Chitosan-Derived Porous Carbon for Efficient Adsorptive Removal of Amoxicillin and Doxycycline Antibiotics from Aqueous Systems

Traditional antibiotic removal techniques-such as coagulation, membrane filtration, ozonation, and biodegradation-are often inadequate for large-scale applications due to limiting factors including high operational costs, complex system design, and the formation of toxic by-products. In addition, the low selectivity levels of these techniques and the need for additional post-treatment make it difficult to achieve effective and sustainable water treatment goals. The phosphoric acid-activated chitosan-derived carbon adsorbent proposed in this study demonstrated superior adsorption capacities for both amoxicillin and doxycycline, owing to its high surface area and abundant functional groups, aligning with sustainability principles. Thus, it stands out as an economical and environmentally friendly alternative that directly solves the shortcomings of previous methods. High-performance activated carbon was synthesized via phosphoric acid activation of chitosan for the removal of amoxicillin (AMX) and doxycycline (DOC) antibiotics from aqueous solutions. The adsorption efficiency was systematically evaluated in batch experiments at temperatures ranging from 30 to 50 degrees C, initial antibiotic concentrations of 50-400 mg/L, and pH levels spanning from 3 to 13. The phosphoric acid activation process significantly influenced the physicochemical properties of the resultant activated carbon, enhancing its structural and textural characteristics. The activated carbon exhibited a substantial surface area of 998.02 m2/g, a pore volume of 0.485 cm3/g, and an average pore diameter of 2.55 nm, structure favorable for adsorption. Furthermore, kinetic analysis revealed that the adsorption process followed the pseudo-first-order model, indicating that physisorption was the dominant mechanism. Equilibrium data were best described by the Langmuir isotherm model, highlighting monolayer adsorption on a homogeneous surface. The maximum adsorption capacities for AMX and DOC were determined to be 227.18 mg/g and 299.07 mg/g, respectively, at 50 degrees C, demonstrating the high affinity of the adsorbent for these pharmaceutical contaminants. These findings indicate that chitosan-derived activated carbon is a cost-effective, sustainable material with strong potential for removing antibiotic contaminants from wastewater.