Poriferous TiO2/GO (denoted as TGO-x%) photocatalysts with ultrathin grapheme oxide (GO) layer were prepared by a hydrothermal method, the adsorption and photocatalytic degradation and its kinetics about Methylene blue(MB) were studied systematically. All the TGO-x% showed improved adsorption and photodegradation performance. TGO-25% had excellent adsorptivity while TGO-20% exhibit the highest visible light photocatalytic degradation activity. The adsorption capacity for TGO-25% was 20.25 mg/gcatalyst along with the k1 was about 0.03393 min·gcatalyst/mg, this enhancement was mainly owing to the strong adsorption capacity of GO and the stacking structure of sheets and nanoparticles. GO sheets prevented the agglomeration of TiO2 particles and TiO2 nanoparticles also prevented the agglomeration of GO sheets, which could provides greater surface area. Besides, the remarkably superior photodegradation activity of TiO2/GO composites is mainly attribute to the strong absorption of visible light and the effective charge separation revealed by the photoluminescence, the total removal rate of MB is 97.5% after 35 min adsorption and 140 min degradation, which is 3.5 times higher than that of TiO2.
The active crystal plane determines the activity of the inorganic metal oxide-based photocatalyst, especially for the degradation of organic pollutants. The ZnO tetrakaidecahedron with different crystal faces ({001}, {101}, and {100}) is efficiently synthesized with tetramethylammonium hydroxide (TMAH) as an additive. The exposed surface of the ZnO tetrakaidecahedron can be controlled by changing the reaction concentration and reaction time. The tetradecahedral ZnO (ZnO-1, ZnO-2) nanoparticles were systematically investigated by various characterizations. On the basis of the experimental results, we speculated the possible formation mechanism of ZnO tetrakaidecahedron. In addition, the photocatalytic activity of the ZnO-1 tetrakaidecahedron is better than that of ZnO-2 nanoparticles in the photodegradation of methylene blue (MB) and rhodamine B (Rh B), which is ascribed to more exposed active crystal faces, large photocurrent density, and large specific surface area.
Aim: During several local COVID-19 outbreaks in China in 2020, SARS-CoV-2 or its RNA was isolated or detected from frozen food or packages, revealing the lack of effective disinfection measures in the frozen food chain and risk of transmission. We explored the possibility that disinfectant plus antifreeze could be delivered as thermal fog to realize effective disinfection at subzero temperatures. Methods and Results:We selected two disinfectant-antifreeze combinations, didecyl dimethyl ammonium bromide (DDAB) -propylene glycol (PPG) and peracetic acid (PAA) -triethylene glycol (TEG), and each combination is used with a customoptimized thermal fogging machine. The two fogs were tested in −20°C freezer warehouses for their disinfection efficacy against a coronavirus porcine epidemic diarrhoea virus (PEDV) field strain, a swine influenza virus (SIV) field strain, and three indicator bacteria, Escherichia coli, Staphylococcus aureus and Bacillus subtilis endospores. At −20°C, the DDAB-PPG or PAA-TEG thermal fogs settle within 3.5 to 4.5 h and effectively inactivated PEDV with median tissue culture infective dose of 10 −3.5 0.1 ml −1 and SIV-H1N1 with hemagglutination titre of 2 6 ml −1 within 15-60 min. DDAB-PPG could inactivate S. aureus and E. coli vegetative cells (10 6 cfu ml −1 ) within 15-60 min but not effective on B. subtilis spores, while PAA-TEG could disinfect B. subtilis spores more effectively than for S. aureus and E. coli. Conclusions:We showed that a practical subzero temperature disinfection technology was effective in killing enveloped viruses and vegetative bacteria or bacterial spores. DDAB-PPG or PAA-TEG thermal fogging may be a practical technology for cold-chain disinfection. Significance and Impact of the Study:This subzero temperature disinfection technology could help to meet the urgent public health need of environmental disinfection in frozen food logistics against pandemic and other potential pathogens and to enhance national and international biosecurity.
TiO2 nanospheres with high specific surface area and good crystallinity were prepared by a hydrothermal method using urea as the capping agent and isopropanol as the solvent. The capping agent effectively controlled the morphology of TiO2 nanospheres and led to improved crystallinity. Using a solvent with a long carbon chain, such as isopropanol, also promoted the formation of TiO2 nanospheres. TiO2 nanospheres with different morphologies were prepared by adjusting the amount of urea. It was found that when TiO2-0.6 was used as the photocatalyst, highest rates of degradation of both methylene blue and rhodamine B under ultraviolet-visible light were observed. Moreover TiO2-0.6 also had the largest hydrogen production efficiency among the different TiO2 samples tested. Thus, TiO2 nanospheres have great development potential and application prospects in environmental management and new modes of energy utilization.
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