Efficiently adsorptive removal of ciprofloxacin from water by using cross-linked carboxymethyl cellulose

A series of cross-linked carboxymethyl cellulose adsorbents (CCMCs) with different degrees of carboxymethyl substitution (the molar ratios of cellulose and chloroacetic acid were 1:0.7, 1:1, 1:1.2 and 1:1.5, respectively) were synthesized through etherification and crosslinking, and were used for the removal of a popular antibiotic, ciprofloxacin (CIP) from water. CCMCs presented high adsorption capacity for CIP owing to the electrostatic adsorption and hydrogen bonding interactions. With the increase of carboxymethyl substitution degree, the adsorption capacity of CCMCs for CIP gradually increased and the maximum theoretical adsorption capacity of CIP on CCMC 1.5 can reach to 2.821 mmol/g at pH 4.0. The adsorption isotherms obeyed the Langmuir model, which infer the adsorption process was monolayer adsorption. The adsorbent reached the adsorption equilibrium in approximately 60 min. The adsorption kinetics corresponded with the pseudo-second-order kinetic model, indicating that the adsorption was dominated by chemical adsorption. The adsorption capacity decreased with the increase of coexistence NaCl concentration, which further confirmed that the adsorption was dominated by electrostatic adsorption. This study demonstrated that CCMC, as an efficient adsorbent, has significant application potentials in removal of antibiotics from water.