Preparation Of Polyphosphazene-based Coated Clay Materials And Their Uranium Removal Properties And Mechanisms

With the current economic development,nuclear power has been considered one of the best alternatives to fossil energy,can provide large-scale electricity without emitting greenhouse gases,is a clean low-carbon green energy.As the main part of nuclear material,uranium is a kind of highly radioactive heavy metal,which has a great impact on human health,even can cause kidney organ damage and some cancer.At the same time,China’s demand for clean energy,especially nuclear energy,is increasing under the background of global restriction and control of global greenhouse gas emissions and China’s“Double carbon”target.The exploitation and utilization of uranium ore has brought a huge amount of uranium-containing sewage.With the impact of rainstorm and the outflow of groundwater,the harm of uranium-containing sewage has rapidly expanded,to the surrounding natural environment and human health has brought a serious threat.In addition,the world’s proven uranium resources total mass of about 7.64×10⁶ tons,according to estimates,only enough for human use for about 120 years.Therefore,from the two aspects of environmental protection and resource utilization,the removal and regeneration of uranium from uranium-containing waste liquid is of great significance.Adsorption has been widely used in wastewater purification.In this study,we used the inexpensive clay mineral halloysite nanotubes and the magnesia-iron layered bimetallic hydroxide as substrates,the adsorption of uranium in wastewater by phosphorylated Mg-Fe layered bimetal oxide nanosheets and polyphosphazene film coated halloysite nanotube composite was investigated.The main research contents and results are as follows:（1）In this work,phosphorylation Mg-Fe layered dioxides（P-Mg-Fe LDOs）nanosheets with favorable memory effect were prepare by a strategy was calcined coupled in-situ phosphorylation,for efficient removal of uranium ions from wastewater.The evenly distributed phosphoric acid functional groups of LDOs gave it greater removal ability.The adsorption capacity of P-Mg-Fe LDOs was 2.31 times that of pure Mg-Fe LDOs.According to the Langmuir model,the theoretical adsorption capacity of P-Mg-Fe LDOs was as high as909.09 mg g^-1,which was far higher than that of similar sorbents.In addition,it had an excellent anti-interference ability and maintained a high removal rate in high concentrations of cations and anions.The results of XPS,FT-IR and XRD showed that the main mechanisms of binding uranium ion were surface complexation,mineralization reaction,dissolution-precipitation and memory effect.（2）the kaolin nanotube composite（HNT@PZM）coated with polyphosphazene film was prepared by chemical cross-linking method and calcined.The HNT@PZM-500 composite is cleverly loaded with highly dispersed PO₄^3-group,which endows the composite with excellent uranium-binding ability.In particular,HNT@PZM-500 reached the adsorption equilibrium within 20 minutes,and had a remarkable adsorption capacity for uranium,which was 1912.9mg g^-1.The removal rate of uranium in simulated uranium-containing wastewater is 98.78%,which was much higher than that of other metal ions.XRD,XPS and FT-IR analysis showed that the uniform anchoring of PO₄^3-group on the adsorbent played an important role in the adsorption of U（VI）.During the reaction,the in-situ release of PO₄^3-ions from HNT@PZM-500 composite accelerated the precipitation of uranium ions.The results show that HNT@PZM-500 can be used to treat emergency U（VI）wastewater.