ABSTRACT
Superabsorbent hydrogels have wide applications in many fields because of their unique water absorbing performance. In spite of decades of research about superabsorbent hydrogels, high water absorbency under pressure and fast-swelling are still challenging and highly desired for their applications in hygienic products and others. Here, we report preparation of fast-swelling porous starch-g-poly(acrylic acid)/poly(vinyl alcohol) superabsorbent hydrogels with high saline water absorbency under pressure by foaming and post surface crosslinking. 2,2'-Azobis(2-amidinopropane) dihydrochloride (AIBA) was used as a new porogen instead of conventional porogens like NaHCO3. Post surface crosslinking of the hydrogel was achieved using glycerol via the esterification reaction. AIBA is a better porogen than NaHCO3 regarding porosity and swelling performance of the hydrogels, and its content has great influences on structure and swelling performance of the hydrogels including water absorbency and swelling rate. Also, the surface crosslinking using glycerol can significantly enhance the saline water absorbency under pressure (2 kPa) but at the sacrifice of the swelling rate. Consequently, the hydrogels show high water absorbencies for deionized water (560 g/g), 0.9 wt% NaCl solution (58 g/g), 0.9 wt% NaCl solution under 2 kPa pressure (28 g/g) and fast-swelling (31 s to achieve a highly swelling state).
ABSTRACT
The ubiquitous presence of contaminants in water poses a major threat to the safety of ecosystems and human health, and so more materials or technologies are urgently needed to eliminate pollutants. Polymer materials have shown significant advantages over most other adsorption materials in the decontamination of wastewater by virtue of their relatively high adsorption capacity and fast adsorption rate. In recent years, "green development" has become the focus of global attention, and the environmental friendliness of materials themselves has been concerned. Therefore, natural polymers-derived materials are favored in the purification of wastewater due to their unique advantages of being renewable, low cost and environmentally friendly. Among them, natural plant gums show great potential in the synthesis of environmentally friendly polymer adsorption materials due to their rich sources, diverse structures and properties, as well as their renewable, non-toxic and biocompatible advantages. Natural plant gums can be easily modified by facile derivatization or a graft polymerization reaction to enhance the inherent properties or introduce new functions, thus obtaining new adsorption materials for the efficient purification of wastewater. This paper summarized the research progress on the fabrication of various gums-based adsorbents and their application in the decontamination of different types of pollutants. The general synthesis mechanism of gums-based adsorbents, and the adsorption mechanism of the adsorbent for different types of pollutants were also discussed. This paper was aimed at providing a reference for the design and development of more cost-effective and environmentally friendly water purification materials.
ABSTRACT
Superamphiphobic coatings have wide potential applications in many fields, however, preparation of superamphiphobic coatings with low sliding angles and high durability is very challenging. Here, we report a facile spray-coating method for the preparation of durable superamphiphobic coatings repelling both cool and hot liquids from polyperfluoroalkylsilane-modified multiwalled carbon nanotubes (MWCNTs@fluoroPOS). The MWCNTs@fluoroPOS suspensions were preparation by hydrolytic condensation of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFDTES) and tetraethoxysilane (TEOS) on the surface of MWCNTs. The suspensions and the superamphiphobic coatings were characterized using a variety of analytical techniques such as scanning electron microscopy, transmitting electron microscopy and X-ray photoelectron spectroscopy. The effects of the diameter of MWCNTs, and the concentrations of MWCNTs, TEOS and PFDTES on wettability and microstructure of the coatings were also investigated. The coatings show high contact angles and low sliding angles for water and organic liquids of low surface tension such as n-hexadecane, toluene and n-decane. The coatings even exhibit excellent superamphiphobicity for hot water and hot organic liquids up to 80°C, which is seldom achieved according to the previous literatures. Moreover, the coatings feature high mechanical, chemical and environmental durability, and are applicable onto various substrates. The simple method, the high superamphiphobicity to both cool and hot liquids, and the excellent durability of the coatings have paved the way for their practical applications in various fields, e.g., anti-icing, anti-oil climbing and oil transportation, etc.
