publications
publications by categories in reversed chronological order. generated by jekyll-scholar.
2025
- Electrochemistry for environmental applications: water disinfection, pharmaceutical analysis, and CO2 reductionPanyawut Tonanon2025Accepted: 2025-01-27T02:00:19Z Publisher: Nanyang Technological University
This thesis explores novel applications of analytical electrochemistry in addressing environmental challenges and advancing pharmaceutical analysis, focusing on three main areas: water disinfection, pharmaceutical compound detection, and carbon dioxide capture and utilization. In the first study, platinized titanium electrodes were investigated for their efficacy in inactivating Escherichia coli in water through electrochemical processes. The research elucidated the mechanisms underlying the disinfection process, particularly the generation and role of reactive oxygen species, demonstrating feasible rapid disinfection even at low electrolyte concentrations. The second study developed and optimized methods for detecting and quantifying praziquantel, an important antiparasitic drug, in water samples. Two techniques were compared: gas chromatography-mass spectrometry (GC-MS) and voltammetry, both utilizing solid phase extraction for sample preparation. While GC-MS showed lower detection limits, the voltametric method demonstrated comparable accuracy and precision, offering a potentially more cost-effective and portable alternative for on-site testing. The final study explored the electrochemistry of organic molecules, specifically quinones and flavins (vitamin B2), for potential applications in carbon dioxide capture and energy storage. The research investigated the molecular interactions between reduced organic species and CO2, as well as their electrochemical behavior under various conditions, providing insights into the development of novel carbon capture technologies and organic-based energy storage systems. Throughout these investigations, the thesis demonstrates the versatility and power of analytical electrochemistry in addressing diverse challenges in environmental remediation, pharmaceutical analysis, and sustainable energy technologies. The research contributes to the advancement of electrochemical methods and their practical applications in these critical areas.
- Electrochemical inactivation of Escherichia coli using platinized titanium electrodes: a comparison between two- and three-electrode configurationsPanyawut Tonanon, and Richard D. WebsterJournal of Solid State Electrochemistry, Mar 2025
This study explores the feasibility of using platinized titanium electrodes for the electrochemical inactivation of Escherichia coli (E. coli), with the aim of developing an efficient and sustainable water disinfection method in low ionic strength media similar to what exists in potable water. A comparative analysis between two-electrode and three-electrode configurations revealed the superiority of the three-electrode system in achieving higher current throughput and enhanced bacterial inactivation efficiency. This improvement is attributed to the potentiostat’s ability to compensate for solution resistance (IR drop) through the inclusion of the reference electrode, ensuring more stable and controlled electrochemical conditions. The inactivation of E. coli in various electrolyte solutions followed a logarithmic decay pattern (pseudo first-order), with no significant difference observed among the electrolytes tested, except for sodium chloride. The enhanced bactericidal activity in the presence of NaCl was attributed to the generation of chlorine species. These findings provide insights into optimizing electrochemical disinfection systems and highlight the potential of three-electrode configurations for practical water treatment applications in low-conductivity environments.
2024
- A comparison of the detection and quantification of praziquantel \textitvia electrochemical and gas chromatography methods in freshwater and saltwater samplesPanyawut Tonanon, Katherine Jalando-On Agpoon, and Richard D. WebsterAnalytical Methods, Mar 2024
Two new techniques for analyzing praziquantel (PZQ), an effective antiparasitic drug used in fresh and saltwater aquariums, were optimized and compared statistically. , Two new techniques for analyzing praziquantel (PZQ), an effective antiparasitic drug used in fresh and saltwater aquariums, were optimized and compared. One method was based on voltammetry and the other method used gas chromatography combined with mass spectrometry (GC-MS), although both procedures utilized the same sample pretreatment strategy which involved the PZQ being quantitatively transferred into acetonitrile using solid phase extraction. GC-MS analysis led to lower limits of detection (0.32 μM, 0.10 ppm) and quantification (0.72 μM, 0.22 ppm) compared to voltammetry, although both methods gave acceptable quantification for levels of PZQ \textgreater 25 μM (7.8 ppm). GC-MS is preferred for the most accurate determination, but voltammetry may provide a cost-effective alternative for detecting PZQ where on site testing is required.
- Versatile Fe3O4-impregnated catalytic ceramic membrane for effective atrazine removal: Confined catalytic oxidation processes, reactive oxygen species selectivity and performance in real wastewaterArvin Liangdy, Panyawut Tonanon, Richard D. Webster, and 2 more authorsJournal of Environmental Chemical Engineering, Jun 2024
An Fe3O4-impregnated catalytic ceramic membrane (CCM) was fabricated through a facile ethylene glycol-gelassisted wet impregnation method. Ethylene glycol played a dual role, acting as a reducing agent for iron (III) nitrate salt and a chelating agent to disperse catalyst uniformly in the CCM. The resulting 5xFe3O4-CCM effi ciently activated peroxymonosulfate (PMS) to generate reactive oxygen species (ROS), achieving a 99% removal of atrazine (ATZ) within a short hydraulic retention time (HRT) of 5.7 s. This was facilitated by the spatial confinement effect in CCMs, enhancing the interaction among ATZ, ROS and CCM. The versatile 5xFe3O4-CCM could also effectively activate H2O2 and peroxydisulfate (PDS). It demonstrated robustness in real wastewater matrices (settled water and RO-reject) collected from local water reclamation and treatment plants. The 5xFe3O4CCM exhibited self-cleaning properties in reducing fouling of CCM by humic acid. ROS scavenging experiments and electron paramagnetic resonance (EPR) spectroscopy revealed the pivotal role of SO4•-, •OH, and 1O2 in ATZ removal. The co-existing anion species HCO3- showed a strong inhibitory effect on ATZ degradation compared to other ionic species (NO3- and Cl-), attributed to different scavenging reaction rate of both SO4•- and •OH by anions in generating less reactive species. Possible degradation pathways of 5xFe3O4-CCM/PMS were proposed based on the LC-QTOF analysis, including oxidation, dealkylation, dealkylation-hydroxylation, dechlorination-hydroxyl ation of both s-triazine ring and side chain. The toxicity of the ATZ by-products was assessed, revealing reduced toxicity after treatment. With optimized operating parameters, Fe3O4-CCM can be utilized effectively in different advanced oxidation processes (AOPs) and real wastewater matrices.
- Surface- and substrate-coated catalytic membrane for mitigating interference of water matrix species in intensified micropollutant confinement oxidationArvin Liangdy, Panyawut Tonanon, Shane Allen Snyder, and 2 more authorsJournal of Environmental Chemical Engineering, Dec 2024
The integration of advanced oxidation processes (AOPs) with membrane technology offers benefits for catalyst recovery and reducing membrane fouling. However, the application of the hybrid process could be hampered by the background species in water matrix. This study addresses this challenge by developing catalytic ceramic membranes (CCMs) with dual mechanisms to intensify acetaminophen (ACT) removal in water. The CCMs effectively activated peroxymonosulfate (PMS), achieving ACT degradation of 85 % and 93 % in real water matrices (reverse osmosis retentate and settled water, respectively) and 99 % in MQ water. The CCMs demonstrated consistent performance across multiple operational cycles, even in the presence of humic acid (HA) (96 % ACT reduction). The CCM design features Co3O4 catalytic layer on CCM surface, facilitating surface oxidation, reducing fouling, and TiO2 intermediate rejection layers serving as barrier for bulk organic pollutants, achieving 50 % HA removal through rejection and 70 % with 1.5 mM PMS. This design facilitates catalytic degradation at the membrane surface, allowing retention and degradation of bulk organic pollutants and intermediates, while ACT permeates into CCM substrate. The surface oxidation and rejection enhanced confinement oxidation within the Co3O4-coated macropores, minimizing interference from background species. LC-QTOF analysis identified multiple degradation pathways, including hydroxylation, acetyl-amino group cleavage, side chain oxidation and benzene ring cleavage, with intermediates showing reduced toxicity. Reactive oxygen species involved in the system were identified and PMS activation mechanism was proposed. This research highlights the potential of the hybrid process, enhancing micropollutant removal by mitigating interference from background species, providing practical implications in water treatment applications.
- Probing the Molecular Interactions of Electrochemically Reduced Vitamin B2 with CO2Panyawut Tonanon, and Richard D. WebsterThe Journal of Physical Chemistry B, Nov 2024Publisher: American Chemical Society
The electrochemical reduction of riboflavin (vitamin B2) in a dimethyl sulfoxide solvent was examined under a CO2 atmosphere and compared with results under an argon atmosphere. Variable-scan-rate cyclic voltammetry combined with controlled potential electrolysis (CPE) and analysis by UV–vis and EPR spectroscopies provided insights into the nature of interactions of reduced flavins with dissolved CO2. Reductive exhaustive CPE experiments under CO2 indicated an overall two-electron stoichiometry, compared to one-electron reduction under an argon atmosphere, due to the lowering of the formal one-electron reduction potential of the flavin radical anion to form the dianion, which can be rationalized by riboflavin–CO2 molecular interactions. UV–vis spectroscopic measurements confirmed complete chemical reversibility of the redox transformations over extended time scales. Digital simulation modeling of the voltammetric data enabled extraction of thermodynamic and kinetic parameters for the proposed mechanism, comprising multiple proton-coupled electron transfer steps, diamagnetic anions, radical anions, and neutral radical intermediates enroute to the fully reduced state, as well as evidence of a long-lived solution phase complex of the reduced riboflavin with CO2.
2023
- Unravelling the synergism of catalytic oxidation and filtration in Co-Mn-oxide impregnated ceramic membrane for intensified degradation of recalcitrant micropollutant with peroxymonosulfateArvin Liangdy, Wen Jie Lee, Panyawut Tonanon, and 3 more authorsChemical Engineering Journal, Feb 2023
In this study, catalytic ceramic membrane (CCM) impregnated with uniform and high purity Co-Mn-oxide was fabricated via citrate sol–gel method. It was applied to activate peroxymonosulfate (PMS) for degradation of sulfamethoxazole (SMX). Due to the synergistic effect between the two cations, the Co-Mn bimetallic oxides exhibited significantly higher catalytic activity in activating PMS and degrading organic pollutants in comparison to their single oxides. Minimum calcination temperature of 700 ◦C was required to form the highly activating CoMn-oxide while higher calcination temperature reduced its catalytic activity. The effect of catalyst loading and the SMX:PMS ratio was investigated, and excessive catalyst loading, and oxidant dosage were found to be detrimental to the SMX removal efficiency. The investigation revealed the importance of process parameters in achieving achieve optimal performance of CCM/PMS process, achieving low specific oxidant consumption of 1.2 M PMS M− 1 TOC. The ratio between catalyst loading in CCM, oxidant concentration and pollutant concentration influenced the availability of active sites on the catalyst to activate oxidants in the process and the possibility of self-scavenging of the generated reactive oxidizing species (ROS). The role of various ROS generated and mechanism of activation of PMS by the catalyst was investigated through radical scavenging experiments and electron paramagnetic resonance (EPR) spectroscopy test. Co2+ can be regenerated from the Mn2+/Mn3+/Mn4+ redox conjugate triplet and concurrently activate PMS to generate ROS, significantly enhancing its catalytic performance. Additionally, based on LC-QTOF analysis, the intermediates, and the possible degradation pathway of SMX degradation in this hybrid process were determined. Overall, the investigation of CCM fabrication and hybrid process operation parameters could provide an insight in the hybrid process to intensify the oxidant utilization and pollutant removal.
- Recent electrode and electrolyte choices for use in small scale water treatment applications—A short reviewPanyawut Tonanon, and Richard D. WebsterCurrent Opinion in Electrochemistry, Apr 2023
Boron-doped diamond and titanium suboxides have been proposed as electrode materials for use as anodes in future electrochemical devices, most likely in remote locations for potable water purification, or for specialized disinfection applications in decentralized systems. A comparison is made between electrochemical purification strategies that do not require added chemicals and systems that do, with emphasis given toward Magnéli electrode-based electrochemical disinfection and iodine-based electrochemical disinfection systems. Both systems with and without added chemicals come with advantages and disadvantages. The outlook of these emerging processes concludes this review.
2021
- Magnetically Directed Co-nanoinitiators for Cross-Linking Adhesives and Enhancing Mechanical PropertiesHaruethai Kongcharoen, Birte Coester, Fei Yu, and 9 more authorsACS Applied Materials & Interfaces, Dec 2021Publisher: American Chemical Society
Magnetically directed localized polymerization is of immense interest for its extensive impacts and applications in numerous fields. The use of means untethered from an external magnetic field to localize initiation of polymerization to develop a curing system is a novel concept, with a sustainable, efficient, and eco-friendly approach and a wide range of potential in both science and engineering. However, the conventional means for the initiation of polymerization cannot define the desirable location of polymerization, which is often exacerbated by the poor temporal control in the curing system. Herein, the copper-immobilized dendrimer-based magnetic iron oxide silica (MNPs-G2@Cu2+) co-nanoinitiators are rationally designed as initiators for redox radical polymerization. The nanoinitiators are magnetically responsive and therefore enable localized polymerization using an external magnetic field. In this work, anaerobic polymerization of an adhesive composed of triethylene glycol dimethacrylate, tert-butyl peroxybenzoate, and MNPs-G2@Cu2+ as the magnetic co-nanoinitiators has been investigated. The use of a magnet locates and promotes redox free radical polymerization through the synergistic functions between peroxide and MNPs-G2@Cu2+ co-nanoinitiators. The mechanical properties of the resulting polymer are considerably reinforced because the MNPs-G2@Cu2+ co-nanoinitiators concurrently play another crucial role as nanofillers. This strategy provides a novel approach for magnetically tunable localized polymerization, which allows new opportunities to govern the formulation of advanced adhesives through polymerization under hazard-free conditions for various promising applications.