Experimental material and equipmentThe primary materials used in the study were sodium dodecyl benzene sulfonate (SDBS), Polyacry lamide (PAM), Glycerol (GLY), 1,2-Propanediol (1,2-PG), and potassium acetate (PA). Figure 1 shows the molecular structure of the reagent used in the study.Figure 1Molecular structure of dust suppressant components.The equipment used to perform measurements were an X-ray fluorescence spectrometer (XRF-1800), a Fourier infrared spectrometer (FTIR) (BRUKER type), a pH acidity meter (PHS-25), a contact angle measuring instrument (SCI3000), a centrifugal blower (DF-4), a portable anemometer (AZ9861 memory), a viscometer (DNJ-8S), an HY-12 tablet press, an antifreeze freezing-point instrument (414HY), a dust dispersion tester (Rise-3022 Pro), an electronic analytical balance (JT1003D), a thermal magnetic stirrer (DF-101SS), and a scanning electron microscope (SEM) (Zeiss Gemini 500).Road dust sample preparationPre-treatment of dust particlesThe dust sample were obtained from the dust of the No. 4 and No. 6 main-roads in the North open-pit coal mine in Huolinhe, Inner Mongolia. The stones with a large particle size were removed; the particles were vibrated and crushed for 4 h using a vibration grinder (XPC-100 × 150) at a speed of 450 r/min, screened and filtered by a 200 mesh (0.075 mm) standard samples, and dried in a blast drying oven for 24 h at 55 ℃ after which they were sealed for later use.Analysis of road dust compositionAfter the dust was prepared, X-ray fluorescence spectrum analyzer was used to analyze the chemical composition of the dust, and the main components were obtained as shown in the following table.As shown in Table 1, the chemical composition of the road dust is mainly silica, ferric oxide, and alumina, where the silica content has the highest proportion of 64.138%, which far exceeds that of the other components. Therefore, SiO2 cell was used to model the dust.
Table 1 Chemical composition of road dust in open-pit coal mine.Preparation of dust suppressantThe experiment was prepared by the orthogonal method; the “two-step method” was used to prepare the antifreeze-type composite dust suppressor, which included the material selection and compounding process. As shown in Fig. 2, the wetting agents, humectants, coagulants, and antifreeze were selected according to the relevant literature17,18,19 and previous monomer experiments. At a room temperature of 25 ℃ a constant-temperature magnetic stirrer with a rotor speed of 600 r/min was used to prepare PAM, SDBS, PA, GLY, and PG raw materials in three suitable mass concentrations selected according to previous monomer experiments. The orthogonal experiments were designed with the mass concentrations of GLY, PAM, SDBS, and PG + PA as factors, and 10 mL of the compounds were added respectively. The four-factor, three-level orthogonal experiment was analyzed using the osmotic rate, moisture content, viscosity, and freezing point as evaluation indexes.Figure 2Preparation of dust suppressant.According to the optimal ratio, solid powders of 0.07 g PAM, 0.3 g SDBS, and 10 g PA were added to the beaker, as well as 50 mL of water to stir at 1000 r/min. After about 5 min, GLY and 1,2-PG were added, and the remaining water was added; the mixture was stirred and left steady for a period of time for the materials to dissolve and permeate each other, ensuring that the dust suppressor solution was in a stable dispersion state for the subsequent performance measurements.Selection of dust suppressantTable S1 compares the K values and ranges of dust suppressant factors in each group under the four indexes, and the significant effect results are shown in Table 2.
Table 2 Evaluation index analysis and summary.As shown in the table, the GLY factor of the humectant had the most significant effect on the moisture content, followed by a secondary effect on the freezing point, which mainly affected the moisturizing effect of the dust suppressant, and the optimal level was GLY2. In particular, the PAM binder had a significant effect on the viscosity index but no obvious effects on other indicators; the viscosity was the highest in PAM3. PG + PA3 had a significant impact on the freezing point and evaporation rate, with the contribution to the freezing point being the highest. This is because PG can be used as a humectant in combination with glycerol and antifreeze, which has hygroscopic and wetting properties and enhances the anti-evaporation performance of dust suppressants. SDBS3 had a maximum permeation rate: the surfactant had strong wettability. As the best K value in the other three indexes affected the strength and cost price, SDBS2 was the optimal choice.Performance characterization and analysis of dust suppressants on dust particlesWettability measurementPermeation rate analysisIn the test tube with a scale line, put equal amounts of dust into the colorimetric tube and beat the test tube to vibrate and tamp. Record the dust sample scale, drop 4 mL of the solution vertically into the test tube and wait for all drops to be deeply stabilized. Record the height and time taken for the solution in the test tube to penetrate the dust sample. Calculate the penetration rate, and repeat the experiment three times, taking the average value as the result, which is calculated as follows:$$\vartheta = \frac{H}{T},$$
(1)
where \(\vartheta\) represents the permeability coefficient, cm/s; H represents the penetration height, cm; and T stands for penetration time, s.Contact angle measurementUse a press to press dust weighing 0.4 g into a dust cake and keep the pressure at 18 MPa for 2 min. Make a round sheet with a diameter of 13 mm and a thickness of 2–3 mm and place it on the slide of the sample table of the instrument used to measure the horizontal contact angle. Drop the prepared solution onto the dust sheet by the seat drop method; the photographic record is completed at the moment the solution touches the coal sheet.Fourier transform infrared spectroscopy analysisThe raw dust and the modified dry dust sample were mixed with KBr, ground, pressed at 20 MPa, and held for 2 min to form a transparent sheet. Then, the infrared experiment was performed in the instrument, and the change of functional groups between the dust suppressor and dust was analyzed by an infrared spectrum.Molecular dynamics simulationThe Visualizer module in Material Studio software was used to build the dust suppressor/dust and water/dust simulation systems. According to the dust XRF test and analysis, SiO2 was the main dust component, and the SiO2-CH3 model was built as the dust interface surface. A periodic solution box (29.46 × 29.46 × 31.04 Å) containing 500 water molecules, 50 PG, 1 PAM, 2 SDBS, 1 GLY, and 10 PA was constructed according to the mole mass fraction of the dust suppressor ratio obtained by the experiment. The box was integrated with the dust cell model, and 30 vacuum layers were added at the top. Under the action of a COMPASSII force field, the shape optimization method was set to Smart, and the quality was set to medium to complete the architectural energy optimization. Then, NVT ensemble, Andersen thermostat, and Berendsen constant voltage were selected at 298 K. The Ewald method was used to calculate the electrostatic force, and the Atom method was used to calculate the van der Waals force. The simulation was performed using a time step of 1.0 fs and a total duration of 1 ns; the first 500 ps was used to balance the system, and the last 500 ps was used to analyze the kinetic calculation results.Moisturizing performance determinationMoisture content testA total of 20 g of the dust sample with a particle size of 200 mesh was laid in a Φ75 mm Petri dish, and 10 mL of the composite dust suppressant solution was uniformly sprayed on the surface of the dust sample. Pure water was used as the control group, the Petri dish was weighed every 10 h at a room temperature of 18–25 ℃ and the weight change was recorded until it became stable. The experiment was repeated three times, the average value was taken, and the moisture content of the dust sample was calculated as follows:$$\alpha = \frac{{M_{0} – M_{i} }}{{M_{2} }} \times {100}\% ,$$
(2)
where \(\alpha\) is the moisture content, %; M0 is the mass of Petri dishes at intervals of 10 h, g; Mi is the mass of the initial sample dish, g; and M2 is the initial dust mass, g.Determination of coagulation propertiesViscosity characterizationAccording to the standard GB/T10247-2008 “Viscosity Measurement Method,” 200 mL of the dust suppressor solution containing components with different proportions was placed under the viscometer, and the No.1 rotor was used to determine the viscosity values of the solution at a set speed of 60 r/min. The experimental data were measured three times, and the average value was taken as the result.Wind erosion resistance testThe screened dust samples were also placed in a Φ75 mm Petri dish in a 60 ℃ electric blower drying oven for 12 h to remove excess dust moisture. Then, 10 mL of the composite dust suppressant was extracted using a pipette gun, and it was evenly sprayed over the dust in the Petri dish. After drying the Petri dish naturally at room temperature, a complete solidified layer was formed on the surface 24 h later. According to the daily maximum wind speed measured on the site (8 m/s), the simulated blower was used to blow the corrosion for 10 min at a 3–6 wind power. The formula for calculating the wind erosion rate of the dust samples is as follows20:$$\varepsilon =\frac{{m}_{1}-{m}_{2}}{{m}_{1}}\times 100\%,$$
(3)
where ε is the loss rate, %; m1 is the mass of the dust sample before blowing, g; and m2 is the mass of the dust sample after blowing, g.Measurement of dust size distributionThe dust dispersion tester was used to test the particle size distribution of the dust samples after water and dust suppressant treatments, and the dust samples with more than 200 particles were selected to analyze their particle size changes.Determination of antifreeze performanceFreezing point characterizationA burette was used to place 2 to 3 drops of the composite dust suppressant evenly onto the surface of the prism of the antifreeze freezing point instrument, and the scale was calibrated. The blue and white scale lines in the eyepiece were observed to read the freezing points of the solution, and the error was ± 1 ℃.Evaluation of dust suppressant toxicitypH testWhen the dust suppressant was configured and stabilized for 10 min, the pH value of the solution was measured with the pH meter. After the reading was stabilized, the average value was measured three times.Corrosivity determinationThe dust suppressor solution was sprayed over the metal parts of the truck frame. A carbon steel (16 Mn) material of the body component was selected and placed in the dust suppressor solution and distilled water for a corrosion test. At a room temperature 25 ℃, according to the JB/T 7901-1999 standard, the sample size was 60 mm (length) × 40 mm (width) × 2 mm (height), and the test duration was 48 h. Three groups were set up, and the average rate was taken. The formula for calculating the corrosion rate is as follows21:$$X=\frac{87600\times ({W}_{1}-{W}_{2})}{STD},$$
(4)
where X is the corrosion rate of the sample, mm/a; W1 is the pre-test weight of the sample, g; W2 is the weight after the experiment, g; S is the surface area of the sample, cm2; T is the test duration, h; and D is the sample material density, g/cm3.Microscopic morphological characteristics and mechanism analysisThe surface morphology of the dust treated with water and the dust inhibitor was examined by scanning electron microscopy (Zeiss GeminiSEM 500). The samples were dried, vacuumed, and sprayed with gold, and the morphologies of the gold-sprayed dust were obtained by a magnifying glass at a magnification of 1000 times and 5000 times. The mechanism of dust suppression was analyzed by comparing the surface morphologies.
Study on preparation and properties of antifreeze compound road dust suppressant
