Background: Volatile organic compounds are the major environmental pollutants causing adverse effects on the human health and the environment, therefore, tremendous effort has been put toward eliminating these compounds. Methods: In this study, the effect of synthesized nanoparticles on the removal of styrene from gas phase by photocatalytic process under UV irradiation in the cylindrical photoreactor was studied. The activated carbon-zinc oxide (AC-ZnO) catalysts were prepared at different weight ratios (6%, 12%, and 18%) of ZnO. The prepared catalyst was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Brunauer-Emmett-Teller (BET) analyses. The effects of various parameters, such as concentrations of styrene, various weight percentage (wt%) of nanoparticles, and UV irradiation, were investigated. The efficiency of the AC-ZnO catalyst was determined based on its adsorption capacity, breakthrough time, and removal efficiency. Results: It was revealed that the photocatalytic removal efficiency of styrene was high in the presence of both ZnO nanoparticle and AC under UV light. Under optimal conditions, the efficiency of UV/ACZnO 18%, UV/AC-ZnO 12%, and UV/AC-ZnO 6% catalysts was 77%, 86%, and 83%, respectively. By increasing the concentration of input styrene, the photocatalytic removal efficiency was reduced, while the adsorption capacity of styrene increased. Conclusion: According to the results, the AC-ZnO 12% exhibited higher activity compared to other photocatalysts. Also, the amount of stabilized ZnO nanoparticles on the activated carbon affects the elimination rate of styrene.
Background and Objective:Incidents are one of the most important causes of damages in an organization often occurring due to a chain of minor and trivial errors. Each error may have minor consequences, but in synergy, the system invariably heads towards serious and disastrous consequences. Therefore, we aimed to identify human errors leading to incidents in a gas refinery using human factors analysis and classification system (HFACS). Materials and Methods: A retrospective study was performed in a gas refinery. Data regarding incidents were gathered from that center. First, root causes analysis reports (RCA) of incidents occurred during the past eight years were prepared. Then, they were analyzed by using the HFACS model. Results: Most errors were associated with the first level, that is, errors caused by unsafe acts, which in the first level they were related to "violations", in the second level to "physical environment", in the third level to "inadequate supervision", and in the fourth level to "management of resources". Conclusion: Our results showed the causes of accidents and several shortcomings in the refinery. Human errors in an organization can be reduced by utilizing administrative controls, creating an appropriate learning environment, and raising employee awareness at the same time.
Introduction: Styrene monomer is a volatile organic compound that has many applications particularly in plastic, rubber and paint industries. According to the harmful effects of these compounds on human and environment, reducing and controlling of them seem necessary. Therefore, in this study removal of styrene was investigated using the photocatalytic process of titanium dioxide nanoparticles stabilized on ZSM-5. Methods: After stabilization of titanium dioxide nanoparticles on ZSM-5 zeolite, Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and X-ray diffractometry (XRD) analyses were used to determine the characteristics of nanoparticles. Experiments were conducted at ambient temperature in a laboratory scale. Concentrations of the produced styrene in the experiments were 50 and 300 ppm, and the input flow rate was 1 l/min. Results: The images and spectra obtained through XRD and SEM-EDAX showed that nano-catalysts are well-stabilized. The results showed that by increasing the input concentration of styrene from 50 to 300 ppm, the photocatalytic removal efficiency was reduced. Also, adsorption capacities of the catalyst bed in concentrations of 50 and 300 ppm were calculated 16.3 and 19.4 mg/g of adsorbent, respectively. Conclusions: The results show that the use of hybrid bed can increase the removal efficiency of contaminants. Also, due to low cost of application of these systems compared to conventional methods, it is recommended that more comprehensive studies be conducted regarding the optimization of the parameters affecting the process of photocatalytic removal.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.