Sustainable pine cone adsorbent: Removal of prednisolone and pre-treatment of a medical lab wastewater
Résumé
The current study aimed to investigate at lab-scale the removal of a steroid anti-inflammatory “prednisolone” from synthetic solutions and the pretreatment of a medical analysis laboratory's wastewater using an efficiently prepared adsorbent. To achieve this goal, two adsorbents were prepared from pine cones. The first one is a pine cones biochar prepared by pyrolysis at 900 °C (PCB-900 °C), while the second adsorbent was phosphoric acid-activated carbon subjected to pyrolysis at 400 °C (PhAC). The obtained results demonstrated that PCB-900 °C outperformed PhAC, achieving an efficiency of 99.10% in prednisolone removal, whereas PhAC attained an efficiency of 31.63% within 30 min equilibrium time. The pseudo-second-order kinetic model describes perfectly the kinetic adsorption data of prednisolone for both adsorbent. The maximum adsorption capacity of Langmuir obtained by the best-prepared adsorbent (PCB-900 °C) was 35.99 mg/L. The adsorption process remained unaffected by variations of pH; electrostatic interactions have not a major effect on the adsorption process. The π-π interactions, pore-filling and hydrophobic interactions were selected as the dominant mechanisms involved in the adsorption process of prednisolone. The thermodynamic study highlighted that the adsorption process of prednisolone on PCB-900 °C was spontaneous, endothermic, and random. The reutilization of PCB-900 °C was tested on 4 consecutive cycles. The results of the degradation of organic matter in laboratory wastewater showed that high dose of PCB-900 °C led to significant reductions in chemical oxygen demand (COD) and turbidity levels. Therefore, pine cone-derived biochar can be considered as a solution for pharmaceutical removal and an eco-friendly method for treating point sources of pharmaceutical effluent.