[en] The sorption/desorption behaviors of benzene, toluene, ethylbenzene, and xylene (BTEX) on soil organic matter (SOM) have a significant influence on their fate and bioavailability in soil. Humic acid (HA) is a major fraction of SOM. And due to its various structural properties and chemical composition, the sorption/desorption characteristics and mechanisms of HA are diverse for organic contaminants. In this study, batch experiments were conducted to investigate the sorption/desorption behavior of benzene on HA at different conditions (temperature, pH, and ionic strength). The particle size of HA increased at lower initial pH which promoted sorption capacity for benzene, illustrating that HA with larger particle size may develop preferential chemical conformation for benzene sorption at lower pH. Sorption isotherms indicated that the sorption of benzene on HA is an exothermic and spontaneous physical process. And kinetic studies showed that the sorption of benzene on HA is controlled by the diffusion process and the availability of sorption sites. Meanwhile, weak sorbent-sorbate interaction is presented in the desorption experiment. There was no obvious effect of ionic strength on benzene sorption, suggesting that the sorption process is not controlled by ion-exchange or electrostatic interaction. Combined with FTIR analysis, the hydrophobic partitioning and π-π conjugative interaction are the possible sorption mechanisms of benzene on HA.

[en] Due to human activities such as uranium mining, processing nuclear materials and nuclear power generation, excessive amounts of uranium have been discharged into the soils, surface water and groundwater. Humic acids(HAs) isolated from lignites have demonstrated beneficial impacts on immobilize radionuclide contaminants in water. The aims of this study is to explore the adsorption and desorption behavior of uranium(VI) on HAs derived from uranium-rich lignites and find out whether the high content of uranium present in these HAs can affect the reaction system. HAs(XZ-HA and BM-HA) were extracted from two uranium-rich lignites from XinZhai and BangMai villages in Yunnan province, China. The properties of obtained HAs were characterized by FTIR, element analysis, determination of HAs acidity and UV-Vis. Different operating conditions of pH, ionic strength, time, initial uranium concentration, and adsorbent amount were investigated. The results showed that HAs were particularly effective for adsorbing uranium(VI) and the optimum pH ranged from 5.0-8.5. The ionic strength(0.001, 0.01 and 0.1 M NaCl) can influence the adsorption behavior by affecting the HAs molecular structure, the adsorption efficiency decreased with increasing of ionic strength. The maximum uranium(VI) adsorption capacity of XZ-HA and BM-HA were 2.9 mg g^-1 and 3.7 mg g^-1 with adsorption efficiency of 72.5% and 92.0% respectively, the chemical characterization of HAs suggested that the carboxylic and phenolic hydroxyl groups were responsible for controlling the adsorption capacity. The pseudo-second-order model was found to explain the adsorption kinetics most effectively, and the adsorption isotherms were fitted well by the Langmuir and Freundlich models. Based on the desorption experiments, the main adsorption mechanism was complexation effect between the organic ligands of HAs and uranium(VI). The uranium present in XZ-HA and BM-HA(9.6 mg kg^-1 and 55.2 mg kg^-1) were released into the solution at the pH values between 1.0-3.0, when the BM-HA dosage was 2.5 g L^-1, the maximum concentration of uranium to be 50.4 μg L^-1, which exceed WHO guideline value for uranium(30 μg L^-1) in drinking water. This shows that uranium-rich lignite-derived HAs may present a potential environmental risk when used in acidic aqueous media.

[en] A simplified two-dimensional axisymmetric model was established based on a typical continental sedimentary basin in China to simulate the thermal evolution of wellbore and reservoir during the injection of CO₂ by taking consideration of lithology heterogeneity of reservoir. By comparing with two simple one-dimensional theory models, the lithology heterogeneity influence on CO₂ mass flow rate distribution along depth in the wellbore is identified. Results suggested that the interaction of multiple layers in the heterogeneous reservoir will influence the CO₂ mass flow rate distribution along depth in the wellbore so as to impact the corresponding temperature and pressure evolution in the wellbore and reservoir. Layer burial depth (or relative location), porosity, permeability and thickness are all important factors that affect CO₂ mass flow rate in wellbore. The variation of CO₂ mass flow rate in the wellbore will change the CO₂ temperature flowing into each layers through impact the heat extraction from rocks, compressibility of CO₂ and potential energy loss, and by varying the CO₂ hydrostatic pressure and pressure drop due to friction to determine the CO₂ injection pressure. Layer burial depth, porosity, permeability and thickness are all important factors that affect the CO₂ mass flow rate distribution in the wellbore. This study may help deepen our understanding of CO₂ flow and thermal evolution in the actual heterogeneous reservoir and provide important knowledge supplement for the liquid injection (especially CO₂) into underground, such as deep saline aquifer, depleted oil/gas reservoir and coal bed.

[en] Highlights: • The mobility of trace elements is dominated by oxidation, acidization, adsorption and precipitation. • Affinity of trace elements with carbonate minerals, pyrite and organic matter significantly affects their mobility. • Adsorption and coprecipitation of secondary minerals reduce the mobility of trace elements. • Mobilization of trace elements strongly depends on oxidant concentration and solid:liquid ratio. Oxidant stimulation is a promising technology for shale permeability enhancement, but it is still faced with the problem of produced water with high total dissolved solids. For the consideration of environmental protection and water reuse, the mobility of trace elements (TEs) should be evaluated before the in-situ application of this technology. In this study, carbonate-rich shale and silicate-rich shale, collected in Yichang, Hubei province of China, were used to react with sodium persulfate (Na₂S₂O₈) at different experimental conditions. The sequential chemical extraction was used to analyze the occurrence of TEs in shales and their mobilization mechanism. Influence factors including oxidant concentration, solid:liquid ratio, initial pH and temperature were systematically investigated to explore their effect on the mobility of TEs. Results showed that a similar affinity between TEs and fractionation phases was observed in both two shales. Tough the TEs associated with residual fraction was most obvious in shales, various associations between TEs and other extractable fractions were also apparent, such as Co (61.7% on average) and Cu (59.2% on average) in organic matter-bound fraction, and Sr (53.2% on average) in carbonates-bound fraction. The occurrence of TEs determined their extent of mobilization during oxidant stimulation, and the complex interactions including acidization, oxidation, adsorption and precipitation influence the mobility of TEs as well. The carbonate minerals and pyrite were both critical minerals for decreasing the mobility of TEs. Carbonate minerals in shale could effectively buffer the pH of the system to mitigate the acidization reaction. The near-neutral environment was also beneficial for the Fe(OH)₃ precipitation then resulted in the fixation of TEs through adsorption. Besides, the generated gypsum from carbonate dissolution also contributed to the incorporation of TEs. Meanwhile, sulfate generated from pyrite oxidation and persulfate hydrolysis also directly precipitated with TEs such as Ba and Sr to reduce their dissolved content in the reaction system. Influence factors analysis showed that the mobility of TEs was strongly dependent on the oxidant concentration and solid: liquid ratio and to a lesser extent on the temperature and initial pH. Considering the environmental risk and water management cost, systematic investigation on shale composition and associated TEs, and optimization of engineering parameters should be carried out before the in-situ application of this technology.

[en] A set of highly branched imidazolium-functionalized poly(arylene ether sulfone)s copolymer bearing with flexible alkyl side chains of different lengths are designed and synthesized. The ion exchange capacity (IEC), ionic conductivity, water uptake, thermal stability, mechanical property and alkaline resistance of the anion exchange membranes (AEMs) were evaluated in detail. Atomic force microscopy and small-angle X-ray scattering are used to study morphology which reveals that the branched membrane with an alkyl side chain (6 carbons) achieves the highest conductivity (up to 115.8 mS cm⁻¹ at 80 °C) due to the well-developed hydrophilic/hydrophobic phase separation. In addition, the branched co-polymer AEM with a longer alkyl side chain (12 carbons) exhibit the best robust alkaline stability, it decreases only 27% of ionic conductivity after 550 h in 1 M KOH. Therefore, this study provides a comprehensive insight into the tuneable membrane properties of highly branched copolymers as a change in the length of flexible alkyl side chains.

[en] To suppress the generation of oxygen vacancy during the PbZr_0.53Ti_0.47O₃ (PZT) film synthesis process, herein, the 0–3 type Ag/PZT film is chosen as a prototype to systematically investigate the mechanisms of oxygen vacancy decrease and the relationship of ferroelectric properties. The uniform and dense films were successfully fabricated on fluorine tin oxide glasses (FTO) by facile sol–gel processes. It is confirmed the existence of silver nanoparticles in the film, indicating the composite ferroelectric films are of 0–3 type. When Ag doping mole concentration is 0.010 in the sol, a large remnant polarization (P_r) of ~ 50.7 µΧ/cm² is got, which is 37.9 µΧ/cm² for pure PZT. UV–vis spectrum confirms the generation of Ag₂O in the process of mixing the sol. Furthermore, the oxygen vacancies caused by natural evaporation of lead specie are effectively reduced because of the decomposition of Ag₂O, confirmed by X-ray photoelectron spectroscopy. This work points out the generated Ag₂O as the intermediate product is the key to achieve high remnant polarization in Ag/PZT based film and make it as a promising candidate for memory applications.

[en] Foodborne pathogens are perpetual threats to human and animal health. Detection of pathogens requires accurate, sensitive, rapid and point-of-care diagnostic assays. In this study, we described a simple and sensitive electrochemiluminescent (ECL) assay to detect the deadly bacteria Escherichia coli O157:H7 by $\mathrm{R}\mathrm{u}{{(\mathrm{b}\mathrm{p}\mathrm{y})}_3}^{2+}$-coated ZnO nanorods arrays (NAs). The $\mathrm{R}\mathrm{u}{{(\mathrm{b}\mathrm{p}\mathrm{y})}_3}^{2+}$-coated ZnO NAs were fabricated by immobilizing $\mathrm{R}\mathrm{u}{{(\mathrm{b}\mathrm{p}\mathrm{y})}_3}^{2+}$ on ZnO NAs with a large specific surface area and good conductivity. An $\mathrm{R}\mathrm{u}{{(\mathrm{b}\mathrm{p}\mathrm{y})}_3}^{2+}$-2-(dibutylamino)-ethanol (DBAE) system coated on ZnO NAs exhibits high ECL intensity, rapid response and good stability. This system was further developed as an ECL immunosensor used in the detection of E. coli O157:H7. The proposed ECL immunosensor exhibits a broad detection range within the scope of 200–100 000 CFU ml⁻¹ and quite a low detection limit of 143 CFU ml⁻¹. The high specificity, remarkable reproducibility and good stability offer a sensitive, selective, and convenient pathway for detecting E. coli O157:H7 in the field of food safety and clinical diagnosis. (paper)

[en] Ag₂WO₄ is a significant photocatalyst that responds to UV light irradiation only, which greatly hinders it for further practical application for solar light. To address this problem, herein, 1D plasmonic Ag/Ag₂WO₄ photocatalysts have been fabricated by a successive process including hydrothermal synthesis to obtain Ag₂WO₄ followed by an additional in situ chemical-reduction process for Ag decoration. Then, the structural features, optical properties, and electronic structures of Ag₂WO₄ and Ag/Ag₂WO₄ nanowires were systematically investigated via a combination of theoretical calculations and experimental evidence. The plasmon-enhanced Ag/Ag₂WO₄ nanowires exhibited higher visible-light-driven photocatalytic activity, which performed a desired photodestruction ratio of 91.2% on methylene blue within 60 min and good stability in five cycles. The Ag decoration greatly facilitates visible-light harvesting and thus promotes photogenerated radical oxidation to dye, which is evidenced by the higher hydroxyl radical level of Ag/Ag₂WO₄ detected in the ESR test during the photocatalytic process. The theoretical calculation based on density functional theory indicates that Ag nanoparticles formed on the surface of Ag₂WO₄ could narrow the band gap of Ag₂WO₄. In addition, the surface plasmon resonance absorption effect and fast charge transfer effect in the metal-semiconductor system contribute to the photocatalytic performance of Ag/Ag₂WO₄. (paper)

[en] While silicon-based negative electrode materials have been extensively studied, to develop high capacity lithium-ion batteries (LIBs), implementing a large-scale production method that can be easily transferred to industry, has been a crucial challenge. Here, a scalable wet-jet milling method was developed to prepare a silicon-graphene hybrid material to be used as negative electrode in LIBs. This synthesized composite, when used as an anode in lithium cells, demonstrated high Li ion storage capacity, long cycling stability and high-rate capability. In particular, the electrode exhibited a reversible discharge capacity exceeding 1763 mAh g⁻¹ after 450 cycles with a capacity retention of 98% and a coulombic efficiency of 99.85% (with a current density of 358 mA g⁻¹). This significantly supersedes the performance of a Si-dominant electrode structures. The capacity fade rate after 450 cycles was only 0.005% per cycle in the 0.05–1 V range. This superior electrochemical performance is ascribed to the highly layered, silicon-graphene porous structure, as investigated via focused ion beam in conjunction with scanning electron microscopy tomography. The hybrid electrode could retain 89% of its porosity (under a current density of 358 mA g⁻¹) after 200 cycles compared with only 35% in a Si-dominant electrode. Moreover, this morphology can not only accommodate the large volume strains from active silicon particles, but also maintains robust electrical connectivity. This confers faster transportation of electrons and ions with significant permeation of electrolyte within the electrode. Physicochemical characterisations were performed to further correlate the electrochemical performance with the microstructural dynamics. The excellent performance of the hybrid material along with the scalability of the synthesizing process is a step forward to realize high capacity/energy density LIBs for multiple device applications. (paper)

[en] Highlights: • Improved depolarization behavior in (Bi_0.5Na_0.5)TiO₃-based ZnO composites. • The influence of internal bias field on temperature-dependent P-E shape. • A new model on the relationship between ZnO enrichment regions and deferred depolarization behavior. (Bi_0.5Na_0.5)TiO₃ (BNT) based ceramics have been restricted by the drawback of the low depolarization temperature T_d and ferroelectric-to-relaxor transition temperature T_F-R. Many works have confirmed conventional improving strategies like doping and forming solid solution are not efficient to solve the problem. To overcome this obstacle, we introduced semiconductor ZnO into 0.93(Bi_0.5Na_0.5)TiO₃-0.07Ba(Ti_0.945 Zr_0.055)O₃:xZnO matrix to prepare 0-3 type ceramic composites (abbreviated as BNT-BZT:xZnO). Energy disperse spectroscopy (EDS) result reveals that there are two distributions of Zn. Most of Zn²⁺ ions gather around the boundaries of BNT-BZT grains to form ZnO enrichment regions, and the others diffuse into the lattice. In consideration of the fact that the distribution of Na also appears to be separated, a new model on the Na migration is proposed to explain experimental results. Both the substitution of lower valent Zn²⁺ ions at B site and the migration of Na are benefit for the formation of oxygen vacancies. As a consequence, the coercive field E_c and mechanical quality factor Q_m have been significantly promoted. In terms of depolarization behavior, the temperature-dependent P-E loops show a completely different polarization process after ZnO incorporation. A slower decay of the remnant polarization P_r indicates ferroelectric state is more stable in the composites. The influence of internal bias field on asymmetric P-E loop has been discussed. The experiments on thermally stimulated depolarization current (TSDC) and temperature-dependent dielectric permittivity demonstrate T_d and T_F-R increase about 17 °C and 19 °C, respectively. Our research confirms forming ZnO composites is an effective method to improve depolarization behavior, and BNT-BZT:xZnO composites should be an alternative for application in electromechanical devices.