Polyoxometalates as highly efficient adsorbents for ciprofloxacin removal: The key role of oxygen vacancies

Abstract

In this study, various silver phosphomolybdates (x-y-z-AgPMo) with oxygen vacancies were successfully prepared through H2 calcination and subsequent chemical precipitation and used for the adsorption of ciprofloxacin (CIP) in water. The microstructures of x-y-z-AgPMo were analyzed by a series of characterization methods. The effects of calcination time, calcination temperature, hydrogen flow rate, and external adsorption conditions on the adsorption performance were investigated. The results showed that the adsorption performance of 1–0.1–250-AgPMo toward CIP could reach 91% within 20 min with a maximum adsorption capacity of 45.5 mg∙g − 1, which was about 1.7 times as that of silver phosphomolybdate (Y-AgPMo) without H2 calcination. The improved adsorption performance of 1–0.1–250-AgPMo was mainly attributed to the presence of oxygen vacancies, which induced more negative surface charges and larger specific surface area in 1–0.1–250-AgPMo. This work provided an excellent adsorbent for CIP removal and forcefully confirmed the important role of oxygen vacancies in the adsorption process.