Alongside my own electrochemistry work, I contributed to a series of collaborative studies (led by Arvin Liangdy and colleagues, NEWRI/NTU) on catalytic ceramic membranes (CCMs) for intensified degradation of recalcitrant water pollutants via advanced oxidation processes.
- A Co-Mn-oxide impregnated CCM activated peroxymonosulfate (PMS) to degrade sulfamethoxazole, exploiting synergy between the two metal cations and the confinement effect within the membrane’s pores 1.
- A Fe3O4-impregnated CCM, fabricated via an ethylene-glycol-assisted wet impregnation method, achieved 99% removal of the herbicide atrazine within a 5.7-second hydraulic retention time, and remained robust when tested in real wastewater matrices 2.
- A dual-layer CCM (Co3O4 catalytic surface layer + TiO2 intermediate rejection layer) mitigated interference from background water-matrix species during acetaminophen degradation, achieving 85–99% removal across MQ water and real wastewater samples 3.
Across this body of work, reactive oxygen species (SO4•⁻, •OH, ¹O2) were identified via radical scavenging and EPR spectroscopy, and degradation pathways/by-product toxicity were assessed via LC-QTOF analysis.
My role: Contributing author — supporting electrochemical/analytical characterization and manuscript review. Lead investigators: Arvin Liangdy, Prof Teik-Thye Lim, and Prof Shane Allen Snyder (NTU).
References
2024
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Versatile Fe3O4-impregnated catalytic ceramic membrane for effective atrazine removal: Confined catalytic oxidation processes, reactive oxygen species selectivity and performance in real wastewater
Arvin Liangdy, Panyawut Tonanon, Richard D. Webster, and 2 more authors
Journal 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.
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Surface- and substrate-coated catalytic membrane for mitigating interference of water matrix species in intensified micropollutant confinement oxidation
Arvin Liangdy, Panyawut Tonanon, Shane Allen Snyder, and 2 more authors
Journal 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.
2023
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Unravelling the synergism of catalytic oxidation and filtration in Co-Mn-oxide impregnated ceramic membrane for intensified degradation of recalcitrant micropollutant with peroxymonosulfate
Arvin Liangdy, Wen Jie Lee, Panyawut Tonanon, and 3 more authors
Chemical 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.