New Schiff-Base’s Modified Chitosan: Synthesis, Characterization, Computational, Thermal Study and Comparison on Adsorption of Copper(II) and Nickel(II) Metal Ions in Aqueous

Abstract

In this paper, four modified chitosan compounds were prepared by reaction between chitosan (CS) and carbonyl groups such as salicylaldehyde (SA), benzaldehyde (BA), para-chloro benzaldehyde (PCBA) and acetanilide (A) as an amide compound. The corresponding Schiff-bases were characterized by FTIR, EDX, FESEM, BET and TGA-DTA techniques. The BET analysis on the prepared Schiff bases shows that the total volume of the pores and their specific surface area is different. The synthesized compounds have got less than 10 nm in diameter. The adsorption of copper and nickel ions in the aqua medium by prepared Schiff bases was studied. A comparison of the adsorption percentage of prepared compounds indicates that Schiff-base CS-A has slightly better adsorption than CS-SA. The calculation of boundary orbital energy (HOMO–LUMO) shows that the chitosan molecule has the highest chemical hardness (η) and the minimum reactivity to synthesized Schiff-Base compounds. The HOMO–LUMO energy gap of all the adsorbed molecules diminished after the adsorption of metal cations. The adsorption efficiency of Cu2+ per molar unit changes as: CS-A (92.5%) > CS-SA (80.4%) > CS-BA (43.2%) > CS-PCBA (42.2%) > CS (30.5%). The adsorption efficiency of Ni2+ per molar unit changes as: CS-A (81.8%) > CS-SA (59.9%) > CS-BA (56.1%) > CS-PCBA (46.6%) > CS (40.25%). Thus, the modified chitosan compounds by imine bonds are well compounds to adsorption of metal ions.