Preparation Of CuHCF/GO Microbead Composites And Their Adsorption Properties For Cesium Ions

With the rapid development of Chinese nuclear industry,the treatment of radioactive nuclear waste has attracted widespread attention.Radiocesium is one of the main pollutants.Because of its long half-life,high activity and water solubility,it is a threat to environmental safety and human health.Therefore,it is necessary to research a method to remove the cesium ions from water.Adsorption is thought to be the most candicate method due to it is high efficiency,low cost and simple process.Hence,the syntheses of high efficient adsorbent materials have become a hotspot of the treatment of radioactive wastewater.In this paper,CuHCF/GO microbead was fabricated though encapsulation method.Firstly,copper hexacyanoferrate?CuHCF?was synthesized as core material,then the Polyvinyl alcohol/Calcium alginate?PVA/CA?mixture acted as the shell skeleton,and its structure was enhanced with graphene oxide?GO?.After that,the static adsorption performance of cesium ions by CuHCF and CuHCF/GO microbead was studied.And the adsorption kinetics and isotherm models were used to describe the process of adsorption.Finally,dynamic adsorption experiments of cesium ions by CuHCF/GO microbead were also performed.The adsorption process was fitted by some dynamic adsorption models.The main research contents and results were as follows:1.Water dispersible CuHCF nanoparticles were prepared by co-precipitation method.The effects of pH,adsorbent dosage,contact time and initial concentration of cesium ions on adsorption by CuHCF were investigated.When the initial concentration of cesium is 4 mg·L^-1,the optimum conditions for the adsorption were as follows:pH 7,adsorbent dosage 0.05 g,adsorption time 90 min.The adsorption process conformed to the pseudo-second-order kinetics and the Freundlich isotherm model.The XRD,FTIR and Raman were uesd to characterize the CuHCF powder,the results showed that the as-prepared CuHCF powder has high crystallinity.TGA test showed that CuHCF powder has good thermal stability.2.The CuHCF and PVA/CA mixture were acted as core material and shell-skeleton,respectively.And its structure was enhanced by GO.Then the CuHCF/GO microbead composites were fabricated.The results showed that the mechanical properties of CuHCF/GO microspheres prepared with a GO concentration of 0.6 mg·mL^-1 and CuHCF of 3 g were optimal.When the initial concentration of cesium was 1 mg·L^-1,the optimum conditions for adsorption were as follows:pH 7,adsorption time 90 min.It worth note that coexistent ions such as K⁺,Na⁺,Ca²⁺and Mg²⁺in the solution affected the adsorption of Cs⁺by CuHCF/GO microbeads.The adsorption process conformed to the pseudo-second-order kinetics and the Freundlich isotherm model.Then,SEM,FTIR and XPS were used to characterize the microbeads,and it showed that CuHCF was successfully loaded on PVA/CA/GO framework.BET analysis showed that the specific surface area of CuHCF/GO microbeads was 28.27m²·g^-1 and the average pore size was 28.58 nm.3.The dynamic adsorption of CuHCF/GO microbeads composite adsorbent was studied by adsorption column experiments with the influences,for instance the height of the filler,the solution flow rate and the initial concentration.The results of dynamic adsorption experiments showed that:with the filler height increasing from 3 cm to 10cm,the exhausted time was delayed from 2 h to 13 h;as the solution flow rate was increased from 1.2 mL·min^-1 to 5 mL·min^-1,the exhausted time was shortened from16 h to 7 h;and with the influent concentration increasing from 20 mg·L^-1 to 80mg·L^-1,the exhausted time was shortened from 12 h to 7 h.The application of several models showed that:the Yoon-Nelson model and Clark model could describe the dynamic adsorption process of CuHCF/GO microbead composite adsorbent well.And the result of nonlinear fitting was better than the linear fitting.In addition,the BDST model could predict the breakthrough time at new flow rate.