In this study, tri-butyl-phosphate (TBP)-kerosene is used as the extraction solvent to remove phenols from coal gasification wastewater, and the complex mechanism of the extraction is investigated. An effect experiment is conducted to determine the complex structures, the enthalpy change of reaction, and the effect of extraction solvent concentration and temperature on the distribution coefficient. To predict the extraction effect before the experiment, the distribution coefficient mathematical model of phenol extraction is established, which is based on a liquid-liquid extraction model and verified for accuracy by the experiment. The effect experiment result shows that with an increase in concentration of TBP and decrease in temperature, the extraction distribution coefficient increases and further determines the complex structures and the enthalpy change of the reaction. Meanwhile, a comparison of experimental and calculated values in the model experiment result shows that the average relative error of extraction distribution coefficient is 5.56% in different concentrations of TBP and 2.72% in different temperatures. Considering the error of the experiment, this work concludes that the distribution coefficient mathematical model of phenol extraction has a high predictive effect on the distribution coefficient and extraction rate of volatile phenol in actual wastewater.

Some provinces in China require zero discharge of coal mine wastewater, with a focus on the disposal of high-salt water, because evaporation ponds have been completely banned. Deep geological storage (DGS) technology is a novel geological environment solution that uses rock pores and microfissures within deep strata for safely storing liquid or gas to avoid its environmental impact on the biosphere. The author and his research team were the first to put forward the research idea of using DGS technology to dispose of high-salinity brine in coal mines in China and performed related research. Taking a coal mine in the south of Ordos Basin as an example, this study designed a conventional, mine-specific, zero-discharge water treatment process route based on a evaporation–crystallization process. This strategy was tailored to the unique water inflow conditions of the mine. Furthermore, the technical and economic efficiencies were assessed for the generation and treatment scenarios of a four-stage highly concentrated brine solution. In addition, the comparative analysis of the economic prospects of using DGS technology to treat high-salinity brine revealed that combining DGS with post-conventional treatment in secondary reverse osmosis, whose flow quality is 481 m³/h and TDS is 24,532.66 mg/L, can maximize the economic benefits. This integration heightened water resource utilization while maintaining a cost-effective, comprehensive water treatment approach. These results provide a valuable reference value for the future zero-discharge treatment of coal mine water.

Deep well injection and storage (DWIS) has recently been proposed and implemented to achieve zero mine water emissions. In 2023, DWIS for highly saline mine water was successfully applied to a local mine in the Ordos Basin for the first time with excellent performance. However, the storage characteristics of highly saline mine water in the storage layer during DWIS remain unclear. This study was conducted in situ with real-time, online monitoring of instantaneous flow and injection pressure, along with synchronous micro-seismic monitoring during the early stages of DWIS, based on the geological conditions and spatial structure of the storage layer. The results indicated that the early seepage characteristics of the fluid geological storage did not conform to Darcy’s law. Within a certain pressure range, as the water pressure increased, the flow also increased. However, beyond this range, further increases in pressure caused a gradual decline in the flow. During the initial phase of storage, the migration of high-salinity mine water within the storage layer occurred in two stages: breakthrough and stabilization. During the breakthrough stage, the water injection pressure propagated to the flooding front, overcoming the formation stress and expanding the storage space. At this stage, mine water primarily filled the pore microcracks within the flooding front. In the initial 10 days of storage, high-salinity mine water in the study area affected approximately 42,104 m² of the storage layer plane. The injection well affected an area nearly 200 m in depth, extending approximately 190 m northward and approximately 40 m upward. The predominant diffusion directions were northeast and east–southeast from the injection well. These findings could provide valuable insights into the treatment of highly saline mine water in the Ordos Basin, demonstrate the feasibility and safety of DWIS, and offer significant scientific contributions to the prevention and control of mine water pollution.

Deep well injection and storage is an emerging technology for realizing the low-cost treatment of extremely large quantities of three types of waste in coal mines in China, while simultaneously supporting coordinated development that considers its impact on the ecological environment. There has been significant progress in research on the geological storage of carbon dioxide in China. However, the geological storage of fluids such as mine water and high-salinity water needs to be studied further. Based on a comprehensive analysis of the lithology, mineral composition, physical and mechanical characteristics, and spatial structure of the Liujiagou and Shiqianfeng formations in a mining area in the Ordos Basin, we determined the geological storage space for fluids, predicted the storage potential, and evaluated the feasibility of deep geological storage of high-salinity water in coal mines. In the study area, the Liujiagou Formation is dominated by fine sandstone and siltstone, while the Shiqianfeng Formation is dominated by medium sandstone and conglomerate. The main storage space comprises micro-cracks, as well as intergranular, dissolution, and intergranular pores. Among these, the intergranular pores are the most conducive to reservoir development. The burial depth intervals of 1820–1835 m, 1905–1920 m, and 2082–2098 m are favorable for storage and are characterized by high porosities, permeabilities, and storage capacities. The effective storage capacity within a 100 m radius of the storage well was estimated to be 33.15 × 10⁴ m³. The effective storage capacity in the favorable area is 27.69 × 10⁴ m³, accounting for 83.50% of the total storage capacity. The Liujiagou and Shiqianfeng formations thus can serve as favorable reservoirs for deep well injection and storage of high-salinity water in the Ordos Basin. This research provides new ideas for the treatment of high-salinity water in coal mines in the Ordos Basin and technical support for deep well injection and the storage of high-salinity water.

Coal mine water in China is mainly mine water containing suspended solids（SS）. The relationship between suspended solids and turbidity in mine water with different SS content gradients was studied and a model formula was established. Finally, the accuracy of the model formula is verified by the actual detection values of five kinds of mine water. Two conversion formulas for turbidity and suspended matter have been obtained in the study. When the suspended matter content is 0-200mg/L, the relationship curve between turbidity and SS is y=0.9336x-3.1393, R²=0.9986; When the suspended matter content is 200-600 mg/L, the relationship curve between turbidity and SS is y=0.5314x+94.421, R²=0.9905. Finally, the study has used the measured values of SS in other coal mines and the calculated values obtained from the formula to carry out error analysis. It is found that the error of the relationship between turbidity and SS with a suspended matter content of 0~200mg/L is controlled within 4%; the error of the relationship between turbidity and SS of mine water with a suspended matter content of 200~600mg/L is controlled within 5%. Considering the unavoidable error factors, it is considered that the model formula can be applied to the detection of suspended solids in actual mine water.