Metal-ion-imprinted thermo-responsive materials obtained from bacterial cellulose: synthesis, characterization, and adsorption evaluation

Abstract

In this study, a novel gradient heating procedure was developed to fabricate the targeted metal-ion-imprinted thermo-responsive material, i.e. ion-imprinted thermo-responsive BC derivative (ITB), from bacterial cellulose using Cu²⁺ as a template and N-isopropylacrylamide (NIPAM) as a monomer; moreover, the structure and properties of ITB were analysed via various analytical techniques including FTIR spectroscopy, DSC, SEM, and Raman spectroscopy. The lower critical solution temperature (LCST) of ITB was 38.57 °C in the heating procedure, whereas it was 30.81 °C in the cooling procedure. The adsorption capacity of ITB for Cu²⁺ reached 95.20 mg g⁻¹ at 45 °C (>LCST), the desorption rate was 98.81%, and desorption could be simply achieved by washing the adsorbents with water at 20 °C (<LCST). After repeating the adsorption–desorption procedure for 5 times, the adsorption capacity and desorption rate only slightly decreased to 91 mg g⁻¹ and 97%, respectively. The adsorption kinetics was shown to follow the pseudo-second-order equation, whereas the adsorption isotherm was better fitted with the Langmuir equation. The maximum theoretical adsorption capacity for Cu²⁺ was achieved to be 140.85 mg g⁻¹. In a mixture containing other metal ions (Mn²⁺, Ca²⁺, Mg²⁺, Fe³⁺, Pb²⁺, Cd²⁺, Zn²⁺, and Cu²⁺), the adsorption capacity for Cu²⁺ was 81.91 mg g⁻¹, whereas that for other ions was between 0.54 and 9 mg g⁻¹. The results indicate that ITB exhibits significant potential for selective separation and enrichment of metal ions by templating with Cu²⁺ ions as a model example.