Preparation Of Bimetal-organic Frameworks And Their Adsorption Performance Towards Phosphate From Water

Phosphorus is an indispensable nutrition for biological growth,while it would cause water eutrophication when its concentration exceeds a threshold.As one of classic technologies,adsorption has always been a research focus and hotspot in the water treatment field.MOFs have unique organic-inorganic hybrid structures,large specific surface areas,regular pore structures,and easy functionalized property.In this study,three new adsorbents of bimetallic MOFs were synthesized by hydrothermal/solvothermal method.By studying their microstructure and physicochemical properties,their phosphorus adsorption properties were compared and analyzed,the formation mechanism of metal doping was clarified,and the mechanism of phosphate enhanced adsorption was explored.The main results were listed as below:A novel MIL-100(Fe/Ce)was firstly fabricated by a solvothermal reaction.Scan electron microscope(SEM)observations suggested MIL-100(Fe/Ce)consisted of irregular polyhedrons with the sizes ranging from several to tens of micrometers and that that Ce atoms were successfully doped into MIL-100(Fe)frameworks,and a bimetal-MOF was thus formed.The adsorption capacity was 12.03 mg/g.By various characterization,the adsorption mechanisms were deeply explored.For MIL-100(Fe/Ce),the introduction of Ce increased the number of new active sites and surface hydroxyl groupsThe precipitation reaction and complex interaction might be dominated by the adsorption.A novel Fe-doped ZIF-8(expressed as ZIF-(2Zn:1Fe))was synthesized by hydrothermal method,and its adsorption properties of phosphate from water were investigated.Scan electron microscope(SEM)observation exhibited polyhedral morphology and that Fe atoms were doped successfully into ZIF-8 frameworks.Batch experimental results indicated that the molar ratios of Fe and Zn had important effects on the adsorption amounts.The adsorption capacity can reach 38.24 mg/g.The characterization analysis clearly showed that the introduction of iron atoms in ZIF-(2Zn:1Fe)materials created a new adsorption site.A novel dual metal-organic framework was first synthesized by a solvothermal method(Labeled MIL-101(Fe/Zr)).Scan electronic microscope observation implied the successful doping of Zr atom as a second metal into the topology structure of MIL-101(Fe).The adsorption capacity of phosphate is 66.00 mg/g,which is considered to be a multilayer adsorption.The characterization analysis clearly showed that the unsaturated metal sites of MIL-101(Fe/Zr)leading to surface hydroxyl groups enhance strong interactions between adsorbents and phosphate species,thereby enhancing adsorption performance.By investigating the adsorption efficiency of the three materials in simulated wastewater and real wastewater,the three adsorbents have strong anti-interference ability to calcium and magnesium ions in water.The results that ZIF-(2Zn:1Fe)has strong anti-interference performance and excellent adsorption performance.