Effect of the degree of template removal from mesoporous silicate materials on their adsorption of heavy oil from aqueous solution

The key aim of this study is to evaluate the adsorption of heavy oil from aqueous solutions with different oil contents over mesoporous silicate materials having different surfactant template contents. The mesoporous silicate materials have been synthesized from tetraethylorthosilicate as a silica precursor and cetyltrimethylammonium bromide as a template using the sol-gel technique. Four samples were prepared by (1) totally removing the template using the calcination process, (2) partially removing the template via ethanol extraction, (3) partially removing the template via water extraction, and (4) keeping the template as synthesized, respectively. These four samples have been characterized using X-ray diffraction, nitrogen adsorption, thermal gravimetric analysis and Fourier transformed infrared. The effect of the degree of template removal of these mesoporous materials for the oil removal has been investigated. The oil removal is inversely proportional to the surfactant content in the mesoporous material, being highest for the calcined sample but lowest for the as-synthesized sample. The kinetic of oil adsorption over the calcined material has been also studied and the data obtained fit well a second-order model

Superabsorbent aerogels from cellulose nanofibril hydrogels

Abstract Deep eutectic solvents (DESs) are promising green chemicals that can function as solvents, reagents, and catalysts in many applications because of their biodegradability, ready availability, and low toxicity. Here, a DES of choline chloride–urea was used as a non-hydrolytic pretreatment medium to obtain cellulose nanofibril (CNF) hydrogels from recycled cellulose pulps (boxboard, milk containerboard, and fluting) and virgin birch cellulose pulp using a mechanical Masuko grinder. The mechanical disintegration of DES-pretreated cellulose fibers resulted in highly viscous, gel-like cellulose nanofibril hydrogels with shear thinning behavior. According to transmission electron microscope (TEM) imaging, the nanofibrils had widths from 2 to 80 nm, possessed the initial cellulose I crystalline structure, and had a crystallinity index of 53–56%. The nanofibril hydrogels obtained were further used to produce low-cost, ultralight, highly porous, hydrophobic, and reusable superabsorbing aerogels that were used as efficient sponges to absorb oil and chemicals. The nanofibril sponges prepared by the consequent hydrophobic modification (silylation) of CNF hydrogels and freeze-drying had ultralow density (0.003 g/cm³) and high porosity (up to 99.8%). The sponges exhibited excellent oil/water absorption selectivity and ultrahigh oil (marine diesel oil, kerosene, gasoline, motor oil, castor oil, or linseed oil) and organic solvent (dimethyl sulfoxide, chloroform, n-hexane, toluene, acetone, or ethanol) absorption capacity. The nanofibril aerogels showed particular selectivity for marine diesel oil absorption from an oil–water mixture and possessed ultrahigh absorption capacities of up to 143 g/g, which were much higher than the commercial absorbent materials (i.e., polypropylenes) (9–27 g/g) used as references. Additionally, the absorbed oil could be recovered by means of simple mechanical squeezing, and the superabsorbent could be reused for at least 30 cycles