Effect of chemical structure of poly(1,4-cyclohexylene-2,6-pyridinedicarboxylate) and poly(hexamethylene-2,6-pyridinedicarboxylate) on the adsorption of Pb(II) and Cd(II) ions on their surfaces

Poly (1,4-cyclohexylene-2, 6-pyridinedicarboxylate), poly (CH-PDC), and poly (hexamethylene-2,6-pyridinedicarboxylate), poly(Hx-PDC) were synthesized. The inherent viscosity, FT-IR, 1H-NMR, 13C-NMR, DSC, TGA, SEM, and BET tests were used to characterize the polymers. The effects of temperature, concentration, and contact time on the surface adsorption properties of Pb and Cd ions were investigated using a batch technique. Pseudo-second-order kinetics and the Langmuir and the Freundlich models were used to assess the kinetics and isotherms of the adsorption process. It has been found that qm(mg/g) for poly(CH-PDC) and poly(Hx-PDC) are higher for Pb(II) than Cd(II), with a negative ∆G°, positive ∆H°, and positive ∆S°. Column technique was also used for adsorption, and then desorption was studied using 0.1 M HNO3, which is greater than 0.1 M EDTA for metal ions from the polymers. However, the desorption of Pb(II) and Cd(II) from poly(CH-PDC) was higher than that from poly(Hx-PDC).