SARS-Cov 2 was present in some air samples that were collected from patient's rooms.• MD8 airscan sampler showed suitable performance for sampling SARS-like viruses. • PTFE and gelatin filters have high performance for the sampling of the viral particle size. • RT-PCR has been commonly used for the detection of SARS-CoV-2 in air samples.
This study aims to investigate the effi ciency of magnesium oxide nanoparticles (MON) in vitro for the removal of lead (II) and chromium (VI) from aqueous environments. The effects of various parameters such as contact time (15 to 280 min), pH (3, 5, 7 and 9), the initial concentration of lead/chromium (10, 20, 30.40 and 50 mg/L), absorbent dose (0.3, 0.5 and 0.8 g/L), and shaking speed (150 to 350 rpm) was investigated. The parameters were optimized by varying one parameter at a time and keeping other parameters constant. The maximum removal effi ciency of MON for lead (II) and chromium (VI) was achieved at contact time 280 min, pH 9, initial concentration of lead/chromium 10 mg/L, adsorbent dose 0.8 g/L, and shaking speed 250 rpm. The results also indicated that MON convert the Pb 2+ to Pb 0 and Cr 6+ to Cr 3+ during the removal process. The adsorption of lead (II) and chromium (VI) follows the Langmuir isotherms, therefore the adsorption was of a physical nature.
Chromium (Cr) is considered to be mutagenic and carcinogenic, and is one of the most important pollutants that have been widely used in various industrial applications. Due to its adverse health impacts, Cr must be removed from effluents before being released into the water environments. The objective of the present study was to investigate the effect of electroFenton process (EFP) using iron electrodes in presence of sodium sulfate salt on the elimination of Cr(VI) from aqueous solution. The effect of various parameters such as pH, voltage, initial Cr(VI) concentration, hydrogen peroxide dosage and cyanide concentration (as interference ion), on the process efficiency of Cr(VI) removal have also been tested. The results indicate that the optimum pH, voltage and hydrogen peroxide dosage in EFP were determined to be 3, 30 V and 50 mL/L, respectively. The results of this research also demonstrated that EFP efficiency decreased with increasing initial Cr(VI) concentration. Moreover, EFP efficiency Cr(VI) removal decreased with increasing cyanide concentration; accordingly, the cyanide acts as interference ion in EFP and can reduce the removal efficiency of Cr(VI). According to the obtained results, the maximum removal efficiency of Cr(VI) at optimum condition was 97 % after 25 min. These findings suggest that EFP is suitable option for removing Cr(VI) from aqueous solution.
A wide variety of methods have been applied in indoor air to reduce the microbial load and reduce the transmission rate of acute respiratory diseases to personnel in healthcare sittings. In recent months, with the occurrence of COVID-19 pandemic, the role of portable ventilation systems in reducing the load of virus in indoor air has received much attention. The present study delineates a comprehensive up-to-date overview of the available photocatalysis technologies that have been applied for inactivating and removing airborne viruses. The detection methods for identifying viral particles in air and the main mechanisms involving in virus inactivation during photocatalysis are described and discussed. The photocatalytic processes could effectively decrease the load of viruses in indoor air. However, a constant viral model may not be generalizable to other airborne viruses. In photocatalytic processes, temperature and humidity play a distinct role in the inactivation of viruses through changing photocatalytic rate. The main mechanisms for inactivation of airborne viruses in the photocatalytic processes included chemical oxidation by the reactive oxygen species (ROS), the toxicity of metal ions released from metal-containing photocatalysts, and morphological damage of viruses.
The aim of this study was photocatalytic degradation of methylene blue (MB) dye using titanium dioxide nanoparticles simulated using ultraviolet in batch and tubular reactors. In this study, the effect of different concentrations of titanium dioxide nanoparticles in the photocatalytic process on MB degradation was examined in batch and tubular reactors. The effect of dye concentration, titanium dioxide nanoparticle concentration and aeration level were examined on the process efficiency. Results showed that the removal of MB dye was directly related to the radiation time. The best removal efficiency of dye and chemical oxygen demand (COD) in the batch reactor was 100% and 42.2%, respectively, while it was 93% and 47.8% in the tubular reactor (in 1.2 g/L of titanium dioxide nanoparticles at 60 min). Moreover, as dye concentration increased, dye removal rate decreased. Making use of the batch model to remove dye and COD is more efficient and can be used on a larger scale due to the required removal efficiency and wastewater discharge standards.
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