Construction of adsorptive nanorods from polyoxometalates and ionic liquid and their adsorption properties for silver ion from AMD

A new structure of hybrid nanorods adsorbent ([n-BBIM]₉PW₉O₃₄) was synthesized by a simple molecular assembly of polyoxometalates with ionic liquids (ILs). The nanocomposite was characterized by Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis), scanning electron microscope, energy dispersive X-ray and X-ray diffractometer. Adsorption of silver from acid mine drainage (AMD) was studied using batch experiments. The impact of several parameters, like ion concentration, pH, adsorbent dosage, and temperature was elucidated and optimization was carried out by single-factor experiment and response surface methodology. Analysis of variance of the quadratic model suggested that experimental data were excellently fitted to the quadratic model. Optimum conditions for removal of Ag⁺ from AMD were determined to be an initial concentration 143 mg/L, adsorbent dosage 2.69 g/L, temperature 35 °C to achieve the maximum adsorption of Ag⁺ 99.03%, which was very close to the predicted value (100%). The adsorption was confirmed as oxidation-reduction mechanism following a complexation process, and has been verified according to results from FT-IR and UV-vis spectra. The selective experiment suggested that the nanorods adsorbent could adsorb silver ions in AMD well. Based on the adsorption/desorption study result, the adsorbent can be efficiently recovered.