Synthesis of N,O-rich active site porous polymers and their efficient recovery of Gd(Ⅲ) from solution

作者：Bin Xiao; Lijinhong Huang; Jiacai Ou; Bin Zeng; Zhiqiang Zou; Xiangrong Zeng; Wanfu Huang^*

来源：Journal of Rare Earths, 2023, 41(09): 1419-1428.

Our previous study found that the adsorption performance of porous carbon for Gd(Ⅲ) could be significantly improved by increasing the N,and O functional groups on its surface.Unfortunately,the adsorption capacity of porous carbon is low due to the limited number of N,and O functional groups that can be loaded on its surface.Due to the advantage of customizable functional groups of porous organic polymers(POPs),the triazine-based Tb-MEL and hydroxyl-modified triazine-based Tp-MEL were synthesized by a one-step hydrothermal method using nitrogen-rich melamine as the raw material and triformylbenzene(Tb) and 2,4,6-triformylphloroglucinol(Tp),respectively.The Gd(Ⅲ) adsorption isotherms and kinetic curves of Tb-MEL,and Tp-MEL at pH=6 and T=25℃ are in high agreement with the Langmuir isotherm(R2>0.998) and pseudo-second-order kinetics(R2>0.993),respectively.The fitted maximum adsorption capacity(qmax) is about 136.05 mg/g,much higher than 58.38 mg/g of Tb-MEL.The adsorption efficiency for Gd(Ⅲ) at pH=7 is close to 100%,and Tp-MEL maintains 62.4% of the initial adsorption capacity after ten cycle s of sorption/desorption of Gd(Ⅲ),with an average elution efficiency of more than 90%.Adsorption selection performance tests show that Tp-MEL has good adsorption selectivity for HREE ions,and the selectivity is as follows:Lu3+>Y3+>Gd3+>Nd3+>La3+>Al3+>Ca2+>Mg2+.Batch adsorption,Brunauer-Emmett-Teller(BET) method,and X-ray photoelectron spectrometer(XPS)tests show that hydroxyl modifications lose the specific surface area of the polymer,and the functional groups contribute more to the adsorption performance than the specific surface area.