Insight into the co-adsorption behaviors and interface interactions mechanism of chlortetracycline and lead onto struvite loaded diatomite

Finding effective methods for simultaneous removal of antibiotics and heavy metals has attracted increasing concerns. Herein, we investigated the co-adsorption behaviors of chlortetracycline (CTC) and Pb (II) onto struvite loaded diatomite (SD) in aqueous solution, and their interface interactions mechanism was investigated using crystal and microstructure analysis combined with density functional theory (DFT) calculations. The adsorption capacity at equilibrium of CTC increased from 44.28 to 87.58 mmol/kg with the presence of Pb (II), but the adsorption capacity at equilibrium of Pb (II) decreased from 4289.70 to 3559.9 mmol/kg with the presence of CTC. Besides, the effect of environmental factors (solution pH and humic acid) was also evaluated. Microstructure analysis for recovered products demonstrated that the interface interactions brought by the surface Pb(II) of Pb5(PO4)3OH and carbonyl-O of CTC could facilitate the removal of CTC but inhibit the removal of Pb(II) by suppressing the crystal growth of Pb5(PO4)3OH, especially the orientation growth of (0 0 1) crystal plane. DFT calculations gave theoretical support for the interface interactions between Pb5(PO4)3OH and CTC. Struvite loaded diatomite (SD) was used for simultaneously removing CTC and Pb (II). This work provides a new perspective for the study of the co-adsorption behaviors of CTC and Pb (II) onto SD. It indicates that the interface interactions brought by the surface Pb (II) of Pb5(PO4)3OH and carbonyl-O of CTC facilitated the removal of CTC but inhibited the removal of Pb (II) by suppressing the crystal growth of Pb5(PO4)3OH, especially the orientation growth of (001) crystal plane. DFT calculations gave theoretical support for the interface interactions between Pb5(PO4)3OH and CTC. [Display omitted] •Struvite loaded diatomite was used for simultaneous removal of CTC and Pb (II).•Microstructure analysis and DFT calculations were applied for mechanism study.•The presence of Pb (II) enhanced the adsorption of CTC onto SD.•Adhesion of CTC to the surface of Pb5(PO4)3OH suppressed the removal of Pb (II).•Effect of humic acid on the co-adsorption of CTC and Pb (II) onto SD was studied.