Preparation Of ZIF-8-derived Carbon And Its Modification For Heavy Metal Ion Adsorption Studies

Due to the high specific surface area and large pore volume of the ZIF-8derived carbon material,it is used as an efficient and recyclable adsorbent for the removal of pollutants.However,the common morphology of ZIF-8 has small specific surface area,and it's derived carbon has lower adsorption active sites,the selective adsorption capacity is weak.In this paper,Non-solvent thermal method was used to prepare ZIF-8 with different morphologies,and the influence of different factors on the morphology of ZIF-8 were explored;ZIF-8 derived carbonwith new morphological structurewas modified by the Hummer method.Then the final materials were used to adsorb Pb²⁺in water.The main research contents of this paper are as follows:(1)First,we explored the influence of different factors on the morphology of ZIF-8,and obtaind the best preparation conditions;New complexes2,2'-bipyridinewith different coordination capabilities were introduced.Then the amount of 2,2'-bipyridine and 2-methylimidazole was regulated.According to the preparation mechanism of ZIF-8,ZIF-8 with octahedral was prepared by the Non-solvent thermal method.Dodecahedron and octadecahedron ZIF-8 with different particle sizes were prepared by adjusting the ratio of 2,2'-bipyridine and2-methylimidazole.And the nitrogen adsorption and desorption data showed that the octahedral ZIF-8 had a microporous structure with the largest specific surface area,and the pore size was mainly about 1.5 nm.(2)The dodecahedron and octahedral ZIF-8 with different particle diameters were directly carbonized to prepare ZIF-8-derived carbon.Finally,the modified Hummer method was used to treat the different particle diameters.The octahedral ZIF-8 derived carbon was oxidized and modified to obtain 1:1 ZO and 1:2 ZO.Scanning electron microscopy showed that the morphology of materials did not change after carbonization and oxidation.The final materials after carbonization and oxidation had a porous structure and obtained a wide pore size distribution,which was conducive to the adsorption of heavy metal ions.(3)The materials 1:1 ZO and 1:2 ZO were used to adsorb Pb²⁺.The effects on the removal of Pb²⁺ions from the material were respectively explored.The best conditions for obtaining 1:1 ZO to adsorb Pb²⁺ions are m=20 mg,t=16 h,C₀=15mg/L,p H=3;the best conditions for 1:2 ZO material to adsorb Pb²⁺ions are m=15 mg,t=18 h,C₀=15 mg/L,and p H=4.The adsorption mechanism of derivatized carbon materials on Pb²⁺ions was described,and the quasi-second-order kinetics was more suitable for describing the adsorption kinetics of materials on Pb²⁺ions,indicating that chemical adsorption played a leading role;and the fitted isotherm adsorption curve was more consistent with Langmiur adsorption model,and obtained the maximum adsorption capacity of modified derivative carbon materials for Pb²⁺ions were 7.66 mg/g(ZO)?15.52 mg/g(1:1 ZO)and 17.8 mg/g(1:2 ZO).