Abstract
The surface ion-imprinting technique was employed in the development of Cd(II) ion-selective chelating sorbent based on cellulosic flax fibers. The flax fibers (F) were first amino-functionalized via grafting of polyacrylamide followed by Hofmann degradation and then the 2-pyridylthiourea (PTU) chelating units were inserted by reaction with 2-pyridylisothiocyanate. The chelating fibers were then loaded with Cd(II) ions and treated with glutaraldehyde before eliminating the metal ions to get the Cd(II) ion-imprinted PTU functionalized F fibers (Cd-PTU-F). The chemical changes along with the Cd(II) ions chelation by the inserted PTU units were investigated by spectral methods including FTIR, and XPS. In addition, the conditions for the Cd(II) ion adsorption were optimized and the maximum adsorption capacity of the obtained Cd-PTU-F sorbent was reached up to 310 mg/g calculated using the Langmuir model, which presents the best correlation with the resulted isotherms. Also, the adsorption kinetics was best described by the pseudo-second-order model. The fiber's selectivity was investigated in a solution mixture of Cu(II), Zn(II), Pb(II), Ni(II), and Cd(II) ions and the calculated parameters revealed the creation of a remarkable affinity for the Cd(II) ions compared to the other coexisting metal ions.
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•Flax fibers were modified via graft copolymerization with polyacrylamide.•The fibers were then amino-functionalized via Hoffmann degradation and 2-pyridylthiourea units are inserted.•The chelating fibers coordinated with Cd(II) ions and then the grafted chains are cross-linked using glutaraldehyde.•The adsorption was optimized at pH 6; with maximum capacity of up to 310 mg/g, and followed pseudo-second-order kinetics.•The fibers was applied to selectively remove Cd2+ from aqueous solutions.