Removal of boron and silicon by a modified resin and their competitive adsorption mechanisms
To prevent the negative effects of both elements in water utilization process, a new diol type T-resin was prepared by a grafting method and investigated the application properties. This resin exhibited good adsorption properties for both boron and silicon in a wide pH range. The adsorption capacity of boron was 21.25 mg/g (1.97 mM/g), which was much higher than those for other modified resins with polyol functional groups. The adsorption capacity of silicon was only 8.36 mg/g (0.30 mM/g), which was lower than boron, suggesting that the adsorption of one molecule of silicic acid required more adsorption sites than the adsorption of one molecule of boric acid. Boron and silicon were competitively adsorbed on T-resin, and the silicic acid molecule replaced boron adsorbed on the resin, indicating a more stable adsorption of silicon compared to that of boron. Different complex types were observed in the complexation reaction involving the adsorption of boron and silicon on resin. While boron was adsorbed via triangular and tetrahedral complexes, silicon was only adsorbed via an octahedral complex. T-resin could be reused after regeneration, and showed a good performance for boron or silicon removal after multiple regeneration cycles.