Adsorption of Tetracycline and Congo Red by a Nitrogen and Sulfur Co‐Doped Crab Shell‐Derived Biochar (BC‐N/S): Mechanism and Estimated Cost

ABSTRACT

The co‐existence of various pollutants in water/wastewater matrices, as well as the indiscriminate disposal of crustacean waste, poses significant environmental challenges that require urgent intervention. To address both issues, this study harnessed crab shell waste as a carbon precursor and thiourea as the N/S source for the preparation of a nitrogen‐sulfur‐co‐doped biochar (BC‐N/S) using a rapid one‐pot synthesis technique. The efficiency of the bare biochar (BC) and BC‐N/S was compared for the adsorption and co‐adsorption of Congo red (CR) and tetracycline (TC) from aqueous solution. Characterization of BC‐N/S and BC using FTIR spectroscopy revealed that BC‐N/S exhibited a new functional group at 2062 cm ⁻¹ , attributed to the isothiocyanate (N = C = S) group, suggesting successful co‐doping. The surface area (11.020 m ² g ⁻¹ ) and pore width (22.13 nm) of BC improved to 13.462 m ² g ⁻¹ and 34.99 nm, respectively for BC‐N/S. The BC‐N/S maintained a constant adsorption capacity of 4.62 mgg ⁻¹ for CR removal in both single and binary system, whereas TC removal slightly declined from 3.81 to 3.72 mgg ⁻¹ in the binary mixture, indicating competitive adsorption due to the presence of CR. Findings from these study suggest that efficient, and affordable adsorbent can be harnessed from crab shell waste for multi‐pollutant sequestration.