Study On Preparation And Uranium Removal Of Polysaccharide-based Composite Adsorbent

In nuclear energy production processes,such as mining,uranium hydrometallurgical processing,and nuclear fuel manufacturing,a large amount of uranium-containing wastewater is produced and discharged into the environment.Uranium,which is usually in a hexavalent form,exists in wastewater and can seriously harm the environment and humans because of its radioactivity and chemical toxicity.There are many technologies currently used to remove uranium from wastewater,such as solvent extraction,chemical precipitation,ion exchange,membrane treatment,phytoremediation and adsorption.In consideration of convenience and economy,adsorption is generally considered to be one of the most practical and effective technologies in water treatment.Polysaccharide is a natural polymer material.In recent years,many researchers have used polysaccharides or their derivatives for heavy metals and toxic dyes removal,because polysaccharide resources are very rich,low-cost and renewable.In this study,composite adsorbents are prepared with polysaccharides as matrix and nanoparticles as fillers to remove uranium.The main research contents are as follows:?1?The composite adsorbent aMSP/SA with particle size of 3⁴mm was prepared by immobilizing amino-functionalized mesoporous silica?aMSP?with sodium alginate?SA?for removing low concentration hexavalent U?VI?.The removal performance and practical application of aMSP/SA were investigated.Results show that the saturated adsorption capacity of aMSP/SA for uranium was 210 mg/g at pH 4.0 and 313 K,and the concentration of U?VI?could be reduced from 1.0 mg/L to 1.31?g/L.The aMSP/SA shows a high efficiency uranium removal of 99.41%in mine water and affinity toward uranium in a mixed metal solution.Additionally,the structure and possible adsorption mechanism of aMSP/SA were characterized by Fourier transform infrared spectrometer?FTIR?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscope?SEM?,and energy-dispersive spectrometry?EDS?.The main interaction mechanisms may be explained by ion exchange with Ca²⁺on carboxyl and coordination with hydroxyl and amino groups.This study highlights that a high removal efficiency?99.41%for 1.0 mg/L?and easy separation of large particle sizes?3–4 mm?makes aMSP/SA a promising material for eliminating low concentration U?VI?in industrial applications.?2?Microalgae based aerogel?CP/CTS?was prepared and utilized to remove uranium from an aqueous solution.Effects of pH,anions,contact time,uranium concentration,coexisting metal ions,and regeneration were systematically investigated.Results showed that U?VI?adsorption by CP/CTS was strongly influenced by hydrogen ions.CP/CTS showed prominent adsorption capability toward U?VI?in NO₃^-,Cl^-,and SO₄^2-solution media with the adsorption characteristics of pseudo-second-order kinetic model and Langmuir isotherm.The maximum calculated U?VI?adsorption capacity was about 751 mg/g in 7h at 313 K,and the distribution coefficient?K_d?of CP/CTS reached 3.2×10⁵ at C₀?U?=10 ppm.It was observed that K⁺,Ca²⁺,Na⁺,Mg²⁺,and NH₄⁺have no or slight effects on U?VI?adsorption by CP/CTS.After adsorption,CP/CTS could be regenerated with 0.5 M EDTA-2Na and reused efficiently.Besides,in the practical leaching solution,CP/CTS also exhibited good adsorption performance for U?VI?.The removal mechanism was ascribed to ion exchange with carboxylic or hydroxyl groups and surface complexation with amino groups.These results demonstrated that CP/CTS have the potential for application in U?VI?-containing wastewater treatment.