Diclofenac sodium removal from aqueous phase using a keratinolytic waste and biodegradation of the adsorbate/adsorbent complex

This research focuses on the removal of diclofenac in aqueous phase using chicken feathers and the evaluation of the subsequent biodegradation of the obtained adsorbate/adsorbent complex using a bacterial consortium. In the first stage, the conditions that affected adsorption were evaluated, in order to optimize the loading of the feathers. Afterwards, the equilibrium was evaluated by three adsorption isotherms at 8, 15 and 25 °C; the experimental data were explained by the Langmuir model, showing that, at 8 °C the highest load was obtained (614.8 mg/g). Additionally, the process was thermodynamically explained as spontaneous and exothermic and governed by chemical and physical processes, in addition to the occurrence of a decrease in molecular disorder at the adsorbate–adsorbent interface. Likewise, the kinetic behavior was studied at 8, 15 and 25 °C, detecting that the adsorption process occurs in two stages described by the intraparticle diffusion model. Finally, an FTIR analysis was carried out, in which the groups participating in the adsorption process were shown. The second stage was the evaluation of the biodegradation process of the adsorbate/adsorbent complex. The biodegradation of diclofenac was evidenced by monitoring laccase, lignin peroxidase, manganese peroxidase and polyphenol oxidase enzymatic activities and quantifying the 50% decrease in diclofenac concentration by HPLC. Simultaneously, the degradation of the chicken feather impregnated with diclofenac was analyzed, evaluating keratinolytic activity, the presence of soluble protein, amino acids and sulfhydryl groups; the positive results of these tests confirmed the biodegradation.