Effect of shell powder on removal of metals and volatile organic compounds (VOCs) from resin in an atmospheric-pressure microwave plasma reactor.

Resin has been widely used for thermosetting printed circuit boards (PCBs) and is a key part of e-waste from scrap PCBs. It requires appropriate treatment because of its harmful elements (metals and metalloids) and organic compounds that are toxic to human health and the environment. The purpose of this study is to eliminate volatile organic compounds (VOCs) and elements (metals and metalloids) in resin via the use of powdered snail shell (Babylonia formosae) in an atmospheric-pressure microwave plasma reactor. Shell powder plays a significant role in the destruction of benzene and toluene with removal efficiency 98.8 % and 100 %, respectively, compared to quartz sand with removal efficiency 44.9 %. A high ratio of shell powder increases the inertization of metals and metalloids by more than 96 %. The crystalline structures of these materials are dominated by calcite formations (CaCO3), confirming the elimination of metals and metalloids. Raman spectroscopy shows that the shell powder vitrifies these elements. The use of shell powder is thus recommended to degrade hazardous substances and to vitrify elements from resin in plasma pyrolysis.

SnO2/TiO2 nanotube heterojunction: The first investigation of NO degradation by visible light-driven photocatalysis.

Titania (TiO2) as a commercial photocatalyst has been continually struggling due to the limitation of ultraviolet light response and the high recombination rate of photoinduced carriers. The development of heterojunction nanostructures provides great promise to achieve the activation by visible light and suppress the photoinduced electron-hole pairs recombination. Herein, we synthesized a SnO2 and TiO2 nanotube heterojunction (SnO2/TNT) via a one-step hydrothermal strategy and systematically investigated NO photocatalytic degradation over the SnO2/TNTs heterojunction under visible light at the parts per billion level. Various physicochemical characterization techniques were conducted to verify the physical and chemical properties of the materials. For example, the morphology and lattice spacings of the materials were examined by high-resolution TEM (HR-TEM) images and selected area electron diffraction (SAED) pattern, X-ray photoelectron spectroscopy (XPS) was employed to study the oxidation states and propose the band alignment diagram of the SnO2/TNTs heterojunction, and photoluminescence spectroscopy was employed for understanding of carrier's trapping, migration and transfer. The photocatalytic results show that the SnO2/TNTs heterojunction exhibits the superior photocatalytic performance, and the photocatalytic degradation efficiency of NO can reach 60% under visible light with effective inhibition of NO2 production. The excellent photocatalytic ability is due to the low recombination rate of the photoinduced electron-hole pairs. Furthermore, a trapping experiment was combined with electron spin resonance (ESR) and utilized to identify the involvement of reactive radicals in the photocatalysis process suggesting that and OH mediated pathways play a predominant role in NO removal.