PEI-grafted boron-selective adsorbent with synergistic adsorption effects

This work presents a novel strategy for the development of boron-selective adsorbent with synergistic adsorption effects, which is achieved by using tannic acid (TA) modified MoS2 nanosheets to graft polyethyleneimine (PEI) onto the boron-selective resin (BSR), preparing the BSR-MoS2-TA/PEI composite material, and leveraging the unique interlayer structure of molybdenum disulfide (MoS2) nanosheets to reduce the resistance of H2O transport, thereby effectively exerting the synergistic adsorption effects of BSR and PEI. The influencing factors of boron adsorption by BSR-MoS2-TA/PEI, such as the PEI grafting amount, adsorbent dosage, pH value, and competitive anions, were investigated. The results revealed a maximum adsorption capacity of 31.10 mg·g-1 at 35°C, which is significantly higher than that of the commercial BSR (5.9-7.2 mg·g-1). The fitting results of adsorption kinetics, isotherms, and thermodynamics demonstrated the characteristics of boron adsorption by BSR-MoS2-TA/PEI, and the adsorption process conformed to the pseudo-second-order kinetic model and the Langmuir model. Owing to the outstanding stability of the BSR substrate, BSR-MoS2-TA/PEI could undergo at least five cycles of adsorption. The mechanism of boron adsorption mainly encompassed complexation, electrostatic attraction, and hydrogen bond formation.