Cd(II) and Chlortetracycline Adsorption by Composite‐Modified Carbonized–Foamed Starch

In the present study, starch (S) was carbonized through anaerobic calcination and subsequently foamed using NaOH treatment to produce carbonized‐S (CS) and carbonized–foamed S (CFS). Chitosan (C) and dodecyl dimethyl betaine (D) were subsequently used for single and combined modifications of CS and CFS, yielding C‐modified CS and CFS (C‐CS and C‐CFS) and D and C co‐modified CS and CFS (D/C‐CS and D/C‐CFS), respectively. The morphological features of various modified CSs and CFSs were characterized using various analytical techniques. The thermodynamic and kinetic characteristics of Cd(II) and chlortetracycline (CTC) adsorption were evaluated through batch experiments, and the effects of temperature, pH, and ionic strength were investigated. After foaming, the void structures of the CFS became more porous, forming a mesh‐like structure with an uneven pore distribution. The D and C modifications altered the physicochemical properties and introduced functional groups onto the CS and CFS. The adsorption isotherms of the modified CSs and CFSs for Cd(II) and CTC were accurately described by the Langmuir model. The maximum adsorption capacity of various modified materials for Cd(II) and CTC ranged from 103.21 to 202.26 mmol/kg and 39.96 to 461.11 mmol/kg, respectively, following the order: D/C‐modified > C‐modified > unmodified CS and CFS. Elevated temperatures and higher pH levels facilitated the adsorption of Cd(II) and CTC. Thermodynamic and kinetic analyses indicated that the adsorption of Cd(II) and CTC was spontaneous, endothermic, and driven by entropy, primarily governed by transfer resistance. After three regeneration cycles, D/C‐CFS maintained 69.32% of its original adsorption capacity for Cd(II) and 78.33% for CTC.