Facile and green synthesis of lignin-based aggregate microparticles adsorbent with hydrothermal regeneration function for ciprofloxacin removal from water

Lignin and its derivatives composites have received increasing interests in the field of water treatment for the features of eco-friendliness, cost-effectiveness and sustainable regeneration. Herein, a lignin-based aggregate microparticles adsorbent (SLS/PEI/GO-P) was synthesized through a green method for the adsorption of ciprofloxacin (CIP) in water. The composition and structure of SLS/PEI/GO-P were characterized by SEM, TEM, FT-IR, TG, XRD, XPS and N2 adsorption-desorption isotherm. The effects of adsorbent dosage, pH, concentration, time, temperature, inorganic salts and HA on CIP adsorption were investigated through batch experiments. The results indicated that the maximum CIP adsorption capacity was 823.3 mg/g with the CIP concentration of 250 mg/L at pH 8 and 30 ℃, which was much higher than that of most reported. The adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherms followed the Langmuir model. The adsorption thermodynamic study indicated that the adsorption process was spontaneous at low temperatures and exothermic. FTIR and XPS analysis indicated that the adsorption mechanism was mainly involved with electrostatic interactions, hydrogen bonding interactions and π-π interactions. After 5 adsorption and hydrothermal regeneration cycles, the adsorption capacity for CIP by the adsorbent decreased only slightly. The adsorbent has the advantages of green preparation process and regeneration method, good adsorption capacity, and high sustainability, which renders it potentially viable in treating real wastewater containing CIP.