Simultaneous removal of pollutants from sub-nanometric to nanometric scales by hierarchical dendrimers modified aerogels

The disposal of dyestuff wastewater containing metal ions and dyes is a tough challenge, due to the competition of adsorption sites. Here, aramid nanofiber (ANF) based aerogels are fabricated, which exhibit excellent adsorption performance for sub-nanometric and nanometric adsorbates, such as Cu2+ and Congo red (CR) in this work. Synthesized hierarchical polyhedral oligomeric silsesquioxanes (POSS) cored polyamide amine (PPAMAM) is used to modify ANF aerogels and molecular dynamics simulation results indicate that the POSS core endows synthesized PPAMAM with cavities and mobile terminal groups on ANF surface, compared to normal PAMAM. When prepared aerogels are applied to treat wastewater with co-adsorbate, small metal ions could enter the cavities and coordinate with internal tertiary amines. In contrast, CR molecules are too large to enter cavities and prefer interacting with external primary amines. In addition, blending PPAMAM also increases the specific surface area, which highly enhances the adsorption performance. As a result, simultaneous and effective removal of Cu2+ and CR is achieved, and in binary system, the adsorption capacities are 248.49 and 1502.95 mg/g, respectively. After five cycles, fabricated adsorbents still maintain excellent adsorption performance. Therefore, this work provides a new way to the preparation of effective adsorbents for simultaneous removal of different sized pollutants.