Efficient Removal Of Phosphate And Arsenate From Water Using Nanostructured Basic Yttrium Carbonate Synthesized Via Hydrothermal Method

Phosphorus,as the main nutrient element,is very important for biological growth,but a large amount of phosphorus entering the water will cause the explosive growth of plankton.When the phosphorus content in the lake exceeds 0.02 mg?L^-1,the eutrophication of water can be caused and the ecological balance of water will be seriously affected.Arsenic and its compounds have certain toxicity and carcinogenicity.Drinking water with excessive arsenic content for a long time will seriously affect people's health.The standard of arsenic content in drinking water has been reduced from 50?g·L^-11 to 10?g·L^-11 in our country.Therefore,it is necessary to remove phosphorus and arsenic from wastewater and reduce the content of phosphorus and arsenic in water.There are many common methods for removing phosphorus and arsenic from water.Among them,adsorption method has become a common method for wastewater treatment because of its economy,efficiency,no secondary pollution and so on.Rare earth elements have a special electronic layer structure that can easily form stable compounds.The adsorbent with rare earth element as the main component would have better adsorption ability to anions.Moreover,the preparation methods and preparation conditions of adsorption materials have significant influence on the properties of adsorption materials.However,the adsorbents prepared by hydrothermal method have the advantages of high purity and good controllability.In this study,the basic yttrium carbonate adsorption material with nanometer structure was synthesized by hydrothermal method with urea as precipitant and glycerol as dispersant.The adsorption properties of phosphorus and arsenic were investigated.The main contents are as follows:?1?The experimental conditions for the synthesis of basic yttrium carbonate by hydrothermal method were determined by orthogonal design.The reaction temperature was 100?.The ratio of urea to yttrium is 5:1 and the ratio of glycerol dispersant is 20%.A kind of basic yttrium carbonate adsorption material with high purity is prepared.?2?Scanning electron microscopy?SEM?and transmission electron microscopy?TEM?analyses indicate that the basic yttrium carbonate is a loose porous structure formed by random stacking of nanoparticles.X-ray powder diffraction?XRD?analysis shows that the basic yttrium carbonate is similar to yttrium carbonate hydrate.The isoelectric point of basic yttrium carbonate measured by salt addition method is 6.8.?3?The basic yttrium carbonate is effective for phosphate removal from water.The maximum adsorption capacity of phosphorus is 139.8 mg·g^-1at pH 7.0.The adsorption of phosphate is very fast and over 90%of the equilibrium adsorption capacity is obtained within 2 h.The pseudo second order model is more suitable to describe adsorption kinetic data.Coexisting ions have little effect on phosphorus adsorption.CO₃^2-?SO₄^2-?SiO₃^2-has slight inhibition on phosphorus adsorption,while Cl^-can slightly promote phosphorus adsorption process.Organic matter has little effect on phosphorus adsorption process.The basic yttrium carbonate has high removal capacity to the phosphorus in the actual water.FTIR analysis shows that the replacement of surface carbonate groups by the phosphate species is the main removal mechanism.?4?The basic yttrium carbonate is also effective for As???removal from water.The maximum adsorption capacity of phosphorus is 349.4 mg·g^-11 at pH 7.0.The adsorption of As???is very fast and over 80%of the equilibrium adsorption capacity is obtained within 1.5 h.The pseudo second order model is more suitable to describe adsorption kinetic data.The common anion in water has an influence on the adsorption process,of which PO₄^2-has the greatest influence,organic matter has little effect on phosphorus adsorption process.FTIR analysis shows that the replacement of surface hydroxyl and carbonate groups by the As???species is the main removal mechanism.