Effect of Polyethylenepolyamine Modification of Flax Fiber on Cu(II) and Cd(II) Ions Sorption

This study investigates the chemical modification of short flax fiber and the resulting sorption properties concerning Cu(II) and Cd(II) ions. A two-stage chemical modification process involving the oxidation of flax fiber with sodium metaperiodate followed by treatment with polyethylenepolyamine produced a new sorbent for water purification from heavy metal ions. Kinetic experiments determined the time to reach sorption equilibrium in the heterophase system “aqueous solution of copper/cadmium sulfates–sorbent” and found that the degree of metal ion extraction by the modified sorbent increased by about 20% compared to the initial fiber. The experimental sorption isotherms were analyzed using the Langmuir model, which was found applicable to describe the sorption process of heavy metal ions by cellulose-based sorbents. The maximum sorption capacities ( А ∞ ) of native and modified flax fibers with respect to heavy metal ions were determined, revealing that Cu(II) ions are more efficiently extracted by the developed sorbent compared to Cd(II) ions. Scanning electron microscopy of the original and modified flax fibers indicated changes in the surface microrelief due to modification. Elemental analysis reflected changes in the composition of the modified sorbent compared to native flax fiber. The improvement in the equilibrium-kinetic characteristics of short flax fiber resulting from its modification with polyethylenepolyamine is attributed to the presence of new sorption-active groups, as confirmed by IR spectroscopy and elemental analysis.