In situ synthesis of ZIF-8 on lignosulfonate functionalized polyethyleneimine/carboxymethyl chitosan hybrid aerogels for efficient tetracycline removal

Abstract

The alarming overuse of antibiotics poses a serious threat to the environmental security. Herein, a hybrid aerogel adsorbent, sodium lignosulfonate functionalized polyethyleneimine/carboxymethyl chitosan@ZIF-8 (CCSL@ZIF-8), was fabricated by introducing sodium lignosulfonate into polyethyleneimine/carboxymethyl chitosan (CSSL) and then in situ uniformly anchoring of ZIF-8 on CSSL aerogel. The incorporation of sodium lignosulfonate not only enhanced the mechanical properties of CCSL, but also provided a large number of chelating sites for Zn2+ and promoted the formation of ZIF-8. The sorption behavior and mechanism were studied by batch adsorption experiments and characterization analysis. The experimental results demonstrated that the maximum adsorption capacity of CCSL-1.0@ZIF-8 was 231.36 mg/g with a tetracycline (TC) concentration of 200 mg/L at 303 K, which was 7 times higher than that of CCSL-1.0 (30.73 mg/g). The absorption process followed the pseudo-second-order kinetic model and Freundlich isothermal model, and the process of adsorbing TC was dominated by multilayer chemisorption. The adsorption mechanism included pore filling, coordination bonds, hydrogen bonding, electrostatic interactions and π-π interactions. Moreover, the removal efficiency of TC by CCSL-1.0@ZIF-8 was maintained above 78 % after 6 cycles. Overall, this work presents a potential bio-based adsorbent for the effective removal of tetracycline from wastewater and provides a novel, facile, and green chemical technique for high-value utilization of lignin. Furthermore, the prepared biomass-based hybrid adsorbent has outstanding reusability and water stability, which has broad practical application prospects in antibiotic wastewater treatment.