Modified Activated Carbons Derived from Chestnut Shell Waste Biomass for the Removal of Triclosan from Aqueous Solution

Triclosan (TCS) is an antimicrobial agent belonging to the bisphenol class, and is widely used in healthcare applications and in personal care products (PCPs). As an emerging pollutant frequently detected in aquatic environments, its toxicity to aquatic organisms and the male reproductive system highlights the need for effective removal methods such as adsorption. In this study, bio-based activated carbon was prepared from chestnut shell as waste biomass (CnSAC), modified by polyethylenimine (PEI) (CnSAC/PEI), manganese oxide MnO2 (CnSAC/Mn) or a combination of these (CnSAC/Mn-PEI). The prepared adsorbents were evaluated for their efficiency in TCS removal. The composite material CnSAC500PEI exhibited improved adsorption efficiency for TCS (99.5%) at pH 3, whereas MnO2 modification alone did not provide a significant improvement over the pristine activated carbon. The pHpzc analysis determined the surface charge of the adsorbent, while SEM, FTIR, EDS, and XRD characterization confirmed that the modification formed a thin, homogeneous PEI layer. This layer introduced N–H and C–N functional groups without affecting the porous structure of the activated carbon. The adsorption kinetics showed excellent agreement between both the PSO and PFO models, a combination of physical adsorption mechanisms and surface interactions. Isotherm analysis revealed a Freundlich behavior, indicating adsorption on a heterogeneous surface and a maximum capacity of 250.33 mg/g at 303 K for the CnSAC500PEI material.