Adsorption of bisphenol A and 2,4-dichlorophenol onto cetylpyridinium chloride-modified pine sawdust: a kinetic and thermodynamic study

Using biomass wastes as adsorbents is a promising option for organic waste reclamation, but unfortunately, their adsorption capacity is usually limited, especially for hydrophobic organic pollutants. To address this issue, this work prepared cetylpyridinium chloride (a cationic surfactant)-modified pine sawdust (CPC-PS) and further demonstrated their performance for hydrophobic bisphenol A (BPA) and 2,4-dichlorophenol (DCP) adsorption. Compared to the PS, the CPC-PS improved the maximum adsorption capacity for BPA and DCP by approximately 98% and 122%, respectively. The kinetic and thermodynamic analyses showed that the BPA and DCP adsorption onto the CPC-PS fitted the pseudo-second-order kinetics and the Freundlich model. After regeneration using NaOH, the adsorption capacity of the CPC-PS for BPA still maintained 80.2% of the initial value after five cycles. Based on the experimental results, the CPC-PS was proposed to enhance the BPA and DCP adsorption through the solubilization of hemimicelles for hydrophobic organic pollutants, the π-π stacking between benzene-ring structures, and the hydrogen binding between the adsorbents and the pollutants. This work provides a viable method to use surfactant-modified pine sawdust as effective adsorbents to remove hydrophobic pollutants.