Application of the classical Langmuir kinetic framework to the adsorption of emerging contaminants onto bituminous activated carbon

The presence of emerging contaminants in aquatic environments has become a major environmental concern due to their persistence and potential toxicological effects. In this work, the classical Langmuir kinetic framework was applied to describe the adsorption behaviour of Cu 2+ , caffeine, metformin, and tetracycline onto commercial bituminous activated carbon (BAC). The adsorbent was comprehensively characterized using scanning electron microscopy and energy dispersive X‐ray spectroscopy (SEM‐EDS), X‐ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), temperature programmed desorption (TPD), temperature‐programmed oxidation (TPO), thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), and N 2 physisorption in order to correlate its physicochemical properties with adsorption performance and validate the assumptions underlying the Langmuir model. Kinetic experiments and equilibrium isotherms were obtained at different temperatures (25–55°C), and the governing differential equation was solved numerically using a fourth‐order Runge–Kutta method validated against the analytical solution available in the literature. The BAC exhibited a predominantly microporous structure (average pore radius = 0.72 nm), moderate surface area (408.68 m 2 g −1 ), and relatively high graphitic organization ( I D / I G = 0.87), which imposed diffusional and steric limitations, particularly for larger molecules. Maximum adsorption capacities at 55°C were 2.08, 0.64, and 0.31 mg g −1 for metformin, caffeine, and tetracycline, respectively. Thermodynamic analysis indicated spontaneous and endothermic adsorption processes dominated by physisorption mechanisms. Quantitative comparison with pseudo‐first‐order and pseudo‐second‐order models demonstrated that the Langmuir kinetic framework provides improved mechanistic interpretation and predictive flexibility. The results highlight the importance of integrating detailed adsorbent characterization with kinetic modelling for the rational design of adsorption systems for emerging contaminant removal.