Ultrafast and efficient removal of anionic dyes from wastewater by polyethyleneimine-modified silica nanoparticles

Trace anionic dyes in wastewater are difficult to be rapidly and efficiently removed because they are completely soluble and poorly biodegradable. Herein, a facile and environmentally friendly adsorbent was fabricated via the surface functioned SiO₂ with abundant amine groups of polyethyleneimine (PEI). The structural characterization indicated that PEI was successfully immobilized on the SiO₂ surface. The adsorption performance of SiO₂-PEI was evaluated using acid orange II (AOII) as model pollutant. The adsorption of AOII on SiO₂-PEI displayed high removal rates in the pH range of 2.0-9.0, and exhibited ultrafast removal (99.1% removal rate at 10 min). The adsorption behavior fitted well with the Langmuir isotherm and pseudo-second-order kinetic model, and the maximum uptake capability of AOII was higher than 705.3 mg/g. The excellent adsorption capacity of AOII on SiO₂-PEI mainly relied on the electrostatic attraction between the sulfonic acid group of AOII and amine group of PEI in the adsorption process. Additionally, other anionic dyes like acid fuchsin and direct sky blue 5B could also be fast and efficiently removed by SiO₂-PEI. This work is expected to open new possibilities for the ultrafast removal of anionic dye pollutants.