Accelerated Photodegradation of Solid Phase Polystyrene by Nano TiO2-Graphene Oxide Composite under Ultraviolet radiation

One stone two birds: a sinter-resistant TiO2 nanofiber-based unbroken mat enables PM capture and in situ elimination

Airborne particulate matter (PM) primarily resulting from fossil fuel burning is an increasingly global issue. In this work, an intrinsically fragile TiO₂ nanofibrous mat was facilely engineered with good structural integrity, flexibility, foldability, and high-temperature resistance (~1300 °C), by suppressing the sintering (i.e., growth) of nanocrystallites in each single nanofiber. Such functionalization enables self-regenerative air filtration for PM capture and in situ catalytic elimination in a "one-stone-two-birds" approach. Finite element analysis simulation revealed the retained nanopores in each anti-sintering nanofiber could facilitate the air flow during filtration. Without any chemical or physical modification, this self-standing and lightweight (7.1 g m^-2) fibrous mat showed 96.05% filtration efficiency for 3-5 μm NaCl particles, with a low pressure drop of only 18 Pa and high quality factor of 0.179 Pa^-1 under an airflow velocity of 32 L min^-1. By utilizing its photocatalytic attribute, the nanofibrous mat in situ eliminated the captured particles from incense burning under one Sun irradiation in 4 h, and thereby spontaneously regenerated in an easy manner. The straightforward grafting of Au nanoparticles onto nanofibers could enable a quick degradation toward cigarette smoke, mainly due to the photothermally elevated local temperature by Au around the reactive sites. The plasmonic fibrous mat kept a high and stable filtration efficiency of PM_0.3, PM_2.5, and PM₁₀ over 98.62%, 99.76%, and 99.99% during an outdoor long-term filtration test for 12 h under sunlight irradiation (Nanjing, China, September, 26^th, 2020, 7:30 to 19:30). This work provides a solution for solving the airborne pollution from its source, prolonging the lifetime of the filter, and avoiding the risk of producing secondary pollution.

Photo-catalytic and biotic degradation of polystyrene packaging film: Effect of zinc oxide photocatalyst nanoparticles and nanoclay

Synergistic effect of zinc oxide nanoparticles (ZnO-NPs) as photocatalyst and organonanoclay (ONC) as biodegradable promoter on the degradation of polystyrene (PS) film was investigated. The films were exposed to ultraviolet irradiation under ambient air at room temperature for photo-catalytic degradation and then submitted to biodegradation test in soil using respirometric procedure. Fourier-transform infrared and ultraviolet-visible spectroscopy, thermogravimetric analysis, colorimeter technique, contact angle measurement, and the carbon dioxide evolution results showed higher photo- and biodegradation efficiency of PS-ONC-ZnO nanocomposite compared to the neat PS, PS-ONC and PS-ZnO nanocomposites. Thermal stability, optical band gap, and water contact angle of photo-degraded PS-ONC-ZnO nanocomposite decreased by 11.37, 18.33 and 63.99%, respectively, while that of PS film was only 6.20, 6.44 and 5.84%, respectively. The photo-degraded PS-ONC-ZnO and PS-ZnO film indicated a biodegradation percentage value of 3.3 and 2.1%, respectively, over 16 weeks of incubation in soil. The possible degradation mechanism of nanocomposites was briefly discussed.