Experimental Study On Liquid-phase Adsorption And Separation Performance Of Metal-organic Frameworks Ang Their Composites

Wastewater treatment is an urgent problem to be solved.Among them,dyes and phenols are two kinds of substances that appear in wastewater.Because of their ubiquity and large treating amount,the ecological environment and the human body have brought great harm.How to deal with dye and phenolic wastewater,has led to more and more researchers thinking.Metal-organic frameworks(MOFs)have the advantages of high specific surface area and porosity,adjustable structural size,etc.,so they have a wide range of applications in gas storage and separation,liquid phase adsorption and separation,membrane separation,industrial catalysis,biomedicine,etc.In this work,we studied the effects of group functionalization on the adsorption and separation of dyes on the water-stable MOFs in water.At the same time,in order to make up for the high cost and poor stability of MOFs,we introduced graphene oxide(GO)into MOFs to synthesis composites,and we studied the adsorption of phenol in water.The concrete contents are as follows:(1)MIL-101(Cr)?MIL-101(Cr)-NH2 and MIL-101(Cr)-SO3H were prepared by hydrothermal method.The properties of the three materials were characterized by PXRD,BET and SEM.(2)The adsorption and separation of the cationic dye methylene blue(MB)and the anionic dye methyl orange(MO)on these three materials were systematically studied.The results showed that comparing with MIL-101(Cr),the sulfonate functionalized of MIL-101(Cr)-SO3H has a strong adsorption capacity for methylene blue(MB),the maximum adsorption capacity up to 1061 mg·g-1,and methyl orange(MO)is nearly not adsorbed.The adsorption thermodynamics of MB on these three materials is in accordance with the Freundlich adsorption model,while the adsorption thermodynamics of MO is in accordance with the Langmuir adsorption model.The adsorption kinetics of MB and MO are both in accordance with the pseudo-second-order kinetic model.Moreover,when at low concentration,MIL-101(Cr)-SO3H has a good separation effect on MB/MO mixture.In addition,when the initial concentration Co?800 mg·L-1,the removal rate of MB on MIL-101(Cr)-SO3H is up to 99%,so it can be used as a highly efficient adsorbent of methylene blue(MB).(3)Composite called GO@MIL-68(Al)was prepared by in situ synthesis method,and the structure and morphology of the composites were characterized by a series of characterization.Then,we studied the adsorption of phenol in water on GO@MIL-68(Al).The results showed that GO@MIL-68(A1)has better adsorption on phenol than raw materials GO and MIL-68(A1).The adsorption capacity of GO@MIL-68(Al)to phenol is increased by 128.1%compared with MIL-68(Al)at Co= 1000 mg·L-1.And the adsorption capacity of phenol is the highest when the GO content is 2%,which is 351 mg·g-1.In addition,even if cycling 5 times,the adsorption capacity can reach 95%of the first use.Hence,it can be used as a highly efficient adsorbent of phenol in water.