The Selective Adsorption Characteristics For Uranium In High Salinity Environment On Leather Adsorbent

In view of the key technical problems of land uranium shortage and the difficulty from seawater,this paper selected the low-cost leather waste containing the rich collagen fibers as raw materials and prepared three kinds adsorbents by the methods of hydrolysis,hydrothermal treatment and tannic acid,respectively,aiming at the development of uranium resources in saline lake.Furthermore,in this paper,the static adsorption and adsorption mechanism of U(VI)were studied systematically,and the effects of high salinity environment on the adsorption property and desorption regeneration of uranium were studied.The results were as following:1.The optimal preparation conditions of alkali-activated leather waste(AALW)were:size of leather(square particle of 0.25 cm);the concentration of NaOH(0.075 mol/L),hydrolytic temperature(50℃),hydrolytic time(4 h)。The optimum pH for adsorption of U(VI)by AALW was 5.The isothermal adsorption data was fitted well with Langmuir isotherm and the fitted maximum adsorption was 163.67 mg/g.The kinetic was followed pseudo-second-order kinetics and the adsorption equilibrium was achieved in 240 min.In the adsorption process,there was ion exchange between U(VI)and Na loaded by alkali activated,and the rest of U(VI)was coordinated with the active groups in AALW.2.The adsorption of U(VI)by HLW was significantly influenced by pH,and the optimal adsorption capacity was achieved at pH=5.The isothermal adsorption data was obeyed well with Freundlich isotherm and the kinetic was followed pseudo-second-order kinetics.It reached equilibrium in 240 min.In the process of adsorption,the uranium were successfully adsorbed onto HLW through complexation and electrostatic attraction with oxygen functional groups generated in hydrothermal process.3.The optimal preparation conditions of sponge leather waste(SLW)were:mass fraction of tannic acid(2%),the dose of AALW(1.25 g),hydrothermal temperature(140℃),hydrothermal time(1.5 h)。The adsorption of U(VI)by SLW was significantly influenced by pH,and the optimal adsorption capacity was achieved at pH＝5.The isothermal adsorption and kinetic datas were obeyed well with Freundlich and pseudo-second-order kinetics models,respectively.It reached equilibrium in 1080 min.In the adsorption process,the modified leather surface is rich in phenolic hydroxyl group,amino group and carboxyl groups which have high affinity to U(VI),and the uranium was mainly adsorbed by coordination complex.4.In the simulated high salinity environment with low concentration of U(VI)(the uranium concentration is 800 ug/L),these three kinds of adsorbents shown high adsorption efficiency for U(VI).The adsorption property of AALW decreased with the increasing of HCO3-.In the adsorption experiment of seven metal ions existing,AALW,HLW and SLW had high selectivity to U(VI)and the adsorption efficiency were 55%,45%and 85%,respectively,which were higher than the others metal ions.5.When AALW was recycled to fourth time,the adsorption efficiency was reduced to 52%,however,the desorption efficiency of AALW was up to 90%.Because of the acid modification,the adsorption efficiency of HLW was not decreased,but increased.After the five adsorption-desorption cycles,the adsorption efficiency of SLW could reach more than 90%.To sum up,the modified collagen collagen adsorption material has good adsorption effect on adsorption of U(VI),and the three modified methods are simple and easy to use,which has a certain reference value for extraction of uranium from saline Lake.