3D printable polyethyleneimine based hydrogel adsorbents for heavy metal ions removal

Abstract

Heavy metal contamination is one of the leading causes of water pollution, with known adverse effects on human health and the environment. This work demonstrates a novel custom-made 3D printable eco-friendly hydrogel and fabrication process that produces stable biocompatible adsorbents with the ability to capture and remove heavy metals from aqueous environments quickly and economically. The 3D printable ink contains alginate, gelatin, and polyethyleneimine (PEI), which binds heavy metals through primary and secondary amine side chains favoring heavy metal adsorption. The ink's rheological properties are optimized to create mechanically stable constructs, in the form of 3D-printed tablets, fabricated entirely by printing. The optimized tablets have high porosity and accessible surface area with multiple binding sites for heavy metal ion adsorption while the printing process enables rapid and affordable production with the potential for scale-up. The results demonstrate the contribution of hydrogel composition and rheology in determining the printability, stability, and heavy metal binding characteristics of the hydrogel, and indicate the critical role of the PEI in increasing stability of the printed construct, in addition to its metal binding properties. The highest removal capacity was obtained for copper, followed by cadmium, cobalt, and nickel ions. In the optimized formulation, each hydrogel tablet removed 60% from 100 ppm copper in 5 h and up to 98% in 18 h. For more concentrated solutions (1000 ppm), ∼25% of copper was removed in 18 h. The printed tablets are stable, robust, and can be produced in a single simple step from inexpensive biomaterials. The ink's tunability, excellent printability, and stability offer a universally applicable procedure for creating hydrogel-based structures for environmental remediation. These unique capabilities open new avenues for manufacturing tailor-made constructs with integrated functionality for water treatment and environmental applications.