Recovery of high value-added pharmaceutical intermediate tenofovir from pharmaceutical wastewater by magnetically recoverable Fe₃O₄@SiO₂@La(OH)₃

To recover the high value-added pharmaceutical intermediate tenofovir from wastewater efficiently and conveniently, a tailored magnetic composites of Fe₃O₄@SiO₂@La(OH)₃ have been prepared via solvothermal and in-situ reduction methods. It exhibits the ability to remove tenofovir with high efficiency and easily separated from matrix. Batch sorption experiments demonstrated that Fe₃O₄@SiO₂@La(OH)₃ can remove tenofovir with the maximum adsorption capacity of 64.53 mg/g, the largest removal of 93.07%, and fast equilibrium time of 5 min. The kinetics of tenofovir adsorption on the magnetic composite is in line with the pseudo-second-order model, while the isotherm is fitted well by the Langmuir model, and thermodynamic parameters represent that adsorption process is spontaneous and endothermic. Moreover, the saturated Fe₃O₄@SiO₂@La(OH)₃ have been desorbed by mechanical stirring with the high desorption rate of 93.02%, and the adsorption capacity maintaining 47.72 mg/g after five cycles. Importantly, the composites can be used for tenofovir removal from crude extracts of pharmaceutical wastewater, with an adsorption capacity of 51.61mg/g in 5 min. Finally, the adsorption mechanisms are explored by pH experimental evidence and XPS analysis, which show that mainly involve electrostatic attraction and the inner-sphere complexation between La(OH)₃ and phosphate groups of tenofovir via ligand exchange. All the results prove that the proposed tenofovir recovery technique, providing new ideas for the recovery of high value-added substances and waste resources rationalization of the application of development.