Water retention of coal dust based on the synergistic effect of multiple factors
[Objective]To ensure the health of coal miners and safe overall production in coal mines,numerous dust-control measures have been implemented to address underground coal-dust disasters.Wet dust suppression and chemical dust inhibition technologies are the primary protective measures employed.The moisture retention capability of dust inhibition technologies directly affects the wetting efficiency of coal dust and the possibility of secondary dust generation after settling.[Methods]This study aims to investigate the dust-inhibiting and moisture retention effects of inorganic salts(potassium sulfate,sodium chloride,and magnesium chloride)and surfactant solutions,both individually and combined,through experiments evaluating water retention capacity via evaporation loss.Through the total weight loss analysis of different types of inorganic salts with different concentrations for different periods,the inorganic salts were optimized,and their moisture retentions were analyzed.Further,through weight loss analysis of surfactant solutions with different concentrations for different periods,the total weight loss analysis of different types of surfactant solutions with different mass fractions,and the surface morphology analysis of coal samples after the experiments,the surfactant solutions were optimized,and their moisture retention analysis was conducted.[Results]A comprehensive comparison of the results for four surfactant solutions(sodium dodecyl benzene sulfonate(SDBS),fatty alcohol polyoxyethylene ether(SDS),alkyl polyglycoside(APG),and polyethylene glycol octyl phenyl ether(Triton X-100)solutions)showed that their distinct molecular structures and properties vary the stability and thickness of the formed molecular layers.Notably,the SDBS solution exhibited the highest moisture retention,followed by the SDS,APG,and Triton X-100 solutions.Without adding the inorganic salts,when the addition amounts of the SDS and SDBS solutions were 0.24％and 0.04％,respectively,the evaporation loss of coal dust was the smallest,the moisture retention rate was the highest when the ratio of the two solutions was 5∶5.When the inorganic salts were added,with increasing concentration of a potassium sulfate solution,the moisturizing ability increased.A higher concentration of the potassium sulfate solution resulted in more ions,increasing the osmotic pressure of the overall solution and reducing the evaporation of water molecules.The synergistic effect with the surfactant solutions further improved the moisturizing performance of coal dust.[Conclusions]A composite solution with 0.24％SDS,0.04％SDBS,0.9 mol/L K2SO4,and a(SDS+SDBS)/K2SO4 ratio of 5∶5 demonstrated the least water loss as well as optimal wetting and moisture retention performance when applied to coal dust.The precipitation effect of a potassium sulfate solution on the hydrophobic end of the surfactant composite solution enhanced the hydrophobicity of coal dust,causing an increased number of surfactant molecules to escape the aqueous phase and aggregate at the liquid-gas interface,thus reducing the surface tension of the solution.
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