Exploring surface chemistry governing benzotriazole removal as a plastic-industry emerging contaminant: Integrated kinetic, equilibrium, and thermodynamic analysis on GO and rGO

Benzotriazole (BTA) is a nitrogen-containing heterocyclic compound widely used as a corrosion inhibitor and stabilizer in polymer and metal-processing industries. Its increasing occurrence in wastewater treatment plant effluents and surface waters has raised environmental concern due to its persistence and resistance to conventional biological treatment. In this work, the adsorption behavior of benzotriazole was systematically investigated on three structurally and chemically different adsorbents—graphene oxide (GO), reduced graphene oxide (rGO), and mesoporous silica SBA-15—in order to elucidate the relative roles of surface chemistry and pore architecture in controlling adsorption performance. Comprehensive structural characterization using N₂ adsorption–desorption, PXRD, Raman spectroscopy, FTIR, XPS, SEM, and thermogravimetric analysis confirmed three distinct adsorption environments : highly oxidized lamellar carbon surfaces (GO), partially restored graphenic domains with enhanced π-electron density (rGO), and an ordered mesoporous silica framework with silanol-terminated channels (SBA-15). Equilibrium adsorption experiments revealed that adsorption capacities follow the order rGO > GO > SBA-15, highlighting the importance of aromatic surface domains in stabilizing benzotriazole through π–π interactions. Nonlinear isotherm modeling showed heterogeneous adsorption behavior best described by the Tóth and Prausnitz–Radke models, while kinetic analysis indicated a combined mechanism involving surface interaction and diffusion . Thermodynamic parameters demonstrated that adsorption is spontaneous and exothermic for all materials, with the strongest enthalpic contribution observed for GO (ΔH° ≈ −28 kJ mol⁻¹), followed by rGO (ΔH° ≈ −21 kJ mol⁻¹) and SBA-15 (ΔH° ≈ −4 kJ mol⁻¹). These results establish a quantitative mechanistic hierarchy in which adsorption affinity is primarily governed by surface electronic structure, as evidenced by the magnitude of adsorption enthalpies and the enhanced capacity of rGO (q max ≈ 51.9 mg g⁻¹), while pore architecture plays a secondary but critical role in controlling mass transport and kinetic accessibility. Thus, benzotriazole adsorption emerges from a coupled mechanism in which surface chemistry dictates interaction strength, whereas pore structure regulates diffusion pathways and adsorption rates.These findings provide mechanistic insight into the design of graphene-based adsorbents for water purification.