Preparation Of Carbon Materials Modified By Phosphate Groups And Their Adsorption Properties On In(Ⅲ)

Indium metal is an extremely rare,non-renewable and irreplaceable element.Currently,there are two main ways to obtain indium from nature,one is to refine it from metallic minerals and the other is to recycle it from waste materials.Phosphate group is a common anionic group,P-OH is easy to ion exchange and electrostatic attraction,commonly used to adsorb uranium,lead and other metal ions.Carbon is an extremely widely distributed element in the world,and materials with carbon skeletons can undergo oxidation reactions to obtain oxygen-containing functional groups on the surface of the material,resulting in modified materials based on carbon materials.Glucose,the most basic monosaccharide,can be obtained in large quantities from plants and is an excellent raw material for the preparation of carbon materials;carbon nanotubes,as one-dimensional carbon nanomaterials,have a large specific surface area and uniform pore structure,which are very suitable as a substrate for adsorbent materials.Therefore,in this paper,glucose and carbon nanotubes were used as carbon base materials to prepare three adsorbents for the efficient recovery of indium,and the adsorption properties of the materials were investigated through a series of adsorption experiments,and the adsorption mechanisms of the materials were investigated with the aid of different characterization tools.The details of the study are as follows:1.In this thesis,glucose carbon spheres were prepared by microwave-assisted synthesis,followed by pretreatment of activated carbon spheres with phytic acid and phosphoric acid,respectively,and two adsorbents,phytic acid-glucose carbon spheres（n-PA-MHC）and phosphoric acid-glucose carbon spheres（n-H₃PO₄-MHC）,were successfully prepared.The adsorption results showed that the adsorbent 5-PA-MHC had the best adsorption efficiency for In（Ⅲ）when the mass ratio of phytic acid to carbon spheres was 5:1,and the saturation adsorption capacity of the material was132.02 mg·g^-1 by Langmuir model fitting;the adsorbent 20-H₃PO₄-MHC was most effective when the mass ratio of phosphoric acid to carbon balls was 20:1,with a saturation adsorption capacity of 156.33 mg·g^-1.Both adsorption materials can reach adsorption equilibrium at 2 h and are in accordance with the proposed secondary kinetic model.The calculated thermodynamic data show that the adsorption of both materials is a spontaneous heat absorption process.Simulating the indium-containing feeds of electronic display（LCD）and sphalerite,it was found that from the LCD feed,5-PA-MHC could successfully separate In（Ⅲ）from Al（Ⅲ）and Zn（Ⅱ）;from the sphalerite feed,both materials could achieve the separation of In（Ⅲ）and Zn（Ⅱ）,Al（Ⅲ）,Mg（Ⅱ）and Ca（Ⅱ）,and the best selectivity for Zn with the selectivity factor（Sel）values of 3.69and 3.37,respectively.In addition,the dynamic adsorption experiment was also explored,and it was found that the maximum dynamic adsorption capacity of 5-PA-MHC to In（Ⅲ）could reach 10.25 mg·g^-1.The maximum dynamic adsorption capacity of 20-H₃PO₄-MHC to In（Ⅲ）was 5.62 mg·g^-1.The mechanism of indium adsorption by n-PA-MHC and n-H₃PO₄-MHC,as shown by Zeta potential and XPS characterization,is mainly the easy departure of negatively charged hydrogen ions on P-OH and the ion exchange of In（Ⅲ）in the adsorption solution through electrostatic attraction.2.To further improve the selectivity and cyclic regeneration performance of the material,a zirconium phosphate@carbon nanotube nano-limited material（n-ZrP@CNT）was prepared in this thesis using a top-down synthesis method as a means to improve the adsorption performance of the material.The results showed that the adsorption of In（Ⅲ）by the adsorbent 2.5-ZrP@CNT was best when the mass ratio of ZrOCl₂-8H₂O to carbon nanotubes was 2.5:1,and the saturation adsorption amount fitted by the Langmuir model could reach 173.19 mg·g^-1 at pH=2.5,and the adsorption equilibrium could be achieved within 6 h.The kinetics are in accordance with the proposed secondary kinetic model;the thermodynamic data indicate that the adsorption process is heat-absorbing and spontaneous.Simulating the coexisting ionic composition of LCD,nitric acid and sulfuric acid were used to dissolve the material respectively,and it was found that the Sel In/Fe value of the material was 1.65 under the nitric acid medium,which could successfully separate In（Ⅲ）and Fe（Ⅲ）,and the adsorbent could successfully separate In（Ⅲ）and Zn（Ⅱ）,Al（Ⅲ）,Mg（Ⅱ）,Ca（Ⅱ）regardless of the simulated LCD feed solution or sphalerite feed solution.separation.The cyclic elution performance of the material was also investigated and it was found that the material could be cyclically eluted seven times and the adsorption efficiency could reach more than 92%in all seven times.In addition,the dynamic adsorption experiments were investigated,and the results showed that the dynamic adsorption saturation amount of the material could reach 58.26 mg·g^-1,and the adsorption efficiency was 48.03%,which was about 1/3 of the static adsorption amount.The adsorption mechanism is that the hydrogen ion on P-OH in n-ZrP@CNT leaves negatively charged and adsorbs the In（Ⅲ）in solution by electrostatic attraction,and ion exchange occurs.In conclusion,2.5-ZrP@CNT is an excellent indium adsorbent with high practical application value.