POSS-crosslinked poly(vinylphosphonic acid) for efficient adsorptive removal of uranium (VI) from nuclear wastewater

Organophosphorus acid polymers with high hydrophilicity and limited swelling capacity have great application potential in disposal of uranium (VI)-containing wastewater due to its high uranium (VI) adsorption efficiency. In this work, POSS-crosslinked poly(vinylphosphonic acid) polymer is synthesized via copolymerization of octavinyloctasilasesquioxane and vinylphosphonic acid for uranium (VI) adsorptive removal from solution. The polymer has a high hydrophilicity and limited swelling capacity. The uranium (VI) adsorptive removal is performed in batch mode and the effects of polymer dosage, pH and ionic strength are investigated. The polymer shows high removal efficiency for uranium (VI) from a 120 mg L−1 solution and can achieve the complete uranium (VI) removal at 30 °C and pH 4.0 with 0.33 g L−1 polymer. The adsorption process is analyzed by comparison with the adsorption kinetic and isotherm models. Uranium (VI) adsorption on this polymer is found to be more consistent with the pseudo-second-order and Langmuir models, and the maximum adsorption capacity attains 714 mg g−1. Competitive adsorption between uranium (VI) and other metal ions on polymer is performed to analyse the adsorption selectivity. The polymer attains a 20 L g−1 uranium (VI) distribution coefficient, higher than other metal ions (0.1–1.8 L g−1). The polymer can be easily recycled for at least five times with removal efficiency above 99% and the polymer can be well applied for dynamic adsorptive removal of uranium (VI) from uranium-containing solution (5 mg L−1) in a fixed-bed column with removal efficiency above 99%. The excellent uranium (VI) removal performances of this composite polymer highlight its great potential in the disposal of uranium-containing nuclear wastewater.