Defect‐Rich Porous Carbon Derived from Sodium Alginate and Its Efficient Dye Removal Performances

Abstract In this study, we reported a defect‐rich porous carbon (SAC) derived from sodium alginate (SA) via combined processes of high‐temperature carbonization at N 2 atmosphere, NaCl hard template, and HCl etching for high‐performance absorbents. Besides the meso/macro‐porous structure characterization performed with usual morphological and structural analysis methods, sub‐nanolevel atomic microdefects of the derived SAC were investigated by positron annihilation lifetime spectroscopy (PALS) for the first time. All the samples displayed hierarchical pore structure, including numerous 3D‐interconnected macroporous (0.5‐2 µm), abundant mesopores (3‐5 nm), and rich intrinsic microdefects (mean size of 0.304 nm). The specific surface area and pore volume of the optimized SAC sample were 1191.3 m 2 ·g −1 and 0.69 cm 3 ·g −1 , respectively. It was confirmed that the adsorption process of the derived SAC to the dye molecules mainly occurred through a chemical and monolayer adsorption mechanism. The SAC sample showed high efficiency in dye removal, with superior removal capacitance of 230.5 mg·g −1 for anionic dye of methyl orange (MO) and 1655.1 mg·g −1 for cationic dye of Rhodamine B (RhB) at pH = 7, respectively, which were about two times of that of commercial AC for the presence of more active sites of the derived SAC. This study also exhibited that the derived defect‐rich porous carbons from natural‐polymers of SA can be considered as an effective adsorbent to remove MO and RhB dyes from industrially polluted water at neutral pH conditions.