Fabrication of 3D compressible polyaniline/cellulose nanofiber aerogel for highly efficient removal of organic pollutants and its environmental-friendly regeneration by peroxydisulfate process

To deal with the challenge in separating nanostructured adsorbents from wastewater and avoid producing highly concentrated wastewater, we developed three-dimensional polyaniline/cellulose nanofiber aerogel (PCNFA) for the applications in organic dye pollutants removal. This new adsorbent was fabricated by a two-step method using the in-situ crosslinking and acid-induced polymerization processes. Owing to the in-situ supramolecular combination of polyaniline nanofibers (PANI-NFs) and carbonylated cellulose nanofibers (CNFs), PCNFAs exhibited the highest compressive stress of 48.2 kPa at a compressive strain of 50% and superior adsorption performance, with the maximum Langmuir adsorption capacity for Acid Red G (ARG, anionic dye) and Methyl Blue (MB, cationic dye) reached around 600.7 and 1369.6 mg g-1, respectively. Moreover, peroxydisulfate (PDS) process was adopted here for the first time to realize the synergistic regeneration of the PCNFA adsorbent and the degradation of dyes by activating PDS on PANI. The adsorption capacity of PCNFA for ARG and MB remained respectively above 84% and 70% after three regeneration cycles in the PDS process and the corresponding COD removal rate achieved around 26% and 60%, respectively. Finally, we explored adsorption and regeneration mechanism showing that the electrostatic and 7C-7C stacking interactions were the driving forces for adsorption, and nonradical reactions may be the main contribution to the oxidation of contaminants and regeneration of PCNFA. The results demonstrated that the fabricated aerogel can be used as an adsorbent for the practical treatment of dyes-containing wastewater and the PDS process provides a promising and viable approach for the regeneration of PANI-based adsorbents.

Automated summary

PCNFA was developed as a nanostructured adsorbent for organic dye pollutants removal, exhibiting high compressive stress and adsorption capacity. The PDS process was used for the regeneration of PCNFA, maintaining high adsorption capacity for dyes even after multiple cycles. The electrostatic and 7C-7C stacking interactions were identified as driving forces for adsorption, with nonradical reactions contributing to the regeneration of PCNFA.