Karen Yuanting Tang

Thermosets with permanent cross-linked structures provide excellent durability but pose significant challenges for reprocessing and recycling, raising engineering and environmental concerns as their usage expands. The advent of covalent adaptable networks (CANs) with dynamic covalent linkages has improved thermoset recyclability and enabled the fusion of identical polymer networks (A-A type fusion). However, fusing different thermosets (A-B type fusion) remains challenging due to their distinct dynamic behaviors and variable activation energies for bond exchange. This study introduces catalyst-free solid-state C═C/C═N metathesis chemistry to achieve A-B type fusion between two distinct thermosets. Furthermore, by simply adjusting the mixing ratio of the parent thermosets, the thermal behavior, mechanical properties, activation energy (E_a), and topology freezing transition temperature (T_v) of the fused networks can be precisely tailored. This approach offers enhanced control over thermal and mechanical characteristics, rendering them suitable for diverse high-performance applications. Our findings represent a significant step forward in developing recyclable thermosets with improved engineering performance, contributing to the advancement of a more sustainable circular economy.

Used surgical masks and nitrile gloves were collected as the most common wastes in the pandemic of COVID-19, which both are widely used personal protective equipment (PPE). An environmental-friendly pathway was proposed in this work to handle the massive disruption in waste disposal system. A mixture of these two wastes were used as feedstock in catalytic pyrolysis to produce multiwall carbon nanotubes (MWCNTs). Nitrile gloves contain nitrogen elements which allows nitrogen doping in MWCNTs, getting N-doped CNTs (N-CNTs). The MgO-supported bimetallic catalyst Fe-Co-Mg was prepared as catalyst for carbon nanotube synthesis. The Fe-Co micro-spinel was formed in pyrolysis and encapsulated in N-CNTs (FeCo-NCNTs). The element distribution and composition of the product, N-doped MWCNTs was characterized by high resolution electron microscope, energy dispersive X-ray spectroscope and X-ray photoelectron spectroscopy. In catalytic pyrolysis, the mask-glove mixture can reach 33 wt. % CNT yield when the weight percentage of nitrile is not more than 20%. The FeCo-NCNTs display a diameter around 25 nm and several micrometers in length. Several as-prepared FeCo-NCNTs were estimated as catalyst for oxygen evolution reaction (OER) after treatment. The FeCo-NCNTs after acid wash shows a good performance as catalysts for OER in water splitting (ηi=10 = 390mV). This result can attribute to the recycle of waste generated in COVID-19 pandemic and the potential application of waste-derive materials.

Titanium dioxide (TiO₂) nanomaterials have been ubiquitously investigated as a photocatalyst for organic contaminant treatment in wastewater due to their exemplary semiconductor properties. However, their huge band gap remains a barrier for visible light absorption, limiting their utility in practical applications. The incorporation of noble metals in the TiO₂ scaffold would help mitigate the problem via plasmonic resonance enhancements. Silver (Ag) is the chosen noble metal as it is relatively cheap and has great plasmonic effects. In this study, the use of electrospun Ag-embedded TiO₂ nanofibers as a photocatalyst is shown to be effective in decomposing rhodamine B and methyl orange dyes under a solar simulator in 3 h, which is more efficacious as opposed to pristine TiO₂ nanofibers. This showcases the potential of a simple and economic wastewater treatment system for the removal of organic pollutants.

Small-sized droplets/aerosol transmission is one of the factors responsible for the spread of COVID-19, in addition to large droplets and surface contamination (fomites). While large droplets and surface contamination can be relatively easier to deal with (i.e., using mask and proper hygiene measures), aerosol presents a different challenge due to their ability to remain airborne for a long time. This calls for mitigation solutions that can rapidly eliminate the airborne aerosol. Pre-COVID-19, air ionizers have been touted as effective tools to eliminate small particulates. In this work, we sought to evaluate the efficacy of a novel plant-based ionizer in eliminating aerosol. It was found that factors such as the ion concentration, humidity, and ventilation can drastically affect the efficacy of aerosol removal. The aerosol removal rate was quantified in terms of ACH (air changes per hour) and CADR- (clean air delivery rate-) equivalent unit, with ACH as high as 12 and CADR as high as 141 ft ³ /minute being achieved by a plant-based ionizer in a small isolated room. This work provides an important and timely guidance on the effective deployment of ionizers in minimizing the risk of COVID-19 spread via airborne aerosol, especially in a poorly-ventilated environment.