Facile Synthesis of Marshmallow‐like Macroporous Gels Usable under Harsh Conditions for the Separation of Oil and Water

Abstract

The separation of oil and water is an important pursuit for saving endangered environments. In 2010, the Gulf of Mexico oil spill widely and seriously damaged the ocean and coast near the oilfield. The number of similar accidents is increasing with the development of industry, and materials that can reduce environmental pollution are in high demanded. At the same time, in the area of analytical chemistry, the efficient separation of molecules is a key technique, which determines the efficiency and accuracy of chemical analysis and detection. For these purposes, hydrophobic porous materials are in common use, because hydrophobic surfaces effectively adsorb/absorb oily target compounds that are mixed with an aqueous phase. Therefore, many researchers have been studying hydrophobic porous materials and their application as oil/water separation media. [1] Various chemical compositions have been investigated, such as carbon-based materials, [2] metal oxide nanowires (such as manganese [3,4] ), biomass nanofibers (such as cellulose [5,6] ), organic polymers (such as polyester, [7] polydivinylbenzene, and polythiophene [8] ) and hydrophobic macroporous aerogels. [9,10] Other materials based on polydimethylsiloxane (PDMS) or fluorocarboncoated materials, [3,7,10, 11] and the design of a biomimetic rough surface, through the use of etching techniques, to enhance hydrophobicity [6,12] are also widely reported. However, these methods have problems such as complicated and lengthy processes and high costs for reagents and devices, which prevents the use of these materials in practical and commercial applications.We have investigated hydrophobic porous polymethylsilsesquioxane (PMSQ, CH 3 SiO 1.5 ) materials, derived from methyltrimethoxysilane (MTMS), consisting of transparent aerogels and xerogels with mesoporous to macroporous monoliths that are created by controlling phase separation in the sol-gel process. [13] Polymethylsilsesquioxane gels have a superhydrophobic surface owing to methyl groups that are directly bonded to silicon atoms; this flexible network structure allows the material to spring back after compression. This mechanical feature allows the preparation of aerogel-like xerogels by ambient-pressure drying. Last year, we first reported bendable, marshmallow-like porous gels derived from a co-precursor system of MTMS and dimethyldimethoxysilane (DMDMS) in almost the same way as PMSQ gels. [14] Marshmallow-like gels not only show compression/ reexpansion properties similar to that of PMSQ gels, but also very soft and bendable mechanical features. A high sound absorption property has also been previously reported, owing to the soft networks. The flexiblity and intrinsic hydrophobicity indicate that these materials can be used like a sponge as an adsorption/absorption media for the quick removal of unwanted organic liquids. Herein, we report the outstanding capability of these materials for absorbing organic liquids over a wide temperature range, and discuss the possibility for their application as separation me...

Underwater Self-Cleaning Scaly Fabric Membrane for Oily Water Separation

“…[4][5][6][7][8][9][10][11][12][13] Through rational design of surface structure and chemical composition, more and more multifunctional materials with special wettability have been fabricated and developed for oily wastewater separation. [14][15][16][17][18][19][20][21][22][23] By constructing the materials' surfaces with superhydrophobicity and superoleophilicity simultaneously, "oil-removal" type materials, such as organic polymer materials, [24][25][26][27][28][29][30][31] inorganic materials, [32][33][34][35][36] and other organic/inorganic hybrid materials [37][38][39][40][41][42] , have been developed for oily waste water separation. However, these "oil-removal" materials membranes are easily fouled, blocked up and even damaged by oils because of their intrinsic oleophilicity, resulting in a quick decrease in separation efficiency, flux, and membrane life, and even secondary pollution.…”

Polyelectrolyte-fluorosurfactant complex-based meshes with superhydrophilicity and superoleophobicity for oil/water separation

“…Recently, inspired by functional interface materials with extreme wetting behaviors, various research groups have tried to develop superhydrophobic and superoleophilic materials for oil/water separation, which can cause water to run off the surface while allowing oil to permeate through [3]. These materials include polytetrafluoroethylene coated mesh [4], metal/metal oxide nanocrystals coated fabric [5], silicone nanofilament deposited polyester materials [6], carbon-based foams [7][8][9], and polymer-based sponges [10][11][12]. However, there are several drawbacks for superhydrophobic and superoleophilic materials to separate oil/water mixtures: (i) water usually settles below oil and against the surfaces owing to its higher density, forming a barrier layer that prevents oil permeation; (ii) they are easily contaminated and plugged by oils during separation process, culminating in a drop in the separation efficiency; (iii) the superhydrophobic property can be destroyed by illumination or corrosive oil-polluted water, leading to water permeation.…”

One-step fabrication of superhydrophobic and superoleophilic cigarette filters for oil-water separation

“…[9] Recently, because of the increasing industrial application of oil-water emulsifications and the frequented offshore oil spillages, porous adsorption materials with special wettability, such as superhydrophobicity and superoleophilicity, have generated extensive attention in the field of oil-water separation. [10][11][12][13] On these porous materials, water droplets can keep in the spherical shapes with the contact angles greater than 150°, while oil droplets can spread over the surfaces with the contact angles of 0°. These materials, including nanoparticle-deposited fabrics, [14,15] polystyrene-coated filter papers, [16] carbon-based foams, [17,18] nanocellulose aerogels, [19,20] and polymer-based sponges, [21,22] can remove oil from oil-water mixtures without absorbing any water, showing high separation efficiency and selectivity.…”