A novel adsorbent CoFe2O4@HAp-GQDs nanocomposites were synthesized through the facile co-precipitation process and used for the removal of Brilliant Cresyl Blue (BCB) dye from aqueous solutions for the first time. FESEM, XRD, EDX, FT−IR, and VSM techniques were used to characterize the prepared nanocomposites. To optimize BCB removal by CoFe2O4@HAp-GQDs, a face-centered central composite design (FCCD) with three levels was utilized. The maximum removal percent (93%) of BCB was obtained at the optimum conditions of initial dye concentration of 221 mg L-1, 0.05 g adsorbent amount, and pH 5.7. The experimental equilibrium data were examined by D-R, Langmuir, Temkin, and Freundlich isotherm models. The adsorption isotherm follows the Langmuir model with a maximum adsorption capacity of about 139.4 mg g-1. Adsorption kinetic data were also considered using pseudo 1st order, Elovich, pseudo 2nd order, and intra-particle diffusion models. Thermodynamic results show that the BCB dye was adsorbed exothermically, and spontaneously
