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The low cost chitosan@attapulgite composite (CS@ATP) were prepared by self-assembly method and applied for U(VI) removal from aqueous solutions. Scanning Electron microscopy (SEM) images showed the uniform decoration of chitosan (CS) on attapulgite (ATP) surface. X-ray diffraction (XRD) patterns indicated that the coating of chitosan altered the structure of ATP to some extents. Batch sorption results showed that sorption ability of ATP toward U(VI) was greatly improved after CS modification above pH 5.0. The ionic strength independent sorption suggested that inner-sphere U(VI) complexes were formed by mainly bonding to the oxygen-containing functional groups of CS@ATP. In the presence of humic substances, U(VI) sorption on CS@ATP was obviously enhanced under acidic conditions, while restrained in alkaline condition. Moreover, the presence of humic acid provoked the desorption of U(VI) from CS@ATP to a certain extent. These findings herein suggested that CS@ATP composite is a potential and suitable candidate for the preconcentration and separation of U(VI) from contaminated natural wastewater and aquifer. [ABSTRACT FROM AUTHOR]

A novel magnesium silicate/diatomite sorbent (MSD) was fabricated using a facile hydrothermal method. The interaction mechanism of U(VI) on MSD was investigated by batch, spectroscopic and modeling techniques. The maximum adsorption capacity of MSD for U(VI) (31.54 mg/g) is significantly higher than that of diatomite (12.74 mg/g). XPS analysis indicated that the oxygen-containing groups (e.g., Si OH) of MSD were responsible for the high efficient removal of U(VI) from aqueous solutions. The fitted results of surface complexation modeling showed that the adsorption of U(VI) on MSD at pH < 4.0 and pH > 4.5 was attributed to cation exchange and inner-sphere surface complexation, respectively. These findings suggested that MSD could be a favorable sorbent for the efficient removal of U(VI) in the environmental cleanup. [ABSTRACT FROM AUTHOR]

Abstract: The original pilot-scale electrokinetic equipment suitable to soil contamination characteristics of Korean nuclear facility sites was manufactured for the remediation of soil contaminated with uranium. During the experiment with the original pilot-scale electrokinetic equipment, lots of metal oxides were generated and were stuck on the cathode plate. The uranium removal capability of the original pilot-scale electrokinetic equipment was almost exhausted because the cathode plate was covered with metal oxides and did not conduct electricity properly. Therefore, the original pilot-scale electrokinetic equipment was improved as follows. First, an immersion-washing device was manufactured for washing the metal oxides from the cathode plate. Second, a metal oxide separator for removal of metal oxide particles below 0.075mm was manufactured. Third, a circulation system for pH control and waste-solution movement was manufactured. The circulation system controls the pH in the cathode room at 1–2, to prevent the generation of metal hydroxide and circulates waste-solution in a cathode room to prevent the increase of metal oxides due to its stagnancy. After the remediation experiment for 25days using improved pilot-scale electrokinetic equipment, the removal efficiency of uranium from the soil was 96.8%, and its residual uranium concentration was 0.81Bq/g. When the initial uranium concentration of the soil was 50Bq/g, the electrokinetic remediation time required to remediate the uranium concentration below clearance concentration of 1.0Bq/g was about 34days. When the initial uranium concentration of soil was 75Bq/g, the electrokinetic remediation time required to remediate below 1.0Bq/g was about 42days. When the initial uranium concentration of soil was 100Bq/g, the electrokinetic remediation time required to remediate below 1.0Bq/g was 49days. [Copyright &y& Elsevier]