Synthesis, characterization, and applications of a novel g-C₃N₅/Starch/carboxymethyl cellulose composite in...

In this research, a new g-C₃N₅/Starch/CMC (CSC) ternary composite was produced and used for the controlled release of Gentamicin (GM). FTIR, XRD, FESEM, BET and TGA techniques were applied to characterize the prepared composite. A Box-Behnken design was employed in the response surface methodology to optimize the adsorption capacity of the CSC composite for GM and investigate the mutual effects of the independent variables [pH of the solution (3-9), Gentamicin concentration (200-600 mg/L) and dosage of CSC (01-0.2 g/50 mL)]. The g-C₃N₅/Starch/CMC composite exhibited a maximum adsorption of GM (87.87 %) at optimum conditions: pH = 9, GM concentration = 300 mg/L and CSC dosage of 0.2 g/50 mL. Kinetic and isothermal studies revealed that the adsorption isotherm best matched both the Langmuir and Freundlich models, and the GM adsorption kinetics onto the CSC composite more fitted with the pseudo-second-order model (R² = 0.99). The study showed the sustained release of the GM at physiological conditions (pH 7.4) at 37 °C for 12 h. Various kinetic models for GM release were also studied. It was found that the Korsmeyer-Peppa kinetic model (R² = 0.98) is the best for predicting the release kinetics of GM.