TiO 2 ‐coated multi‐walled carbon nanotubes as a reusable nano adsorbent for diclofenac elimination: Adsorption characteristics and comparative RSM – ANN optimization

Abstract TiO 2 ‐coated multi‐walled carbon nanotubes (TiO 2 –MWCNTs) were prepared and examined for the removal of diclofenac from aqueous solution. FTIR, FESEM–EDS, BET, and TGA analyses were used to characterize the surface chemistry, morphology, elemental composition, textural properties, and thermal behavior of the prepared material. Batch experiments were performed by varying pH, temperature, contact time, and adsorbent dosage. The highest diclofenac removal of 91.9% was obtained at pH 5, 40°C, 60 min, and 0.03 g adsorbent. Equilibrium behavior was examined using Langmuir, Freundlich, and Dubinin–Radushkevich models, with linear and nonlinear fitting used for comparison. The Langmuir model gave a maximum adsorption capacity of 105.26 mg g −1 . For the kinetic data, nonlinear PFO fitting provided a better statistical description than nonlinear PSO fitting, while the intraparticle‐diffusion analysis indicated that pore diffusion was not the only rate‐influencing step. The adsorption process was spontaneous and endothermic based on the thermodynamic results. Ethanol desorption reached 90.65%, indicating that the material could be regenerated under the conditions tested. RSM identified pH 5, 40°C, and 60 min as the optimum conditions, with an experimental removal of 91.9%, while the ANN model gave R 2 values of 0.998–0.999 and low MSE values. These findings show that TiO 2 –MWCNTs can provide effective diclofenac removal with regeneration capability, while RSM and ANN offer complementary approaches for process optimization and prediction.