Hydrophilic, hydrophobic, Janus and multilayer xanthan based cryogels

Xanthan gum (XG) was applied for the creation of hydrophilic, hydrophobic and layered cryogels. Firstly, the correlation among synthesis parameters, such as solvent composition and polymer concentration (C_p) in the precursor gel and mold diameter (Φ), with physicochemical properties and morphological parameters of resulting hydrophilic XG cryogels was investigated. The addition of acetic acid to the precursor led to stiffer XG cryogels. The reduction of C_p and Φ promoted the increase in the cryogels surface area and porosity. Then, XG cryogels were silanized in order to produce hydrophobic cryogels, which presented sorption capacities for diesel, mineral and sunflower oils of 28 ± 2 g/g, 16 ± 2 g/g and 5.2 ± 0.3 g/g, respectively. The hydrophobic XG cryogels were considerably more efficient to remove ethinyl estradiol, an estrogenic pollutant, from liquid media than the hydrophilic cryogels. Hydrophilic and hydrophobic XG cryogels presented similar capacity to remove bisphenol A, another estrogenic pollutant, from liquid media. A new family of alternated hydrophobic/hydrophilic "Janus" like and multilayered cryogels was created and applied in mixtures of diesel oil and water or oil/water emulsions. The "Janus" like and multilayered cryogels remained at the interface, where the hydrophobic and hydrophilic layers adsorbed oil and water selectively.