Efficient and selective recovery of Gd(Ⅲ)via polyethyleneimine modification of lanthanum-based metal-organic frameworks

With the development of the economy and the increasing demand for environmental protection,the efficient and selective recovery of Gd(Ⅲ)from actual wastewater is of critical importance.In this work,lanthanum-based metal-organic framework(LaBDC)materials were prepared by a hydrothermal method,and then polyethyleneimine(PEI)and LaBDC were combined by an impregnation method to form a novel LaBDC@xPEI composite.The prepared materials were characterized using Fourier transfo rm infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDX),B runauer-Emmett-Teller(BET),thermogravimetric analysis(TGA)and X-ray photoelectron spectroscopy(XPS).Experiments show that LaBDC@50%PEI has the highest adsorption capacity(181.77 mg/g)among lanthanum-based MOFs with different PEI loadings at pH=5.5,which is about 5.1 times that of bare LaBDC.The adsorption isotherm analysis shows that LaBDC@50%PEI follows the Langmuir model.In addition,the adsorption kinetics of LaBDC@50%PEI follows a pseudo-second-order kinetic model,indicating that the adsorption process is chemical adsorption.It is worth noting that LaBDC@50%PEI maintains good adsorption performance and stability after three recycling tests,and exhibits excellent selectivity in cation interference experiments.Overall,the LaBDC@50%PEI composites possess good stability and hold great promises in rapid recovery of Gd(Ⅲ)from practical aqueous environments.

Synthesis and properties of hyper-dispersants

The synthesis and properties of three kinds of hyper-dispersants are studied in this paper, which are non-terminated, carboxyl-terminated and polyethylene imine grafted poly（hydroxyl carboxylic acid） ester. The hyper-dispersants are synthesized by the materials of 12-hydroxy-stearic acid, stearic acid and polyethylene imine, which are used to improve the dispersion properties of nano titanium dioxide （nano-TiO2） in low-concentration resin solution system. The influences of hyper-dispersants on the viscosity and stability of the system are studied. It is found that polyethylene imine grafted hyper-dispersant has the best dispersion performance in nano-TiO2 dispersion system, and the optimal content of the hyper-dispersant is 4%.