Coadsorption of Cu(II) and tylosin/sulfamethoxazole on biochar stabilized by nano-hydroxyapatite in aqueous environment

Antibiotics and heavy metals are frequently detected simultaneously in water environment. In this study, a biochar stabilized by nano-hydroxyapatite (nHAP@biochar) was used for the coadsorption of tylosin (TYL)/ sulfamethoxazole (SMX) and Cu(II) in aqueous environment, which was well suited for real water samples. The physicochemical properties of nHAP@biochar were characterised by SEM image, zeta potential, FTIR, BET analysis, XPS and XRD. The pseudo-second-order model was better fit for the sorption kinetics data. Background electrolytes, ionic strength, humic acid (HA) and addition sequences presented a significant effect on the adsorption of TYL/SMX and Cu(II) when with or without Cu(II). The adsorption of TYL and Cu(II) increased with the increasing of ionic strength and HA, and compared with TYL, the influence on SMX was not obvious. Adsorption results exhibited that TYL obviously enhanced the Cu(II) adsorption capability and Cu(II) obviously enhanced the SMX adsorption capability. According to the results of FTIR and XPS, H-bond may be one of the main interactions of TYL with nHAP@biochar adsorption and weak p-p interactions and H-bond were two of the main interaction of SMX. TYL/SMX-Cu complexes were formed. In the system, the complexes were more on the formation of nHAP@biochar-TYL-Cu and nHAP@biochar-Cu-SMX, rather than on nHAP@biochar-Cu-TYL and nHAP@biochar-SMX-Cu, respectively.