Experimental design of reagent adsorption and characterization of low-rank porous coal in mineral separation
[Objective]Low-rank coal constitutes a significant portion of China's energy resource derived from coal.The most prevalent and efficient method for processing fine-grained,low-rank coal slime is interface sorting technology.However,the inherent characteristics of low-rank coal,which include a high surface content of polar functional groups,abundant pores and fissures,and the presence of various embedded gangue minerals,render this type of coal highly hydrophilic,thereby complicating the sorting process.The identification and application of a novel compound reagent for adsorption and modification purposes may not only facilitate efficient sorting but also hold profound implications for the comprehensive utilization of currently available low-rank coal resources.[Methods]This paper initially performs proximate and ultimate analyses on coal samples to understand their fundamental properties,followed by scanning electron microscopy to examine the surface morphology and elemental atomic content of the samples.Subsequently,a pore structure test,Brunauer-Emmett-Teller,is conducted to gain insights into the specific surface area and pore structure of the coal samples.In the subsequent phase,adsorption tests were conducted on the coal samples using 0# diesel and W-l compound reagents as collectors to compare the effects of adsorption modification induced by these reagents.Fourier transform infrared spectroscopy tests were then performed on the samples pre-and post-W-1 adsorption to qualitatively analyze the types of functional groups present on the coal surface and to comprehend the shifts in the proportions of hydrophilic and hydrophobic functional groups.Simultaneously,inductively coupled plasma testing was utilized to characterize the amount of W-1 adsorbed on the coal surface.The elemental contents of sodium and phosphorus in the solution before and after adsorption were measured to calculate the content of the surfactants sodium petroleum sulfonate and trioctyl phosphate in the solution.The concentration method was ultimately employed to compute the content of the reagent adsorbed on the coal particle surface.The results were then integrated with contact angle measurements to assess changes in wettability.[Results]The results from the tests and analyses indicate the following:1)Compared with the experimental parameters using 0# diesel alone,the usage of a flotation reagent was reduced by nearly 45％,the ash content of clean coal was decreased by 0.49 percentage points,and the yield of clean coal was 2.02 times that of the original.2)After the adsorption modification with the W-1 reagent,the intensity of the characteristic peaks of polar groups on the coal sample surface was weakened.The relative content of carbon(C1s)increased by 10.4％,the relative content of oxygen(O1s)decreased by 5.76％,and the proportion of hydrophobic groups(C-C/C-H)increased by 32.42％.The total proportion of hydrophilic groups(C-O/C=O)decreased by 34.22％,resulting in a significant improvement in hydrophobicity.3)The surfactant was adsorbed on the coal sample surface,and because of differences in electronegativity,the phosphate group(-PO43-)exhibited a higher adsorption intensity than that of the sulfite group(-SO3-).These findings suggest that the W-1 compound reagent can effectively modify the coal surface,enhancing its hydrophobicity and thereby improving the efficiency of coal sorting,which leads to more sustainable and efficient utilization of low-rank coal resources.[Conclusions]The surface-active ingredients present in the compound reagent W-1 enhance the collector's ability to collect and select.These ingredients can effectively adsorb onto the polar hydrophilic sites on the surface of coal particles,thereby covering these hydrophilic areas.This process inhibits the formation of a hydration film,which usually occurs because of hydrogen bonding between oxygen-containing functional groups and water molecules.Consequently,the hydrophobicity of the coal particles is improved,strengthening the effect of interfacial sorting.
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