ABSTRACT
The intricate role of temperature in the structure-property relationship of manganese oxide nanoparticles (Mn3O4 NPs) remains an open question. In this study, we successfully synthesized Mn3O4 NPs using the hydrothermal method with two differing temperatures, namely, 90 and 150 °C. Interestingly, a smaller average particle size is found when Mn3O4 NPs are synthesized at 150 °C compared to 90 °C, corresponding to 46.54 and 63.37 nm, respectively. This was confirmed by the time variation of temperature setting of 150 °C where the size evolution was insignificant, indicating a competing effect of nucleation and growth particles. Under varying NaOH concentrations (2-6 M) at 150 °C, a reduction in the particle size is found at the highest NaOH concentration (6 M). The particle grows slightly, indicating that the growth state is dominant compared to the nucleation state at low concentrations of NaOH. This finding implies that the high nucleation rate originates from the excessive monomer supply in the high-temperature reaction. In terms of crystallinity order, the structural arrangement of Mn3O4 NPs (150 °C) is largely decreased; this is likely due to a facile redox shift to the higher oxidation state of manganese. In addition, the higher ratio of adsorbed oxygen and lattice oxygen in Mn3O4 NPs at 150 °C is indirectly due to the higher oxygen vacancy occupancies, which supported the crystallinity decrease. Our findings provide a new perspective on manganese oxide formation in hydrothermal systems.
ABSTRACT
Nanofiber membranes were successfully synthesized from expanded polystyrene (EPS) waste with the addition of poly(vinylpyrrolidone) (PVP) for water microfiltration using the electrospinning method. The EPS-based nanofiber membranes exhibited a smooth morphology and were uniform in size. The concentration of the EPS/PVP solution changed some of the physical parameters of the nanofiber membrane, such as viscosity, conductivity, and surface tension. Greater viscosity and surface tension increase the nanofiber membrane diameter, whereas the addition of PVP results in hydrophilicity. Additionally, increasing the pressure increased the flux value of each variation of the nanofiber membranes. Furthermore, the rejection value was 99.99% for all variations. Finally, the use of EPS waste for nanofiber membranes is also beneficial for decreasing the amount of EPS waste in the environment and is an alternative to the current membranes available in the market for water filtration applications.
ABSTRACT
Acrylonitrile butadiene styrene (ABS) is one of the most common fused-filament feedstocks for 3D printing. The rapid growth of the 3D printing industry has resulted in huge demand for ABS filaments; however, it generates a large amount of waste. This study developed a novel method using waste ABS to fabricate electrospun nanofiber membranes (ENMs) for water filtration. Polyvinylpyrrolidone (PVP) was employed to modify the properties of waste ABS, and the effect of PVP addition in the range of 0-5 wt% was investigated. The results showed that adding PVP increased the viscosity and surface tension but decreased the conductivity of the precursor solution. After electrospinning, PVP could reduce the number of beads, increase the porosity and fiber diameter, and improve the wettability of the fabricated fibers. Moreover, the bilayer of ABS ENMs achieved a high flux value between 2951 and 48 041 L m-2 h-1 and a high rejection rate of 99%. Our study demonstrates a sustainable strategy to convert waste plastics to inexpensive materials for wastewater treatment membranes.
