Preparation and adsorption properties of cotton linters and coal-gangue-based cellulose/SiO2 composite aerogels

Abstract

High-value comprehensive utilization of coal gangue solid waste, reducing synthesis cost and environmental hazards has become an important research direction for green development. In this study, acid–alkali treated coal gangue was used as the silica source, and abundant cotton short staple in Xinjiang was used as the raw material of aerogel. Cellulose/SiO₂ composite aerogels were prepared by sol–gel method using N–N methylenebisacrylamide (MBA) as cross-linking agent and hydrochloric acid (HCl) as catalyst. The samples were characterized and analyzed by XRD, SEM, FT-IR, XPS, EDS, BET, and mechanical property tests. The results show that the composites exhibit low density and high porosity. The density ranges from 0.118–0.290 g/cm⁻³ with a high porosity of 92.5%. SEM and BET results showed that the composites showed a three-dimensional mesh structure, and the specific surface area was as high as 325.742 m²/g, with a pore size of 21.997 nm, which is a mesoporous material. The adsorption performance of the composite aerogel was tested by simulating wastewater with the dye methylene blue (MB), which showed that the adsorption amount of MB was 82.3 mg/g, and the adsorption amount showed a tendency of increasing and then decreasing with the increase of SiO₂, and adsorption kinetics, adsorption isotherm and adsorption thermodynamic models were established to investigate the adsorption mechanism. The results showed that the adsorption process was more in line with the proposed secondary kinetics and Langmuir isothermal adsorption, which indicated that the adsorption process was a synergistic action of chemical adsorption and physical adsorption, and it was a monomolecular layer adsorption; thermodynamically, the adsorption process belonged to the spontaneous exothermic reaction. In addition, we explored the cyclic regeneration performance of the material, and after 5 cycles of adsorption experiments, the decrease rate was 3.9%, presenting good cyclic regeneration. Therefore, the results of this study provide new ideas and methods in solving the problem of environmental pollution caused by excessive accumulation of coal gangue, as well as providing a good new application prospect for composite aerogel and a theoretical basis for the development of low-cost new advanced materials.