Radiation Preparation Of Functionalized Cellulose Microspheres And Their Application In Separation Of Valuable Metals

The electronic waste and slag pose a threat to the environment and human beings during the development and utilization of gold,gallium,indium,molybdenum,rhenium,bismuth and other metal resources.Nevertheless,electronic waste and slag are important sources of valuable metals.The recovery of high value-added products from secondary resources is an effective way to alleviate the resource and environment crisis.Compared with other methods,adsorption is a generally preferred method for metal ions recovery because of its simple operation and suitability for low concentration treatment.However,there are still some drawbacks in adsorption materials,such as high cost,low adsorption capacity,poor selectivity,and difficulty in filling and using in column experiments.Microcrystalline cellulose microspheres with abundant reserves,biodegradability and low cost were selected as the substrate in this paper in order to solve the above problems.The various types of polyhydroxy compounds and functional monomers containing sulfur and nitrogen were introduced into cellulose microspheres via electron beam pre-irradiation technology.In addition,the modified cellulose microspheres were applied in adsorption column,slag and actual groundwater to evaluate their potential for practical application.The following are the key research findings of this paper:（1）The four kinds of purine modified adsorbents were obtained by ring-opening reactions between glycidyl methacrylate grafted cellulose microspheres using electron beam pre-irradiation technology and guanine,xanthine,hypoxanthine and adenine.The adsorbents possessed fast adsorption kinetics for Au（Ⅲ）with the maximum theoretical adsorption capacity of 307.69～510.20 mg/g.The four adsorbents also exhibited excellent regeneration and selectivity.The interactions between the four purine modified adsorbents and Au（Ⅲ）were chelation,ion exchange and oxidation-reduction according to mechanistic studies.（2）Pentaethylenehexamine was introducd onto cellulose microspheres via electron beam pre-irradiation technology to develop nitrogen-containing adsorbent（N-CM）.Then,NS-CM containing high-density sulfur and nitrogen was synthesized by nucleophilic substitution reaction between N-CM and ethylene sulfide.Compared with N-CM,NS-CM exhibited ultrahigh adsorption capacity（4656.9 mg/g）for Au（Ⅲ）.The column adsorption capacity reached 3110 g/L in the simulated acidic waste liquid.Finally,NS-CM was able to efficiently and selectively recover trace Au（Ⅲ）from the actual gold slag leaching solution with adsorption efficiency of 95.17%.（3）The tannic acid functionalized cellulose microspheres（MCC-g-GMA-TA）prepared by electron beam pre-irradiation technology could efficiently recover Ga（Ⅲ）and In（Ⅲ）.The maximum theoretical adsorption capacity for Ga（Ⅲ）and In（Ⅲ）was 26.55 and35.61 mg/g at p H=3,respectively.In addition,MCC-g-GMA-TA displayed excellent selectivity for Ga（Ⅲ）and In（Ⅲ）even in the presence of more competing ions.The hydroxyl groups on MCC-g-GMA-TA coordinated with Ga（Ⅲ）and In（Ⅲ）in the adsorption process.（4）The electron beam pre-irradiation technology was employed to synthesize gallic acid modified cellulose microspheres（MCGA）,which was applied to separate Mo（VI）and Re（VII）.It was found that the separation factorβ_{Mo（VI）/Re（VII）}of MCGA for Mo（VI）and Re（VII）in the blend system was 5.23～735.53 under different p H conditions,while the optimum separation factor at p H=2.Furthermore,the step-by-step elution of Mo（VI）and Re（VII）can be realized by various eluents.Mo（VI）was captured by coordination and hydrogen bonding,while Re（VII）was mainly related with MCGA by hydrogen bonding.（5）The three novel adsorbents（MCGA,MCPC and MCSA）with polyhydroxy structure were prepared by introducing gallic acid,protocatechuic acid and shikimic acid onto cellulose microspheres using electron beam pre-irradiation.The theoretical adsorption capacity of MCGA and MCPC for Bi（Ⅲ）was 155.28 and 93.46 mg/g,respectively,which was significantly higher than that of MCSA for Bi（Ⅲ）（3.90 mg/g）.DFT calculation was employed to explore the effect of the difference in the type and amount of hydroxyl groups on adsorption capacity.In addition,MCGA and MCPC could efficiently adsorb trace Bi（Ⅲ）from actual groundwater.