At the end of December 2019, the rapid spread of the COVID-19 (SARS-CoV-2) disease and, subsequently, deaths around the world, lead to the declaration of the pandemic situation in the world. At the ...beginning of the epidemic, much attention is paid to person-to-person transmission, disinfection of virus-contaminated surfaces, and social distancing. However, there is much debate about the routes of disease transmission, including airborne transmission, so it is important to elucidate the exact route of transmission of the COVID-19 disease. To this end, the first systematic review study was conducted to comprehensively search all databases to collect studies on airborne transmission of SARS-CoV-2 in indoor air environments. In total, 14 relevant and eligible studies were included. Based on the findings, there is a great possibility of airborne transmission of SARS-CoV-2 in indoor air environments. Therefore, some procedures are presented such as improving ventilation, especially in hospitals and crowded places, and observing the interpersonal distance of more than 2 m so that experts in indoor air quality consider them to improve the indoor air environments. Finally, in addition to the recommendations of the centers and official authorities such as hand washing and observing social distancing, the route of air transmission should also be considered to further protect health personnel, patients in hospitals, and the public in other Public Buildings.
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•The SR was conducted to compile studies on airborne transmission of virus in indoor air.•In total, 14 relevant and eligible studies were included.•There is a great possibility of airborne transmission of SARS-CoV-2 in indoor air.•Improving ventilation is essential, especially in hospitals and crowded places.
While the distribution and effects of microplastics (MPs) have been extensively studied in aquatic systems, there exits little information on their occurrence in the terrestrial environment and their ...potential impacts on human health. In the present study, street dust and suspended dust were collected from the city and county of Asaluyeh, Iran. Samples were characterized by various microscopic techniques (fluorescence, polarized light, SEM) in order to quantify and classify MPs and microrubbers (MRs) in the urban and industrial environments that are potentially ingestible or inhalable by humans. In < 5-mm street dust retrieved from 15 sites, there were an average of 900 MPs and 250 MRs per 15 g of sample, with MPs exhibiting a range of colours and sizes (<100 to >1000 μm). Most street dust samples were dominated by spherical and film-like particles and MRs largely made up of different sizes of black fragments and fibrous particulates. Airborne dust collected daily over an eight-day period at two locations revealed the ubiquity of fibrous MPs of sizes ranging from about 2 μm to 100 μm and an abundance of about 1 per m−3. These samples contained small MR fragments whose precise characteristics were more difficult to define. Based on the median concentrations in street dust, estimates of acute exposure through ingestion are about 5 and 15 MP d−1 and 2 and 7 MR d−1 for construction workers and young children, respectively. Quantities of inhalable particulates were more difficult to define but the potential toxicity of MPs and MRs taken in by this route was evaluated from assays performed using particulates isolated from street dusts in the presence of an artificial lung fluid. Both types of particle exhibited oxidative potential, with MPs displaying consumptions of different antioxidants that were comparable with corresponding values for a reference urban particulate dust but lower than those for London ambient particulate matter. Thus, MPs and MRs contribute towards the health impacts of urban and industrial dusts but their precise roles remain unclear and warrant further study.
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•900 MPs and 250 MRs of varying size and shape were present in 15 g street dust.•MPs in air were fibrous but MRs were more difficult to characterise.•Acute exposure estimates via ingestion are 15 MP d−1 and 7 MR d−1 for children.•MPs and MRs exhibit oxidative potential that contributes to the toxicity of urban dust.
Recently, an outbreak of a novel human coronavirus which is referred to as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (COVID-19) by the World Health Organization (WHO) was ...identified in Wuhan, China. To help combat the pandemic, a systematic review (SR) was performed to collect all available studies concerning inactivation methods, environmental survival, and control and prevention strategies. A comprehensive literature survey yielded 42 eligible studies which included in the SR. The results confirmed that the WHO recommended two alcohol-based hand rub formulations (ethanol 70–95% and 2-propanol 70–100%) had an efficient virucidal activity in less than 60 s by more and equal 4 log
10
(≥ 99.99) approximately and could be used for disinfection in public health and health-care facilities. The findings indicated that SARS-CoV-1 and SARS-CoV-2 can survive under different environmental conditions between 4 and 72 h approximately. The results also demonstrate that temperature and relative humidity are important factors in the survival of SARS-CoV-2. The main strategies recommended by the WHO to avoid contracting SARS-CoV-2 are hand washing several times in the day and maintaining social distancing with others. It is important to note that the more studies require addressing, the more possible airborne transmission due to the survival of SARS-CoV-2 in aerosols for 3 h approximately. We hope that the results of the present SR can help researchers, health decision-makers, policy-makers, and people for understanding and taking the proper behavior to control and prevent further spread of SARS-CoV-2.
Abstract
In the present study, the magnetic NH
2
-MIL-101(Al)/chitosan nanocomposite (MIL/Cs@Fe
3
O
4
NCs) was synthesized and used in the removal of azithromycin (AZT) from an aqueous solution for ...the first time. The as-synthesized MIL/Cs@Fe
3
O
4
NCs was characterized by SEM, TEM, XRD, FTIR, BET, and VSM techniques. The effect of various key factors in the AZT adsorption process was modeled and optimized using response surface methodology based on central composite design (RSM-CCD). The low value of p-value (1.3101e−06) and RSD (1.873) parameters, along with the coefficient of determination > 0.997 implied that the developed model was well fitted with experimental data. Under the optimized conditions, including pH: 7.992, adsorbent dose: 0.279 g/L, time: 64.256 min and AZT concentration: 10.107 mg/L, removal efficiency and AZT adsorption capacity were obtained as 98.362 ± 3.24% and 238.553 mg/g, respectively. The fitting of data with the Langmuir isotherm (R
2
: 0.998, X
2
: 0.011) and Pseudo-second-order kinetics (R
2
: 0.999, X
2
: 0.013) showed that the adsorption process is monolayer and chemical in nature. ΔH° > 0, ΔS° > 0, and ∆G° < 0 indicated that AZT removal was spontaneous and endothermic in nature. The effect of Magnesium on AZT adsorption was more complicated than other background ions. Reuse of the adsorbent in 10 consecutive experiments showed that removal efficiency was reduced by about 30.24%. The performance of MIL/Cs@Fe
3
O
4
NCs under real conditions was also tested and promising results were achieved, except in the treatment of AZT from raw wastewater.
Soil pollution by heavy metals is a major concern in agricultural area. Potential impact of heavy metals in agricultural soil on human health by accumulating in food chain demonstrated elsewhere.
In ...this regard Mian-Ab plain as a major agricultural site of Khuzestan province considered for Arsenic, cadmium and lead concentration as the main potential toxic pollutants in soil. 50 topsoil samples were collected and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Also Contamination level of selected heavy metals in Mian-Ab Plain, was assessed by single factor contaminant index (PI) and pollution load index (PLI). Results show mean concentration of arsenic, cadmium and lead were 2.52, 0.30 and 7.21mgkg−1. Base on PLI results 12 point (24%) of the studied area show moderately polluted and 38 point (76%) show unpolluted area.
Chitosan (CS), synthesized from chitin chemically extracted from shrimp shells, was used for the synthesis of magnetic chitosan nanoparticles (Fe
3
O
4
-CSN), which makes the adsorbent easier to ...separate. Fe
3
O
4
-CSN was used for the removal of toxic metals such as vanadium (V(V)) and palladium (Pd(II)) ions from aqueous solutions. Influencing factors on the adsorption process such as pH, contact time, adsorbent dosage, and agitation speed were investigated. A competitive adsorption of V(V) and Pd(II) ions for the active sites was also studied. The monolayer maximum adsorption capacities (
Q
m
) of 186.6 and 192.3 mg/g were obtained for V(V) and Pd(II) ions, respectively. The pseudo-second-order equation gave the best fit for the kinetic data, implying that chemisorption was the determining step. Freundlich model yielded a much better fit than the other adsorption models assessed (Langmuir, Temkin and Dubinin-Radushkevich). Thus, the adsorption of V(V) and Pd(II) ions onto Fe
3
O
4
-CSN is a combination of physical and chemical adsorption, as based on the kinetics and equilibrium study. Generally, physical adsorption is the mechanism that governs the system, while chemical adsorption is the slowest adsorption step that takes place. Thermodynamic studies displayed that the adsorption process was exothermic and spontaneous. Removal efficiencies of 99.9% for V(V) and 92.3% for Pd(II) ions were achieved, implying that Fe
3
O
4
-CSN adsorbent had an excellent ability for the removal of the metal ions from real industrial wastewaters without remarkable matrix effect.
Graphical abstract
ᅟ
TiO
2
–FeZn nanocatalyst combined with sonolysis were used to activate peroxymonosulfate (PMS) as a highly efficient advanced oxidation process (US/TiO
2
–FeZn/PMS) for the decoloration of orange II ...dye (OII) and real textile wastewater. The characterization of the as-synthesized NPs was performed by SEM, FTIR, EDX and XRD analyses. Optimal experimental conditions of operational parameters were obtained: pH = 3, 15 mg/L initial OII concentration, 0.2 g/L PMS, 0.7 g/L nanocatalyst dosing, and 300 W ultrasonic power. The decolorization was observed to increase with increasing the dose of nanocatalyst and the ultrasonic power, and with decreasing pH (under acidic conditions). Under optimal experimental conditions, decolorization and COD removal of textile wastewater were 99.9% and 74.6%, respectively, at 40 min. The TiO
2
–FeZn/PMS/US as a novel process exhibited a higher removal of OII (95%) than TiO
2
NPs/PMS/US process (54%). The OII removal efficiency by the different processes decreased in the following order: TiO
2
–FeZn/US/PMS > TiO
2
–FeZn/PMS > TiO
2
–FeZn/US > TiO
2
/US/PMS > US/PMS > TiO
2
–FeZn > PMS > US. The recyclability study revealed that the process could be reused up to three consecutive cycles. The current US/nanocatalyst/PMS system was concluded to be an efficient, reusable and stable nanocatalyst for the oxidation of textile dyes.
Background: Nanocomposites have received remarkable attention as effective adsorbents for removal of coexisting pollutants over the last decades. The presence of heavy metals (HMs) in wastewater has ...caused a global health concern. Therefore, the aim of this study was to review the most relevant publications reporting the use of nanostructures to simultaneous adsorption of HMs in mixed aqueous systems. Methods: In this systematic review, 9 studies were included through a systematic search in the three databases (ISI, Scopus, and PubMed) during 1990-2021. The optimal value of simultaneous adsorption parameters such as initial concentration, contact time, adsorbent dosage, and pH was discussed. Results: Findings indicate that the Langmuir and Freundlich models and the pseudo-second-order kinetic model have been widely used and the most popular models to describe the equilibrium of HMs by nanoadsorbents. This study confirmed that the simultaneous removal rate of HMs decreased with an increase in pH value. It was found that the major mechanisms of HMs adsorption onto nanostructures were electrostatic interactions and precipitation. Conclusion: Nanocomposites have remarkable adsorption performance for HMs with the highest adsorption capacity (qe(mg/g)).
Sludge conditioning is an important stage in sludge management. In the present study, a sequence of freeze/thaw-electro-Fenton process was designed and specific resistance filtration (SRF) was ...monitored during sludge conditioning as an important factor in sludge dewaterability. Furthermore, protein and polysaccharide concentrations were measured during the experiments. Results showed that the lowest SRF value contributed to −10°C in freezing process which showed a reducing trend by decreasing solution pH. In addition, results revealed that solution pH less than 3 caused a significant improvement in sludge dewatering; so the lowest SRF has been registered at pH = 2. By increasing current intensity from 0.5 to 1A, SRF values were reduced and then followed by an enhancement with increasing current intensity to 3.2 A. The lowest SRF value (6.1 × 10
m/kg) was obtained at H
= 30 mg/L which was the best conditions for sludge dewatering.
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