Biomass-derived branched polyamine-functionalized chitosan/sodium alginate aerogels for efficient indoor...

Indoor low-concentration formaldehyde (HCHO) remains a health concern, while many amine-functionalized adsorbents show reduced performance at high relative humidity (RH). Herein, chitosan/sodium alginate aerogels functionalized with cyanuric chloride (CYC) and tetraethylenepentamine (TEPA) were developed for HCHO capture. The unmodified aerogel was designated CSA. CSCPA-1, CSCPA-2, and CSCPA-3 were prepared at CSA: CYC: TEPA feed mass ratios of 5:1.8:2.8, 5:4.6:7.1, and 5:7.4:11.4, respectively. Scanning electron microscopy and Brunauer-Emmett-Teller analyses showed that polyamine functionalization altered the pore-wall morphology and porous structure, with CSCPA-2 retaining a relatively open and intact pore architecture and exhibiting the largest specific surface area and pore volume among the modified samples. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy supported the incorporation of triazine- and polyamine-containing functionalities, while XPS further indicated enrichment of nitrogen-containing chemical environments. At an initial HCHO concentration of 0.6 mg·m^-3 and 25 °C, CSCPA-2 achieved removal efficiencies of 89%, 92%, 98%, and 93% at 30%, 50%, 70%, and 90% RH, respectively. At 70% RH, its adsorption capacity reached 0.264 ± 0.017 mg·g^-1 (n = 3), approximately 3.5-fold that of pristine CSA. HCHO adsorption kinetics of the CSCPA aerogels were better described by the pseudo-second-order model, while spectroscopic changes before and after adsorption supported the involvement of amine-containing sites in HCHO capture. In the fourth adsorption-regeneration cycle, CSCPA-2 retained 95.98% removal efficiency and 0.2286 ± 0.0023 mg·g^-1 adsorption capacity. These results highlight its potential for indoor low-concentration HCHO removal and provide a facile strategy for designing humidity-tolerant biomass-derived adsorbents.