Study on preparation and properties of antifreeze compound road dust suppressant

Abstract

Open-pit mine pavement dust dries and breaks easily. As such, a composite pavement dust suppressant with good wettability, moisturizing, coagulation, and antifreezing properties in winter was investigated. Monomer screening and orthogonal experiments were conducted, using evaporation rate, permeability rate, viscosity, and freezing point as evaluation indexes. Consequently, a dust suppressant solution is a mixture of glycerol (GLY), sodium dodecylbenzene sulfonate (SDBS), polyacrylamide (PAM), compound propylene glycol (PG), and potassium acetate (PA). The characteristics of the dust suppressant and its interaction mechanism with road dust were measured and analyzed. The results showed that the optimal ratio of the antifreeze-type composite dust suppressant is 3%GLY, 0.30%SDBS, 0.07% PAM, and 50%PG + 10%PA; the contact angle is 27.62°, which can effectively wet coal dust. Moreover, it easily forms hydrogen bonds with water molecules to release free -OH, which increases the oxygen-containing functional groups in the dust. The maximum viscosity is 25.4 mPa·s, and the hydrophobic groups adsorbed on the surface of the dust can condense and agglomerate the dust to form large particles, and effectively inhibit the occurrence of dust. It freezes at − 34.2 ℃, resists a temperature of − 30 ℃ without freezing, and improves dust suppression efficiency and antifreezing effect in cold areas.

Introduction

The largest source of dust pollution in open-pit coal mines is the road dust generated by dump trucks in the mine, accounting for approximately 70–90% of the total amount of dust produced in the mining area^1,2. Moreover, the instantaneous concentration of dust produced can be as high as 100 mg·m⁻³, far exceeding the amount stipulated for workplaces according to the “Dust Concentration Standard in Coal Mine Safety Regulations”³. Under open ventilation conditions, dust spreads with air flow in a large area. High dust concentrations affect the ambient air quality in the mining area, deplete transportation equipment, and reduce the working efficiency of personnel; additionally, human health is considerably endangered by health risks such as pneumoconiosis and other lung tissue lesions^4,5. Dust also reduces visibility for truck drivers, which poses safety risks to transportation in the coal mine⁶.

Road dust in open-pit coal mines is traditionally controlled using sprinklers. Recently, chemical dust suppressants have been used effectively for controlling road dust in open-pit mines. Chemical dust suppressants are of different types: wetting, bonding, agglomeration, and composite types. The first three types (single-type dust suppressants) have a short moisturizing time and a high cost, bonded organic dust suppressants have poor permeability, and inorganic salts such as agglomerative CaC1₂ and MgCl₂ have certain corrosive properties^7–9. The composite dust suppressant or modified composite dust suppressant has good environmental and economic benefits because of it can accumulate two or more effects in the four functions of moisture absorption, moisturization, coagulation, and consolidation, indicating extremely broad development prospects¹⁰. Jin¹¹ used a high-molecular-weight polymer soybean protein isolate modified by sodium dodecyl sulfonate to create a complex dust suppressant that can achieve water retention capacity, consolidation capacity and dust suppression efficiency at the same time and has better viscosity and wind erosion resistance than those of commercially available dust suppressants. Yu¹² grafted soybean protein isolate (SPI) with polyacrylamide (PAM) and glycerol (GI) to prepare a polymer dust suppressant with wetting, bonding, hygroscopic absorption, water retention and other properties. Wang¹³ used the dust inhibition of polyacrylamide (PAM) modified moss dust suppressant to obtain that its viscosity was 25.1 mPa·s, the surface tension was 27.05 mN/m, and it had good coagulation, water retention and wettability. From the point of view of economy and efficiency, the material cost can be saved by 30%, and the dust suppression efficiency can reach 89–94%. Zhou¹⁴ used bagasse cellulose as the matrix, added polyvinyl alcohol and polyacrylamide, and developed a composite dust suppressant with high strength and good permeability of the consolidated layer, and the biomass raw material was prepared with good degradability. The wettability and dust suppression mechanism of the dust suppressant were illustrated by MS simulation. Niu¹⁵ used the mixture design method to prepare rhamnolipid composite wetting agent (CS-A-S), which enhanced the hydrophilicity of pulverized coal and made it easier for pulverized coal particles to agglomerate and settle into larger particles, and analyzed the wetting mechanism at the microscopic level through molecular dynamics, and it was obtained that the dust suppressant molecules were easier to form adsorption on the coal surface, and the water molecules were easier to penetrate, showing better dust suppression effect.

Most dust suppressants have achieved a good dust suppression effect. However, most of China’s mining activities are conducted in alpine areas, and the temperature in severe-winter regions can be lower than − 30 ℃ which generates road surface ice that causes the skidding of large transport vehicles, posing serious safety risks¹⁶. Therefore, in order to meet the dust reduction requirements of open-pit mines and the normal and safe operation of vehicles in winter, it is crucial to ensure that dust suppressants have a good antifreeze performance. In this study, an antifreeze-type composite dust suppressor was designed, which integrates antifreeze, wetting, coagulation, and moisturizing functions. Sodium dodecyl benzene sulfonate was used as the anionic surfactant, glycerin as a moisturizer, and acrylamide as a binder; moreover, propylene glycol and potassium acetate were added as the antifreeze. Molecular dynamics simulation and electron microscope characterization were also performed from a macro and micro perspectives. The properties of the composite dust suppressant, such as wind erosion rate, water content, penetration rate, contact angle, viscosity, and freezing point, were evaluated and characterized, while its toxicity was tested. Finally, the mechanism of interaction between the composite dust suppressant and dust was analyzed from a microscopic perspective.

Materials and methods

Experimental material and equipment

The 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 1.

Molecular 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 preparation

Pre-treatment of dust particles

The 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 composition

After 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.

Composition	SiO2	Fe2O3	Al2O3	K2O	CaO	Na2O	TiO2	MnO
Content (%)	64.138	13.539	13.313	3.782	3.091	1.168	0.898	0.067

Preparation of dust suppressant

The 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 literature^17–19 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 2.

Preparation 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 suppressant

Table 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.

Level	Range result	Significant action factor
Penetration rate	SDBS3 > PAM2 > GLY2 > PG + PA1	SDBS: significant
Water loss rate	GLY2 > PG + PA3 > SDBS2 > PAM3	GLY: High significance; PG + PA: significant
Viscosity	PAM3 > GLY3 > SDBS2 > PG + PA3	PAM: High significance
Ice point	PG + PA3 > GLY3 > PAM1 > SDBS2	PG + PA: High significance; GLY: significant

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 particles

Wettability measurement

Permeation rate analysis

In 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 measurement

Use 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 analysis

The 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 simulation

The 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 determination

Moisture content test

A 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; M_i is the mass of the initial sample dish, g; and M₂ is the initial dust mass, g.

Determination of coagulation properties

Viscosity characterization

According 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 test

The 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:

$$\epsilon =\frac{m_1-m_2}{m_1}\times 100\%,$$ 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 distribution

The 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 performance

Freezing point characterization

A 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 toxicity

pH test

When 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 determination

The 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:

$$X=\frac{87600\times (W_1-W_2)}{\mathit{STD}},$$ 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 analysis

The 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.

Results and discussion

Analysis of wettability results

Contact angle and permeation rate results

Figure 3 illustrates the value of the contact angle between the dust suppressor, the water solution, and the dust, and the change in the contact angle with time. When the contact angle between the dust suppressor and the dust sample was 27.62° and the contact angle between the water and the dust reached a maximum of 69.33°, the wetting effect on the dust was poor, meaning the dust was hydrophobic²². Within 1 to 10 s, the contact angle between the two particles and the dust sample decreased by different degrees. The contact angle of the dust suppressor was much smaller than that of water; the smaller the contact angle, the better the wettability²³. Similarly, the wetting rate of the two was measured: the penetration rate was 0.53 and 0.22 cm/min, respectively. The wetting rate of the dust suppressor was clearly better than that of water on dust, leading to a better wetting effect on the coal sample.

Figure 3.

Contact angle contrast.

Analysis of FTIR results

The changes in the surface functional groups of the dust samples sprayed with a dust suppressant and water were analyzed by FITR, as shown in Fig. 4. As shown in the figure, the symmetric stretching vibration absorption peak of Si-O is located near the wavelength of 467.6 and 793.31 cm⁻¹, the out-of-plane bending vibration absorption peak of C-H containing aromatics is located near the wavelength of 693 cm⁻¹, and the N-H bending vibrations absorption peak of polyacrylamide is located at 1576. However, the dust sample after water immersion lacked this oxygen-containing group. Because SDBS contains hydrophobic carbon chains, the group is larger than the water dust sample. The OH absorption peak of the hydroxyl O-H stretching vibration is 3390 cm⁻¹, and the C-O-C stretching vibration is 1034 cm⁻¹ ref²⁴. In general, the wettability of coal is mainly determined by the oxygen-containing functional groups, which are characterized by the oxygen-containing functional groups (C-O-C) and (-OH) in the dust sample²⁵. OH can enhance the wettability of the dust by hydrogen bonding with water on the surface or by the hydrogen bonding of SDBS with water.

Figure 4.

FTIR spectra of the modified dust sample.

The peak fitting of the modified dust-like, oxygen-containing functional group is shown in Fig. 5 and Table 3. According to the fitting, the area of the oxygen-containing functional groups-OH and C-O-C modified by dust suppressant increased from 2.55 to 6.76 and 25.08 to 27.91, respectively. Among them, the increase in -OH was larger, with an increase of 165.1%, that is, the addition of the dust suppressant increased the hydrogen bonds between water molecules, promoted the adsorption of water molecules on the coal surface, and increased the hydrophilicity of the dust, thereby increasing its wettability²⁶.

Figure 5.

Peak fitting of oxygen-containing functional groups in two wet dust samples: (a) Spray dust with dust suppressant; (b) Spray dust with water.

Table 3.

Peak fitting results.

Fitting method	Functional group	Wavenumber range	Area
			Sprinkling dust	Dust suppressant modified dust
Gaussian	Hydroxyl (-OH)	3200–3500	2.55	6.76
	ether group (C–O–C)	900–1220	25.08	27.91

Analysis of molecular dynamics simulation results

The dynamic equilibrium configuration of the simulated dust suppressor/dust system is illustrated in Fig. 6. As the simulation reaction progressed, the diffusion degree of water molecules over the coal seam gradually increased, and the contact structure of coal and water remained unchanged. Compared with the initial configuration, the surfactant molecules in the equilibrium system gradually dispersed towards the end of the powder layer and towards the end of the water phase. As the surfactant contained both hydrophilic groups and hydrophobic groups, the hydrophilic head group of SDBS extended to the water phase, and the hydrophobic tail group extended to the dust surface. These extensions increased the probability of the hydrophilic groups colliding with water molecules and attracting water molecules to migrate and spread to the coal seam.

Figure 6.

Molecular dynamics equilibrium model.

Relative concentration analysis

Figure 7 shows the relative concentration distribution curves of dust and water molecules in the two systems along the Z axis. The figure reveals that the distance of water molecules in the water/dust system and the dust suppressor/dust system was 17.43–42.68 Å and 16.09–81.52 Å, respectively. By adding a dust suppressor, the spatial distribution range of water molecules in the system was wider. As the surface of SiO₂-CH₃ dust contains hydrophobic groups of -CH₃, water molecules could react with the dust surface to form hydrogen bonds. Moreover, a large distance existed between the water and dust, but the thicknesses of the water/dust interface and the dust suppressant/dust interface were 0.51 and 1.01 Å, respectively. That is, after adding the dust suppressor, the thickness of water molecules at the water/dust interface doubled. This shows that the dust suppressor promotes the adsorption of water molecules on the dust surface and can effectively improve the wettability of the dust surface^27,28.

Figure 7.

(a) Relative concentration profiles of water molecules in a water/dust system; (b) relative concentration distribution curves of water molecules in a dust suppressant/dust system.

Mean square displacement

Figure 8 illustrates the diffusion degree of water molecules in the two systems on the dust surface. Within a 0–300 ps time, the MSD curve fitting R² is greater than 0.99, which can be well fitted. The slope of water molecules in the water/dust system is higher than that in the dust suppressor/dust system, and the diffusion coefficient D is 6.42e–5 and 4.1e–5, respectively. That is, the movement of water molecules in the system was relatively slow after the addition of the dust suppressor. This is because SDBS molecules continue to ionize anionic hydrophilic groups and tend to the aqueous phase, while hydrophobic groups are adsorbed on the surface of the dust, carboxyl polar groups are introduced, and more water molecules are adsorbed on the dust. Therefore, the water molecules are attracted to the coal molecules to migrate and diffuse, so it has good adsorption and wetting effects^29,30.

Figure 8.

Diffusion curves of water molecules in water/dust systems and dust suppressant/dust systems.

Analysis of moisturizing performance

Figure 9 shows that the moisture content of the composite dust suppressant, modified dust sample and the spray dust sample gradually decreased with time; the water loss accelerated within 30 h and then moved from a slow water loss stage to a constant water loss stage. When the water loss reached 70 h, the water loss rates of both stages were 41.1 and 50.95%, respectively, and the moisture content of the dust sample with dust suppressant was significantly higher than that of water. The water loss effect of the sprayed dust was obvious, and the moisture content of the modified dust sample was greater than 10% in 70 h, showing a good water retention effect. Meanwhile, the dust surface sprayed with distilled water was completely dry and loose, while the dust surface sprayed with a dust suppressor formed a dense solidified layer with a certain strength, inhibiting water evaporation.

Figure 9.

Change in dust water loss rate with time.

Analysis of consolidation performance results

Viscosity characterization analysis

According to the previous orthogonal experiment, the maximum viscosity was 25.2 mPa·s, while according to the optimal ratio, the viscosity of the dust suppressor was 25.4 mPa·s, and the viscosity value increased. The greater the viscosity, the better the condensation effect to a certain extent, and the easier the agglomeration of dust particles. However, when the viscosity is too large, the spray resistance will increase. The obtained dust suppressor solution was easy to disperse and had a certain cohesiveness, achieving the effect of dust coagulation and agglomeration.

Analysis of wind erosion resistance

Figure 10 shows that the wind erosion rate of the composite dust suppressant and water increased gradually with the increase in the wind power level. The wind erosion rate of the dust suppressant was much lower than that of water. At the maximum air flow, the wind erosion rate of sprinkling dust was 30.12%, while that of the dust suppressant was only 13.33%, which reduced the wind erosion rate by 16.79%. In addition, the figure shows that the water of the sprinkler dust evaporated, the surface became soft, and no agglomeration occurred between the particles. However, the surface of the dust after the modification of the dust suppressant was in an agglomerated form, and the dust particles were consolidated to form a dense shell film layer, which can effectively resist the wind erosion of the dust sample, indicating that the dust suppressant has better bonding and dust suppression performances.

Figure 10.

Dust erosion rate under different wind conditions.

Particle size dispersion analysis

Figure 11 illustrates the particle size interval distribution of the water-treated dust samples and dust-suppressor-modified dust samples. The figure reveals that the particle size of the dust sample soaked by the dust suppressor solution increased more than that of the water-moistened dust particles. The particle size of the dust sample treated with water was 48.46% in the range of 10–50 μm, while that of the dust sample treated with a dust suppressor was 40% in the range of 100–100 μm. The particle size of dust smaller than 10 μm accounted for 18.08 and 10%, respectively, and the particle size ratio of dust larger than 50 μm accounted for 33.46 and 58.57%, respectively. The proportion of the particles with a large size after spraying the dust suppressant was 75.04% higher than that of the large particles of water. The added dust suppressant penetrated the pores between dust particles. The collision and aggregation of dust particles increased, and the particle size was increased from a macroscopic perspective. The larger the particle size, the easier it is for the coal dust to settle.

Figure 11.

Distribution of dust particle size dispersion.

Frost protection performance analysis

Freezing point detection and analysis

The freezing point of the antifreeze dust suppressant was − 34.2 ℃. It was put in a centrifuge tube and placed in a refrigerator at a temperature of − 30 ℃ for 6 h. The appearance was observed as shown in the Fig. 12, the solution turned white after freezing and the solution state is no longer clear, but did not freeze, indicating that the dust suppressant had a better antifreeze effect and could withstand weather of -30℃ without freezing.

Figure 12.

Appearance of dust suppressant frozen for six hours.

Dust surface morphology and causation analysis

Figure 13 shows the morphology of dust surface magnified by 1000 and 5000 times after water spraying and dust suppressant, respectively. Figure 13a,b show that the coal particles are loose and dispersed after water evaporation. As can be seen in Fig. 13c,d, the gap between dust particles is reduced, and the dust is tightly bonded into large clumps. The surface is covered with a thick curing film, and the particles are closely bonded.

Figure 13.

SEM images (a and b are dust surfaces with water; c and d are dust surfaces with the dust suppressant).

The antifreeze-type composite dust suppressant condenses and aggregates fine pavement dust into large particles and delays water evaporation. It also has a certain wetting and penetration effect. By reducing the surface tension of the solution, the suppressant accelerates the infiltration rate of road dust³¹, forming a dense and solidified shell on the coal dust surface, which is sufficient to resist wind erosion and achieve good dust removal effect. As shown in Fig. 14, SDBS anionic surfactants are typically composed of hydrophilic head groups and hydrophobic tail groups. The hydrophilic groups are attached to water molecules, hydrophobic base to dust, and the contact range of shielding water and air. The attachment occurs as the tail groups attempt to become attached to the hydrophobic water level on the coal dust surface, orienting the hydrophilic head toward the surrounding water phase³². This process converts the hydrophobic sites on the dust surface into hydrophilic sites, thus improving the wettability of the coal dust. In addition, the network structure formed by the long chains of PAM and SDBS polymers³³ presents a relatively regular flocs shape, which can effectively adsorb and tightly encapsulate dust particles, improve dust consolidation strength, and reduce crack generation. Meanwhile, the stability of the three-dimensional PAM structure prevents the molecules from escaping easily, which improves the dust capture ability. The dense film prevents water evaporation and dust entrainment. When the dust pile contains a large amount of water, the dust particles adhere to one other because of the capillary force of water, improving the overall integrity and strength of the dust suppression film. The addition of PG and PA antifreezing materials effectively reduces the freezing point. PG contains the -OH hydroxyl group, and glycerol has the same effect of increasing wettability. Additionally, the interaction with an anionic surfactant is more suitable for reducing the freezing point further.

Figure 14.

Analysis of dust suppression mechanism.

Toxic properties

pH determination

The pH of a dust suppressant is crucial for preserving the ecological environment. Extreme pH values can have adverse effects, salinizing or acidifying the soil and further contaminating groundwater Fig. 14. The average pH of the measured solution was 7.58, and the dust suppressor was basically neutral after reaction; it has no adverse effect on the ecological environment.

Corrosive determination

The uniform corrosion results of the dust suppressor and aqueous solution on the material are shown in Table 4 and Fig. 15. The average corrosion rate of carbon steel hanging plates soaked in the dust suppressor solution and distilled water for 48 h was 0.0998 and 0.0883 cm/h, respectively. The average corrosion rate of the composite dust suppressor on the carbon steel samples was slightly higher than that under distilled water, and the corrosion rate was low. The corrosion effect of the dust suppressor solution on the metal parts of the frame was weak, and there was no obvious corrosion phenomenon.

Table 4.

Corrosion rate of carbon steel.

Sample Sample solution	Ordinary carbon steel
	Density (g/cm3)	Mean total surface area	Average corrosion rate (cm/h)
Water	7.85	17.56	0.0883
Dust suppressant	7.85	17.56	0.0998

Figure 15.

Carbon steel average corrosion rate.

Conclusion

• A theoretical analysis and an experimental study were conducted in this research, taking permeability rate, moisture content, viscosity, and freezing point as the evaluation indexes. In particular, orthogonal experiments were conducted to propose an antifreeze composite dust suppressant integrating wetting, moisturizing, coagulation, and antifreezing functions. Its optimal dust suppressant ratio was 3%GLY + 0.3%SDBS + 0.07%PAM + (50% + 10%)PG + PA, the optimal viscosity was 25.4 mPa·s, and the freezing point was − 34.2 ℃.

• The multi-functional characteristics of the sprinkling dust suppression system and dust suppression agent system were compared and analyzed, and the contact angle of the dust suppression agent and water on dust was 27.62° and 69.33°, respectively. That is, the composite dust suppression agent had good wettability, and the dust was hydrophobic dust. After adding the dust suppression agent, the amount of oxygen-containing groups -OH and C-O-C increased. The diffusion and adsorption of water molecules in the dust interfacial layer were increased by 165.1 and 11.3%, respectively. Meanwhile, the surface of the dust was agglomerated, and the dust particles were consolidated to form a dense shell layer, which still had more than 10% moisture content within 70 h, effectively resisting the corrosion of the dust sample by a grade 6 wind. The solution was safe and non-corrosive.

• From a microscopic morphology perspective, the dust suppressor film contains fewer micro-cracks. SDBS anionic surfactant hydrophilic groups extend to water molecules, and hydrophobic tails are attached to the dust surface to shield the contact range between water and air. Meanwhile, the tail group converts the hydrophobic part of the dust surface to the hydrophilic part, improving the wettability of the coal dust. In addition to playing an antifreezing role, the added PG can also play a moisturizing role in combination with GLY, while PA can effectively reduce the freezing point as an antifreezing material. The network structure composed of a PAM and SDBS polymer long chain can effectively adsorb and tightly wrap dust particles to form a dense and solidified shell on the dust surface, improve the dust consolidation strength, and achieve a good dust removal effect.

Author contributions

All authors contributed to the study conception and design. S.X. was responsible for data collation, writing manuscript—original draft and investigation. Z.S. and X.Z. contributed to writing—review and editing. Z.M. and J.L. was involved in material preparation and data collection. All authors read and approved the final manuscript.

Data availability

The authors declare that the data supporting the findings of this study are available within the paper and its Supplementary Information files.

Competing interests

The authors declare no competing interests.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-024-67683-6.