-Like Catalysis and Oxidation/Adsorption Performances of Acetaminophen and Arsenic Pollutants in Water on a Multimetal Cu-Zn-Fe-LDH

Acetaminophen can increase the risk of arsenic-mediated hepatic oxidative damage; therefore, the decontamination of water polluted with coexisting acetaminophen and arsenic gives rise to new challenges for the purification of drinking water. In this work, a three-metal layered double hydroxide, namely, Cu-Zn-Fe-LDH, was synthesized and applied as a heterogeneous Fenton-like oxidation catalyst and adsorbent to simultaneously remove acetaminophen (Paracetamol, PR) and arsenic. The results showed that the degradation of acetaminophen was accelerated with decreasing pH or increasing H2O2 concentrations. Under the conditions of a catalyst dosage of 0.5 g·L(-1) and a H2O2 concentration of 30 mmol·L(-1), the acetaminophen in a water sample was completely degraded within 24 h by a Fenton-like reaction. The synthesized Cu-Zn-Fe-LDH also exhibited a high efficiency for arsenate removal from aqueous solutions, with a calculated maximum adsorption capacity of 126.13 mg·g(-1). In the presence of hydrogen peroxide, the more toxic arsenite can be gradually oxidized into arsenate and adsorbed at the same time by Cu-Zn-Fe-LDH. For simulated water samples with coexisting arsenic and acetaminophen pollutants, after treatment with Cu-Zn-Fe-LDH and H2O2, the residual arsenic concentration in water was less than 10 μg·L(-1), and acetaminophen was not detected in the solution. These results indicate that the obtained Cu-Zn-Fe-LDH is an efficient material for the decontamination of combined acetaminophen and arsenic pollution.

Micelle Catalyzed Oxidative Degradation of Paracetamol by Water Soluble Colloidal MnO2 in Acidic Medium

The catalytic effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the MnO2-paracetamol (PCM) redox reaction has been examined spectrophotometrically in acidic medium at 298 K. The reaction demonstrates that the stoichiometric ratio of MnO2 and PCM is 1 : 1. The reaction exhibited first order kinetics with respect to [MnO2] and [PCM] but a negative fractional order was observed with respect to [H2SO4]. Various effects such as ionic strength, dielectric constant, [Mn(II)], [salts] and temperature have been studied. The catalytic effect of CTAB has been treated quantitatively by the well known Menger Portnoy and Piszkiewicz model. The values of binding constant (Ks), rate constant in the micellar phase (km), cooperativity index (n) and dissociation constant (KD) have also been calculated. From the several observations, a reaction mechanism has been proposed and the rate law has been derived. Applying the Arrhenius equation, various thermodynamic activation parameters have also been evaluated.

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 2.0 mg/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 pH 9.0, and the minimum was 0.27 M(-1) · min(-1) at pH 11.0. 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.

Degradation of p-nitrophenol using CuO/Al2O3 as a Fenton-like catalyst under microwave irradiation

The CuO/Al₂O₃ was used as a heterogeneous catalyst for Fenton-like oxidation of PNP under microwave and the PNP removal was enhanced greatly by microwave.

Ultrasonic degradation of acetaminophen in water: effect of sonochemical parameters and water matrix

This paper deals about the sonochemical water treatment of acetaminophen (ACP, N-acetyl-p-aminophenol or paracetamol), one of the most popular pharmaceutical compounds found in natural and drinking waters. Effect of ultrasonic power (20-60 W), initial ACP concentration (33-1323 μmol L(-1)) and pH (3-12) were evaluated. High ultrasonic powers and, low and natural acidic pH values favored the efficiency of the treatment. Effect of initial substrate concentration showed that the Langmuir-type kinetic model fit well the ACP sonochemical degradation. The influence of organic compounds in the water matrix, at concentrations 10-fold higher than ACP, was also evaluated. The results indicated that only organic compounds having a higher value of the Henry's law constant than the substrate decrease the efficiency of the treatment. On the other hand, ACP degradation in mineral natural water showed to be strongly dependent of the initial substrate concentration. A positive matrix effect was observed at low ACP concentrations (1.65 μmol L(-1)), which was attributed to the presence of bicarbonate ion in solution. However, at relative high ACP concentrations a detrimental effect of matrix components was noticed. Finally, the results indicated that ultrasonic action is able to transform ACP in aliphatic organic compounds that could be subsequently eliminated in a biological system.