Effective removal of acetaminophen from aqueous solution using Ca (II)-doped chitosan/β-cyclodextrin composite

Abstract

The aim of this study was to synthesize Ca (II)-doped chitosan/β-cyclodextin and to investigate its potential as a sorbent for removal of acetaminophen from aqueous solution. The material was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray diffraction and thermogravimetric-differential thermal analysis. The effects of experimental parameters such as pH, adsorbent dose and initial concentration on the adsorption of acetaminophen were optimized by response surface methodology using central composite design. The obtained results revealed that 0.01 g of adsorbent was able to remove 99.88% of acetaminophen from 20.0 ml of 20.0 mg/L aqueous solution at pH 7.2. The experimental adsorption capacity for acetaminophen was found to be 200.86 mg/g. The study of isothermal adsorption data indicated that the data were best fitted to Freundlich model with high correlation coefficient (R2 = 0.999) and lower error values (x2 ≤ 1.70 × 10−5 and average percentage error ≤2.0 × 10−5) as compared to Langmuir and Temkin isotherm models. The experimental kinetic data were analyzed by pseudo first-order, pseudo second-order, Elovich and double exponential models. The kinetic data were best fitted to pseudo second order with R2 of 0.999 at all temperatures studied. The fitting of kinetic data with Elovich model (R2 > 0.99) indicted the chemisorption process whereas double exponential model suggested that the uptake of acetaminophen was governed by both film and particle diffusion processes. Negative values of ΔGo confirmed the spontaneous nature of acetaminophen adsorption onto Ca (II)-doped chitosan/β-cyclodextrin composite. Positive values of ΔHo (116. 404 kJ/mol) and ΔSo (0.438 kJ/mol) confirmed the endothermic nature of adsorption process and randomness at solid/liquid interface, respectively. The adsorption/desorption cycling test revealed that the prepared composite material had good reusability performance upto 6 cycles. The results demonstrated that the material could be a promising adsorbent for removal of acetaminophen from aqueous solution.