Assessment of graphite electrode on the removal of anticancer drug cytarabine via indirect electrochemical oxidation process: Kinetics & pathway study

Performance evaluation of hybrid electrochemical oxidation and ultraviolet light-based persulfate process for the abatement of sodium dodecyl sulfate from wastewater

The application of hybrid advanced oxidation processes (AOPs) is an efficacious way to remediate emerging contaminants from wastewater. In the present research work, a hybrid electrochemical oxidation and ultraviolet light-based persulfate activation processes (EO-UV/PS) were used to efficiently degrade sodium dodecyl sulfate (SDS) surfactant from synthetic and municipal wastewater. By operating the EO-UV/PS at optimum operating conditions at pH of 7.0, NaCl of 0.02 M, current density of 6.4 mA/cm2, persulfate dose of 2.5 mM, and operating period of 180 min, about 94.5 ± 2.8% of SDS (20 mg/L) removal was achieved from synthetic wastewater. The abetment of SDS in both EO and UV/PS obeyed pseudo-first-order kinetics with a rate constant of 0.012 and 0.019 min-1, respectively. Moreover, the economic analysis revealed 0.23 $ m-3 order-1 as the operating cost for degrading SDS in EO-UV/PS. The degradation pathway experimentation suggested the generation of lauric acid by-product during SDS abatement. Besides, nearly 89.3 ± 2.9% of SDS and 58.7 ± 2.4% of total organic carbon reduction was also achieved from real municipal wastewater. Phytotoxicity test on Vigna radiata affirms the non-toxic nature of the EO-UV/PS effluent.

Mechanistic and reactional activation study of carbons destined for emerging pharmaceutical pollutant adsorption

In this review, several factors have been collected from previous studies on emerging pharmaceutical pollutant adsorption to explain and describe the mechanisms and determine the reactions involved: X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), and the Boehm titration are the most used characterization techniques to determine activated carbons' surface functional groups. Some studies have confirmed that the specific surface area and the pore structure are not more important than the functional groups present in the adsorbent surface to explain the amount of adsorption obtained and to describe correctly the interaction between the adsorbent-adsorbate. After the analysis of several studies, we concluded that to have good adsorption, it is necessary to choose the right treatment with the right activating agent to obtain the appropriate functions that will enhance the adsorption process. In addition, the functions that can react with the pharmaceutical pollutants are the oxygenated functions such as hydroxyl function, carboxylic function, and carbonyl function.

Degradation of cytostatics methotrexate and cytarabine through physico-chemical and advanced oxidative processes: influence of pH and combined processes on the treatment efficiency

Environmental release of wastewater that contains cytostatic drugs can cause genotoxic impact, since these drugs act directly on the genetic material of aquatic organisms. Thus, the aim of this study was to evaluate the removal of the cytostatic drugs cytarabine (CTR) and methotrexate (MTX) using different physico-chemical methods individually (i.e. US, O3, H2O2 and UV) and combined (i.e. O3/US, US/H2O2, O3/H2O2 and O3/US/H2O2) under different pH conditions (4, 7 and 10). In the degradation tests, the efficiency of the methods applied was found to be dependent on the pH of the solution, with the degradation of CTR being better at pH 4 and MTX at pH 7 and pH 10. The US, H2O2 and US + H2O2 methods were the least efficient in degrading CTR and MTX under the pH conditions tested. The highest MTX degradation rate after 16 min of treatment at pH 7 was achieved by the O3 + H2O2 method (97.05% - C/C0 = 0.0295). For CTR, the highest degradation rate after 16 min of treatment was achieved by the O3 process (99.70% - C/C0 =  0.0030) at pH 4. In conclusion, most of the treatment methods tested for the degradation of CTR and MTX are effective. Notably, ozonolysis is an efficient process applied alone. Also, in combination with other methods (US + O3, O3 + H2O2 and O3 + H2O2 + US) it increases the degradation performance, showing a rapid removal rate of 70-94% in less than 4 min of treatment.

A review of electrooxidation systems treatment of poly-fluoroalkyl substances (PFAS): electrooxidation degradation mechanisms and electrode materials

The prevalence of polyfluoroalkyls and perfluoroalkyls (PFAS) represents a significant challenge, and various treatment techniques have been employed with considerable success to eliminate PFAS from water, with the ultimate goal of ensuring safe disposal of wastewater. This paper first describes the most promising electrochemical oxidation (EO) technology and then analyses its basic principles. In addition, this paper reviews and discusses the current state of research and development in the field of electrode materials and electrochemical reactors. Furthermore, the influence of electrode materials and electrolyte types on the deterioration process is also investigated. The importance of electrode materials in ethylene oxide has been widely recognised, and therefore, the focus of current research is mainly on the development of innovative electrode materials, the design of superior electrode structures, and the improvement of efficient electrode preparation methods. In order to improve the degradation efficiency of PFOS in electrochemical systems, it is essential to study the oxidation mechanism of PFOS in the presence of ethylene oxide. Furthermore, the factors influencing the efficacy of PFAS treatment, including current density, energy consumption, initial concentration, and other parameters, are clearly delineated. In conclusion, this study offers a comprehensive overview of the potential for integrating EO technology with other water treatment technologies. The continuous development of electrode materials and the integration of other water treatment processes present a promising future for the widespread application of ethylene oxide technology.

Fast and Complete Destruction of the Anti-Cancer Drug Cytarabine from Water by Electrocatalytic Oxidation Using Electro-Fenton Process

The fast and complete removal of the anti-cancer drug cytarabine (CYT) from water was studied, for the first time, by the electro-Fenton process using a BDD anode and carbon felt cathode. A catalytic amount (10−4 M) of ferrous iron was initially added to the solution as catalyst and it was electrochemically regenerated in the process. Complete degradation of 0.1 mM (24.3 mg L−1) CYT was achieved quickly in 15 min at 300 mA constant current electrolysis by hydroxyl radicals (●OH) electrocatalytically generated in the system. Almost complete mineralization (91.14% TOC removal) of the solution was obtained after 4 h of treatment. The mineralization current efficiency (MCE) and energy consumption (EC) during the mineralization process were evaluated. The absolute (second order) rate constant for the hydroxylation reaction of CYT by hydroxyl radicals was assessed by applying the competition kinetics method and found to be 5.35 × 109 M−1 s−1. The formation and evolution of oxidation reaction intermediates, short-chain carboxylic acids and inorganic ions were identified by gas chromatography-mass spectrometry, high performance liquid chromatography and ion chromatography analyses, respectively. Based on the identified intermediate and end-products, a plausible mineralization pathway for the oxidation of CYT by hydroxyl radicals is proposed.

Advanced oxidation processes: Performance, advantages, and scale-up of emerging technologies

Advanced oxidation processes (AOPs) are promising technologies for partial or complete mineralization of contaminants of emerging concern by highly reactive hydroxyl, hydroperoxyl, superoxide, and sulphate radicals. Detailed investigations and reviews have been reported for conventional AOP systems that have been installed in full-scale wastewater treatment plants. However, recent efforts have focused on the peroxymonosulphate, persulphate, catalytic ozonation, ultrasonication and hydrodynamic cavitation, gamma radiation, electrochemical oxidation, modified Fenton, and plasma-assisted AOPs. This critical review presents the detailed mechanisms of emerging AOP technologies, their performance for treatment of contaminants of emerging concern, the relative advantages and disadvantages of each technology, and the remaining challenges to scale-up and implementation. Among the evaluated technologies, the modified electrochemical oxidation, gamma radiation, and plasma-assisted systems demonstrated the greatest potential for successful and sustainable implementation in wastewater treatment due to their environmental safety, compatibility, and efficient transformation of contaminants of emerging concern by a variety of reactive species. The other emerging AOP systems were also promising, but additional scale-up trials and a deeper understanding of their reaction kinetics in complex wastewater matrices are necessary to determine the technical and economic feasibility of full-scale processes.

Treatment of aquatic medium containing common and emerging contaminants using an aero-electrochemical process based on graphite cathode and three metal oxides alloy as anode: Central composite design and photo/sono-enhancement

An aero-electrochemical advanced oxidation process (aero-EAOP) equipped with graphite cathode and dimensionally stable anodes was utilized for the treatment of aquatic media containing common and emerging contaminants. Among various anode materials, the application of Ti/RuO₂/IrO₂/SnO₂ anode resulted in the highest effectiveness. Central composite experimental design (CCED) was used to attain the optimum operational parameters in terms of chlorine generation. Simultaneous decolorization and ammonium removal by the aero-EAOP process were investigated. Accordingly, the decolorization efficiency of 94%, along with the ammonium removal of 65.2%, was obtained within 30 min. Implementation of ultrasound and UV irradiation resulted in the complete decolorization within 25 and 20 min, respectively. In comparison, the influence of ultrasound and UV irradiation on the ammonium removal by the aero-EAOP reactor was not remarkable. Mineralization efficiency of 75.1% was obtained during the short reaction time of 30 min. With increasing hydraulic retention time (HRT) from 2 to 20 min, decolorization efficiency increased from 12.0 to 55.7% and ammonium removal efficiency increased from 16.6 to 37.8%, respectively. The complete degradation of amoxicillin (AMX) and tetracycline (TC) antibiotics were achieved within 25 and 30 min, respectively. The degradation efficiencies of ibuprofen (IBP), acetaminophen (APAP) and endocrine disrupting compound of bisphenol A (BPA) were obtained to be 58, 66 and 78% within 30 min, respectively. Photo-assisted aero-EAOP was more efficient than the aero-EAOP in degrading target emerging pollutants.

A label-free electrochemical biosensor based on 3D cubic Eu3+/Cu2O nanostructures with clover-like faces for the determination of anticancer drug cytarabine

The present research utilized a simplified procedure for developing a novel electro-chemical DNA biosensor based on a carbon paste electrode (CPE) modified with three-dimensional (3D) cubic Eu³⁺/Cu₂O nanostructures with clover-like faces (Eu³⁺/Cu₂O CLFNs). The modified electrode was applied to monitor electro-chemical interactions between dsDNA and cytarabine for the first time. Then, the decreased oxidation signal of guanine following the interactions between cytarabine and dsDNA was utilized as an indicator for selectively determining cytarabine using differential pulse voltammetry (DPV). According to the findings, the oxidation peak current of guanine was linearly proportionate with the cytarabine concentration in the range between 0.01 and 90 μM. Additionally, the limit of quantification (LOQ) and the limit of detection (LOD) respectively equaled 9.4 nM and 2.8 nM. In addition, the repeatability, applicability and reproducibility of this analysis to drug dosage forms and human serum samples were investigated. Furthermore, UV-vis spectroscopy, DPV, docking and viscosity measurements were applied to elucidate the interaction mechanism of dsDNA with cytarabine. It was found that this DNA biosensor may be utilized to sensitively, accurately and rapidly determine cytarabine.

Development of a novel graphitic carbon nitride and multiwall carbon nanotube co-doped Ti/PbO2 anode for electrocatalytic degradation of acetaminophen

In this work, we have constructed a novel graphitic carbon nitride/multiwall carbon nanotube (GCN/CNT) doped Ti/PbO₂ as anode for highly effective degradation of acetaminophen (ACE) wastewater. The ACE removal efficiency of 83.2% and chemical oxygen demand removal efficiency of 76.3% are achieved under the optimal condition of temperature 25 °C, initial pH 7, current density 15 mA cm^-2 and Na₂SO₄ concentration 6.0 g L^-1. The excellent electrocatalytic activity of Ti/PbO₂-GCN-CNT anode for ACE oxidation is ascribed to the effective suppression of oxygen evolution and the enhanced electron transfer after introducing GCN and CNT. Furthermore, Ti/PbO₂-GCN-CNT electrode displays excellent stability and reusability. ACE degradation is accomplished by direct oxidation and indirect oxidation, and ∙OH radical plays primary role in the indirect oxidation of ACE wastewater. The intermediates of ACE degradation are detailly investigated using LC-MS analysis and a possible degradation mechanism is proposed.