Preparation and application of nano dendritic polyurethane for high-efficiency boron adsorption

Boron adsorbents with high adsorption capacities have long been a focus of research for a long time. This study used small molecular polyols with different hydroxyl groups as functional monomers and as end-capping agents, functional dendritic polyurethanes with nano structure were successfully prepared by one-pot method. The single molecule size and surface morphology were characterized by dynamic light scattering, transmission electron microscopy and scanning electron microscopy, and the molecular size in the dry state was 11 to 18 nm. The prepared materials were used as the boron adsorbents, and the effects of pH, time, boron solution concentration and temperature on the adsorption were studied. The results showed that the capacity of adsorbed boron could reach 110–130 mg·g –1 . Adsorption was a homogeneous monolayer adsorption controlled by chemisorption, and adsorption thermodynamics showed that was a spontaneous endothermic process. Adsorption behavior was best described by the pseudo-second-order kinetic model and the Langmuir isotherm. This study also showed that it was difficult for ortho/meta-hydroxyl groups to chelate with H 3 BO 3 and other polyborates, and the chelates mainly had good chelating properties with B(OH) 4 – , and the chelates formed had large steric hindrance. At the same time, increasing the number of hydroxyl groups of functional monomers was beneficial to increase the adsorption capacity of materials. In addition, the cyclic adsorption/desorption experiments showed that DPUs have good cyclic stability. At the same time, the adsorption results of the original salt lake brine showed that other metal ions in the brine had little effect on the adsorption of boron, and the adsorption capacity was as high as 52.93 mg·g –1 , and the maximum adsorption capacity was obtained by Adams–Bohart model to 58.80 mg·g –1 . The outstanding selectivity and adsorption capacity of these materials have broad potential application, and are expected to be used for the efficient adsorption and removal in boron-containing water bodies.