Preparation Of Sodium Copper Ferrocyanide And Its Adsorption Mechanism On ¹³⁷Cs And Its Application

Effective removal of ¹³⁷Cs from radioactive wastewater and seawater is of great significance to environmental protection and human health.Therefore,it is urgent to develop a low-cost and high-performance adsorbent.In this paper,Cu-based organic frameworks（Cu-MOFs）were used to prepare sodium copper hexacyanoferrate powder（Na Cu FC-M）,and copper alginate was used to prepare sodium copper hexacyanoferrate/copper alginate aerogel（Na Cu FC/CA）for the adsorption of Cs⁺from wastewater and seawater.The main contents are as follows:（1）Na Cu FC-M powder was prepared using the preparation strategy of Cu-MOFs as a copper ion source,and characterized by XRD,FT-IR,TGA,and SEM.The static adsorption experiment using Cs⁺as the target pollutant was conducted to investigate the adsorption performance of Na Cu FC-M for Cs⁺.The main results are as follows:Na Cu FC-M has excellent adsorption performance,which can achieve adsorption equilibrium within 15 minutes,with a maximum adsorption rate of 99.4%,and a maximum adsorption amount of 1158 mg/g,which is twice the adsorption amount of traditional preparation methods;After using five adsorption-desorption cycles,Na Cu FC-M still retains 77.54%of the adsorption effect,with good reusability;The static adsorption experiment found that the solution p H and interfering ions had little effect on the adsorption of Cs⁺;The increase in solution temperature is conducive to the adsorption process,while the addition of sodium ferrocyanide will lead to a sharp decrease in the maximum adsorption capacity;The Cs⁺adsorption process of Na Cu FC-M conforms to the pseudo second order kinetic model and Langmuir isotherm model,which confirm that the adsorption is a complex heterogeneous diffusion process and chemical adsorption process.At the same time,thermodynamic calculations reveal the spontaneity of adsorption.（2）In order to further understand the Cs⁺adsorption mechanism of sodium copper ferrocyanide,the structure of sodium copper ferrocyanide before and after adsorption of Cs⁺was analyzed by various characterization methods such as SEM,ICP-MS,XRD,FT-IR,Raman,TGA,and XPS,and the adsorption mechanism was explained.The main results were as follows:Raman spectroscopy showed that Na Cu FC produced Cs-CN sub peaks after adsorption of Cs⁺,while the relative strength of Na-CN sub peaks decreased,ICP-MS also detected a decrease in the concentration of Na⁺and an increase in the concentration of Cs⁺in Na Cu FC after adsorption of Cs⁺,confirming the fact that Na⁺exchanges with Cs⁺;The TGA curve shows that there is no significant change in the thermal properties of Na Cu FC before and after the adsorption of Cs⁺.XRD and FT-IR spectra confirm that the adsorption of Cs⁺does not cause changes in the crystal structure and chemical groups.XPS analysis shows that the adsorption of Cs⁺does not cause changes in the elemental valence,which confirms that the adsorption process of Cs⁺in Na Cu FC is a simple ion exchange behavior;Based on the results of ICP-MS,the concentrations of metal ions before and after the adsorption of Cs⁺by Na Cu FC were accurately calculated.The results showed that the crystal defect vacancy of Na Cu FC also had the ability to adsorb Cs⁺,and its adsorption contribution accounted for about 0.493%of the total adsorption amount.（3）In order to solve the problem of difficult separation caused by the small size of sodium copper ferrocyanide,copper alginate was used as a carrier to prepare sodium copper ferrocyanide/copper alginate aerogel（Na Cu FC/CA）and investigate its Cs⁺adsorption performance.The main results are as follows:according to the results of XRD and FT-IR,sodium copper ferrocyanide was successfully coated in copper alginate;SEM and EDS showed that Na Cu FC was evenly distributed in Na Cu FC/CA and retained the ability to adsorb Cs⁺.At the same time,the porous layered structure of Na Cu FC/CA provided rich ion channels for the adsorption of Cs⁺;Na Cu FC/CA obtained good adsorption performance,with a maximum adsorption capacity of 129.2mg/g and an adsorption equilibrium time of 30 minutes.After five cycles of adsorption and desorption,51.13%of the adsorption effect was retained,while the change in p H had almost no impact on its adsorption performance.