Effectiveness of Aluminum‐based Drinking Water Treatment Residuals as a Novel Sorbent to Remove Tetracyclines from Aqueous Medium

Low levels of various veterinary antibiotics (VAs) have been found in water resources across the United States as a result of nonpoint‐source pollution. As the first phase of developing a potential green sorbent for tetracycline (TTC) and oxytetracycline (OTC), we examined the effects of solution chemistry, pH, ionic strength (IS), sorbate:sorbent ratio (SSR), and reaction time on TTC and OTC sorption by a waste byproduct of the drinking‐water treatment process, namely, Al‐based drinking‐water treatment residuals (Al‐WTR). The sorption of TTC and OTC on Al‐WTR increased with increasing pH up to pH 7 and decreased in the pH range of 8 to 11. A concentration of 20 g L −1 was deemed as optimum SSR, where more than 95% of the initially added TTC and OTC were sorbed and equilibrium was reached in 2 h. A pseudo–second‐order model ( R 2 = 0.99) was used for Al‐WTR sorption for TTC and OTC. The data best fit the linearized form of the Freundlich isotherm ( R 2 = 0.98). No significant effect ( p > 0.05) of IS on sorption of TTC and OTC was observed between 0.05 and 0.5 mmol L −1 . However, at higher initial concentrations (>1 mmol L −1 ), IS dependence on TTC and OTC sorption was observed. Surface complexation modeling and Fourier transform infrared spectroscopy analysis indicated the possibility of TTC and OTC forming a mononuclear monodentate surface complex through strong innersphere‐type bonds on Al‐WTR. The results show promising potential of Al‐WTR for use as a “green” and cost‐effective sorbent to immobilize and stabilize TTC in soils and waters.