Experimental Study On Adsorption Of Phosphate From Aqueous Solution By Rare Earth Loaded Modified Ferric Tetroxide

Phosphorus is a non-renewable resource.With the increase of exploitation,the phosphate resources will be exhausted within 100 years,furthermore a large amount of phosphorus is discharged into natural water with agricultural and urban wastewater,causing eutrophication of water and aggravating environmental pollution.Therefore,recovering phosphorus from sewage can not only purify water quality,but also meet the requirements for sustainable development of phosphorus resources.Among many water treatment technologies,adsorption method is popular because of its advantages of simple technology and low cost.In this thesis,modified Fe₃O₄?CMIO?is used as a magnetic source with a certain adsorption capacity,and it is loaded on waste rare earth polishing powder?PP?containing La and Ce,thus the rare earth loaded modified Fe₃O₄ composite?CMIO@PP?was prepared,which makes it has a high adsorption capacity and magnetic at the same time,and make it easy to separate from the water using an external magnetic field.The X-ray powder diffractometer?XRD?,X-ray fluorescence spectrometer?XRF?,transmission electron microscope?TEM?,and vibration sample magnetometer?VSM?were used to characterize and analyze the adsorbent,and to explore the effects of phosphate adsorption factors and adsorption mechanism.The specific results are as follows:Firstly,the modified Fe₃O₄was prepared by coprecipitation method,using Ca O₂ as oxidant and calcium dopant to partially oxidize Fe???,thereby synthesizing calcium doped Fe₃O₄?CMIO?.CMIO is a spinel shaped crystal structure of Fe₃O₄,composed of many irregular nanoparticles,and calcium is doped in the amorphous phase of CMIO.The saturation magnetization of CMIO is 38.82 emu/g,and it can be easily separated from water under the external magnetic field.The adsorption process of phosphate by CMIO follows the pseudo-second-order kinetic equation,and the adsorption isothermal data conform to the Langmuir isothermal adsorption model.At p H=2.0 and T=25?,the maximum adsorption capacity of phosphate was 24.10 mg/g.In addition,acidic conditions are favorable for CMIO to adsorption phosphate,and its adsorption capacity decreases with the increase of p H.CMIO has strong anti-anion interference ability and good phosphate adsorption selectivity.The phosphate adsorbed on CMIO can be desorbed by 0.5 mol/L Na OH solution,so it can be recycled,and the mass loss rate of CMIO does not exceed 4%in each cycle.Further,the CMIO is loaded on the rare earth by acid leaching and precipitation method,a novel phosphate adsorbent rare earth loaded modified ferric oxide composite material with magnetic recovery?CMIO@PP?was synthesized.CMIO@PP presents a crystal structure comprising La?OH?₃,Ce?OH?₃,and Fe₃O₄.Many La?OH?₃ and Ce?OH?₃ nanoparticles are attached to the CMIO.Its saturation magnetization is 10.96 emu/g and can be separated from aqueous solution under an external magnetic field.The adsorption of phosphate by the CMIO@PP accords with the Langmuir isotherm model,and its maximum adsorption capacity is 53.72 mg/g at p H=4.0 and T=25?,and the adsorption process follows the pseudo-second order model.CMIO@PP can maintain a higher adsorption capacity at a p H between 2.0 and 6.0.The adsorption mechanism of phosphate on CMIO@PP is mainly electrostatic attraction and ligand exchange.CMIO@PP has good phosphate adsorption selectivity.Phosphate adsorbed on CMIO@PP can be desorbed with 1 mol/L Na OH solution,which has great regeneration ability,and the mass loss rate of CMIO@PP does not exceed5%in each cycle.In the experiments of phosphate adsorption in actual wastewater,0.4 g/L of CMIO@PP reduced the phosphate concentration to 0.05 mg/L within 2 h,indicating that CMIO@PP is a promising adsorbent for phosphate recovery.