Self-assembly cellulose nanocrystals/SiO2 composite aerogel under freeze-drying: Adsorption towards dye contaminant

• Highest yield (74%) of CNCs were obtained by mathematical orthogonal experiment design. • One-step hybrid preparation of CNCs/SiO 2 aerogel is a relatively innovative idea. • The adsorption capacity of CNCs/SiO 2 aerogel for MB is slightly higher than other similar materials. • The removal rate of MB adsorbed by aerogels remained above 60% after 5 adsorption cycles. Using cheap sodium silicate as raw material, a novel composite aerogel of self-assembled cellulose nanocrystals (CNCs)/SiO 2 was successfully prepared by freeze-drying method, which can effectively to adsorb methylene blue (MB) pollutants in water and reduce the burden on the water environment. By investigating the effects of mass fraction of sulfuric acid, hydrolysis temperature, hydrolysis time and liquid–solid ratio on hydrolysis yield, the maximum CNCs yield (74%) obtained from orthogonal experiment was designed. The morphology, important functional groups and key structural elements of the aerogel were characterized by SEM, FTIR and XPS, respectively. Meanwhile, the mesoporous structure of the aerogel was analyzed by BET test, and it was found that its specific surface area could reach 440.715 m 2 /g. Besides, the adsorption results for MB showed that the Langmuir isotherm model and the pseudo-second order model can better fit the experimental data well with a maximum adsorption capacity of 190.85 mg/g. Adsorption thermodynamics study reveals that the adsorption process is spontaneous and endothermic. Hence, the findings of this research offer a more market application prospect for the composite aerogel, and provide a certain reference basis for the dye wastewater treatment.