A chitosan-Staphylococcus epidermidis bacterial biocomposite adsorbent for removal of reactive orange 16 dye: Box–Behnken design optimization

A biocomposite material of chitosan/Staphylococcus epidermidis bacterial biomass (CS/STEPI) was developed for removal of reactive orange 16 (RO16) dye. The properties of the CS/STEPI biocomposite were characterized using XRD, FESEM-EDX, FTIR spectroscopy and pHpzc. The adsorptive capacity of the CS/STEPI biocomposite for removal of RO16 dye was optimized through a Box-Behnken design employing a desirability function to achieve a 92.7 % dye removal. Three types of operational biosorption parameters were considered: CS/STEPI dose (0.02 to 0.1 g/100 mL), contact time (20 to 120 min), and solution pH (4 to 10). Kinetic and equilibrium biosorption isotherms revealed that the biosorption of RO16 dye onto the CS/STEPI biocomposite was described by the pseudo-second-order kinetic and the Langmuir adsorption models, respectively. The maximum dye adsorption capacity was estimated to be 119 mg/g at pH 4.3. The thermodynamic analysis of the biosorption process reveals that the process is exothermic and spontaneous overall. Biosorption of the RO16 dye onto the surface of the CS/STEPI biocomposite is attributed to multiple types of interactions: n-π, electrostatic, and hydrogen bonding. A reusability test shows that CS/STEPI biocomposite was reusable for five cycles of applications. Therefore, the CS/STEPI biocomposite has favourable potential for the removal of anionic dyes from wastewater. © 2025 Elsevier B.V.