Adsorption of Ag+ by persimmon tannins immobilized on collagen fiber

In the present work, a novel adsorbent to effectively adsorb Ag+ from an aqueous solution has been prepared by immobilizing persimmon tannin (PT) on collagen fiber. The adsorption capacity of Ag+ on the immobilized PT were evaluated under various treatment conditions, including the initial solution pH, solid-liquid ratio, temperature, and initial concentration of Ag+. The results showed that the effect of initial solution pH, solid-liquid ratio, and initial concentration of Ag+ on the adsorption capacity were remarkable, while the influence of temperature was insignificant. The adsorption capacity reached 1947 mg/g at 303 K and pH 7.0 when the initial concentration of Ag+ was 800 mg/L and solid-liquid ratio was 0.4. Adsorption equilibrium isotherms of Ag+ on the surface of the adsorbent fibers were studied using Freundlich and Langmuir isotherms. The experimental data fitted best to the Freundlich models. Also, the immobilized PT before and after adsorption of Ag+ was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, and scanning electron microscopy. All these results indicated that the immobilized PT adsorbed efficiently and could be used as a low-cost alternative for the adsorption of Ag+ in wastewater treatment.