Tannin modified aminated silica as effective absorbents for removal of light rare earth ions in aqueous solution

A series of novel absorbents (SiO2-BT, SiO2-BWT and SiO2-BT and BWT) were prepared by immobilizing plant tannins onto amine-modified silica. The as-prepared absorbents were characterized by field emission scanning electron microscopy and Fourier transform infrared spectrometer. Subsequently, the absorbents were utilized for the removal of Pr3+ and Nd3+ from aqueous solution. We systematically investigated the influences of pH values, initial concentration of metal on the adsorption capacity, as well as the adsorption kinetics and adsorption isotherms. The obtained experimental results suggested that among these absorbents, SiO2-BT exhibited the best performances for the removal of both Pr3+ and Nd3+ in aqueous solutions. Under the optimum conditions, the adsorptive removal efficiency could reach the adsorption equilibrium just within 60 min, and the adsorption capacities of Pr3+ and Nd3+ on SiO2-BT were 329.2 and 341.5 mg/g, respectively. It was found that the adsorption kinetics was well described by the pseudo-second-order kinetic model while the adsorption isotherms followed the Langmuir adsorption model.