Study Of Adsorption Behavior Of²³⁹Pu On GMZ Bentonite

²³⁹Pu nuclide is a typical and critical radionuclide, which is contained inradioactive waste. It has long half-life and toxicity. It occupies an important position inhigh level radioactive waste safety and Environmental Assessment. Carried out theadsorption behavior of²³⁹Pu radionuclides in geological media, having importantguiding significance about the secutity of radioactive waste repositories. Bentonite isthe ideal buffer/backfill material recognized in international. It is the last artificialbarrier materials in the underground repository of high level radioactivewaste.Bentonite plays an important role in conduct and dissipate the decay ofradioactive waste. After years inspection, GMZ bentonite deposit as the preferredsupply base of China’s buffer/backfill material. This paper studies the Adsorptionbehavior of²³⁹Pu on GMZ bentonite, investigating the adsorption mechanism ofradionuclide. The study includes adsorption equilibrium time of²³⁹Pu on GMZbentonite, the impact on the adsorption of²³⁹Pu under different conditions, theadsorption isotherm and desorption behavior of²³⁹Pu, experimental results shows that:1.The level of sdsorption of²³⁹Pu on bentonite is high. Before studying the experimrntof the adsorption behavior of²³⁹Pu on bentonite, we must first determine theSaturation adsorption capacity, from the experiment we determine the Saturationadsorption capacity is0.8g/mL. With the extension of sdsorption time, the adsorptiondistribution ratio, value of Kdis gradually increase and eventually tends to a constant,the adsorption reach equilibrium. The time of reaching equilibrium of adsorption is24hours.2. with the pH of water phase increased，the adsorption distribution ratio ofplutonium also increased, when the solution is acidic, which is hinder the adsorptionbehavior of²³⁹Pu on bentonite, and the stronger of the acid, the greater of the level ofhindered. when the solution is alkaline, which is conducive the adsorption behavior of²³⁹Pu on bentonite. 3. With the liquid-solid ratio of bentonite decreases,the adsorption of²³⁹Pu onbentonite is graduslly increasing, the adsorption distribution ratio Kdof plutonium isfirst decrease, and then increases.4.The anion CO₃^2-has a larger effect than other anion, the adsorption distributionratio Kdof plutonium is smaller, followed by HCO₃-and SO4^2-, Cl-and NO₃-had noeffect. The cation Fe³⁺has a larger effect than other cation, the adsorption distributionratio Kdof plutonium is smaller, followed by Ba²⁺and Ca²⁺, K+had no effect. Withthe concentration of CO₃^2-, HCO₃^-, Fe³⁺, Ca²⁺increasing, he adsorption distributionratio Kdof plutonium gradually decrease. A higher concentration of CO₃^2-, Fe³⁺hasa larger effect on adsorption.5. With the increase of initial concentration of plutonium, the adsorptiondistribution ratio Kdof plutonium on bentonite gradually decrease. When the initialconcentration of plutonium is less than8Bq, plutonium will be adsorpted by bentonitecompletely. With the increase of initial concentration of plutonium, the level of theadsorption of plutonium on bentonite gradually increase.6.The adsorption of plutonium on bentonite is in line with the Langmuir isotherm,the linear correlation coefficient R²=0.8714, the maximum amount of monolayeradsorption qmax=769mg g^-1, it indicate the extent of adsorption is high. The adsorptionof plutonium on bentonite is in line with the Freundlich isotherm, the linearcorrelation coefficient R²=0.9463, adsorption index1/n=0.2136, the values of1/nbetween0.1to0.5indicating plutonium is easy to absorb by bentonite, indicating thatthe bentonite absorbe plutonium nuclides easily.7. With the increase of desorption time increases, the desorption rate of theplutonium nuclides gradually increases, and the desorption process is faster. With theincrease of pH value of the desorption solution, the desorption rate of the plutoniumnuclides decreases. With the desorption number, solution ionic strength, and theconcentration of HNO₃increases, the desorption rate of plutonium nuclides graduallydecreases; when desorption for the first time, the desorption rate is maximum. Whenthe ionic strength is0.1mol/L, the desorption rate reach46.06%. When the theconcentration of HNO₃is3mol/L, the desorption rate can reach89.01%.