Zhibin Zhang

Amidoxime-functionalized hydrothermal carbon materials for uranium removal from aqueous solution

A novel solid-phase extractant, i.e., amidoxime-functionalized hydrothermal carbon (AO-HTC), has been synthesized, with acrylonitrile grafted starch serving as the precursor, via a simple, economic and green hydrothermal reaction to separate uranium from nuclear industrial effluents selectively. The characterization and analysis indicated that abundant amidoxime groups (approximately 6.56 mmol g−1) were introduced onto the surface of hydrothermal carbon. The AO-HTC was applied to adsorb U(VI) from aqueous solutions and exhibited a high sorption capacity towards U(VI) due to the strong chelation between amidoxime groups and U(VI). The main results are as follows: (1) AO-HTC could reach its limiting saturation capacity of 724.6 mg g−1 at pH = 5.0 and T = 298.15 K in pure-U(VI) solution, which was an improvement of approximately 18.2 times relative to the raw hydrothermal carbon; (2) the selectivity was above 60% for a wide pH range from 1.0 to 5.0, which has not been reported to date, and reached a maximum of 68.92% in a weak acidic multi-cation solution (pH = 2.0); (3) the uranium sorption on the AO-HTC was a pH-dependent, endothermic and spontaneous process. Furthermore, possible mechanisms for the selective recognition of uranyl ions onto the AO-HTC surface were explored based on experimental characterization and chemical rationales.

Adsorptive removal of uranyl ions in aqueous solution using hydrothermal carbon spheres functionalized with 4-aminoacetophenone oxime group

Hydrothermal carbon spheres (HCSs) functionalized with 4-aminoacetophenone oxime group (HCSs-oxime) were prepared by a grafting method and explored to adsorption of uranyl ions from aqueous solution. The results of FT-IR, elemental analysis and zeta potential indicate a successfully modification with oxime group. The adsorbent shows an excellent adsorption capacity (Langmuir, qmxa0=xa0588.2xa0mgxa0g−1) and quick adsorption kinetic (equilibrium time of approximately 60xa0min) at optimal pH of 6.0. The adsorptive selectivity for uranyl ions has been also great improved in present with various co-existing ions. Overall, HCSs-oxime is a potentially promising material for selective removal of uranium in the contaminated solution.

Off-on-off detection of the activity of acetylcholine esterase and its inhibitors using MoOx quantum dots as a photoluminescent probe

AbstractThe authors describe a fluorometric off-on-off method for the determination of the activity of acetylcholine esterase (AChE). Molybdenum oxide quantum dots (QDs) are used as a fluorescent probe having excitation/emission peaks at 405/525 nm. It is found that the photoluminescence of such QDs is quenched by Cu(II) ion but that it can be restored by acetylcholine which is formed by AChE-catalyzed hydrolysis of acetylthiocholine. The effect is due to the strong affinity between Cu(II) and the thiol group of acetylthiocholine. Hence, quenching is increasingly reversed with increasing concentrations of AChE. However, fluorescence is not restored if the activity of AChE is inhibited by an inhibitor. Under optimal conditions, a linear relationship is founded in the 0.05 to 15 mU·mL−1 AChE activity range, with a limit of detection of 35 μU·mL−1 (applying the 3σ/k criterion). Three organophosphate pesticides and propazine were used to validate the assay. All showed strong inhibition, with IC50 values (the concentration required for 50% inhibition to occur) to be 52, 221, 48 and 9 nM for diazinon, chlorpyriphos, monocrotophos and propazine. Benefitting from its sensitivity, specificity and simplicity, the assay in our perception provides a valuable tool for detection of AChE activity and in screening for its inhibitors.n Graphical abstractA novel “off-on-off” assay is constructed for acetylcholine esterase (AChE) activity and inhibitor screening benefitting from the phenomenon that the photoluminescence of molybdenum oxide quantum dots (MoOx QDs) is quenched by Cu2+ and that the quenched photoluminescence can be restored due the strong affinity between Cu2+ and thiocholine (Tch) which is the hydrolysis product formed due to catalysis by AChE.

Amperometric sensing of hydrazine using a magnetic glassy carbon electrode modified with a ternary composite prepared from Prussian blue, Fe3O4 nanoparticles, and reduced graphene oxide

AbstractA magnetic glassy carbon electrode (mGCE) was modified with a ternary composite prepared from Prussian blue (PB), magnetite (Fe3O4) nanoparticles, and reduced graphene oxide (rGO) in order to obtain an amperometric sensor for hydrazine. The utilization of Fe3O4 facilitates the magnetic immobilization and separation of sensing material, while the use of rGO enhances sensitivity. The surface coverage and the stability of the PB on the modified electrode were considerably improved. The electro-oxidative response to hydrazine was investigated with this modified mGCE using cyclic voltammetry and amperometric. The sensor, typically operated at a voltage of 0.2xa0V (vs. SCE), displays superior response hydrazine, with a response time of 4xa0s, a sensitivity of 97.73 μA μM−1xa0cm−2 and a 13.7xa0nM detection limit.n Graphical abstractA magnetic glassy carbon electrode was modified with a ternary composite prepared from Prussian blue, magnetite nanoparticles, and reduced graphene oxide to obtain a selective amperometric sensor for dissolvedxa0hydrazine.

Phosphorylation of graphehe oxide to improve adsorption of U(VI) from aquaeous solutions

The graphene oxide (GO) was functionalized with phosphate groups and applied as an effective adsorbent for the removal of uranium from aqueous solutions under various environmental conditions (e.g., solution pH, ions strength, contact time and temperature). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy have confirmed that the phosphorylate group was successfully introduced on the surface of GO. The adsorption experiments indicated that the monolayer adsorption capacity has been increased from 249.38xa0mg/g (GO) to 336.70xa0mg/g [phosphorylated graphene oxide (PGO)] calculated by Langmuir model. Moreover, the adsorptive selectivity coefficients SU(VI)/M(x) increase from 42.43 to 51.96% after functionalized with phosphate group. The mechanism of U(VI) absorbed on PGO surface was dominated by surface complexation and electrostatic interaction. The results demonstrate that PGO will be a promising material for the efficient removal of U(VI) in the environment pollution remediation.

Removal of U(VI) from aqueous media by hydrothermal cross-linking chitosan with phosphate group

For the selective adsorption of U(VI) from aqueous solutions, the hydrothermal cross-linking chitosan (HCC) and its phosphorylation production (HCC-TPP) were synthesized by hydrothermal reaction. The monolayer maximum capacity of HCC-TPP was improved from 200xa0mgxa0g−1 of HCC to 409.2xa0mgxa0g−1 at 298xa0K. Calculated thermodynamic parameters showed endothermic property of the adsorption process, while kinetic parameters indicated that the interaction followed pseudo-second kinetic model. Selective separation of U(VI) from effluent by HCC-TPP was achieved.

Adsorption of U(VI) on montmorillonite pillared with hydroxy-aluminum

Hydroxy-aluminum pillared Na-montmorillonite(OH–Al-MT) was prepared for studying sorption of U(VI) in the existence of soluble calcium (Ca2+), carbonate ion (CO32−) and humic acid. Various characterizations confirm that hydroxy-aluminum was successfully pillared into Na-montmorillonite (Na-MT). The effects of pH, concentration of Ca2+ and CO32− as well as HA on the sorption capacity of Na-MT and OH–Al-MT for U(VI) has been investigated by batch experiments. Additionally, the kinetics, isotherms and thermodynamics of adsorption of U(VI) were discussed in detailed. The study indicates that OH–Al-MT can be a potentially promising low-cost adsorbent for removal of U(VI) in wastewaters.