Modified sodium alginate-based three-dimensional network hydrogel dust suppressant: Preparation, characterization, and performance

Chemical dust suppression is typically associated with high economic costs, unclear efficacy, and poor degradability. In this study, sodium alginate (SA) was extracted from kelp and cross-linked with polyvinyl alcohol (PVA) and polyacrylamide (PAM). Sulfonated castor oil (CAS) was subsequently added to generate a three-dimensional network hydrogel dust suppressant (PVA-SA-PAM/CAS). Using single-factor experiments, the optimal reaction temperature (60 °C) and dosages of PVA, PAM, and the cross-linking agent (2.5, 4.5, and 0.1 g, respectively) were determined. The viscosity and compressive strength of the prepared hydrogel were 86 mPa·s and 218 kPa, respectively, which meet the requirements for mine dust suppression. Various analyses revealed the hydrogel's reaction process and microstructure changes. Additionally, thermogravimetric experiments proved that the hydrogel had good thermal stability. The specific surface area and pore size of the hydrogel were 0.0278 m2/g and 11.8 nm, respectively, improving its adsorption capacity. Additionally, PVA-SA-PAM/CAS exhibited a good water retention rate. The dust suppression efficiency of PVA-SA-PAM/CAS was >98 % under strong winds (12 m/s). Moreover, the degradation rate of PVA-SA-PAM/CAS was 37 % after eight cycles (56 d) under environmental conditions. Therefore, PVA-SA-PAM/CAS exhibits good wetting, dust suppression, and degradation properties, which can effectively alleviate mine dust pollution.

A novel approach to forecast dust concentration in open pit mines by integrating meteorological parameters and production intensity

Mine dust pollution poses a hindrance to achieving green and climate-smart mining. This paper uses weather forecast data and mine production intensity data as model inputs to develop a novel model for forecasting daily dust concentration values in open pit mines by employing and integrating multiple machine learning techniques. The results show that the forecast model exhibits high accuracy, with a Pearson correlation coefficient exceeding 0.87. The PM2.5 forecast model performs best, followed by the total suspended particle and PM10 models. The inclusion of production intensity significantly enhances model performance. Total column water vapor exerts the most significant impact on the model's predictive performance, while the impacts of rock production and coal production are also notable. The proposed daily forecast model leverages production intensity data to predict future dust concentrations accurately. This tool offers valuable insights for optimizing mine design parameters, enabling informed decisions based on real-time forecasts. It effectively prevents severe pollution in the mining area while maximizing the use of natural meteorological conditions for effective dust removal and diffusion.

Effect of Sodium Carboxymethyl Cellulose on the Dynamic Wetting Characteristics of the Dust Suppression Droplet Impacting the Coal Surface

The dynamic wetting behavior of droplets impacting the coal surface directly affects the efficient application of water-based dust suppression materials in coal-related industrial production. In this paper, ultrapure water, Tween-80, and sodium carboxymethyl cellulose are taken as the research objects. Using high-speed photography technology, the spreading, oscillation process, and splash morphology of many kinds of droplets during impacting the coal surface are captured. The effects of viscosity, surface tension, and impact velocity on dynamic wetting characteristics were studied. The results show that with the decrease of surface tension, the retraction and oscillation of droplets are significantly reduced. For the same kind of droplets, the greater the impact velocity, the faster the droplet spread, and the dimensionless maximum spreading coefficient (β_max) and dimensionless steady-state spreading coefficient (β_e) of droplets are bigger. With the increase of velocity, the time for different kinds of droplets to reach the β_max increases. At the same impact velocity, β_max and β_e of droplets (0.2% Tween-80 + 0.1% sodium carboxymethyl cellulose) are the largest, indicating that adding a small amount of sodium carboxymethyl cellulose can promote droplet spreading. With the increase of sodium carboxymethyl cellulose content, β_max and β_e decreased gradually. The results have a great significance to the research, development, and scientific utilization of water-soluble polymer dust inhibitors.

Study on characteristics and microscopic mechanism of composite environment-friendly dust suppressant for urban construction site soil fugitive dust based on response surface methodology optimization

Soil fugitive dust pollution caused by urban construction sites is a significant problem. To improve the dust suppression efficiency on the urban construction sites, hydroxypropyl guar (HPG), dodecyl dimethyl amine oxide (OB-2), and hydroxypropyl methylcellulose (HPMC) were selected as individual components of the composite dust suppressant using a single-factor test. The response surface methodology (RSM) was used to determine the optimal mixing proportions. After preparation, the characteristics of the composite dust suppressant were tested. Fourier-transform infrared spectroscopy and scanning electron microscopy (SEM) were used to characterize the composite dust suppressant and explore its mechanism. The results showed that 0.327% HPG, 0.6% OB-2, and 0.5% HPMC were the best compound concentrations. Under optimum conditions, the viscosity of the composite dust suppressant was 151.1 [Formula: see text], penetration time was 61.4 s, and water retention rate was 30.67%. Compared with traditional dust control by spraying water, it showed better resistance to evaporation at high temperatures and better wind erosion resistance. The antievaporation rate was 39.42% at 60 °C. After 11 d of continuous wind erosion at level 7, the wind erosion resistance rate was as high as 98.24%. The reason for the excellent dust suppression effect of the composite dust suppressant is that the methyl and hydroxyl groups in the solution diffuse to the surface of the soil fugitive dust particles using Brownian motion and gradually approach the corresponding groups in the soil fugitive dust particles. When the distance between the two reaches 10 [Formula: see text], adsorption occurs, causing small dust particles to stick together. Because of the stability of the covalent bonds in the methyl and hydroxyl groups, a stable solidified layer is formed on the soil fugitive dust surface after the evaporation of the composite dust inhibitor solution, thereby avoiding secondary dust. In addition, the composite dust suppressant is noncorrosive and friendly to the construction site environment. Therefore, the composite dust suppressant can effectively reduce soil fugitive dust, alleviate environmental pollution, and provide a reference for preventing and controlling soil fugitive dust on urban construction sites and preparing composite environment-friendly dust suppressants.

Dust dispersion during the pulse-jet cleaning process with the diffuser effect of the cartridge filter

A special conical diffuser was presented and fixed on the top of the filter cartridge to improve the flow field. The existence of the diffuser can disperse the jet flow from the nozzle, and the high-speed airflow can act on more areas of the filter cartridge, including the top area of the filter cartridge. To improve the cleaning efficiency, the present study is aimed at optimizing the structure of the filter cartridge. The DPM model was used to simulate the dust dispersion process and the falling dust sedimentation from the filter under the action of the pulsed airflow. To validate the established model, the pressure values at the monitoring points were analyzed and compared with the related experimental results. It is found that the pressure values are consistent with the experimental results. Moreover, the installation distance and the size of the diffuser were studied and their influence on the dust distribution on the surface of the filter cartridge. It is found that the dust removal effect is relatively better when the installation distance is 90 mm and the size radius is 25 mm. The maximum dust concentration can be reduced by 15 mg/m³. The present research results can provide theoretical guidance for the cleaning process of the filter cartridge and finally improve the dust-removal efficiency of the dust collector.

Study on Crust-Shaped Dust Suppressant in Non-Disturbance Area of Open-Pit Coal Mine-A Case Study

Dust pollution in open-pit coal mines severely restricts the green development of mines. Therefore, dust control has become an important requirement for the sustainable development of the mining industry. With the goal of dust pollution prevention and control in open-pit coal mines, this paper puts forward the concept of a non-disturbance area of an open-pit coal mine. It clarifies the characteristics of dust generation, the coverage area, and the dust particle size distribution characteristics of the non-disturbance area. Taking the dust control at the dump site as an example, the study comprehensively utilizes indoor tests and field tests to develop a dust suppressant for the dump site and determine its dust suppression efficiency and effective service cycle. The results show that the D10, D50, and D90 particle sizes of dust in the non-disturbance area are smaller than those in the disturbance area, and the difference in particle size of D90 is the most obvious. Gelatinized starch and non-ionic polyacrylamide, as the main components of the dust suppressant, can effectively reduce dust pollution in the dump; the optimal concentration is 1.0%, and the dust suppression service cycle is more than one month. The developed dust suppressant does not contain corrosive, toxic, or heavy metal elements. Although the application of a dust suppressant will cause plant growth to lag, it does not affect plant health. The research findings serve as a reference for the zoning treatment of dust in open-pit mines.

Optimization via response surface methodology of the synthesis of a dust suppressant and its performance characterization for use in open cut coal mines

To relieve dust pollution in open cut coal mines and reduce the hazards of coal dust pollution to the environment and workers we optimized the synthesis of a dust suppressant by graft copolymerization of environmentally friendly soy protein isolate with methyl methacrylate. This dust suppressant could effectively control dust pollution in open cut coal mines. The optimized conditions for graft copolymerization in this case were determined by a response surface experiment designed with Design-Expert 10 software. Characterization by scanning electron microscopy showed a significant morphology change of the dust suppressant and the generation of a rigid and dense layer on its surface after interacting with coal dust. The layer exhibited good bonding and dust suppression performance. The analysis with Fourier-transform infrared spectroscopy revealed the appearance of new absorption peaks near 1300, 1072, and 1631 cm^-1, demonstrating effective graft copolymerization. The proposed dust suppressant exhibited excellent wind erosion resistance, with a resistance that exceeded 90% at a wind speed of 6.5 m/sec. The successful graft copolymerization and effective bonding and curing of the dust suppressant on coal dust were experimentally verified. This is of great significance to the control of coal dust pollution.

Biochar granulation reduces substrate erosion on green roofs

Green roofs are exposed to high winds and harsh environmental conditions that can degrade vegetation and erode substrate material, with negative consequences to ecosystem services. Biochar has been promoted as an effective substrate additive to enhance plant performance, but unprocessed biochars are susceptible to wind and water erosion. Applications of granulated biochars or chemical dust suppressants are suggested as a means to mitigate biochar and substrate erosion; however, research on biochar type and chemical dust suppressant use on biochar and substrate erosion is lacking. Vegetation is a crucial factor that influences substrate erosion, yet plant responses may vary with biochar type and chemical dust suppressant; thus, the effects of possible mitigation measures on biochar and substrate erosion are unclear. We investigated the effects of surface-applied granulated and unprocessed biochars and an organic dust suppressant (Entac™) on biochar and substrate erosion on green roofs with Sedum album L. and a native plant mix. Our results show that 94% of unprocessed biochars were lost from green roofs after 2 years regardless of the Entac™ amendment, likely due to the lightweight nature and fragmentation of biochar particles. In contrast, granulation of biochars reduced the biochar erosion and total substrate erosion by 74% and 39%, respectively, possibly due to enhanced biochar bulk density and particle size and improved moisture retention of biochar-amended substrates. Additionally, Sedum album better reduced biochar and substrate erosion than the native plant mix, likely due to rapid development of high vegetation cover that reduced wind exposure and enhanced substrate moisture retention. We conclude that applications of granulated biochars can substantially reduce biochar and substrate erosion on green roofs, improving green roof sustainability.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42773-022-00186-7.

Effect of Mixed Acid Fluid on the Pore Structure of High Rank Coal and Acid Fluid Optimization

Acidizing technology is an important means to increase production in oil-gas reservoirs. In recent years, acidizing technology has been widely used to increase the permeability of coal seams to enhance gas extraction, where acidizing fluid is the key factor to determine the permeability improvement effect by acidizing technology. In order to clarify the influence of mixed acid fluid on the pore structure of high rank coal and seek the optimal mixed acid fluid suitable for acidizing and permeability improvement of high rank coal in the Jiaozuo coal mine area. Taking the Jiulishan Mine in the Jiaozuo mining area as an example, low field nuclear magnetic resonance (LFNMR) test and static dissolution test were conducted to obtain the T ₂ spectrum, porosity, movable fluid saturation, pore throat distribution, nuclear magnetic permeability, and dissolution rate of coal samples before and after treatment with distilled water and three mixed acid fluids. On this basis, the influence of mixed acid fluid on the pore structure of high rank coal was analyzed and the optimal mixed acid fluid suitable for high rank coal was selected. The results showed that the pore size, number, and volume of all kinds of pore sizes of coal samples treated with distilled water all decreased, which was manifested by the decrease of effective porosity and nuclear magnetic permeability. After acidification, the proportion of micropore volume in coal decreased significantly, the number and proportion of pore volume of mesopores and macropore-microfractures increased significantly, and the connectivity between mesopores and macropore-microfractures was enhanced, which was characterized by the increase in effective porosity and nuclear magnetic permeability of coal samples. After acidification, the pore-throat ratio of adsorption pores of all coal samples decreased, while the pore-throat ratio of seepage pores increased. By comparatively analyzing the change law of pore structure of coal samples before and after acidizing with three kinds of mixed acid fluids, the optimal mixed acid fluid suitable for acidizing and permeability improvement of high rank coal in the Jiaozuo coal mine area was selected, which was 12%HCL +3%HF.

Annual dust pollution characteristics and its prevention and control for environmental protection in surface mines

Dust pollution is a critical challenge in achieving green mining of open-pit coal mines. The scientific basis for dust prevention and management hinges on a thorough understanding of the long-term characteristics of dust pollution. However, analyzing the characteristics of long-term dust pollution in open-pit coal mines has always been a void in research due to the effect of the mines' geographical location and operating conditions. This research investigated the dust pollution and delved into its key production and meteorological influencing elements in a cold-region open pit coal mining. The real-time data was monitored on-site during the four seasons of the year. The characteristics of dust pollution were determined by statistical analysis. The main factors affecting the dust concentration in different seasons were calculated using the comprehensive grey correlation degree. Finally, dust pollution from the mine to the surrounding area was simulated using the Hybrid Single Particle Lagrangian Integrated Trajectory model. The results revealed that dust pollution was most serious in winter, followed by autumn, spring, and summer. The concentrations of PM10 and PM2.5 exceed the national limit. Meteorological elements that substantially impact dust concentration vary season by season. The dew point temperature in spring, the solar radiation in summer and autumn, and the boundary layer height in winter were the most important elements. Mining activities pollute the surrounding areas more in winter, followed by autumn and spring. During the winter, the pollution is concentrated in Shanxi, while in the autumn and spring, it is concentrated in Inner Mongolia. Based on the research findings, optimal mine design strategies can be devised to avoid and regulate dust in mining and neighboring areas, especially during winter.

Experimental study on coal dust wettability strengthened by surface active ionic liquids

The water wettability of coal dust was very important for dust control when using water-based dust suppressant materials. The coal dust wettability strengthened by surface active ionic liquid was studied in this paper. The surface activity of ten ionic liquids with different anions Cl^-, Br^-, [BF₄]^-, [NTf₂]^- and cations [HOEtMIm]⁺, [C_nmim]⁺ (n = 4, 12, 14, 16) was studied by surface tension test. The water wettability of raw coal dust can be improved individually by adding ionic liquid to water or pre-treating coal dust by ionic liquids. The wettability of lignite was improved little, but that of bituminous coal and anthracite were improved much. The dual strengthened effects of ionic liquids on coal dust wettability were studied by the wetting results between ionic liquids solutions and ionic liquid-treated coal samples. The wettability of lignite can be strengthened under the combined action of [HOEtMIm][NTf₂] and [C₁₂MIm]Br, while other dual effects were not satisfactory. All ionic liquids combination had strengthened effects on the wettability of bituminous coal and anthracite, especially the [C₁₂MIm]Br treatment and [C₁₂MIm]Br solutions together had the best dual effects. The functional groups results indicated that the hydrophilic oxygen-containing functional groups in treated coal samples increased, the hydrophobic aliphatic hydrocarbon functional groups decreased and part of ionic liquids were adsorbed on the coal surface. These changes together enhanced the wettability of coal with high coalification degrees.

Field measurement and numerical simulation of dust migration in a high-rise building of the mine hoisting system

Dust pollutants generated from the coal transfer process in a high-rise building of the mine hoisting system not only undermine the operating environment but also reduce the surrounding air quality. Therefore, this study aimed to determine the spatiotemporal distribution of coal dust in the high-rise buildings using field measurement and numerical simulation. Based on the discrete phase model (DPM), the dust migration process under the hybrid ventilation system was investigated in detail. Then, the feasibility of the established model to predict the spatiotemporal distribution of dust pollutants was proven through the measurements of both the airflow and the dust concentration. The present study showed that dust distribution is not uniform in time and space, which also differs for different floors. The dust concentration of the 3^rd floor is relatively larger when compared with those of other floors. The dust concentration increases for the upper floors when the upward air velocity increases, while those of the lower floors are not always low due to the backflows, particularly for the 2^nd floor. PM_2.5 takes up more than 20% of all discharged particles.

Preparation and performance characterization of a new dust suppressant with a cross-linked network structure for use in open-pit coal mines

In an effort to control dust pollution in open-air environments such as pit coal mines and coal transportation systems, a new dust suppressant with a cross-linked network structure was prepared. Graft copolymerization of soy protein isolate (SPI) and methacrylic acid (MAA), using potassium persulfate (KPS) as the initiator and hexametaphosphoric acid (SHMP) as the cross-linking agent, formed the network structure. The optimal MAA/SPI mass ratio for the dust suppressant was determined through a single-factor experiment to be 3:4, with 0.8 and 0.2 g of SHMP and KPS, respectively. The grafting reaction required 30 min at 60 °C. Scanning electron microscopy, energy-dispersive x-ray spectroscopy, Fourier-transform infrared spectroscopy, and differential scanning calorimetry were used to characterize the structure and application performance of the dust suppressant. The experimental results showed that the graft copolymerization reaction successfully formed the desired cross-linked network, and that when the cross-linked network material was sprayed on coal dust, it formed a dense, solidified shell, which effectively resisted wind erosion and served as a dust suppressant. The average reduction of the total suspended particulate matter of an open-air coal pile reached 79.95%, demonstrating effective dust suppression.

A research on dust suppression mechanism and application technology in mining and loading process of burnt rock open pit coal mines

In order to solve the serious dust pollution problem in mining and loading process of burnt rock open-pit coal mines, a dust suppression technology was proposed to investigate the compound dust suppressant with four functions of wetting, coagulation, moisture absorption, and moisture retention, and improve the hydrophilicity and dust suppression efficiency of burnt rock. Through single-factor experiments, four functional reagents were selected. Determined the best mass concentration ratio by orthogonal test, and the optimum dilution ratio was determined through the contact angle verification test. Fourier infrared spectroscopy (FTIR) analysis of the functional group of the compound dust suppressant showed that the hydrophilic functional group was increased. The scanning electron microscopy (SEM) revealed that the dust surface formed a dense film after spraying the dust suppressant, and the effect of fine dust coagulation was obvious. The results of the wind tunnel simulation test revealed that the inhibitory efficiency of the compound dust suppressant on total dust and respirable dust could reach up to 81.90% and 87.06%, respectively, under a wind speed of 4.00 m/s. The field test data for mining and loading spray dust suppression in open-pit coal mines revealed that the dust suppression efficiency of whole dust and respirable dust was greater than 85.70%, which indicates that the compound dust suppressant can effectively suppress the dust of burnt rock, and effectively improve the working environment quality of mining and loading in open-pit coal mines.Implications: Open-pit coal mines located in arid areas will produce a large amount of dust during the mining and loading process, which will cause serious air pollution. In particular, the burnt rock is highly hydrophobic, and it is difficult to achieve effective removal by water spraying. The open-pit coal mine face advances faster and has strong mobility, There are few researches on dust reduction in this link. Therefore, in this study, in order to improve the dust suppression efficiency in the mining and loading process, a compound dust suppressant to improve the hydrophilicity of the burnt rock was developed through single-factor experiments and orthogonal experiments. Microscopic analysis using FTIR and SEM confirmed the wetting and coagulation effect of the dust suppressant. Then designed a spray dust suppression program for the mining and loading process and achieved good results.

Formulation Development and Performance Characterization of Ecological Dust Suppressant for Road Surfaces in Cities

In order to solve the problem of road dust pollution, an ecological dust suppressant for road surfaces has been developed using monomer, orthogonal, and optimization experiments and based on the dust raising mechanism. A humectant, hygroscopic agent, coagulant and surfactant and their concentration ranges have been determined through monomer experiment. The preliminary formula of the dust suppressant has been obtained through orthogonal experiment, with the water loss rate, moisture content rate, viscosity value, and surface tension value serving as experimental indexes. The optimal formula for the dust suppressor has been calculated through an optimization experiment, with the toxicity, moisture absorption and retention performance of plants, and the relative damage rate of plant seeds serving as experimental indexes. Based on the performance characterization of ecological road dust suppressant, the ecologically and environmentally friendly dust suppressant demonstrates fine moisture absorption and retention performance, good wind and rain erosion resistance, and no toxicity. The ecological road dust suppressant developed herein covers extensive raw material sources. It is ecologically and environmentally friendly, fit for most urban roads, and has a fine dust suppression effect. Meanwhile, it also can bring in good economic and social benefits, demonstrating its broad application prospects.

Environment-friendly dual-network hydrogel dust suppressant based on xanthan gum, polyvinyl alcohol and acrylic acid

Hydrogen bonding interactions among poly vinyl alcohol (PVA), xanthan gum (XG) and acrylic acid (AA) molecules have been utilized to prepare an environment-friendly interpenetrating double-network hydrogel dust suppressant (PVA-XG-PAA/SDBS) with the aim of enhancing the poor mechanical performance of current hydrogel dust suppressants. A single factor test was used to determine the optimal formulation conditions for the PVA-XG-PAA/SDBS, and the viscosity, surface tension, compression strength, wind resistance, water retention and biodegradability of the samples were measured. The results showed that the hydrogel with optimal usage contained 1.5 g, 0.1 g, and 6 g of PVA, XG and AA, respectively and the optimal reaction temperature was 55 °C. Under the optimal conditions, the viscosity was 45 mPa s, the surface tension was 30 mN/m, the compression strength of the dust suppressant-solidified coal pillar reached 126 kPa, and the degradation rate at the 8th cycle (40 days) after being buried in soil was 34%. Compared with a conventional hydrogel dust suppressant, like poly acrylic acid (PAA), and the dust suppressant sodium dodecyl benzene sulfonate (SDBS), the PVA-XG-PAA/SDBS showed better water retention, wind erosion resistance, and dust-solidifying properties. On the basis of these remarkable properties, the PVA-XG-PAA/SDBS is applicable for dust prevention during coal mining, transport, and storage, which enhances the dust suppression efficiency obviously and has significant meaning to the sustainable development of the coal mining industry while protecting the environment.

Synthesis of starch-based super absorbent polymer with high agglomeration and wettability for applying in road dust suppression

Dust pollution is an important factor restricting social development and affecting human health, especially in some developing countries. Herein, mechanical activation-assisted solid phase reaction (MASPR) and conventional liquid phase (LP) method were employed to synthesize different superabsorbent polymers (SAPs), defined as SAP-MA and SAP-LP, respectively. The rheological properties, crystal structure, changes of functional groups, and dust suppression performance of the SAPs prepared by these two methods were compared, and the dust suppression mechanism of SAPs was discussed via the adsorption experiment between dust suppressant and dust particles. The results showed that SAPs were successfully prepared by the two methods. Compared with SAP-LP, SAP-MA with lower molecular weight, higher grafting rate, and better fluidity and water absorption showed excellent suppression performance. This enhancement could be attributed to that the SAP-MA exhibited lower crystallinity and better film-forming ability, anti-evaporation, anti-consolidation, and permeability induced by MA. Furthermore, the effective chemical adsorption between SAPs and dust particles had a stable consolidation effect. This environmentally-friendly method for the preparation of starch-based super absorbent polymer for road dust suppressant may provide new insights for the valorization of cassava starch and large-scale production of dust suppressant.

Preparation and performance of DOPO-nano-SiO2 modified polyacrylic acid-based flame retardant dust suppressant for coal

Based on the synergy of N, P and Si, a type of soft-film flame retardant dust suppressant for coal with both flame-retardant and dust-suppression functions was prepared, aiming to slow down spontaneous coal combustion and coal dust pollution.

Preparation and Characterization of a Composite Dust Suppressant for Coal Mines

In an effort to effectively control coal dust pollution and thereby reduce the harm of coal dust to human health, we prepared a highly efficient composite dust suppressant. First, dynamic contact angle and zeta potential measurements were used to select sodium dodecyl sulfonate (SDS) over sodium carboxymethyl cellulose and trisodium methyl silicon as the complementary additive to soy protein isolate for the dust suppressant. We employed viscosity and wind erosion resistance tests to compare the performance of the composite dust suppressant with three common, commercially available suppressants. As the concentration of the composite dust suppressant was increased, the viscosity increased, reaching a maximum value of 22.7 mPa·s at a concentration of 5 wt%. The 5 wt% concentration of the composite dust suppressant provided the lowest wind erosion rate (20.62%) at a wind speed of 12 m/s. The composite dust suppressant also had good bonding performance and wind erosion resistance. Scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis were used to characterize the properties of the dust suppressants. The dust suppressant, which had a crystal-like structure, could easily capture coal dust and form an effective package. In addition, the density of the dust suppressant film increased as its crystallinity increased. The increased density was beneficial in that it enabled the dust suppressant to form a hard, solidified shell on the surface of coal dust, which improved dust suppression. The composite dust suppressant also had good thermal stability.

Recent Progress in Polymer-Containing Soft Matters for Safe Mining of Coal

Safe mining is the premise and guarantee of sustainable development of coal energy. Due to the combination of excellent properties of polymers and traditional soft matters, polymer-containing soft matters are playing an increasingly important role in mine disaster and hazard control. To summarize the valuable work in recent years and provide reference and inspiration for researchers in this field, this paper reviewed the recent research progress in polymer-containing soft matters with respect to mine dust control, mine fire control, mine gas control and mine roadway support. From the perspective role of polymers in a material system, we classify mine polymer-containing soft matters into two categories. The first is polymer additive materials, in which polymers are used as additives to modify fluid-like soft matters, such as dust-reducing agents (surfactant solution) and dust-suppressing foams. The second is polymer-based materials, in which polymers are used as a main component to form high performance solid-like soft matters, such as fire prevention gels, foam gels, gas hole sealing material and resin anchorage agent. The preparation principle, properties and application of these soft matters are comprehensively reviewed. Furthermore, future research directions are also suggested.

Novel sodium silicate/polymer composite gels for the prevention of spontaneous combustion of coal

Novel gel materials are proposed for fire prevention and extinction in coal mines, where spontaneous combustion of coal continues to pose a significant risk. Cationic polyacrylamide (CPAM), anionic polyacrylamide (HPAM), and carboxymethyl cellulose (CMC) were each introduced separately into a sodium silicate (WG) gel, to obtain three gels labeled as CPAM/WG, HPAM/WG, and CMC/WG. A crosslinking agent, aluminum citrate, was subsequently added to the HPAM/WG and CMC/WG gels to afford two novel interpenetrating network hydrogels, HPAM-Al³⁺/WG and CMC-Al³⁺/WG, respectively. Among the various gels, the HPAM-Al³⁺/WG hydrogel exhibits the best seepage capacity, water retention capacity, compressive strength, and inhibition characteristics, which effectively resolve the post-water-loss cracking and pulverization problems commonly associated with inorganic consolidated silica gels. The microstructures of all the gels were investigated by scanning electron microscopy and their inhibitory effects on the oxidation of hydroxyl and methylene groups in coal at high temperatures were analyzed by Fourier transform infrared spectroscopy. Elemental mapping by energy dispersive X-ray spectroscopy indicated that the inorganic silica gel blends uniformly with the polymeric gel. Fire extinction experiments indicated that the HPAM-Al³⁺/WG gel reduces the fire-source temperature, heat radiation, and CO generation. Thus, the HPAM-Al³⁺/WG gel is an ideal fire prevention and extinction material.

Experimental Research on Heat Transfer and Strength Analysis of Backfill with Ice Grains in Deep Mines

In deep mines, two urgent problems are a high temperature thermal environment and solid waste. Filling the goaf with slurry mixed with ice grains is an effective way to solve these two problems simultaneously. The thermal property and mechanical property of the ice-added backfill have a great influence on the cooling effect in the deep mine. In this study, an experimental facility for measuring the temperature distribution of ice-added backfill slurry was established, and the temperature of backfill slurry with different proportions was measured. Then, the thermal properties of temperature distribution and cooling capacity and the mechanical property of uniaxial compressive strength of the backfill specimens were analyzed, and the results indicated the following: firstly, the cooling capacity of ice-added backfill specimens is negatively related with the slurry concentration C and is positively related with the ice-water ratio Ω; secondly, the strength of backfill specimens is affected by the slurry concentration C and ice-water ratio Ω by a contrary law compared to the cooling capacity; thirdly, ice-added backfill slurry with an ice-water ratio Ω of 1:1 has the best mechanical property after solidification. The effects of the slurry concentration and ice-water ratio on the thermal and mechanical properties were analyzed, and the results indicated that the optimum proportion of ice-added backfill slurry is a slurry concentration of 74% and an ice-water ratio of 1:1 in the present research range. This study is significant for the deep mine cooling method with ice-added backfill.

Development of Environmental Friendly Dust Suppressant Based on the Modification of Soybean Protein Isolate

Aiming to further improve the dust suppression performance of the dust suppressant, the present study independently develops a new type of biodegradable environmentally-friendly dust suppressant. Specifically, the naturally occurring biodegradable soybean protein isolate (SPI) is selected as the main material, which is subject to an anionic surfactant, i.e., sodium dodecyl sulfonate (SDS) for modification with the presence of additives including carboxymethylcellulose sodium and methanesiliconic acid sodium. As a result, the SDS-SPI cementing dust suppressant is produced. The present study experimentally tests solutions with eight different dust suppressant concentrations under the same experimental condition, so as to evaluate their dust suppression performances. Key metrics considered include water retention capability, cementing power and dust suppression efficiency. The optimal concentration of dust suppressant solution is determined by collectively comparing these metrics. The experiments indicate that the optimal dust suppressant concentration is 3%, at which level the newly developed environmentally-friendly dust suppressant solution exhibits a decent dust suppression characteristic, with the water retention power reaching its peak level, and the corresponding viscosity being 12.96 mPa·s. This performance can generally meet the requirements imposed by coal mines. The peak efficiency of dust suppression can reach 92.13%. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to analyze the dust suppression mechanism of the developed dust suppressant. It was observed that a dense hardened shell formed on the surface of the pulverized coal particles sprayed with the dust suppressant. There is strong cementation between coal dust particles, and the cementation effect is better. This can effectively inhibit the re-entrainment of coal dust and reduce environmental pollution.

Resilient Modulus—Physical Parameters Relationship of Improved Red Clay by Dynamic Tri-Axial Test

As one of the important parameters used in the analysis and design of subgrade, resilient modulus is directly related to the safety, economic and life time of subgrade structure. In this paper, the characteristics of resilient modulus of improved red clay at different additive content were studied through conducting laboratory repeated load tri-axial tests. The influence of stress state, moisture content, compactness, additive types, and content on resilient modulus were analyzed. In addition, the regression analysis of resilient modulus, was carried out referencing three existing prediction models. The results showed that the Andrei model can better fit the resilient modulus of red clay and have a higher determination coefficient. However, the Andrei model and other existing prediction models, reflect only the influence of stress state on resilient modulus, without considering the influence of moisture content, compactness and additive content. Therefore, based on the Andrei model, a comprehensive prediction model, which can reflect the influence of compactness, moisture content, additive content, and stress state on resilient modulus was introduced. Good agreement between the regression results and the measured ones demonstrated the integrative ability of the introduced model.

Behavior of Fiber-Reinforced and Lime-Stabilized Clayey Soil in Triaxial Tests

The beneficial role of combining fiber reinforcement with lime stabilization in altering soil behavior has been established in the literature. However, the coupling effect of their combination still remains unclear in terms of its magnitude and microscopic mechanism, especially for natural fibers with special microstructures. The objective of this study was to investigate the coupling effect of wheat straw fiber reinforcement and lime stabilization on the mechanical behavior of Hefei clayey soil. To achieve this, an experimental program including unconsolidated–undrained (UU) triaxial tests and SEM analysis was implemented. Static compaction test samples were prepared on untreated soil, fiber-reinforced soil, lime-stabilized soil, and lime-stabilized/fiber-reinforced soil at optimum moisture content with determining of the maximum dry density of the untreated soil. The lime was added in three different contents of 2%, 4%, and 6%, and 13 mm long wheat straw fiber slices with a cross section one-quarter that of the intact ones were mixed in at 0.2%, 0.4%, and 0.6% by dry weight of soil. Analysis of the derived results indicated that the addition of a small amount of wheat straw fibers into lime-stabilized soil improved the intensity of the strain-softening behavior associated with mere lime stabilization. The observed evidence that the shear strength increase brought by a combination of 0.4% fiber reinforcement and 4% lime stabilization was smaller than the summation of the shear strength increases brought by their presence alone in a sample demonstrated a coupling effect between fiber reinforcement and lime stabilization. This coupling effect was also detected in the comparisons of the secant modulus and failure pattern between the combined treatment and the individual treatments. These manifestations of the coupling effect were explained by a microscopic mechanism wherein the fiber reinforcing effect was made more effective by the ways in which lime chemically stabilized the soil and lime stabilization development was quickened by the water channels passing through the surfaces and honeycomb pores of the wheat straw fibers.