Preparation and Formaldehyde Adsorption of Cellulose–Chitosan Composite Aerogel

Formaldehyde, as an indoor pollutant and carcinogen, exists commonly in building materials and furniture products, posing a serious threat to human health. To address this issue, cellulose aerogel materials with their porous network structure can effectively remove pollutants. Cellulose aerogels exhibit a great potential in the field of adsorption due to their advantages of abundant raw material sources and environmental friendliness. Chitosan, due to the presence of amino groups, is widely studied for various applications, particularly for formaldehyde adsorption. Its adsorption performance is especially remarkable, as it can form specific interactions with formaldehyde, enabling an efficient removal. In this paper, a commonly available poplar wood powder was used to directly extract cellulose from plant-based raw materials. Cellulose-chitosan composite aerogels were prepared by a sol-gel method for the adsorption of formaldehyde gas. The structure, morphology, and adsorption conditions of the composite aerogels were investigated to evaluate their performance.

The round-bottom flask containing formaldehyde aqueous solutions of different concentrations was placed in a heater of the gas device to vaporize the solution, allowing formaldehyde gas to fill the apparatus. After 2 h, the formaldehyde adsorption tests were initiated when the formaldehyde gas concentration in the device reached a stable level. Adsorption tests were conducted separately on chitosan, cellulose aerogel, and cellulose-chitosan composite aerogel. The adsorption experiment for chitosan lasted for 12 h, with samples collected every hour to measure the formaldehyde concentration. For cellulose aerogel and cellulose-chitosan composite aerogel, the adsorption experiments lasted for 2 h, with samples taken every 15 minutes to monitor the formaldehyde concentration.

At a formaldehyde concentration of 8 mg/m³, the formaldehyde adsorption capacities at equilibrium for CS, CA, and CCA were 0.412, 2.336 mg/g, and 15.681 mg/g, respectively. CS exhibits the minimum adsorption performance, while CCA shows the most significant adsorption effect, outperforming CA. The removal efficiencies are 53.85%, 74.06%, and 98.00%, respectively when using 1 mg, 3 mg, and 5 mg of CCA at an initial formaldehyde concentration of 8 mg/m³. The 5 mg dosage of CCA achieves a removal efficiency of close to 100%, making it the most economical option for formaldehyde removal. Formaldehyde adsorption tests are conducted on 5 mg of CCA at different formaldehyde concentrations ranging from 2 mg/m³ to 16 mg/m³. The adsorption capacity increases significantly as the concentration increases from 2 mg/m³ to 8 mg/m³, indicating that formaldehyde concentration affects the adsorption performance. The maximum formaldehyde adsorption capacities at equilibrium for CCA-1, CCA-2, and CCA-4, with chitosan proportions of 0.05%, 0.10%, and 0.20% (in mass), are 13.264, 15.681 mg/g, and 15.877 mg/g, respectively. The difference in maximum adsorption capacities between CCA-2 and CCA-4 is relatively small, indicating that the optimal chitosan proportion is 0.1% to avoid resource wastage.

The results showed that the cellulose-chitosan composite aerogel exhibited a superior formaldehyde adsorption performance, compared to cellulose aerogel and pure chitosan. A significant advantage of introducing chitosan was its ability to specifically bind with formaldehyde, effectively enhancing the adsorption performance and broadening the application scope of cellulose aerogels, thereby achieving a high-value utilization of plant-based raw materials. Moreover, the composite aerogel demonstrated an effective adsorption at different formaldehyde concentrations, further expanding its applicability under varying conditions. In summary, the cellulose-chitosan composite aerogel exhibited excellent formaldehyde removal capabilities, showing a great potential for applications, particularly in household environments.