Surface-washing agents are an option to enhance the removal of oil spilled or stranded on shorelines. The use of nanocellulose-based nanofluid as a surface-washing agent was studied by investigating its reactivity and effectiveness. Salinity was found to be the most influencial factor to facilitate oil removal with the nanofluids. Cations from salt can promote the adsorption of nanocellulose on the oil/water interface by reducing the surface charges. The experimental results revealed the nanocellulose could be effective at low concentrations but an excess of nanocellulose hindered oil removal due to an increase in fluid viscosity. A miscibility model was applied to verify this finding in a thermodynamics context. The biotoxicity tests showed that nanocellulose-based nanofluid did not have negative effects on algae growth and introducing nanocellulose into an oiled culture medium can actually mitigate the toxicity of the oil on algae. A comparison in removal efficiency with other surfactants demonstrated the potential value for shoreline cleanup due to the superior effectiveness of nanocellulose-based nanofluids. Overall, a nanocellulose has a high potential for application as a surface-washing agent for shoreline cleanup due to the low cost, low toxicity, and high efficiency.
Severe haze events with exceedingly high-levels of fine aerosols occur frequently over the past decades in the North China Plain (NCP), exerting profound impacts on human health, weather, and climate. The development of effective mitigation policies requires a comprehensive understanding of the haze formation mechanisms, including identification and quantification of the sources, formation, and transformation of the aerosol species. Haze evolution in this region exhibits distinct physical and chemical characteristics from clean to polluted periods, as evident from increasing stagnation and relative humidity, but decreasing solar radiation as well as explosive secondary aerosol formation. The latter is attributed to highly elevated concentrations of aerosol precursor gases and is reflected by rapid increases in the particle number and mass concentrations, both corresponding to nonequilibrium chemical processes. Considerable new knowledge has been acquired to understand the processes regulating haze formation, particularly in light of the progress in elucidating the aerosol formation mechanisms. This review synthesizes recent advances in understanding secondary aerosol formation, by highlighting several critical chemical/physical processes, that is, new particle formation and aerosol growth driven by photochemistry and aqueous chemistry as well as the interaction between aerosols and atmospheric stability. Current challenges and future research priorities are also discussed.
In present study, we fabricated sulfhydryl modified covalent organic frameworks (COF-‒SH) through one-step reaction for the removal of Hg(II) from water. Different techniques were employed to characterize the fabricated COFs. We find that COF-‒SH exhibits great adsorption capacity (1283 mg/g) towards Hg(II), which is over 25 times higher than that of COF-1 without ‒–SH (53.1 mg/g). COF‐SH has fast adsorption kinetics with the removal of 95% of 1000 μg/L Hg(II) within 30 min and over 99% after 2 h. Under a wide pH range (from 4 to 9), COF-‒SH exhibits high removal efficiencies (>99%). Moreover, COF‐SH can selectively adsorb Hg(II) in the presence of other metal cations up to 1000 μg/L. X-ray photoelectron spectroscopy analysis reveals the presence of high affinity between thiol-S atom and Hg(II), which is also responsible for the high selectivity towards Hg(II) compared with other cations. Because of the transfer from enol form to keto form during synthesis, COF‐SH exhibit remarkable stability during 10-cycle regeneration and reuse test. During utilization in wastewater extracted from Hg contaminated sludge, COF-‒SH displays high Hg(II) removal efficiency (>95%) under multiple coexisting ions conditions. The results suggest that COF-‒SH have great potential for Hg(II) removal from water under complex conditions.
This study is an exploration of the digital divide between urban and rural areas, and it was conducted to assess the impact of the minimum living guarantee system on online education in China. The results of the research showed that 83.38% of students in low-income families have been able to participate in online education at home during the pandemic, while 16.62% of students in low-income families have been unable to do so. The absence of computers, smartphones, and broadband Internet access in low-income households reduces the likelihood of children being able to participate in online education at home. In terms of accessing online education at home, students from urban areas have obvious advantages over those from rural ones, and students from minimum living guarantee families have obvious advantages over those from marginal minimum living guarantee ones. This study also showed that the presence of online education-related amenities, including computers, smartphones, and Internet access, mediates the relationship between the subsistence allowance system, Hukou, and accessibility of online education. To address this issue, this paper includes suggestions for bridging the digital divide in online education.
A three-port plasmonic array is proposed to achieve a dual-field superfocusing using the forward-propagation method based on spatial Fourier transform. The algorithm of fast Fourier transform is used to facilitate the design process. Both the electric and magnetic fields can be superfocused on the focal plane of z = 0.1λ (λ is the free-space wavelength) based on an effect of radiationless electromagnetic interference. The full widths of the half-maximum of both two fields are 0.060λ and 0.072λ, respectively. Besides, the metrics of the dual-field superfocusing are 1.67 and 1.39. The proposed theory can simplify the design process of superfocusing, and the plasmonic array with brief three ports can sufficiently facilitate the construction of the desired source. This letter can be beneficial for the development of beam steering, sophisticated holography, super-resolution imaging, and other applications of near- or far-field devices.
The occurrence of man-made antibiotics in natural environment has aroused attentions from both scientists and publics. However, few studies tracked antibiotics from their production site to the end of disposal environment. Taking the coastal region of Hangzhou Bay as the study area, the fate of 77 antibiotics from 6 categories in two-step wastewater treatment plants (WTPs, i.e. pharmaceutical WTP and integrated WTP) was focused; and the antibiotics in both dissolved and adsorbed phases were investigated simultaneously in this study. The ubiquitous occurrence of antibiotics was observed in the two-step WTPs, with antibiotic concentrations following the order of PWTP (LOQ - 1.0 × 105 ng·L−1) > IWTPi (for industrial wastewater treatment, LOQ - 3.7 × 103 ng·L−1) > IWTPd (for domestic sewage treatment, LOQ - 1.3 × 103 ng·L−1). And the types of antibiotics detected in excess sludge and suspended particles were in accordance with those in wastewater. Quinolones were invariably dominant in both dissolved and adsorbed fractions. High removal efficiencies (median values >50.0%) were acquired for the dissolved quinolones (except for DFX), tetracyclines, β-lactams, and lincosamides. Anaerobic/anoxic/oxic achieved the highest aqueous removal of antibiotics among the investigated treatment technologies in the three WTPs. PWTP and IWTP removed 9797 and 487 g·d−1 of antibiotics, respectively; and a final effluent with 126.4 g·d−1 of antibiotics was discharged into the effluent-receiving area (ERA) of Hangzhou Bay. Source apportionment analysis demonstrated that the effluents of IWTPd and IWTPd contributed respectively 39.3% and 8.9% to the total antibiotics in the ERA. The results illustrate quantitatively the antibiotic flows from engineered wastewater systems to natural water environment, on the basis of which the improvements of wastewater treatment technologies and discharge management would be put forward.