Preparation Of Chitosan-based Adsorbents And Study On Adsorption Performance Of Rare Earth Metal Ions

Rare earth metals?REMs?,with superior catalytic,optical and magnetic performances,place a high value on the field of chemical engineering,nuclear energy and high temperature superconductors.At present,there is a serious supply crisis in rare earth resources.Therefore,it is of great significance to study how to purify REMs from waste and successfully recycle them,so that the sustainable development of REMs can be achieved.Compared to the traditional methods of separation of REMs includeing precipitation method,liquid-liquid extraction method and so on,the adsorption,possessing easy process,low-cost,without secondary pollution,is a green and sustainable method.In this paper,we combined multifunctional monomers,the chitosan-based materials and the ion-imprinted technology to explore new and green adsorbents for selective adsorption of REMs.The relationship of structure,chemical composition,surface properties of adsorbents and adsorption performance were studied.And the intrinsic mechanisms and behaviours existed in the adsorption process were explored deeply.The dominating research works of this paper are as follows:?1?A magnetic adsorbent was first prepared via a simple "surface deposition-stepwise grafting"method.The results show that the adsorption capacities of representative Dy³⁺,Nd³⁺ and Er³⁺ to as-obtained FCCD are about 28.3 mg g^-1,27.1 mg g^-1 and 30.6 mg g^-1,respectively,at 25 °C and optimal pH?7.0?.Experimentally,FCCD has a specific surface area of 20.86 m2g^-1 and a saturation magnetic value of 63 emu g^-1.The inner layer of FCCD is composed of hydrophobic n-octadecyltriethoxysilane,which can effectively avoid the magnetic leakage of FCCD in the regeneration process.The as-synthesized adsorbent?FCCD?can be regenerated and reused using 0.05 M hydrochloric acid as the eluent,and the remarkable magnetic response capability is conducive to the subsequent magnetic recovery and separation of FCCD.?2?A novel ion-imprinted membrane material?II-MAC?with interconnected macroporous structure was firstly prepared by a simple solution evaporation method for the selective extraction of Dy³⁺.Adsorption experiments show that the maximum adsorption capacity of II-MAC to Dy³⁺ is 23.3 mg g^-1 in the optimal pH?7.0?at 25 °C.II-MAC shows superior selectivity to Dy³⁺.Moreover,II-MAC can be easily retrieved due to the membrane structure.The reusability tests demonstrate that II-MAC possesses good regeneration capacity.This work not only provides a more straightforward and high-efficiency means in selective extraction of Dy³⁺,but also promotes the development of green and sustainable material.?3?A novel Gd³⁺ imprinted membrane material?II-CPNP?with porous structure was prepared by one-step polymerization-evaporation method,which was applied to selective adsorption of Gd³⁺.Saturation adsorption capacity for Gd³⁺ is 23.0 mg g^-1 at 298 K,pH?7.0?.The distribution coefficient relative to Gd³⁺ is 353.1 mL g^-1.Compared to other adsorbents,II-CPNP not only has a higher adsorption capacity,but also has efficiently selective capability for Gd³⁺.The flexible membrane structure of II-CPNP is conducive to the subsequent recovery and separation of the adsorbent,avoiding a greater loss of quality.Test of reusability has demonstrated that II-CPCP can be recycled and its regeneration performance is good.Moreove,II-CPNP is made of non-hazardous materials such as chitosan,carboxylated carbon nanotubes and some simple processes.Therefore,II-CPNP is a green and economical adsorbent.