Synthesis Of Zirconium Titanium Pyrophosphate And Its Adsorption To Cesium Ion

Following Fukushima Daiichi nuclear event, the prevention and cure technologyof radionuclide contamination in water has become one of the key research contents.Cesium is one of the main contaminants released by nuclear leak, due to its longhalf-time, cesium would cause great damage to the health of human body. Thus, targetthe removal of cesium ion in water, zirconium titanium pyrophosphate (ZTPP), onetype of tetravalent bimetallic acid salt, was synthesized in this paper. In this study, wemake a comprehensive review on the application of ZTPP for cesium ion removal andexpound the mechanism of adsorption process.ZTPP has been synthesized by a sol-gel method and the optimum syntheticconditions are determined through cesium adsorption experiments. The materialshows high ion-exchange capacity for cesium ion which can reach up to1.3mmol/gwith an initial cesium ion concentration of10mmol/L. Various characterizationmethods including SEM, TEM, BET were utilized for the evaluation of the material.The results indicate that ZTPP is an amorphous and porous material formed by nanolamellar structure with high thermal stability, which can improve the adsorptioncapacity and selectivity of the adsorbent. ZTPP has a large specific surface area asmuch as38m2/g. Based on the EDS analysis conclusion, molecular formula of ZTPPcan be inferred as Zr2.06Ti2.68P8.60O30.98.The adsorption kinetics experiment showed that apparent adsorption rate is quite fastand the adsorption mass transfer process mainly is influenced and controlled by bothinterfacial diffusion and particle diffusion as particle diffusion is the predominantfactor. It has demonstrated that the adsorption process of cesium on ZTPP iscompatible physically with the mechanism of monolayer adsorption throughadsorption isotherm test. Thermodynamic parameters include G°, H°and S°at different temperatures were calculated and all the parameters are negativeindicating that the adsorption is an exothermic process and increasing temperaturewill adversely affect the adsorption process.Effects of pH values, coexisting competitive cations, different concentration ofsodium ion, and material amounts were studied to evaluate its absorption properties.Basing on adsorption experiments, it has demonstrated that the adsorption capacity ofcesium ion on ZTPP can be effective at a wider pH values from3to13; coexistingcompetitive cations also have a minimal effect on its extracting ability as cesium ion and other cations in the same concentration respectively. However, as theconcentration of sodium ions is more than100times than the cesium ion in solution,the adsorption capacity of ZTPP decrease significantly. The removal rate of cesiumion can reach approximately100%by adding more material. Ammonium chloridesolution with concentration of4mol/L can be used as eluent and desorptionexperiments demonstrate that cesium can be washed out from ZTPP effectively.On the whole, adsorption experiments results show that zirconium titaniumpyrophosphate have such characterizations as good thermal stability, high removalrate of cesium ion, high adsorption speed and adsorption capacities. It can be used asabsorbent to remove cesium ion quickly and effectively in water which has apromising prospect in radionuclide contamination emergency treatment.