Adsorption of dibutyl phthalate on Burkholderia cepacia, minerals, and their mixtures: Behaviors and mechanisms

Microorganisms and clay minerals play vital roles in the adsorption of organic chemicals in soils and sediments. In the present study, we conducted batch adsorption experiments, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and relative hydrophobicity tests to investigate the sorption of dibutyl phthalate (DBP) by a DBP-tolerant bacterium (Burkholderia cepacia, Bc), clay minerals (montmorillonite, goethite and kaolinite), and their mixtures. The adsorption isotherms of DBP were best fitted with the Freundlich equation. The order of DBP adsorption capacity was montmorillonite > goethite > Bc > kaolinite, which were 13.83, 12.62, 9.04 and 5.09 mg g^‑1, respectively. The addition of Bc reduced the adsorption of DBP to montmorillonite and goethite, but increased it on kaolinite. The desorption results showed that the binding strengths of DBP to minerals were also as follows: montmorillonite > goethite > kaolinite. SEM and hydrophobicity tests further confirmed these results, suggesting that the hydrophobic distribution interaction played an important role in the DBP adsorption by the Bc-minerals mixtures, but it might not be the control mechanism for the adsorption of DBP by the individual component. Moreover, FTIR spectra suggested that cell wall proteins, phosphate and CH₂ groups involved in DBP adsorption on Bc, and DBP interacted with minerals through H-bonding between CO groups and adsorbed H₂O.