Polyethylenimine embellished multiwalled carbon nanotube (MWCNTs) for efficiently enhancing sequestration of uranium(Ⅵ) from seawater

There are abundant uranium resources in seawater, and the development of low-cost and high-efficiency adsorbents for uranium extraction from seawater has high economic and environmental-friendly benefits. In this work, a polyethyleneimine modified MWCNTs adsorbent was fabricated and used for uranium capture. The prepared samples exhibited excellent removal efficiency (∼ 82.39∼96.98%) and adsorption selectivity (with a K d ∼2.34 ×10 4 ∼1.61 ×10 5 mL/g) in the pH range of 4.0–8.0, which obviously superior than that of pure MWCNTs (∼ 36.16∼52.65%, K d ∼2.83 ×10 3 ∼5.56 ×10 3 mL/g). The adsorption process followed a pseudo-second-order kinetic model, and its maximum adsorption capacity reached 97.60 mg/g. In addition, due to the existence of various chelating ligands in PEI, the specimen showed excellent adsorption performance in various interfering ions and simulated seawater. Therefore, the adsorbed samples can be easily regenerated in low-concentration hydrochloric acid solution, and the removal efficiency still reaches 85.83% after five consecutive adsorption-desorption experiments, showing fine regeneration performance. XPS analysis indicated that chelation between nitrogen- and oxygen-containing functional groups with UO 2 2+ was the dominant removal mechanism. The excellent adsorption efficiency and regeneration performance, as well as low preparation cost and environmental friendliness, make it a potential seawater uranium sorbent. Schematic illustration of the interaction mechanism between PEI@MWCNTs and U(VI) ions. • Polyethyleneimine-modified MWCNTs were prepared by a facile hydrothermal covalent grafting method. • The PEI@MWCNTs samples exhibited excellent removal efficiency (∼82.39% ∼ 96.98%) and adsorption selectivity (with a K d ∼2.34 ×10 4 ∼1.61 ×10 5 mL/g) in the pH range of 4.0–8.0. • The sufficient UO 2 2+ Chelation sites were responsible for the higher UO 2 2+ removal efficiency in various competing ions (K + , Ca 2+ , Mg 2+ , Na + ) and simulated seawater. • The PEI@MWCNTs shown fine regenerated and stability in low-concentration hydrochloric acid solution. • XPS analysis indicated that chelation between nitrogen- and oxygen-containing functional groups with UO 2 2+ was the dominant removal mechanism.