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 SO 4 2− 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.