In situ immobilization of ZIF-8 on sodium lignosulfonate/chitosan foams for the efficient removal of ciprofloxacin from water

Ciprofloxacin (CIP) contamination can induce the growth of antibiotic-resistant bacteria, which poses a great threat to the environment. Herein, a composite adsorbent material, sodium lignosulfonate/chitosan@ZIF-8 (SLS/CS@ZIF-8), was synthesized by introducing sodium lignosulfonate into chitosan foams (CS-FM) and then loading ZIF-8 onto the resulting foams (SLS/CS-FM) by in situ immobilization to effectively remove CIP from water. The adsorption behaviour and mechanism were studied through batch experiments and characterization analysis. The results showed that the maximum adsorption capacity of SLS/CS@ZIF-8 was 413 mg/g with a CIP concentration of 250 mg/L at 303 K, which was more than most previously reported adsorbents. The CIP adsorption of SLS/CS@ZIF-8 was better described by the pseudosecond-order kinetic model and Langmuir isothermal model. The adsorption was a spontaneous and endothermic physical adsorption process with increased entropy. The adsorption involved electrostatic interactions, hydrogen bonding interactions and π-π interactions. This work provides a potential adsorbent for the effective removal of CIP from wastewater and a new, low-carbon, green chemical technology for the high-value utilization of lignin.