To provide more reasonable references for remedying underground water, fuel leak was simulated by establishing an experimental model of a porous-aquifer sand tank with the same size as that of the actual tank and by monitoring the underground water. In the tank, traditional gasoline and ethyl alcohol gasoline were poured. This study was conducted to achieve better understanding of the migration and distribution of benzene, toluene, ethyl benzene, and xylene (BTEX), which are major pollutants in the underground water. Experimental results showed that, compared with conventional gasoline, the content peak of BTEX in the mixture of ethyl alcohol gasoline appeared later; BTEX migrated along the water flow direction horizontally and presented different pollution halos; BTEX also exhibited the highest content level at 45 cm depth; however, its content declined at the 30 and 15 cm depths vertically because of the vertical dispersion effect; the rise of underground water level increased the BTEX content, and the attenuation of BTEX content in underground water was related to the biodegradation in the sand tank, which mainly included biodegradation with oxygen, nitrate, and sulfate.

Mineral extraction can significantly affect the groundwater flow and hydrochemical environment. However, for hilly areas, significant ground elevation changes and complex geological conditions make it difficult to accurately analyze and predict the impact of mineral mining. This study takes the Nuodong rare earth mining area as an example. Based on field investigations and experiments, GOCAD software (version 2022) was used to establish a geological model in combination with GMS numerical simulation software, which was used to build a groundwater flow model and a solute transport model. The flow model in the hilly area indicated that the absolute error between the simulated and measured water levels of each observation well is 0.554 m. The solute-transport model showed that the maximum pollutant concentration of ammonia-nitrogen (NH₃-N) in the liquid injection area, stream area, and village area monitoring wells reaches 139.15, 27.9, and <0.5 mg/L, respectively. During the mining period, streams in the area are affected by NH₃-N, which threatens the safety of the water for mine area residents. To control pollutant transport, two stages of pumping were adopted to reduce NH₃-N concentrations in groundwater. After adopting the first stage, the peak concentration of the stream area monitoring wells decreased significantly, with the maximum peak concentration decreasing from 27.9 mg/L to 5.51 mg/L. Based on the results of the first stage of the pump-out treatment, a second stage was adopted. The model results showed that the peak concentration of NH₃-N pollutants discharged into the stream is less than 0.5 mg/L. The results provide a theoretical basis and reference for groundwater monitoring and pollution control after mining in this area.

Antimony (Sb), as a toxic heavy metal, has drawn worldwide attention, and its efficient removal from water has become increasingly urgent. In this study, an iron-modified alkaline lignin chitosan (Fe-ALCS) gel bead is prepared by the freeze-drying method to remove Sb(III) from the aqueous solution. The static adsorption experiment discusses the various environmental influences on the adsorption performance of Fe-ALCS for Sb(III) removal. The adsorption mechanism is explored by combining adsorption kinetics, isothermal adsorption, and characterization methods (such as FTIR, XRD, XPS, etc). The results show that the equilibrium adsorption capacity of Sb(III) decreases with the increase in pH and mass–volume ratio. With the increase in the initial Sb(III) concentration, Q_e showed a rapid increasing trend in the range of 50–100 mg/L and continued to rise with the extension of contact time (t), reaching the maximum value at 3540 min. Under the optimal conditions of pH = 3, m/v = 1.0 g/L, and C₀ = 20 mg/L, the removal efficiency (R_e) value is 95.07%, which is still approximately 86.8% after five adsorption–desorption cycles. The maximum adsorption capacity is 266.58 mg/g fitted by the Langmuir model. The adsorption mechanism is mainly related to the iron-based active site of Fe–O(OH), where the O–H on its surface undergoes ligand exchange with Sb(OH)₃ to form a stable Fe–O–Sb coordination structure. Additionally, C–OH, C–O, and other functional groups in ALCS also contribute to Sb adsorption. Fe-ALCS is an environmentally friendly, renewable, and convenient biomass adsorbent with good potential for wastewater treatment.

Heavy metal contamination, particularly lead (Pb) pollution in aquatic environments, poses serious threats to ecosystems and human health, necessitating the development of efficient and cost-effective adsorbents. In this study, potassium permanganate-modified areca fiber biochar (PAFB) is successfully synthesized for Pb(II) removal from aqueous solutions. Characterization results confirm the successful loading of MnO₂ nanoparticles and the introduction of abundant –OH, –COOH, and Mn–OH active sites onto the biochar surface. Batch adsorption experiments reveal that Pb(II) removal by PAFB is highly pH- and temperature-dependent, with optimal performance at pH = 6.0 and 25 °C. The adsorption process follows the pseudo-second-order kinetic model (R² = 0.9997) and the Freundlich isotherm model (R² = 0.9363), indicating chemisorption-dominated adsorption on heterogeneous surfaces. Thermodynamic analysis confirmed the spontaneous and endothermic nature of the adsorption process. The maximum adsorption capacity reaches 45.62 mg/g at 25 °C, comparable to or higher than that of many similar biochar-based adsorbents. Mechanistic analysis revealed that Pb(II) removal by PAFB proceeds via a synergistic electrostatic attraction–surface complexation mechanism, wherein Pb(II) forms inner-sphere complexes with –OH, –COOH, and ≡Mn–OH groups, as evidenced by FTIR and XPS analyses. The Pb4f spectrum exclusively displayed Pb(II) complexation peaks without detectable Pb⁰ precipitates, confirming the immobilization of Pb(II) as amorphous surface complexes. Moreover, PAFB maintains an 87.00% removal efficiency after four regeneration cycles, demonstrating excellent reusability. This study provides an environmentally friendly adsorbent for Pb(II) removal, showing promising potential for heavy-metal-contaminated wastewater treatment.