The Study Of Sediments Adsorption Of Uranium In Phosphorus-enriched Water System

Phosphorite is one of the important mineral resources in our country,while the uranium bearing phosphate deposits which distributed in the southwest region and Hunan province account for more than 25%of the total reserves in China.Chinese Phosphorite is mainly used for the production of phosphate fertilizer.With the continuous increase of population,the rapid development of agriculture,the exploitation of phosphate rock and the mass production of phosphate fertilizer,while promoting agricultural production,they also cause environmental problems like the eutrophication of phosphorus,and radioactive pollution of uranium.Previous researchers have investigated the adsorption of uranium in Single mineral of stream sediments in the phosphate-rich system.This paper on the basis of previous studies,clinged to the National Natural Science Fund Project "Occurrence forms and Distribution of Uranium in Phosphate-rich System?41373120?",which is studied the adsorption of radioactive uranium and mineral from different rivers in terms of the water system rich in phosphorus and uranium.The physical and chemical properties of sediment mineral were measured by means of X-ray diffraction and specific surface area measuring instrument.Through the adsorption of uranium experiments,the acidity and alkalinity of the solution,phosphate concentration,ionic strength,solid-liquid ratio,initial uranium concentration,as well as the law of adsorption of uranium by different mineral composition and the influencing mechanism were discussed.The isothermal model is used to study the process of uranium adsorption by sediment minerals,and to determine the adsorption mechanism of sediment minerals to uranium.It has practical significance for phosphate mining area,phosphate fertilizer production area and the safety of agricultural living water.The experimental results show that:?1?The pH of the solution is the main factor affecting the adsorption of uranium by the sediment minerals.The concentration of phosphate,the ionic strength,the ratio of solid to liquid,the initial uranium concentration also have some influence on uranium adsorption.When pH is abrove 2 and below 4,the uranium adsorption increases with the increase of pH value;when the pH value is above 4,the uranium adsorption is stronger.With the increase of pH value,the adsorption decreased,but the change was little.?2?The change of phosphate concentration has certain influence on the adsorption of uranium by sediment minerals,but there is no obvious rule.The variation of ionic strength also has some influence on the adsorption of uranium minerals in sediments of Jinghu.For Jinghu sediments,the greater the ionic strength is,the stronger the adsorption does.However,the change of ionic strength of river sediment has little influence on adsorption,and the regularity is not obvious.The change of the ratio between solid and liquid also has some influence on the adsorption process.For the sediment from Jinghu,solid-liquid ratio is larger,the smaller the K_d;For sediment from No.1,the greater the solid-liquid ratio,the greater the K_d.This has a lot to do with the ability of the sediment minerals to absorb uranium.?3?Changes in initial uranium concentration also affect the sorption of uranium by sediment minerals.With the increase of initial uranium concentration,the adsorption capacity of uranium on minerals is also increasing.When the concentration of uranium reaches 1?g/mL,the adsorption of uranium on minerals reaches the maximum.When the initial uranium concentration continues to increase,the adsorption of uranium on minerals decreases sharply until it is stable.?4?The experimental data were fitted by isotherms,and the results showed that:isotherm of the adsorption of uranium on minerals is consistent with the Freundlich adsorption model(R² _Jinghu=0.966 and R² _NO.1=0.908).?5?In the same condition,the adsorption of uranium on minerals in sediments of Jinghu is stronger than No.1.This is mainly because clay minerals are different in content.And the method of the adsorption of sediment mineral with uranyl ion is by means of ion exchange adsorption,the surface sites adsorption and layer-coordination adsorption.