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In this study, the halloysite nanotubes was characterized and the adsorption of Th(IV) and U(VI) on halloysite nanotubes was investigated as a function of contact time, adsorbent dosage, pH, ionic strength, initial U(VI) concentration and temperature using batch method. Meanwhile, the adsorption mechanism of uranium and thorium on halloysite nanotubes was discussed. The microscopic results displayed that halloysite nanotubes was tubular morphology and highly porous and high specific surface area of ca. 55.65 m2/g. The adsorption results showed that the adsorption of U(VI) and Th(IV) on halloysite nanotubes followed pseudo-second-order kinetic model. The strong pH dependent adsorption of U(VI) and Th(IV) displayed their strong surface complexation with the surface of halloysite nanotubes. The adsorption of Th(IV) and U(VI) increased with elevating temperature and was an endothermic and spontaneous process. The adsorption isotherms of Th(IV) and U(VI) can be better described by Freundlich and D–R model. The effect of ionic strength on the adsorption of thorium on halloysite nanotubes was much greater than that on uranium(almost unaffected), which suggested the adsorption of Th(IV) on halloysite nanotubes was most probably based on the formation of inner-sphere complexes, while that of U(VI) was based on the formation of outer-sphere complex on the edge surfaces. Th(IV) and U(VI) adsorption–desorption isotherm on halloysite nanotubes indicated adsorption process was irreversible. The selectivity order of adsorption by the halloysite nanotubes was Th(IV) > U(VI). The higher adsorption efficiency of the halloysite nanotubes for Th(IV) could be utilized for selective separation of Th(IV) from U(VI) aqueous with pH 4.1–4.3. The novel and environmentally friendly adsorption material is feasible to extract thorium from waste aqueous solution.

The modified polyacrylonitrile fibers (ACPAN fibers) was synthesized by oximation reaction and alkaline hydrolysis. ACPAN fibers was characterized by means of SEM, FTIR, XPS and elementary analysis. The effects of contact time, solid–liquid ratio, pH, ionic strength, initial concentration and temperature on U(VI) adsorption onto ACPAN fibers was studied and the adsorption mechanism was also discussed. The experimental data fitted well pseudo-second-order kinetics model and Freundlich and D–R models, and thermodynamic process was an endothermic and spontaneous reaction. The maximum adsorption capacity was 163 mg/g, and U(VI) and ACPAN fibers possible formed more stable penta-coordination complexation. This paper highlighted ACPAN fibers as a good adsorbent to remove efficiently and economically uranyl from radioactive wastewater.

With the development of nuclear power and the depletion of uranium resources on land, extracting uranium from seawater has become a grand task. In particular, the synthesis of highly efficient and selective adsorbents becomes very important. Three copolymers (P(AO/C2VIM+Br−)-6, P(AO/C6VIM+Cl−)-3 and P(AO/C12VIM+Cl−)-2 were synthesized by radical polymerization, alkyl substitution and the amidoximation reaction of hydroxylamine. The copolymers were characterized by using FTIR, XPS, 1H NMR, and elemental analysis. The effects of different amount of imidazole cation and different length of branched chain on the adsorption were investigated by batch experiments, including solid-liquid ratio, contact time, pH, ionic strength, and coexisting ions. Meanwhile, the adsorption thermodynamics and kinetics of U(VI) on the copolymers were carried out. The results proved that the U(VI) adsorption by the copolymers strongly depended on ionic strength and pH, and fit well with pseudo–second-order model and Langmuir model and displayed endothermic, spontaneous process. Based on FTIR and XPS analysis, the possible binding mechanism involved uranyl with oxime O and amino nitrogen by bidentate coordination model or through bidentate coordination of oxime O, amino N and imidazole N. In addition, a little uranium might be adsorbed with positive charges by coulombic interaction, especially the adsorption of uranium on copolymer P(AO/C12VIM+Br−)-2. Finally, reuse performance of copolymers and adsorption of uranium in simulated seawater were studied comparatively. The results showed that P(AO/C2VIM+ Br−)-6 can be regarded as a good adsorbent for extracting uranium in simulating seawater.

The phosphorus (P) fractions and adsorption-desorption characteristics in the Wuliangsuhai Lake were investigated through molybdenum blue/ascorbic acid method and indoor simulation experiments, respectively. The results showed that the highest total phosphorus concentration in overlying water (W-TP) was found in S1 which was in the hypereutrophic type. The mean concentration of particulate organic phosphorus (POP) was the most abundant P fraction (31.35% of the W-TP). The results of TP contents in sediments (S-TP) indicated that the most sampling sites were in the mild level of pollution. The contents of calcium-bound P (HCl-P) and residual P (Res-P) fractions together comprised 83.03-98.10% of the S-TP. Pseudo-second-order models fitted well with the adsorption-desorption kinetic of P fractions. The Langmuir and Freundlich models well described the adsorption isotherm of P fractions. The results of adsorption-desorption of P fractions indicated that the adsorption capacity was strong, the chemical adsorption was dominant, and the sediments was a source of P. Accordingly, we concluded that the Wuliangsuhai Lake was in the moderate pollution level, and the sediments as a source could desorb P in natural aquatic environment.

The effects of pH, ionic strength and humic substances on the sorption and desorption of Co(II) on alumina and silica were, respectively investigated by using radiotracer 60Co. The distribution coefficients, the breakthrough curves and the displacement curves were experimentally determined in the batch and the column experiments. The pH and the humic substances influenced the sorption of Co(II) on alumina greatly as compared with the sorption of Co(II) on silica. It was found that the sorption characteristics of Co(II) onto alumina and silica are distinctly different, that the strong chemical bonds are formed between the bare alumina surface and Co(II) and between the coated alumina surface and Co(II), and that a transition from the adsorption to the surface-induced precipitation of Co(II) on the bare alumina surface takes place.

The distribution coefficients, Kd of 36 elements from Na to Bi on a silica were determined at pH 4, 7, 9 and in the absence and presence of fulvic acid (FA) using a multitracer technique. The multitracer solution was prepared by irradiation of Th(NO 3)4 with 40 Ar ion beam. The effects of pH and fulvic acid on the Kd values of 36 elements were studied. It was found that the sequences of the Kd values of alkali elements (Cs>Rb>K>Na) and of alkaline earth elements (Ba>Ca>Mg) in the absence of FA can be qualitatively explained in terms of chemical bond formati on and hydration. Various effects of pH and the negative or positive effect of FA on the adsorption of 36 elements were observed and a re probably related to the species of 36 elements in the aqueous solutions containing CO 3 2– , OH – , Cl – and FA. For most of the elements studied here the Kd values are increased with increasing pH and are decreased with adding FA.