3D-printed highly porous and reusable chitosan monoliths for Cu(II) removal

Removal of heavy metal pollution has received considerable research attention due to its severe effects on human health. In the present study, for the first time, a reusable monolithic 3D porous adsorbing filter was fabricated by integrating 3D printing technique with a natural adsorbent (chitosan), which is a low-cost and highly effective solution for heavy metal removal. The –NH2 and –OH functional groups found on the highly porous monoliths were capable of adsorbing metal ions. Further analyses revealed that the adsorption capacity increases with the filter’s surface area, with T = 25 °C and pH 5.5 representing the optimal working conditions. The maximum adsorption capacity of 13.7 mg/g (calculated by using the total mass) was measured for the filter with skewed hexagonal holes. The pseudo-first-order equation and Langmuir isotherm model presented a good fit to the experimental data, thus accurately describing the adsorption kinetics and the adsorption equilibrium. The monolithic chitosan-loaded filter exhibited a superior adsorption kinetics of 2.2 mg/(g min) for Cu(II) removal. Findings yielded by the desorption experiment also demonstrated that EDTA can desorb the metal ions from the monoliths, and its ~ 92% desorption capacity indicates high reusability. All results reported in this work indicate that 3D printing offers an alternative, cost-effective and facile approach for fabricating structured adsorbents with tunable structural and chemical properties for use in metal ion removal.