Kinetic, isotherm, and thermodynamic analysis of the simultaneous adsorption of ciprofloxacin, moxifloxacin, levofloxacin, and sparfloxacin onto sulfonated graphene oxide in binary, ternary, and quaternary aqueous solutions

• SGO removed multiple antibiotics in binary, ternary, and quaternary systems. • Adsorption followed pseudo-second-order and Langmuir isotherm models. • Physisorption dominated with E < 8 kJ/mol and ΔH < 40 kJ/mol. • High adsorption capacities: 370.37, 357.14, and 333.33 mg/g across systems. • SGO maintained >92% capacity after five reuse cycles. Pharmaceutical, hospital, and agricultural effluents often contain antibiotic residues, posing serious environmental concerns. This study examined the simultaneous adsorption of multiple antibiotics onto sulfonated graphene oxide (SGO) in equimolar binary (ciprofloxacin–moxifloxacin), ternary (ciprofloxacin–moxifloxacin–levofloxacin), and quaternary (ciprofloxacin–moxifloxacin–levofloxacin–sparfloxacin) aqueous systems. Batch experiments evaluated key operational parameters, including contact time, solution pH, SGO dosage, initial antibiotic concentration, and temperature. Equilibrium data showed that the Langmuir isotherm best describes multicomponent adsorption, while kinetic analysis confirmed that the pseudo-second-order model accurately captures the process. The multilinear shape of intra-particle diffusion plots indicated that surface adsorption and pore diffusion both contribute. The maximum adsorption capacities ( q m ), calculated by the Langmuir model at 25°C, were 370.37 mg/g for the binary system, 357.14 mg/g for the ternary system, and 333.33 mg/g for the quaternary system. Energy (E < 8 kJ/mol) and enthalpy (Δ H° < 40 kJ/mol) values indicate that physical adsorption dominates across all systems. Thermodynamic analysis further confirmed that antibiotic adsorption onto SGO is both spontaneous and endothermic. Desorption experiments showed that over 97% of antibiotics could be recovered with DMF containing 1 mol/L HCl, and SGO maintained more than 92% of its initial performance after five adsorption–desorption cycles. With high stability, a broad pH range tolerance, and excellent reusability, SGO proves to be an effective and durable adsorbent for treating real wastewater contaminated with multiple antibiotics.