Construction Of Three-dimensional Ion-imprinted Mesoporous Silicon-based Materials And Their Adsorption Behavior On Rhenium And Gallium

In this paper,a series of three-dimensional biomass/mesoporous silica-based composite adsorbents were successfully constructed by one-step method using ion-imprinting technique,the structure and properties of the materials were characterized.The rare metal ions rhenium and gallium are selectively separated as follows:Glutaraldehyde and chitosan were used as template ions,crosslinkers and monomers in the imprinting process,three-dimensional mesoporous silica KIT-6was constructed with TEOS as silicon source.A three-dimensional molybdenum-imprintedchitosan/mesoporoussilicacompositematerial I-CTS-KIT-6 was synthesized.The adsorption experiment showed that the I-CTS-KIT-6 had good adsorption capacity for Re?VII?under pH 3.Moreover,the equilibrium isotherms were in accordance with Langmuir model and the maximum adsorption capacity was 389.76 mg·g^-1,which was significantly higher than N-CTS-KIT-6.The adsorption mechanism is determined by FT-IR and XPS analysis:the chelation between R-NH₃⁺,-N=C and ReO₄^-and the electrostatic attraction between R-NH₃⁺and ReO₄^-.It can be seen from the results of selective experiments that the adsorption rate of I-CTS-KIT-6 is slightly reduced in the presence of different high concentrations of Cl^-,NO₃^-,SO₄^2-,SO₃^2-anions,but still can reach More than 80%;in the mixed system of Zn?II?,Cu?II?,Fe?III?and Mn?II?,I-CTS-KIT-6 still has good selectivity and can make up for the problem that N-CTS-KIT-6 has low selectivity in Cu/Re separation.Moreover,it has potential application value through six adsorption/desorption cycles.In order to deeply explore the adsorption performance of three-dimensional ordered mesoporous silicon matrix composites on rare metal ions,TEOS was used as a silicon source,gallic tannin was used as the adsorption source and glutaraldehyde as the cross-linking agent.A three-dimensional gallic tannin/mesoporous silica composite material 1.2-PT-10-KIT-6 was successfully prepared by one-step method.The adsorption experiment showed that the maximum adsorption capacity of 1.2-PT-10-KIT-6 on gallium could reach 186.73 mg?g^-1under pH 10,and the equilibrium isotherms were in accordance with Langmuir model.The 1.2-PT-10-KIT-6 has good selectivity for gallium in the binary system of Ga/Ge and Ga/As.The adsorption mechanism was confirmed by FTIR and XPS,it was found that O-Ga bond was formed between the phenolic hydroxyl group of1.2-PT-10-KIT-6 and Ga?OH?₄^-under alkaline conditions.The O atom also chelated with Ga?OH?₄^-to form chelates.In order to improve the adsorption capacity and selectivity of the adsorbent,a three-dimensional gallic tannin/mesoporous silica composite material combined with ion imprinting technology.TEOS,gallium,glutaraldehyde is used as the silicon source,template ion,crosslinking agent,respectively.The concentration of the template ions was determined to be 150 mg·L^-1 during the preparation.The adsorption selectivity in the binary system of Ga/Ge and Ga/As is better than that of the non-imprinted adsorbent N-PT-KIT-6.The adsorption experiment found that the maximum adsorption capacity of I-PT-KIT-6@150 was 286.50 mg?g^-1,which was significantly higher than the maximum adsorption amount of N-PT-KIT-6.The adsorbent has good cycle performance through six cycles of elution experiments.