Fir sawdust as a low-cost and easily recyclable adsorbent: efficient removal of Pb(II), Cu(II), and Zn(II) contaminants from wastewater.

The main pollution sources of heavy metals are the arbitrary discharge of industrial wastewater and waste residues, which cause serious harm to the water environment, soil environment, and human health. In this study, following the principle of waste utilization, a gel adsorbent (AA-SW-AMPS) was prepared by microwave-assisted chemical cross-linking using fir sawdust as raw material. A scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and swelling dynamic experiments were used to investigate the microstructure, reaction mechanism, and water absorption performance of AA-SW-AMPS. The N2 adsorption-desorption curve shows that the porous structure of AA-SW-AMPS creates 240.75 cm2/g of specific surface area to enable excellent heavy-metal sorption. It was determined by adsorption experiments that the optimal adsorption state was when the dosage of AA-SW-AMPS was 5 g/L, the pH of the solution was 5, the adsorption time was 45 min, and the initial heavy metal ion concentration was 250 mg/L. In addition, the adsorption mechanism was investigated using adsorption dynamics, adsorption isotherm, and Materials Studio simulation. The results show that the maximum adsorption capacities of AA-SW-AMPS for Pb(II), Cu(II), and Zn(II) were 253.49 mg/g, 237.29 mg/g, and 232.15 mg/g, respectively, and the adsorption mechanism is monolayer chemisorption. The adsorbent showed great potential in removing heavy metals from wastewater.

Preparation and characterization of modified dual network dust suppression gel based on sodium alginate and soluble starch.

Aiming at the problems of complex environment and serious dust pollution in large open-pit coal yards, a dust suppression gel with a dual network structure was prepared by modifying the soluble starch and sodium alginate with iron ions. The changes of functional groups, thermal stability, and morphology structure before and after the reaction were analyzed by FTIR, TG-DSC, and SEM, and the formation mechanism of the dual network was revealed by XPS. Furthermore, the water absorption and water retention experiments proved that the dual network structure is more conducive to water retention than the single-layer network. According to molecular dynamics simulations and contact angle experiments, gel and adsorbed water molecules can approach coal dust molecules on their own to contact, wet, and combine with coal dust. The adhesion test proved that the dust suppression gel with iron ions had better adhesion to dust. The anti-freezing test shows that the dust suppression gel has good anti-freezing performance. The antifreeze test shows that the dust suppression gel still has excellent freeze-thaw resistance at the test temperature of -20℃. The mechanical property test shows that the dust suppressant gel can prevent the product from being damaged by external force. The acid and alkali resistance experiments showed that the acid and alkali resistance of the gel was improved under the condition of iron ion modification, and the flying of coal powder was effectively prevented. This research provides a new theoretical idea for coal dust control in complex environment.

Research on the wetting mechanism of coal dust by different surfactants: combination of experimental characterization and molecular dynamics simulation.

Surfactants can reduce the surface tension of water and improve the efficiency of spray dust reduction, but the synergistic mechanism of composite surfactant solutions wetting coal dust remains unclear. In this study, sodium dodecyl sulfonate (SDDS)/sodium dodecylbenzene sulfonate (SDBS) solution and SDDS/primary alcohol ethoxylate (AEO-9) solution were prepared to wet three types of coal with different deterioration degrees. The surface tension, contact angle, and functional group composition were measured. The results show that SDDS/AEO-9 solution had lower surface tension and critical micelle concentration than SDDS/SDBS solution at the same mixing ratio. When the ratio of SDDS: SDBS was 2:1, it had the best wetting effect on coal dust. It is found that for SDDS/SDBS solutions, aliphatic hydrocarbons and surface tension have a positive correlation with the contact angle, and hydroxyl groups have a negative correlation with the contact angle. For SDDS/AEO-9 solution, only the surface tension and contact angle show a significant linear relationship. The main factors that affect the wetting change with the combination of surfactants. AEO-9 has an electrostatic shielding effect on SDDS, while SDBS increases the electrostatic repulsion between SDDS solution and electronegative functional groups of coal. The synergism among these surfactants plays an important role in the process of wetting coal.

Research on dust dispersion law of fully mechanized mining faces under different inclinations and tracking closed dust control method.

Based on the gas-solid two-phase flow theory, numerical simulation of the dust dispersion law of fully mechanized mining work under different inclination angles and comparative analysis of field-measured data show that with the increase of working face inclination, the inclination of airflow into the unmined zone increases from 25° to 50° and the maximum wind speed increases from 2.16 to 2.25 m/s after the mixing of cutting turbulent wind and system ventilation. Meanwhile, the range of high-concentration dust clusters, suspension time, lateral migration intensity, and deposition zone increase to varying degrees; dust clusters increases from 62.02 to 202.46 m3. When X < 53.96 m, the dust concentration in the sidewalk-breathing zone shows a sine function with the length of the working face, and when X ≥ 53.96 m, it satisfies the exponential decay function. Based on this, the tracking closed dust control technology is proposed. Combining the offset angle of the airflow and t the gathering position of dust mass, the wind curtain angle and air velocity are automatically controlled to ensure that the dust is restricted to one side of the cable trough.

CFD simulation of multi-phase and multi-component diffusion of air-dust-gas in a fully mechanized mining face.

To explore the rule of airflow-dust-gas dispersion and interaction in a fully mechanized mining face, the airflow current vector, the dust trajectory, and the gas spatial distribution were numerically simulated by Fluent. The results show that under the influence of airflow, respiratory dust diffuses to the leeward side of each dust-producing point and footway space and forms a high-concentration (peak concentration 2000 mg/m3) dust mass at 2 m on the leeward side of the advancing support. Gas tends to accumulate near the coal cutter drum, the roof, and the return air corner of the mining face, and the peak concentration exceeds the lower limit of explosion. Near the rear drum of the coal cutter and at the advancing support, considering that the gas and coal dust concentrations are both high and dust and gas can reduce each other's explosion limit, serious gas and coal dust explosions are extremely likely to occur in the presence of a fire source, which may result in serious consequences. Therefore, the two areas can be regarded as key areas of gas and coal dust explosion prevention and control.