Co-doped NH2-UiO-66 for fast and effective adsorption of oxytetracycline: Kinetics, thermodynamics and mechanism

Novel type of micro mesoporous materials Co-doped NH 2 -UiO-66 had been successfully prepared. The properties of the material were understood through a series of characterization. When the dosage of Zr:Co is 2:1, the modified material showed specific surface area of 840.02 m 2 ∙g −1 , which is larger than the material without Co. Especially, the material was transformed from microporous NH 2 -UiO-66 to micro-mesoporous Co-doped NH 2 -UiO-66 through the adjustment of metal Co. The Co-doped nanocomposite was then applied to the adsorption of oxytetracycline. The effects of initial concentration, pH, humic acid and ionic strength on the adsorption were investigated. It was found that 50 mg∙L −1 oxytetracycline can be effectively adsorbed by Co-doped NH 2 -UiO-66 in pH 7. Further research showed that adsorption was pseudo-second-order kinetics and fitted Freundlich model with the maximum adsorption capacity 223.7 mg∙g −1 . In addition, the adsorption equilibrium time was only 2 h, which is shorter than the adsorption time of most adsorbents. The mechanism of pore adsorption, π-π interaction, hydrogen bonds and electrostatic interactions was deeply discussed. In conclusion, Co-doped NH 2 -UiO-66 was a fast and effective absorbent for the removal of oxytetracycline in aqueous solution.