Study On Adsorption Behaviour And Enrichment Process With Collagen-based Adsorbent For Uranium In High Salinity Environment

The demand for nuclear fuel from the national defense and nuclear power industries has promoted the development of uranium resources.However,with the deep mining of uranium ore and metallurgy,the uranium resources on land have become scarce.Salt lake is rich in uranium and is a potential"liquid uranium deposit".In this paper,modified waste leather adsorbents and modified collagen fiber adsorbents were prepared by simple hydrolysis of low-cost leather collagen matrix materials.The dynamic adsorption characteristics of U???were systematically studied.By comparing the dynamic adsorption characteristics with the physical characteristics,the adsorption materials with better adsorption properties were selected for the study of dynamic adsorption process,and the adsorption effect and practical application value in the process were investigated.The results of the studies are listed as follows:?1?The leather waste is hydrolyzed by sodium hydroxide to obtain a modified leather waste adsorbent?AALW?.This study mainly investigated the dynamic adsorption characteristics of U???by the adsorbent,and discussed the height of the filler,the initial U???concentration and the influent flow rate.It was found that the column height was3⁵cm,the initial U???concentration was 12mg/L,the flow rate was 1.7mL/min,the unit adsorption amount was 4.811,7.357,11.421mg/g,respectively.The initial concentration of U???was 6¹8mg/L,flow rate was 1.7mL/min,column height was 4cm,the unit adsorption amount was 6.519,7.357,8.545mg/g.The flow rate was 0.85².55mL/min,initial U???concentration was 12mg/L,column height 4cm,the unit adsorption amount was8.695,7.357,8.038mg/g.The Thomas,Yoon-Nelson and BDST models were fitted.The dynamic adsorption penetration curve of the adsorbent conforms to the Thomas model?R²>0.95?.The predicted value of the adsorption amount under different conditions?4.77¹0.65mg/g?is close to the actual test value?4.811¹1.421mg/g?.The penetration curve conforms to the Yoon-Nelson model?R²>0.90?.The predicted value of 50%penetration time under different conditions?1569.56⁸251.68min?is close to the actual value?1480⁹120min?.The penetration time is related to the height of the packing,and the linear fitting is performed by the BDST model.When only the initial U???concentration and flow rate were changed,the predicted penetration time?155¹327min?was close to the actual test value?195¹245min?,indicating that the BDST model can determine the dynamic adsorption cycle of the fixed bed.The dynamic desorption experiment of modified waste leather adsorbent was also carried out.The modified leather waste adsorption column with different column height was desorbed with 0.05 mol/L HNO₃,and the desorption rate was92.96,93.9 and 95.2%.?2?The optimum conditions for the preparation of AACF were:NaOH concentration?0.075mol/L?,hydrolysis time?6h?,and hydrolysis temperature?60??.The static adsorption of U???indicated that the optimum pH of AACF for U???adsorption was 5.when the dosage was 0.02g,and the initial U???concentration was 20mg/L,the adsorption amount of the adsorbent can reach 49.662mg/g.The adsorption process conforms to the pseudo-second kinetic model and the Langmuir isotherm adsorption model.The high temperature is favorable for the adsorption.The adsorption equilibrium is reached in 360 min.The adsorption of U???by AACF is mainly based on coordination complexation and ion exchange,and belongs to chemical adsorption.The high-salinity system was simulated by the six ions with the highest concentration in the salt lake.The adsorption performance of adsorbent on U???in binary solution(U-Na⁺,U-K⁺,U-Mg²⁺,U-Cl^-,U-HCO₃^-,U-SO₄^2-)was investigated.AACF was greatly affected by HCO₃^-,while in other binary solutions,the adsorption rate of U???by adsorbent is above 80%.Finally,the regeneration performance of the adsorbent was studied.The adsorbent had better regeneration performance during the multiple cycles of adsorption.?3?The effect of modified collagen fiber adsorption column on the adsorption U???under different design parameters?filler height,flow rate and initial concentration?was discussed.When the height of the column was 2⁴cm,initial U???concentration was10mg/L and flow rate was 11.9mL/min,the unit adsorption amount was 14.723,17.363,18.751mg/g.The initial U???concentration was 5¹5mg/L,flow rate was 11.9mL/min and the column height was 3cm,the unit adsorption amount was 13.878,17.363,18.599mg/g.The flow rate was 10.2¹3.6mL/min,the initial U???concentration was 10mg/L and the column height was 3cm,the unit adsorption amounts was 18.357,17.363,and 14.449 mg/g,respectively.The Thomas and Yoon-Nelson models were used to fit the experimental data under different conditions.The experimental data of the penetration curves under different conditions were in accordance with the Thomas model?R²>0.94?and the Yoon-Nelson model?R²>0.93?.The predicted values of adsorption amount?12.612¹6.647mg/g?and 50%penetration time?167.81⁴53.32min?were respectively compared with the actual test value of adsorption amount?13.878¹8.751mg/g?and the actual test value of 50%penetration time?160⁴00min?closer.The BDST model to fit the penetration time of different filler height.It was found that the predicted penetration time?46¹94min?was close to the actual test value?28¹63min?,indicating that the BDST model could determine the dynamic adsorption cycle of the fixed bed.Further,the dynamic desorption experiment of modified collagen fiber adsorbent was carried out,and the desorption rate at different heights was92.86,94.5,96.63%,which had better desorption effect.?4?Comparing the dynamic adsorption performance of the two adsorbents.It was found that the modified leather waste had a unit adsorption capacity of 7.357mg/g at column height of 4 cm,a flow rate of 1.7mL/min,and a concentration of 12mg/L,while the modified collagen fiber adsorption capacity was 17.363mg/g at a column height of 3cm,a flow rate of11.9mL/min,and a concentration of 10 mg/L.In summary,it is shown that the collagen fiber adsorbent has a better adsorption effect and will be used in the subsequent process research.Then,the modified collagen fibers were used in a series of dynamic adsorption processes.The unit adsorption amount of the series adsorption column was 20.042mg/g,which was higher than the unit adsorption amount of the single adsorption column?17.363 mg/g?.Then,using the custom dynamic adsorption device to carry out the series dynamic adsorption amplification experiment under the high salinity complex system.It is found that the total adsorption amount is over 67%,which can be applied to the actual conditions.