Experimental and simulation studies on the improvement of coal dust pollution by an aqueous solution of sodium α-alkenylsulfonate and amino acid-based surfactants.

The use of surfactants is crucial for the prevention and control of coal dust pollution in coal mining operation areas, yet there still exist many challenges in the control of coal dust pollution. In this paper, the green biomass-based amino acid surfactant sodium myristoyl glutamate (SMG) and the anionic surfactant sodium α-alkenyl sulfonate (AOS) were selected to investigate the improvement of coal dust wettability by single and binary solutions from the macroscopic and microscopic perspectives. Molecular simulations were used to reveal the microscopic mechanism of the wettability of coal dust by the different solutions. Experimental measurements showed that the contact angle of the AOS + SMG aqueous solution was as low as 13.8° on a coal surface. Coating the coal dust with the AOS + SMG solution reduced the surface tension by 12.02% compared to coating the coal with a single component solution. Additionally, the use of the binary AOS + SMG solution increased the hydrophilic group content in the coating by 11.77% compared to a single component solution, and the linkage between hydrophilic groups was enhanced, which pulls the water molecules to wet the coal dust. These research results should provide a new way to promote more environmentally friendly coal dust pollution control technology.

Study on the effect of Ce-Cu doping on Mn/γ-Al2O3 catalyst for selective catalytic reduction in NO with NH3.

A series of Mn/γ-Al2O3, Mn-Cu/γ-Al2O3, Mn-Ce/γ-Al2O3 and Mn-Ce-Cu/γ-Al2O3 catalysts were prepared by equal volume impregnation. The denitrification effects of the different catalysts were studied by activity measurement, X-ray diffraction, Brunauer, Emmett, and Teller surface area tests, Scanning electron microscopy, H2-temperature programmed reduction and Fourier-transform infrared spectroscopy. The experimental results show that Ce and Cu are added to a Mn/γ-Al2O3 catalyst as bimetallic additives, which weakens the interaction between Mn and the carrier, improves the dispersion of MnOx on the surface of the carrier, improves the specific surface area of the catalyst, and improves the reducibility. Mn-Ce-Cu/γ-Al2O3 catalyst reaches a maximum conversion of 92% at 202 °C. Also, the addition of the auxiliary metals promotes the reaction mechanism to a certain extent, and the addition of Ce especially promotes the conversion of NO-NO2, which is conducive to the production of intermediate products that promote the NH3-SCR reaction.

Development and characterization of a high efficiency bio-based rhamnolipid compound dust suppressant for coal dust pollution control.

Surfactants make a significant contribution to the suppression of coal dust fly in underground coal mines, but are hazardous to the environment and human health. It is therefore crucial to develop more environmentally friendly and efficient wetting agents using non-polluting eco-friendly surfactants. In this study, the wetting properties of the biosurfactant rhamnolipid were investigated and the rhamnolipid composite wetting agent (CS-A-S) was prepared by mixing design after preferring different surfactants by means of experiments and quantum mechanical simulations. The dust suppression properties were compared by means of infrared spectroscopy, scanning electron microscopy and molecular dynamics simulation. The results showed that the critical micelle concentration (CMC) of rhamnolipid was 0.04 wt% and the surface tension was 25.9 mN/m, which had the basis to become an underground dust suppressant; the surface tension of CS-A-S was reduced to 23.95 mN/m and the contact angle to coal dust was 25°; after spraying CS-A-S, the median particle size of coal dust reached 125.76 µm, an increase of 849.13%; the specific surface area was reduced to 2.24 m2/g, a decrease of 51.06%; the oxygen-containing groups on the coal surface increased by 55.87-246.7%, making it easier to form hydrogen bonds, the coal dust became more hydrophilic, and coal dust particles easily agglomerated into larger sizes and settled rapidly under gravity; the CS-A-S simulated system showed the greatest degree of water molecule penetration, with a minimum of 71 Å, and a water molecule diffusion coefficient of 1.06 Å2/ps, a decrease of 75%, and the interaction energy with coal molecules is 155.6 kcal/mol, an increase of 66.9%, making it easier for the dust suppressant molecules to form adsorption on the coal surface, showing a better dust suppression effect.

Study of wetting and adsorption mechanism of mixed anionic-nonionic nonhomologous surfactants on coal dust based on intermolecular interactions.

The research found that mixed anionic-nonionic surfactants have synergistic wetting performance which can be added to the spray solution to greatly enhance the wettability to coal dust. In this study, based on the experiment data and some synergism parameters, and a 1:5 ratio of fatty alcohol polyoxyethylene ether sulphate (AES)-lauryl glucoside (APG) has the best synergism, resulting in a highly wettable dust suppressant. Additionally, the wetting processes of different dust suppressant on coal were comparatively simulated by molecular dynamics. Then, the electrostatic potential on the molecular surface was computed. Following this, the mechanism of surfactant molecule regulation of coal hydrophilicity and the advantage of the interspersed arrangement of AES-APG molecules in the mixed solution were proposed. Also, based on the computation of highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels and binding energy calculations, a synergistic mechanism of the anionic-nonionic surfactant is proposed from the perspective of enhanced hydrogen bonding between the hydrophilic part of the surfactant and the water molecule. Overall, these results present a theoretical basis and development strategy for the preparation of highly wettable mixed anionic and nonionic dust suppressants for different coal types.

Carboxymethyl cellulose sodium gel: A modified material used to suppress coal dust pollution.

To reduce the environmental pollution caused by coal dust, a new type of dust inhibitor with a wide application range, high efficiency, and production simplicity was synthesized by modifying sodium carboxymethylcellulose (CMC-Na) with acrylamide (AM). Through molecular dynamics simulations and experiments, the surfactant composition and concentration were optimized. The experimental results showed that the graft copolymer of CMC-Na and AM (CMC-Na-co-AM) had more pores on the microscopic surface and a unique fiber network structure, which greatly increased its contact area with coal dust. After 14 h of drying at 60 °C, coal samples that were sprayed with the dust suppression agent retained >50% of the water in the spray, which was 9 times greater than the water retention of coal samples sprayed with just water. Additionally, the ability of the dust suppression agent to resist wind erosion was 6 times that of water. The CMC-Na-co-AM dust suppression agent showed that it could effectively inhibit the spread of coal dust under strong winds, offering a solution to the problem of coal dust pollution in coal production and storage.

Simulation study of the mechanism of mesoscopic adsorption and the evolution of molecular dynamics of a surfactant/polymer composite on the surface of low rank coal.

In this paper, the head group, tail group, and main chain of a single type of surfactant were constructed by a mesoscopic simulation, and the interaction between the simulated surfactant and coal dust both on its own and in a composite with polyacrylamide (PAM) was studied. The molecular adsorption behavior of cetyltrimethylammonium chloride (CTAC) surfactant mixed in different ratios with PAM was also experimentally characterized. The results showed that. From the above results, we can see that CTAC and PAM can form spherical, rod-shaped, and wormlike aggregates and a network structure as their volume fraction increases in an aqueous solution. The energy spectrum showed that when CTAC adsorbed on the surface of the coal, the content of carbon on the surface decreased from 63.8 to 50.4%, and the content of oxygen increased from 35.2 to 41.8%. The study on the adsorption mechanism of surfactants and polymers on the surface of low rank coal and the hydrophilicity of low rank coal is of great significance in developing efficient dust prevention technology for low rank coal to reduce coal dust pollution.