Effect of natural pyrite oxidation on the U(VI) adsorption under the acidic and neutral conditions

The U(VI) immobilization efficiency and mechanism of natural pyrite were investigated under both acidic and neutral oxidization conditions. The results show that, the final U(VI) removal rate was only 20% under acidic condition; however, a small amount of pyrite oxidation could enhance the immobilization of U(VI) under neutral oxidizing conditions, with the removal rate reaching 95%. A ferric hydroxide colloid, goethite and lepidocrocite were formed in the neutral oxidizing environment. It was speculated that the main U(VI) immobilization mechanisms of pyrite oxidation were adsorption. The adsorption behaviour of U(VI) to pyrite conformed to the pseudo second-order adsorption model (R2 = 0.9996).