An acid-resistant polyethyleneimine-phosphate co-modified chitosan-SiO₂ hybrid aerogels: Ultra-high capacity for...

The development of adsorbents with high stability and efficiency under strongly acidic conditions remains a critical bottleneck for uranium(VI) removal from wastewater. This work innovatively fabricates polyethyleneimine-enhanced phosphate-doped chitosan-SiO₂ hybrid aerogels (Pi-P@CSHA) via a facile sol-gel and freeze-drying route. The novelty lies in the synergistic dual-modification strategy: polyethyleneimine acts as a cross-linker, which substantially enhances the structural stability of the aerogel in acidic media, while phosphate provides specific, high-affinity binding sites for uranium(VI) complexation. Systematic characterizations confirmed the successful preparation of Pi-P@CSHA and revealed that it has a well-defined porous structure. Pi-P@CSHA exhibits exceptional adsorption performance, achieving a maximum static adsorption capacity of 244.9 mg/g (m/V = 1 g/L) and a dynamic saturation adsorption capacity of about 230.0 mg/g at pH = 4. Notably, the adsorption efficiency remains above 58.8% even at pH = 2 and exceeds 91.9% in the presence of coexisting cations at pH = 4, significantly surpassing most reported counterparts. The high-efficiency adsorption is achieved through the synergistic complexation of uranium(VI) with functional active sites such as phosphate, -NH₂ and -OH. In a word, the study provides a novel, robust and highly efficient adsorbent, highlighting the critical role of component synergy for treating acidic uranium-containing wastewater.