The demand for rapid, sensitive, and portable analytical tools to detect biologically and environmentally significant targets, such as Cu2+, S2−, and glutathione, has accelerated the development of high-performance fluorescent probes. Herein, we report the design and synthesis of a novel water-soluble, peptide-based probe, L (FITC–Ahx-His-Pro-Thr-His-NH₂), using solid-phase peptide synthesis. The probe features two histidine imidazole groups that selectively coordinate with Cu2+ in a 2:1 stoichiometry, resulting in significant fluorescence quenching (a “turn-off” response). Subsequent introduction of S2−, cysteine, or glutathione to the L-Cu complex leads to competitive sequestration of Cu2+, thereby restoring the probe's fluorescence (a “turn-on” response). This reversible process establishes a robust “on–off–on” sensing cycle for sequential detection. The probe demonstrates high sensitivity, excellent water solubility, and outstanding biocompatibility and cell-membrane permeability, enabling real-time fluorescence imaging of the target analytes in living cells. Furthermore, L reliably detected Cu2+ in real environmental water samples, including tap water and lake water. To facilitate visual detection, Rhodamine B was incorporated as a colorimetric enhancer. Upon Cu2+ binding, the system exhibited a distinct colorimetric transition from grass-green to orange-red, enabling clear naked-eye discrimination. The probe was further integrated into test strips coupled with a smartphone-based color-recognition application, achieving semi-quantitative Cu2+ detection by analyzing the red-to-green (R/G) channel ratio. This portable, low-cost detection platform provides a practical solution for on-site environmental monitoring and rapid bioanalysis.
Grinding is a critical stage in ultra-clean coal preparation to achieve sufficient liberation of valuable components from gangue minerals. Under identical energy inputs, this study systematically investigates the mechanisms by which rod and ball milling modulate the surface micro-properties of coal particles and their subsequent flotation enrichment behaviors. Multi-scale characterization and molecular dynamics (MD) simulations reveal that rod milling achieves superior physical liberation efficiency during the low energy-consumption stage (＜32.1 kJ), yielding a liberation degree of 70.66% (higher than the 67.95% of ball milling) along with a more uniform particle size distribution and distinct angular morphologies. Conversely, ball milling induces more intense mechanical activation and surface oxidation, causing the C–C bond content to decrease sharply to 65.43% and the C-O bond content to surge to 27.56% (compared to 74.08% and 18.47% for rod milling, respectively). Inverse gas chromatography (IGC) confirms that the polar component of surface energy for ball-milled coal (6.67–45.04 mJ·m−2) is significantly higher than that of rod-milled coal (3.89–33.12 mJ·m−2), exhibiting pronounced surface heterogeneity. MD simulations further elucidate the negative impact of polar group exposure on flotation from a microscopic perspective: the ball-milled coal (Wiser2 system) exhibits greater water penetration depth (14.34 Å) and a higher hydrophilic MSD slope (0.57) than the rod-milled system (11.83 Å and 0.52), while the contact angle drops to 106.5°, thereby enhancing steric hindrance and imposing kinetic limitations on collector adsorption. Flotation experiments ultimately validate these microscopic mechanisms; rod-milled coal achieves the highest clean coal yield of 76.57% with an ash content of 1.56%, markedly outperforming ball-milled coal (60.59 %yield). From a multi-scale perspective of liberation-surface energy-functional groups-flotation response, this study clarifies the distinct microscopic mechanisms of different milling methods, providing theoretical guidance for optimizing grinding processes in ultra-clean coal preparation.
To investigate the strain behavior of the coal matrix during N2-enhanced coalbed methane (N2-ECBM) under different nitrogen injection pressures, saturated methane samples of four different coal ranks (Ro,ran = 0.41-3.23%) were selected. Nitrogen injection and sealing (N2-IS) was performed under pressures of 1.5-5.5 MPa, followed by desorption with stepwise depressurization (DSD). The induced strain characteristics, strain kinetics, and desorption response were analyzed based on volume strain, residual gas volume, and the stretched exponential equation (SE equation) fitting. The results indicate that the residual gas volume of the coal samples ranged from 3.01 to 15.55 cm3/g after the N2-IS phase and further decreased to 0.30-3.02 cm3/g after the DSD phase. A clear linear relationship (R2 >= 0.88) exists between the adsorption/desorption-induced swelling/ shrinkage strain of the coal matrix and the residual gas volume. The strain response of coal samples of different ranks is jointly governed by pore structure and elastic modulus; coal samples with well-developed micropores exhibited stronger swelling during the N2-IS phase and shrinkage during the DSD phase under higher nitrogen injection pressures. When the nitrogen injection pressure was three times the reservoir pressure, the cumulative volume shrinkage rates of all coal samples increased by more than 10%, including 29.96% for coal C; at 3.67 times the reservoir pressure, all samples increased by more than 15%. For reservoirs with well-developed micropores, high elastic modulus and poor permeability, higher nitrogen injection pressures are more effective in reducing residual gas volume, increasing the cumulative volume shrinkage rate and promoting methane desorption.
To investigate potassium (K) migration during biomass gasification, the transformation mechanisms of K in sunflower stalk (SS) ash and the effects of aluminosilicate-rich solid wastes (coal gangue and coal fluidized-bed gasification fly ash) were explored under a reducing atmosphere. The potassium transformation behavior and aluminosilicate structural evolution were characterized by XRD, ICP OES, Raman spectroscopy, SEM EDX, and FactSage simulations. With increasing temperature, K in SS ash, mainly existing as KCl, was gradually released into the gas phase. The addition of aluminosilicate rich wastes redirected potassium transformation toward stable potassium aluminosilicate phases, resulting in the increase of potassium content after high temperature treatment. However, at high additive dosages, K+ in silicate phases may have been partially substituted by Ca2+ and Mg2+, which may have promoted potassium release and the formation of low melting-point akermanite, leading to the slagging risk increase slagging, Thermodynamic analysis suggested that potassium aluminosilicate formation was thermodynamically more favorable than potassium volatilization. This study reveals K migration and ash fusion mechanisms during biomass gasification.
Coal-and-gas co-mining involves the pre-extraction of coalbed methane (CBM) prior to coal mining, and pressurized acid injection for permeability improvement in coal mass is widely adopted to increase gas production in CBM wells. However, insufficient attention has been given to its effects on spontaneous combustion of coal in the subsequent underground coal mining. In this study, high-rank bituminous coal samples were immersed in acid pressurized at 10 MPa at six hydrofluoric acid concentrations, 0%, 3%, 6%, 9%, 12%, and 15%, and then laboratory tests were conducted to explore the influence of acid etching on the oxidation characteristics of coal. Temperature-programmed oxidation, low-temperature nitrogen adsorption, fourier transform infrared spectroscopy, and wavelength-dispersive X-ray fluorescence spectroscopy were used to characterize variations in oxidation characteristics, pore structure, oxygen-containing functional group composition, and elemental content of coal after high-pressure acidification. The research results show that (1) high-pressure acid etching altered coal spontaneous combustion tendency from spontaneous combustion of raw coal to easily spontaneous combustion of the acid-etched coal due to the obvious change in oxidation characteristics of coal; (2) compared with those of high-pressure water-immersed coal, the specific surface area and average pore diameter of acid-etched coal increased by maximums of 78.5% and 92.8%, respectively, improving coal–oxygen contact efficiency and expanding the reaction scale; (3) compared with those of high-pressure water-immersed coal, the maximum relative contents of oxygen-containing functional groups and Fe2O3 in acid-etched coal increased by 36.8% and 138%, respectively, increasing the intensity of coal–oxygen reactions.
