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A novel ferrate(VI)/titanium dioxide/ultraviolet [Fe(VI)/TiO2/UV] system was successfully established for the photocatalytic oxidation of dimethyl phthalate (DMP). This system demonstrated a higher removal efficiency of DMP (95.2%) than the conventional TiO2/UV and Fe(VI) alone systems (51.8% and 23.5%, respectively) and produced obvious synergistic effects. Response surface methodology (RSM), based on a three level, three independent variables design, was conducted through Design Expert 8.0.6 program, and a second-order polynomial model (R2 = 0.998) was developed to quantitatively describe the photocatalysis of TiO2 combined with Fe(VI) oxidation under ultraviolet irradiation. The fresh TiO2 and photochemical reacted Fe(VI)/TiO2 were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and element dispersive spectrum (EDS), which indicated that Fe(VI) was imprinted into the TiO2, and the surface adsorbed Fe-O-(organic) materials inhibited DMP degradation. This photocatalytic oxidant showed high activity and stability after nine cycles without loss of its effectiveness (counting from the second cycle). The intermediates/products of DMP were analyzed by gas chromatography-mass spectrometry. The proposed pathway for DMP degradation involved one electron transfer of hydroxyl radical and breaking of the ester bond and benzene ring. The mineralization efficiencies of DMP in actual industrial wastewater and simulated water were 87.1% and 95.2%, respectively, suggesting practical field applications. A ecotoxicity test (17.3% inhibition on bioluminescence) in treating actual industrial wastewater containing DMP implied that the proposed Fe(VI)/TiO2/UV had a potential for industrial water treatment. [ABSTRACT FROM AUTHOR]

Due to the essential role of Fe3+ in physiological and pathological processes, the detection of Fe3+ has drawn increasing attention in the field of disease diagnosis and environmental protection. However, most existing methods require either cumbersome sample pretreatment or sophisticated and expensive test equipment. Recently, carbon quantum dots have found a wide range of applications such as nanoprobes for Fe3+ determination, albeit with limited sensitivity and selectivity. Herein, we report core–shell carbon quantum dots B1N2CQDs via a two-step hydrothermal approach using citric acid, boric acid and ethylenediamine as precursors. The obtained B1N2CQDs exhibit excellent water solubility and remarkable stability as well as a high fluorescence quantum yield of 15.4%. In addition, the fluorescence of B1N2CQDs is quenched exclusively by Fe3+ with minimal interference from other metal ions. A linear relationship with R2 = 0.998 was observed between the fluorescence quenching capacity and the Fe3+ concentration in the range of 2–160 μM, with the limit of detection calculated to be 80 nM. Finally, the as-prepared B1N2CQDs were successfully applied as a highly efficient fluorescent probe for Fe3+ detection in river water samples and intracellular Fe3+ imaging in biological systems. [ABSTRACT FROM AUTHOR]

• A two-phase flow model coupled with geomechanics to investigate the transient flow behaviour. • Using dynamic fracture properties improves the model accuracy at early-time period. • Physical constraints in a gas reservoir are considered to capture its actual flow dynamics. • Triangular/rectangular fracture geometries exhibit the lowest/largest deformation, respectively. • Effects of fracture properties/capillary pressure dominate flow behaviour at early stage. A robust and efficient two-phase flow model integrated with geomechanics has been developed, validated, and subsequently utilized to investigate the transient flow characteristics in an unconventional reservoir with consideration of fracture geometry and capillary pressure. As for a fracture subsystem, various hydraulic fracture (HF) geometries are applied to capture a loss in the fracture conductivity due to an alteration in the effective normal stress on the fracture surface during the flowback period. Different from the traditional treatment by assuming it as a constant, a function of interfacial tension between gas and water as well as fracture aperture is employed to obtain the capillary pressure within a fracture, during which the gas/water saturation and the fracture aperture in each fracture segment with an equal length can be iteratively obtained and updated. Not only does the proposed model offer the flexibility to investigate the effects of dynamic fracture properties (i.e., aperture and conductivity) and capillary pressure on the two-phase flow behaviour in the fractures with various fracture geometries, but also its precision has been validated through numerical simulations and subsequently applied in the field cases with outstanding performance. Dynamic fracture properties and capillary pressure are found to exert considerable influences on the gas/water daily production rates and cumulative production at the early time flow. It is worthwhile noting that capillary pressure shows a more pronounced effect on the transient flow behaviour due to a reduction in fracture aperture during production. Moreover, the fracture with a triangular shape exhibits the lowest gas/water production rate, whereas a rectangular fracture results in the largest gas/water production rate. On the basis of fracture geometry and geomechanics, the former shows the smallest deformation induced by the effective stress, and the latter suffers the largest deformation under the same stress condition. In addition, a poorly propped HF exhibits a large aperture reduction, resulting in a reduction in gas/water production rate. As for field cases, the gas/water production rate obtained from the two-phase flow model demonstrate a strong agreement with the observed data, providing further confirmation of the dependability and robustness of the proposed model. [ABSTRACT FROM AUTHOR]

The process of lignin extraction often involves intricate chemical transformations, influencing its potential for high-value utilization. By investigating the process of lignin derivatives extraction from hemp fibers using supercritical CO 2 , ethanol, and water, we identified the relationship between the chemical structure of lignin derivatives and temperature. This discovery contributes to controlling the chemical structure of lignin derivatives through temperature modulation. We observed that lignin derivatives extracted within the temperature range of 100–120 °C exhibited the lowest average molecular weight and polydispersity index, presenting a disordered microstructure with the highest hydroxyl content. Lignin derivatives extracted between 140 and 160 °C showed an increase in average molecular weight and polydispersity index, decreased hydroxyl content, and a gradual transformation of microstructure into spherical particles. At 180 °C, the average molecular weight and polydispersity index of lignin derivatives decreased, the microstructure of lignin derivatives showed fewer spherical particles, while its hydroxyl content exhibited a partial recovery. Chemical analysis revealed a lower degree of condensation in lignin derivatives at 100–120 °C. Between 120 and 160 °C, the degree of condensation increased. At 180 °C, extensive degradation occurred in lignin derivatives. This research advances innovative techniques for lignin derivative separation, contributing to their utilization in higher-value applications. • We have discovered a method that allows for the controlled manipulation of the chemical structure of lignin derivatives by adjusting the temperature during the separation process. • Lignin derivatives extracted at different temperature ranges exhibits distinct chemical characteristics, enabling diverse applications based on its unique properties. • A more specific description of the chemical structure changes that lignin undergoes during the separation process using supercritical CO 2 , ethanol, and water is presented. [ABSTRACT FROM AUTHOR]