Search

A membrane for efficient oil-in-water emulsion separation requires a surface with hydrophilic/underwater oleophobic properties. In this study, a simple and facile sol–gel strategy was proposed for preparing oil-in-water emulsion separation membrane with hydrophilic/underwater oleophobic surface by growing amorphous SiO2 sheets on an electrospun polyacrylonitrile nanofiber membrane (PAN NFM). The composite membranes (PAN@SiO2 NFMs) showed excellent properties in mechanical strength, hierarchical microporous structure, hydrophilicity and underwater oleophobicity, as well as remarkable performance in water flux, separation efficiency and cyclic stability. Under a low pressure of 1 kPa driven by the self-weight of emulsion, the PAN@SiO2 NFM demonstrated a large flux of 3994.3 ± 356.0 L m−2 h−1 and a high separation efficiency of 99.50%. In ten successive cycle tests, fluxes of the PAN@SiO2 NFM remained above 3000 L m−2 h−1, while the residual TOC in filtrate was stable at around 30 mg L−1, indicating the PAN@SiO2 NFM has excellent cyclic stability. It is also demonstrated that the PAN@SiO2 NFM is suitable for the separation of various kinds of emulsions, such as toluene, n-heptane, paraffin liquid, n-hexane and xylene. Hence, the prepared PAN@SiO2 NFM is a promising hydrophilic/underwater oleophobic membrane for efficient emulsion separation. [ABSTRACT FROM AUTHOR]

Massive amount of CO 2 emission, which could cause climate change, has been recognized as a serious environmental issue. Chemical adsorption is generally considered as a promising technology for CO 2 capture in low CO 2 partial pressure. Physical properties and chemical components of the adsorbent are important to CO 2 adsorption performance. To address structure limitation and complicated preparation process of the conventional adsorbent, herein, we reported a rapid and simple route to synthesis amine-modified silica aerogel monolith by co-precursor sol-gel method. Microstructure and the surface functional groups of the amine-modified silica aerogel could be easily manipulated. The products were characterized by SEM, XPS, NMR, in situ DRIFT and CNS elemental analyzer. The amine-modified silica aerogel exhibited good physical properties and demonstrated excellent CO 2 adsorption performance. The density, porosity and BJH pore volume of the amine-modified silica aerogel were 0.12 g/cm 3 , 94.5% and 2.39 cm 3 /g, respectively. The maximum static and dynamic adsorption capacities of CO 2 on the amine-modified silica aerogel were 2.2 mmol/g and 5.59 mmol/g under anhydrous and humid mixed gas conditions, respectively. The as-prepared aerogel also showed good cyclic ability for CO 2 adsorption and desorption. The CO 2 adsorption on the amine-modified silica aerogel is by the formation of carbamate through a two-step zwitterion mechanism. This easily prepared amine-modified silica aerogel could be a promising adsorbent for CO 2 capture. [ABSTRACT FROM AUTHOR]

Semiconductor photocatalysis is a promising technology for removing contaminants from water. Particularly, visible-light photocatalysis has attracted much attention because of its potential to utilize solar energy. However, nano-sized visible-light-driven photocatalysts easily aggregate during water treatment. Besides, it is difficult to recycle them from treated systems. Therefore, it is of great importance to develop visible-light-responsive immobilized photocatalysts with high activity. In this work, MWCNTs/Ag3PO4/polyacrylonitrile (PAN) ternary composite fiber membranes (TCFMs) with good photocatalytic performance were fabricated by electrospinning technique combined with in situ Ag3PO4 forming reaction. Due to the addition of MWCNTs, the band gap of MWCNTs/Ag3PO4/PAN TCFMs became narrower than that of Ag3PO4/PAN binary composite fiber membranes (BCFMs), which made MWCNTs/Ag3PO4/PAN TCFMs be able to use light at longer wavelengths. Compared with Ag3PO4/PAN BCFMs, the as-prepared MWCNTs/Ag3PO4/PAN TCFMs showed enhanced photocatalytic activity and stability for degrading rhodamine B (RhB) in batch processing systems, which mainly ascribed to fast electron transfer from Ag3PO4 to MWCNTs and the resulting high electron-hole (e−-h+) separation efficiency. Radical trapping experiments revealed that holes (h+) and superoxide radicals (·O2−) played primary roles in RhB degradation. In addition, the flexible MWCNTs/Ag3PO4/PAN TCFMs also showed potential practical application in the continuous wastewater treatment by a suitable photocatalytic membrane reactor. This work provides a facile approach to prepare flexible supported photocatalytic membrane with visible-light response, high activity and good stability. [ABSTRACT FROM AUTHOR]

Oil contamination will seriously affect the health of water environment, so it is necessary to design ideal oil absorbents with large absorption capacity and high selectivity for effectively purify the oil contaminated water. Preparing high performance carbon aerogel for oil absorption has attracted growing attention, but challenges remain. Here we report a facile approach to fabricate mechanical strength enhanced three-dimensional (3D) nanofibrous aerogel principally through supporting agent liquid assisted collection-electrospinning technology, in which the immersion work was applied to measure the immersion capacity of nanofibers according to liquid-solid interfaces theory. Particularly, electrospun polyacrylonitrile (PAN) nanofibers (NFs) were collected directly in graphene oxide (GO) aqueous dispersion, and the continuous fibrous skeleton assembled with two-dimensional (2D) GO sheets to form open porous networks during the electrospinning process, which basically avoided the tedious preparation steps (nanofiber membrane cutting and re-crosslinking) that have been used previously. Due to the open porous networks promising structure stability of the aerogel, the GO sheets content required in the aerogel stacking process was largely reduced, and there was no strict requirement on the pre-freezing temperature and manner in the subsequent freeze-drying process. Furthermore, followed by thermal treating the PAN NFs/GO composite aerogel, fluffy carbon nanofibers/GO aerogels (CNF/GOAs) were obtained, which exhibited ultra-low density (2–3 mg/mL) and great compressibility (80%). After hydrophobic modification of polydimethylsiloxane by vapor deposition, the CNF/GOAs performed high absorption capacity (120–286 wt/wt) toward diverse oils. Owing to the fire-resistance and great elasticity, the CNF/GOAs could be recycled simply by combustion or mechanical squeeze, and still showed great absorption capacity after 10 cycles, which were feasible for large scale application. A mechanical strength enhanced three-dimensional (3D) fluffy carbon nanofibers/graphene oxides aerogels (CNF/GOAs) with ultralow density was prepared by a facile supporting agent liquid assisted collection-electrospinning technology. The hydrophobic modified CNF/GOAs demonstrated highly effective for oils and organic solvents absorption. Unlabelled Image • A facile method for carbon aerogel adsorbent building was developed. • The CNF/GOAs performed high absorption capacity (120–286 wt/wt) toward diverse oils. • The CNF/GOAs exhibited enhanced mechanical compressive strength compared to CNFAs. • The saturated CNF/GOAs could be recycled by combustion and mechanical squeezing. • Compared to previous studies, GO content in aerogel stacking process was reduced. [ABSTRACT FROM AUTHOR]

A fish scale-based porous activated biochar with defined pore size (DPBC) was fabricated by a one-step calcination and activation method. The DPBC possessed an ultrahigh specific surface area of 3370 m 2  g -1 and its pore diameter centered at 1.49 nm which fits into the ciprofloxacin (CIP) molecular dimension, making it an ideal adsorbent for CIP adsorption due to the molecular pore-filling effect. The maximum Langmuir monolayer adsorption capacity of DPBC for CIP was higher than 1000 mg g -1 and the equilibrium time was less than 4 h, superior to most adsorbents reported in literature. Thermodynamic analysis indicated the adsorption process was spontaneous and endothermic. Notably, fixed-bed experiments showed an encouraging adsorption performance towards CIP, with a high saturated dynamic adsorption capacity of 880.3 mg g -1 . Both Thomas and Yoon-Nelson models predict the fixed-bed column adsorption performance well. Hydrophobic effect, π-π interaction, π-π EDA, cation exchange, hydrogen bonding formation, pore filling effect, electrostatic and cation-π interaction involved in the CIP adsorption on the DPBC., (Copyright © 2021 Elsevier Ltd. All rights reserved.)