Metal-chelate sorbents based on carboxyalkylchitosans: Ciprofloxacin uptake by Cu(II) and Al(III)-chelated cryogels of N-(2-carboxyethyl)chitosan

Here we propose a metal-chelate approach to removal of fluoroquinolones from aqueous solutions using their ability to bind strongly divalent and trivalent metal ions immobilized in a polymer matrix. Metal-affine sorbents for ciprofloxacin uptake have been fabricated via chelation of Cu(II), Al(III), and Fe(III) ions by supermacroporous cryogel of carboxyalkyl chitosan derivative (N-(2-carboxyethyl)chitosan, CEC) cross-linked with hexamethylene diisocyanate in aqeous medium. We have shown that virgin CEC cryogel adsorbed ciprofoxacin in a cationic form via electrostatic interactions at pH > pICEC, but the efficacy of recovery was below 50% and strongly pH-dependent. Modification of CEC cryogel with Cu(II) and Al(III) ions improved the ciprofloxacin (CIP) recovery by up to 98% in the pH range 7–10, the sorption capacity and affinity for CIP of metal-chelate sorbents increased with metal content and reached maximum values of 280 and 390 mg/g for Cu(II) and Al(III)-chelated cryogels, respectively. The metal-chelated CEC cryogels were efficient for ciprofloxacin removal from solutions with environmentally relevant concentration (50 μg/L) and were applicable as monolith sorbents under dynamic conditions. •Metal-chelate approach is suggested for fluoroquinolones removal from water•Cu(II) and Al(III)-chelated cryogels of carboxyethylchitosan were fabricated•92–98% of ciprofloxacin was recovered at pH 7–10 using metal-chelated cryogels•Sorption capacity of metal-chelated cryogels for ciprofloxacin reaches 350 mg/g•Cu(II)-chelated monolith cryogels can be regenerated and reused