Study On Behaviors And Mechanism Of Flotation Of High-Ash Oxidized Coal Using Surfactants

Coal surface contains a large number of polar groups which elevate it's hydrophilicity and decrease the flotation performance because of the oxidation.In order to improve the hydrophobicity and the flotation effect of high-ash oxidized coal,adsorption and desorption of the four surfactants with the same hydrophobic groups and different hydrophilic groups onto high-ash oxidized coal were studied.FTIR and wettability heat measurement were used to study the differences between adsorption and desorption of the four kinds of surfactants onto organic matters and minerals.The proper structure model and the frontier orbital energy gap ? ELUMO-HIMO/eV of four kinds of surfactants was established by using the quantum chemistry calculations,which were verified with the experimental results of adsorption quantity and wettability heat measurement.In this paper,test samples were prepared by the laboratory method of Wang ping coal.Adsorption experiments of DTAB,SDS,Gemini and C₁₂EO₉ on oxidized coal and the pure minerals were studied respectively.FTIR and wettability heat measurement were used to study adsorption characteristics and the result of flotation.Hydrothermal pretreatment show that desorption of the surfactant from organic matters and minerals impacts the flotability.Main conclusions of the paper are as follows:?1?Based on the analysis of FTIR,wettability heat measurement and cleaned coal yield,the degree of oxidation deepens the hydrophilic group of coal surface,the content of oxygen functional groups,like-OH and-COOH were increased.The wetting heat of the coal oxidized by concentration of 9 % hydrogen peroxide was 2.7 times than raw coal.Cleaned coal yield decreased from 79.5% to 45.3%.?2?The hydrophobicity and flotability of high-ash oxidized coal adsorbed surfactants effectively promoted,however the differences of the results exist.In 0³00 mg/L,the cleaned coal yield increased in the order,SDS,DTAB,C₁₂EO₉ and Gemini,and the yield of the coal adsorbed C₁₂EO₉ reached the peak at 100 mg/L.?3?The wettability of organic matters and minerals adsorbed surfactants effectively promoted.The result of oxidized coal adsorbed surfactants show that the cleaned coal yield and ash content were effectively promoted.?4?The results of hydrothermal pretreatment show that part of oxygen functional groups could be removed,and the differences of the desorption between organic matters and minerals were exist.It was proved that the hydrothermal pretreatment before flotation operation lead to clean coal ash decreasing efficiently.?5?Based on the frontier orbital energy gap ? ELUMO-HIMO/eV,reactivity of the surfactants increased in the order,SDS,DTAB,C₁₂EO₉ and Gemini,which were verified with the experimental results of adsorption quantity and wettability heat measurement.