A study on adsorption isotherm and kinetics of petroleum by cellulose cryogels

The development of cellulose aerogels for the adsorption of petroleum becomes interesting due to the cellulose being obtained from biomasses, thus being a natural and biodegradable source. The study of adsorption kinetics and isotherms for this material and application are not reported in the literature. So the objective of this work was to evaluate the behavior of the adsorption process through isothermal and kinetic adsorption models of cellulose cryogels. The cryogel was produced from a cellulose suspension in water obtained by mechanical fibrillation of 1.5% (w/w) unbleached long fiber cellulose of the species Pinus elliotti. The suspension received 4% (w/w) of sodium hydroxide NaOH, and subsequently was frozen and freeze-dried. After freeze-drying, 2 mL of methyltrimethoxysilane (MTMS) was vapor deposited in the cryogel. The study of the kinetics (pseudo-first and second order) and isotherms (Langmuir and Freundlich) of adsorption was performed. Cryogels presented a porosity of 93.51 ± 0.77% and a specific mass of 0.034 ± 0.004 g cm⁻³, in addition to being hydrophobic (water contact angle of 128.7° ± 3.81). Heterogeneous adsorption capacity was of 23.19 g g⁻¹ with 94% oil retention. In the study of isotherm and kinetics of adsorption, the models that fit the process were pseudo-second order and Langmuir, respectively. Based on the results the adsorption process of oil by the cellulose cryogels samples occurs in monolayer. In addition, the cellulose cryogel developed in the present work is suitable for use in the adsorption of petroleum.