Abstract In this work, a tannic acid‐coated CoCr 2 O 4 ‐decorated silica composite (TA‐CoCr 2 O 4 @SiO 2 ) was synthesized via sequential CoCr 2 O 4 formation/deposition on SiO 2 followed by tannic acid (TA) functional coating, aiming to enhance adsorption of methylene blue (MB) from water. The composite exhibited a mesoporous texture with a specific surface area of 132.9 m 2 /g and a total pore volume of 0.739 cm 3 /g, facilitating dye transport to active sites. Batch adsorption experiments indicated rapid MB uptake, achieving high removal efficiency within 180 min under near‐neutral conditions. Kinetic data were best described by the pseudo‐second‐order model (R 2 = 0.94), while equilibrium was well fitted by the Langmuir isotherm (R 2 = 0.97) with a maximum adsorption capacity (Q max ) of 21.1 mg/g. Thermodynamic analysis yielded ΔH° = −26.42 kJ/mol and ΔS° = −103.9 J/mol·K, indicating an exothermic and more ordered adsorption process, consistent with mixed noncovalent interactions (electrostatic attraction, hydrogen bonding, and π‐π interactions) promoted by the TA/oxide surface chemistry. Regeneration results (adsorption–desorption cycling) provide initial evidence of partial capacity recovery, supporting the potential for reuse‐oriented operation. Overall, TA‐CoCr 2 O 4 @SiO 2 offers a simple, functionalized composite platform for MB removal and provides a basis for further evaluation under realistic water matrices.
Hoang et al. (Thu,) studied this question.