Beta-cyclodextrin functionalized cellulose nanofiber for the removal of palmitic acid

Abstract

Functionalization of cellulose nanofibers with beta-cyclodextrin (CNF/ ß-CD) were performed. ß-CD functionalization onto CNF was achieved by polymerization between ß-CD and citric acid as crosslinker. ß-CD coating was permanently adhered onto the surface of CNF. Fabrication of CNF with 15% concentration of cellulose acetate had produced average fiber diameter of 312 nm and 177 nm for CNF and CNF/ ß-CD, respectively when characterized by using SEM analysis and revealed that functionalization of CNF with ß-CD did not deform the original nanofibrous structure of CNF mats. The Fourier Transfer Infrared (FTIR) spectrum that showed adsorption band of carbonyl group due to high intensity peak at 1740 cm-1 of CNF/ ß-CD confirmed the chemical linkages between CNF and citric acid via ester bonds. Thermal decomposition of CNF/ ß-CD was higher than CNF when characterized by using thermogravimetric analyser (TGA) and onset degradation temperature of CNF/ ß-CD was 20 oC higher than CNF which suggested the successful functionalization of the CNF/ ß-CD. The highest removal of palmitic acid by 33% at 60 minutes of contact time was recorded by CNF/ ß-CD that were functionalized with 7% of ß-CD concentration and 8% of citric acid concentration during crosslinking process. It was recorded that rate of absorption of CNF/ ß-CD was 17% higher compared to CNF. Reusability of CNF and CNF/ ß-CD were also investigated and CNF/ ß-CD was found to have similar removal percentage (±30%) even after four attempts compared to CNF which can only reused for two times. The adsorption process of the modified CNF on the removal of palmitic acid concentration was best-explained by Langmuir isotherm model and the adsorption kinetics for the palmitic acid was found to follow pseudo second order kinetic model. These findings suggested that ß-CD-functionalized CNF can be a very good candidate as an adsorbent for removal of palmitic acid from wastewater or for wastewater treatment owing to their very large surface area as well as inclusion complexation capability of surface associated ß-CD.