Polyethylenimine-Impregnated Powdered Activated Carbon for Efficient Removal of Reactive Yellow 2 from Aqueous Solutions

This study optimizes polyethylenimine (PEI) impregnation on powdered activated carbon (PAC) to maximize adsorption of the anionic dye Reactive Yellow 2 (RY2). Three factors, namely PEI molecular weight (600, 800, 1200, 10,000 and 70,000 g mol⁻¹), PEI content (0.1–10 wt.%), and impregnation stirring speed (0–200 rpm), were systematically evaluated in triplicate. Under optimal conditions (PEI Mw = 800 g mol⁻¹, PEI content = 1.0 wt.%, stirring = 40 rpm), PEI-impregnated PAC achieved a maximum adsorption capacity of 477.02 mg g⁻¹, which is 7.4-fold higher than raw PAC (64.13 mg g⁻¹). FT-IR, BET, FE-SEM/EDS, and zeta potential analyses showed that although PEI impregnation reduced surface area, the introduced amine groups increased the surface charge by + 52.64 mV at pH 2, driving the enhanced adsorption. These results demonstrate that PEI-impregnated activated carbon is a strong and efficient adsorbent for RY2 removal in textile wastewater treatment.