Study On Preparation And Hydrophobicity Of Resorcinol Formaldehyde Aerogels

Aerogels are porous material with a three-dimensional network structure. Because of their many unique characteristics, such as low density(0.003-0.5 g/cm3), high porosity(70%-99.8%), low dielectric constant(~1.1) and high surface area(100-1600 m2/g), aerogels have drawn great interest in a wide range of applications, including adsorbent, heat insulator, sound attenuator and support for catalysts.Aerogels can be roughly divided into two types of inorganic and organic, inorganic aerogels were greatly restricted in application because of the poor mechanical properties and instability. Compared with inorganic gas gel, organic aerogels has good mechanical properties, which were first prepared in the 80’s of last century, more attention and development are taken on organic aerogels study in recent years. Resorcinol-formaldehyde(RF) aerogels are high-performance resins possessing high thermal stability and good mechanical property. However, Resorcinol-formaldehyde(RF)-based aerogels have not been reported too many.The preparation program of RF aerogels have been very skilled, but the main drying process method is the Supercritical fluid drying, which is expensive and complex, it can not be for large-scale industrial production. In addition,due to the existence of the phenolic hydroxyl group, the RF aerogels are particularly prone to absorbing water. So it is very important to get rid of the hydrophilic property of aerogels.Thus, the following works have been carried out in the essay:1、The RF aerogels were prepared via ambient pressure drying and freeze drying derive from hydrogels synthetised by sol-gel process. Compare with ambient pressure drying and freeze drying through the density, shrinkage rate, scanning and BET test, the best technology of preparing RF aregels were obtained. The average pore size of the production in this paper is 8.9457 nm, the density is 0.1330g/cm3 and the specific surface area is 406.9936m2/g.2、In this paper the RF aerogels were modified with 1,2 epoxydodecane and epoxy-terminated polydimethylsiloxane(E-PDMS), the contact angle of the water becomes larger under the premise of keeping its pore size and specific surface area. The optimum concentration was confrimed by measuring the contact angle of different concentration of modifier on RF aerogels, the contact angle can reach 124°with 20% of modifier with the modified wet gel quality as the standard. So the E-PDMS make it more operational as hydrophobic modifier if we take production cost into account in industrial production.3、The adsorption experiments were carried out that put the RF aerogels we prepared in last two section into the standard solution of methylene dye, and they show good adsorption properties. The composite aerogels that compound resorcinol, formaldehyde and clay did the same adsorption experiments, which show better sdsorption performance, they were both good for purification of drainage.In this paper, we prepared hydrophobic RF aerogels by freeze drying, and study the adsorption properties of aerogels based phenolic resin simply, low production costs and easy to operate, which were expected to become excellent adsorbent materials and be industrialized production, they not only have a broad prospect in the field of wastewater treatment, but also further increase the application of RF aerogels.