Controlled Synthesis Of Several Kinds Of Porous Composite Adsorbent And Their Simultaneous Selective Recovery Of Lithium And Rubidium

With the widespread use of lithium-ion batteries,the demand for lithium resources has surged.Although there are abundant lithium resources in seawater and salt lakes,the concentration of Li（I）in seawater is very low.Therefore,how to recover Li（I）from salt lakes brine is an urgent problem to be solved.Salt Lakes brine also contain some high-value metal ions such as Rb（I）,which have important applications in the fields of thermionic conversion,energy and medicine.In view of the difficulty in recovering Li（I）and Rb（I）from salt lakes brine,this paper improves the adsorption capacity and selectivity of Li（I）and Rb（I）through the functionalization of porous materials and the design of nanostructures.Studying the adsorption properties of Li（I）and Rb（I）,and the corresponding mechanisms were analyzed.The application of these materials in the recovery of Li（I）and Rb（I）from salt lakes brine was researched.The main research contents are as follows:（1）Fixing the lithium manganese ion sieve（HMO）on mesoporous silica films,then the Rb（I）ion-imprinted layer was grafted onto the surface of mesoporous silicon films.The prepared independent bifunctional mesoporous films（DIMFs）was used as an adsorbent to study the adsorption properties of Li（I）and Rb（I）.The surface morphology and structure of DIMFs were characterized through series of methods.DIMFs has the highly uniform pore size and good cell connectivity.Under optimal conditions,the saturated adsorption capacities of DIMFs for Li（I）and Rb（I）were 6.30mg g^-1 and 6.21 mg g^-1,respectively.The adsorption process of Li（I）and Rb（I）accords with the Pseudo-second-order kinetic equation and the Langmuir isotherm equation（R²>0.99）.Moreover,the adsorption capacity after five adsorption-desorption cycles was about 81⁸2%of the first time,exhibiting excellent reusability.HMO and ion imprinting help DIMFs reach adsorption equilibrium in a short time and maintain excellent adsorption efficiency.The use of green template（cellulose nanocrystals,CNCs）also can reduce environmental pollution.As an effective adsorbent for the simultaneous selective extraction of Li（I）and Rb（I）,DIMFs has great potential in industrial applications.（2）The uniform particle size mesoporous hollow silicon sphere（HS）was firstly synthesized by a simple surfactant-directed sol-gel method.Then manganese-based lithium ion sieve（HMO）was supported on the surface of the silicon sphere by the dipping method and（3-aminopropyl）triethoxy silane（APTES）was finally modified.The obtained modified mesoporous hollow silicon sphere adsorbent（APTES/HMO-HS）was used as an adsorbent to study the adsorption properties of Li（I）and Rb（I）.APTES/HMO-HS has an inorganic-organic composite framework,high specific surface area,uniform particle size（200 nm）and mesoporous hollow structure.It indicates that the immobilization of HMO and APTES has no effect on the mesoporous hollow structure.At the pH value of 6.0,the adsorption capacity of APTES/HMO-HS reached a maximum of 1.22 mg·g^-1 to Li（I）and 8.31 mg·g^-1 to Rb（I）.Comparing the correlation coefficient（R²）,the adsorption process of Li（I）and Rb（I）by APTES/HMO-HS is more in line with the Pseudo-second-order kinetic equation and the Langmuir isotherm equation.The"ion sieve"effect of lithium ion sieve（HMO）makes APTES/HMO-HS have great selectivity for Li（I）.Due to the similar size,APTES with an amino group can combine with Rb（I）to form a stable chelate.Thus,APTES/HMO-HS performs high efficiency and selectivity for the adsorption of Li（I）and Rb（I）.（3）Cellulose nanocrystals（CNCs）were used as templates to prepare silica films by doping imprinted p-carboxyphenyl azocalix[4]arene（IPCA4A）by simple evaporation self-assembly method.After that,the imprinted calix[4]arene（IC4A）was loaded on the surface of the silicon films by the dipping to obtain double-imprinted porous silicon films（DIMFs）.And DIMFs was used as an adsorbent to study the adsorption properties of Li（I）and Rb（I）.DIMFs reached the maximum adsorption capacity of 16.07 mg·g^-1 to Li（I）and 10.59 mg·g^-1 to Rb（I）at pH=6.0 and 25°C.The adsorption process of DIMFs conforms to the Pseudo-second-order kinetic equation and the Langmuir isotherm equation（R²>0.99）.After five adsorption-desorption cycles,the adsorption capacity was about 85%of the first time.The ring size of PCA4A and C4A is exactly matched with lithium ion and rubidium ion,respectively.Combined with ion imprinting technology,DIMFs can efficiently and selectively adsorb Li（I）and Rb（I）.The prepared DIMFs are structurally stable,separated easily,environmentally friendly,with excellent selectivity and repeatability,providing a new direction for the simultaneous selective extraction of Li（I）and Rb（I）.（4）Using carbon nanotubes,γ-（2,3-epoxypropoxy）propytrimethoxy silane（KH560）,and 4-tert-butylcalix[4]arene（TB4A）as raw materials,an imprinted porous adsorbent（ITB4ABC）was prepared by chemical bonding in combination with ion imprinting.ITB4ABC was used as an adsorbent to study the adsorption properties of Li（I）and Rb（I）.The surface morphology and structure of DIMFs were characterized through series of methods.It was found that with the truncating of MWCNTs,the entanglement and agglomeration phenomenon was alleviated.The original hollow tubular structure was not damaged.The adsorption kinetics of ITB4ABC for Li（I）and Rb（I）follows the Pseudo-second-order kinetic equation.Moreover,the Langmuir isotherm equation can fit well to the isothermal adsorption data of ITB4ABC（R²>0.99）.The adsorption capacity of ITB4ABC at the fifth adsorption-desorption cycle was approximately 90%of the first time.All above results demonstrate that ITB4ABC has high adsorption capacity,specificity and reusability for Li（I）and Rb（I）.