Interfacial removal of amoxicillin from water using a dendrimer-functionalized graphene-silica hybrid: mechanistic...

Pharmaceutical pollutant, such as amoxicillin was selected because it is one of the most widely consumed antibiotics worldwide and is frequently detected in hospital and municipal wastewater. Its high excretion rate in active form and persistence in aquatic environments make it an important target contaminant for water treatment studies. To address this issue, we developed a dendrimer-functionalized graphene quantum dot-mesoporous silica hybrid (GQDs@mSiO₂@Dend.G₃) as an effective and reusable adsorbent. AMX is an ideal model contaminant for studying adsorption mechanisms and evaluating the performance of this advanced hybrid material. Mechanistic interpretation suggests that hydrogen bonding, π-π, and electrostatic interactions collectively contribute to antibiotic binding at the hybrid interface. The nanoadsorbent was characterized using XRD, TGA, FTIR, BET-BJH, FE-SEM, EDX, and zeta potential measurements. Response surface methodology with a central composite design was used to optimize and validate the removal efficiency, yielding statistically significant results. The drug removal efficiency of 96% was achieved under the following optimal conditions: pH 6, temperature of 35 °C, and contact time of 45 min. The kinetics followed the pseudo-second-order model (R² = 0.9979) and the equilibrium fit the Langmuir isotherm (R² = 0.9657-0.9675) confirming monolayer physisorption onto uniform active sites. Thermodynamics showed that the process was spontaneous and endothermic (ΔH° = 8562.589 J mol^-1, ΔS° = 155.530 J mol^-1 K^-1, and ΔG° = -37.808 to -40.919 kJ mol^-1). The nanoadsorbent showed consistently high removal efficiency in real water samples. It retained over 70% of its original performance after multiple regeneration cycles. This indicates that GQDs@mSiO₂@Dend.G₃ is a promising and reusable solution for reducing pharmaceutical pollution in environment samples.