Research On Preparation Of UiO-66 Series MOFs And Graphene Oxide Composites And Their Removal Performance Of Pollutants In Water

With the social and economic development and progress,lots of production and living pollutants have entered the water environment,causing serious damage to the water ecology.Therefore,improving the water environment and developing materials to remove pollutants in water have become the top priority.Emerging metal organic framework materials(MOFs)have received extensive attention due to their large specific surface area,open metal active sites,and easy chemical modification.Among many MOFs,UiO-66 series MOFs have good thermal stability,acid-base stability,water stability,and functional group modification,so they become our first choice.Graphene oxide is a good adsorption material with a large specific surface area and has more hydrophilic functional groups.When it is combined with MOFs,it can provide more active sites for MOFs.Therefore,based on the development of UiO-66 series MOFs and graphene oxide composites,this paper has prepared UiO-66-(COOH)2/GO and GA-UiO-66-NH2 metal-organic framework composites and explored their adsorption performance for the pollutants tetracycline hydrochloride(TC)and Cr(VI)in water.Furthermore,the photocatalytic degradation performance of Cr(VI)by GA-UiO-66-NH2 was also explored.The specific research contents are as follows(1)In-situ growth method was used to combine UiO-66-(COOH)2 with graphene oxide(GO)nanosheets to form the UiO-66-(COOH)2/GO composite,which was used as an adsorbent to explore the study of the adsorption performance of organic pollutants TC in water.The maximum adsorption capacity of UiO-66-(COOH)2/GO for TC reached 164.91 mg/g,which was nearly five times higher than that of UiO-66(31.75 mg/g).The enhanced adsorption performance of UiO-66-(COOH)2/GO is predominantly attributed to increased adsorption active sites caused by the introduction of GO and carboxyl groups.In particular,the UiO-66-(COOH)2/GO adsorbent is pH-universal,showing ultra-high acid-base adsorption stability in an acidic,alkaline and neutral media(i.e.pH 1-11).The adsorption kinetics,isotherms and thermodynamics indicate that the adsorption model of TC on UiO-66-(COOH)2/GO conforms to the pseudo-second-order kinetic model and Langmuir model.The study of the adsorption mechanism indicated that the adsorption of TC by UiO-66-(COOH)2/GO is mainly chemical adsorption and accompanied by physical adsorption,including chemical bonding,?-?interaction and weak electrostatic adsorption effect.(2)UiO-66-NH2 was combined with graphene aerogel(GA)by in-situ growth method to form the GA-UiO-66-NH2 composite.The maximum adsorption of Cr(VI)in aqueous solution by GA-UiO-66-NH2 reached 75.34 mg/g,which is more than three times that of UiO-66(21.15 mg/g).The enhanced adsorption performance of GA-UiO-66-NH2 is predominantly attributed to increased adsorption active sites caused by the introduction of GA and amino groups.Through the investigation of adsorption kinetics,it can be found that the adsorption of Cr(VI)on GA-UiO-66-NH2 belongs to a pseudo-second-order kinetic model.In addition,GA-UiO-66-NH2 has good photocatalytic degradation performance.The 20 mg catalyst reached 100%degradation efficiency for 40 mL of 10 ppm Cr(VI)solution in 120 minutes.And after 3 consecutive cycle tests,the photocatalytic degradation performance of GA-UiO-66-NH2 did not decrease significantly.