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, 10000 and 70000 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 ). FTIR, BET, FESEM/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 PEIimpregnated activated carbon is a strong and efficient adsorbent for RY2 removal in textile wastewater treatment.