Chuanqin Xia

Preparation of graphene oxide-manganese dioxide for highly efficient adsorption and separation of Th(IV)/U(VI)

Manganese dioxide decorated graphene oxide (GOM) was prepared via fixation of crystallographic MnO2 (α, γ) on the surface of graphene oxide (GO) and was explored as an adsorbent material for simultaneous removal of thorium/uranium ions from aqueous solutions. In single component systems (Th(IV) or U(VI)), the α-GOM2 (the weight ratio of GO/α-MnO2 of 2) exhibited higher maximum adsorption capacities toward both Th(IV) (497.5mg/g) and U(VI) (185.2 mg/g) than those of GO. In the binary component system (Th(IV)/U(VI)), the saturated adsorption capacity of Th(IV) (408.8 mg/g)/U(VI) (66.8 mg/g) on α-GOM2 was also higher than those on GO. Based on the analysis of various data, it was proposed that the adsorption process may involve four types of molecular interactions including coordination, electrostatic interaction, cation-pi interaction, and Lewis acid-base interaction between Th(IV)/U(VI) and α-GOM2. Finally, the Th(IV)/U(VI) ions on α-GOM2 can be separated by a two-stage desorption process with Na2CO3/EDTA. Those results displayed that the α-GOM2 may be utilized as an potential adsorbent for removing and separating Th(IV)/U(VI) ions from aqueous solutions.

Removal of Th4+ ions from aqueous solutions by graphene oxide

The removal of Th4+ ions from aqueous solutions was investigated using single-layer graphene oxide (GO) as a sorbent which was prepared by the modified Hummers’ method through batch adsorption experiments at room temperature. Structural characterizations of the sorbent were also investigated. The influences of the pH value of solution, contact time, sorbent dose, ionic strength, the initial metal ion concentration and temperature on the adsorption of Th4+ were also investigated. These results indicated that the adsorption of Th4+ was dependent on the pH and independent on the ionic strength. The sorbent provided significant Th4+ removal (>98.7xa0%) at pH 3.0 and the adsorption equilibrium was achieved after only 10xa0min. The Langmuir adsorption isotherm fit the absorption profile very closely, and indicated that a maximum adsorption capacity of 1.77xa0mmolxa0g−1 of GO (411xa0mgxa0g−1) after 2xa0h. The thermodynamic parameters showed that this adsorption process was endothermic and spontaneous. Moreover, the desorption level of Th4+ from GO, by using 0.1xa0mol L−1 H2SO4 as a stripping agent, was 84.2xa0±xa01.2xa0%, and that of 0.5xa0molxa0L−1 HNO3 as a stripping agent, was 79.8xa0±xa03.0xa0%.

New cyclen derivative ligand for thorium(IV) separation by solvent extraction

A new N-containing ligand, 1,4,7,10-tetra-(4-nitrobenzyl)-1,4,7,10-tetraazacyclo-dodecane (L), was synthesized, and its structure was determined by 1H NMR, high resolution mass spectrometry and X-ray diffraction. L crystallized in the monoclinic system (P21/n space group; axa0=xa07.7895(2)xa0Å, bxa0=xa022.9592(5)xa0Å, cxa0=xa09.9204(2)xa0Å; αxa0=xa090.00°, βxa0=xa0105.481(3)°, γxa0=xa090.00°; Zxa0=xa02). Slope analysis and the continuous variation method demonstrated that 1:2 complexes between Th(IV) and L are formed; furthermore, the XPS analysis suggested that two oxygen atoms might be provided by two water molecules and that eight nitrogen atoms might be provided by two L molecules to form a ten-coordinate compound with Th(IV). The extraction equilibrium constant for the complex formation between Th(IV) and L was logKexxa0=xa06.95xa0±xa00.15 (25xa0°C), and the Gibbs free energy, ΔGo (25xa0°C), of the 1:2 Th–L complex in dichloromethane was −39.56xa0kJ/mol. The L ligand in dichloromethane only slightly extracted Th(IV) from HNO3 solution at pHxa0=xa01–3; however, an extraction efficiency of Exa0=xa094.9xa0±xa00.3xa0% was observed at pHxa0=xa04.63. The selectivity of L for the Th(IV) cation over other cations (i.e., Cs(I), Sr(II), Y(III), La(III), Sm(III), Eu(III), U(VI), and 241Am(III)) was evaluated. Furthermore, the stripping experiments showed that the stripping agent (0.5xa0mol/L Na2CO3xa0+xa00.1xa0mol/L EDTA) could provide an optimal condition for stripping thorium, and thorium recovery was up to 91.6xa0±xa00.1xa0%.

The influence of different hydroponic conditions on thorium uptake by Brassica juncea var. foliosa

The effects of different hydroponic conditions (such as concentration of thorium (Th), pH, carbonate, phosphate, organic acids, and cations) on thorium uptake by Brassica juncea var. foliosa were evaluated. The results showed that acidic cultivation solutions enhanced thorium accumulation in the plants. Phosphate and carbonate inhibited thorium accumulation in plants, possibly due to the formation of Th(HPO4)2+, Th(HPO4)2, or Th(OH)3CO3− with Th4+, which was disadvantageous for thorium uptake in the plants. Organic aids (citric acid, oxalic acid, lactic acid) inhibited thorium accumulation in roots and increased thorium content in the shoots, which suggested that the thorium-organic complexes did not remain in the roots and were beneficial for thorium transfer from the roots to the shoots. Among three cations (such as calcium ion (Ca2+), ferrous ion (Fe2+), and zinc ion (Zn2+)) in hydroponic media, Zn2+ had no significant influence on thorium accumulation in the roots, Fe2+ inhibited thorium accumulation in the roots, and Ca2+ was found to facilitate thorium accumulation in the roots to a certain extent. This research will help to further understand the mechanism of thorium uptake in plants.

Impact of mixed low-molecular-weight organic acids on uranium accumulation and distribution in a variant of mustard (Brassica juncea var. tumida)

The impact of a mixture of low-molecular-weight organic acids (LMWOAs) composed of CA/MA/OA/LA with a molar ratio of 2.5:2.31:1.15:0.044 on uranium (U) accumulation and distribution in mustard (Brassica juncea var. tumida) was studied in this paper in order to understand the mechanism of rhizosphere-exudation assisted phytoremediation by hydroponic and pot culture experiments. The impact of the mixture of LWMOAs (Mix) on U accumulation showed that in hydroponic conditions Mix could enhance U translocation from root-to-shoot in mustard, but inhibit U uptake in root. In pot experiments, Mix enhanced both root and shoot U accumulation in mustard. The time-dependent kinetics of U uptake in mustard on Mix treatment showed that U content in plant shoots and roots increased with time increasing, and the steady state conditions were obtained at the 8th and 5thxa0day with the U content of 1,528 and 2,300xa0mg/kg, respectively. Transmission electron microscope and energy dispersive X-ray spectrometry analysis for mustard roots showed that U was mainly observed on cell membrane of mustard roots on Mix treatment. This study would provide new insights for the mixture of LWMOAs-assisted phytoremediation of U-contaminated soil.

Chaos to order: an eco-friendly way to synthesize graphene quantum dots

We developed a rapid, simple and pollution-free method to synthesize highly ordered graphene quantum dots (GQDs), which adopts cheap and readily available activated carbon and environmentally friendly hydrogen peroxide as raw materials through simple microwave and hydrothermal treatment, and the fine products are obtained as uniformly sized particles. The proposed strategy enables the difficult transformation from amorphous carbon to highly ordered GQDs for the first time while completely avoiding the use of concentrated sulphuric acid, concentrated nitric acid and other caustic reagents, and the purification procedure is relatively simple. Furthermore, the as-prepared products possess low toxicity, high biological compatibility and good fluorescence properties, which are excellent properties for bio-labelling applications.

The effect of U speciation in cultivation solution on the uptake of U by variant Sedum alfredii

In the present study, five plant species were screened for uranium uptake using a hydroponic experimental set-up. The effect of the U concentration, pH, as well as the presence of carbonates, phosphates, and organic acids (lactic acid, malic acid, citric acid) on the uptake of U by variant S. alfredii (V S. alfredii) and wild S. alfredii (W S. alfredii) were investigated. Results showed that V S. alfredii exhibited higher U content in the roots than the other four plants and with the increase of U concentration in the solution, the U uptake by V S. alfredii and W S. alfredii increased. The results also showed that different U speciation in different cultivation solution took an important role on the uptake of U in variant Sedum alfredii: at pH 6.5, U hydrolysis species (UO2)3(OH)5+is predominant and the U concentrations in V S. alfredii roots reached a maximum value (3.7u2009×u2009104xa0mg/kg). U complexation with carbonates, phosphates, and some organic acids in the solution resulted in a decrease in the U content in the roots except for lactic acid. Our researches highlight the correlations between U speciation and the uptake on V S. Alfredii, which will be helpful for improved removal of U from the groundwater using phytoremediation method.

Preparation and evaluation of 131I-quercetin as a novel radiotherapy agent against dedifferentiated thyroid cancer

AbstractnHere we reported the radiolabeling and evaluation of a novel 131I-radiolabeled quercetin for the treatment of dedifferentiated thyroid cancers. The human thyroid cancer cell lines (FTC-133, TT and DRO) experienced much higher uptake of 131I-quercetin as compared to the free 131I. And the proliferation inhibition rate of 131I-quercetin on in vitro DRO cell line was 86.87xa0±xa07.15%. Biodistribution and SPECT analysis demonstrated that the injected radioactivity mainly accumulated in tumors. The tumor volume in the treatment group was dramatically inhibited in comparison with the control group.

Subcellular distribution and chemical forms of thorium in Brassica juncea var. foliosa

Brassica juncea var. foliosa (B. juncea var. foliosa) is a promising species for thorium (Th) phytoextraction due to its large biomass, fast growth rate and high tolerance toward Th. To further understand the mechanisms of Th tolerance, the present study investigated the subcellular distribution and chemical forms of Th found in B. juncea var. foliosa Our results indicated that in both roots and leaves, Th contents in different parts of the cells follow the order of cell wallxa0>xa0membranes and soluble fractionxa0>xa0organelles. In particular, Transmission Electron Microscope (TEM) analysis showed that Th was abundantly located in cell walls of the roots. Additionally, when plants were exposed to different concentrations of Th, we have found that Th existed in B. juncea var. foliosa with different chemical forms. Much of the Th extracted by 2% acetic acid (HAc), 1xa0M NaCl and HCl in roots with the percentage distribution varied from 47.2% to 62.5%, while in leaves, most of the Th was in the form of residue and the subdominant amount of Th was extracted by HCl, followed by 2% HAc. This suggested that Th compartmentation in cytosol and integration with phosphate or proteins in cell wall might be responsible for the tolerance of B. juncea var. foliosa to the stress of Th.

Adsorption and desorption of uranium(VI) by Fe–Mn binary oxide in aqueous solutions

AbstractThe adsorption and desorption behaviors of uranium(VI) by a synthetic Fe/Mn (mass ratio of 57:1) binary oxide (FMBO) has been investigated. The pseudo-second-order kinetic and the Dubinin–Radushkevich isotherm models showed.that the adsorption process involved chemical adsorption. The calculated thermodynamic parameters (ΔH°, ΔS°, ΔG°) indicated that the adsorption process of uranium(VI) onto FMBO was spontaneous and endothermic. The desorption experiments indicated that the high desorption rate of uranium(VI) from FMBO by organic acids would increase the total solubility of uranium (in the exchangeable form), which would in turn enhance bio-absorption of uranium from soil via phytoremediation.n