Copolymerization of catechol and polyethyleneimine onto activated carbon for efficient removal of Congo red dye.

In this work, a new AC@Catechol/PEI adsorbent was prepared via the copolymerization of catechol and polyethyleneimine (PEI) onto pretreated commercial activated carbon (AC). It achieved a high adsorption capacity of 411.52 mg/g for the anionic dye Congo red (CR), which was approximately 7 times that of pretreated AC without modification. In bath adsorption experiment, 1 g of adsorbent was used to treat 4 L of 100 mg/L CR solution, resulting in 98.5% CR removal. In addition, the prepared AC@Catechol/PEI adsorbent exhibited highly efficient CR competitive adsorption against SO42− ions and cationic malachite green dye. The adsorption mechanism was mainly attributed to electrostatic interactions, hydrogen bonding, and π–π stacking. Catecholamine modification greatly improved the adsorption capacity and adsorption selectivity of commercial AC for CR dyes. This low‐cost adsorbent may have broad prospects for the removal of anionic dyes in wastewater. [ABSTRACT FROM AUTHOR]