Study On The Enhancement Of Coal Slurry Water Sedimentation By Regulating The Hydrophobicity Of Kaolinite Surfac

Coal slime water is an industrial wastewater produced by wet coal preparation process,and its treatment is an indispensable part of the production process of coal preparation plant.In recent years,with the improvement of mechanization of coal mining,both of the ash content of raw coal and the proportion of coal fines are relatively high,and a large amount of high-mudified coal slime water is produced in the process,which increases the difficulty of slime water treatment.Kaolinite is the main mineral component in the solid phase material of high-mudified coal slime water.It has the characteristics of fine particle size,easy mudding,surface charge and strong hydrophilicity,which makes it more difficult to settle.Kaolinite was used as the research object and the effect of common metal cations,inorganic anions,anionic polyacrylamide（APAM）,cationic polyacrylamide（CPAM）,nonionic polyacrylamide（NPAM）,cetyl trimethyl ammonium bromide（CTAB）,octadecyl trimethyl ammonium chloride（STAC）and their combinations and addition sequence on the sedimentation characteristics of kaolinite was investigated.On the basis of this,Zeta potential,Fourier transform infrared spectroscopy,microcalorimetry,contact angle,laser particle size analyzer and optical microscope were used to reveal the mechanism of different agents in kaolinite sedimentation process.The results show that compared with Na⁺,K⁺,Ca²⁺and Mg²⁺,the addition of Al³⁺has better effect on reducing the turbidity of kaolinite suspension.Compared with SO₄^2-and NO₃^-,the sedimentation effect of adding inorganic anion Cl^-is better,the addition of APAM is beneficial to accelerate the sedimentation rate of kaolinite and obtain a smaller compression layer thickness.The addition of STAC is beneficial to obtain a smaller compression layer thickness and lower supernatant turbidity.Compared with the single agent,the combination of APAM,STAC and Al Cl₃has better sedimentation performance.The effect of adding order of agents on kaolinite sedimentation is obvious,specifically,adding APAM first and then STAC and Al Cl₃is the best.The sedimentation test of the actual slime water with an initial concentration of 60 g/L shows that when 0.2 g/LAPAM,0.2 g/LSTAC and 0.08 g/LAl Cl₃are added,the thickness of the settlement compression layer of the slime water is 4.5 cm,the turbidity of the supernatant is 21.2 NTU（36.5 mg/L）,and the sedimentation rate is 27cm/min.The mechanism analysis shows that Al Cl₃mainly promotes the agglomeration of kaolinite particles by reducing the absolute value of Zeta potential on kaolinite surface and enhancing the hydrophobicity of kaolinite surface.APAM promotes the increase of kaolinite particle agglomeration mainly through electrostatic adsorption and bridging.STAC promotes the hydrophobic aggregation of kaolinite particles mainly by enhancing the hydrophobicity of kaolinite surface and inhibiting the hydration of kaolinite.The combination of APAM+STAC+Al Cl₃reduces the electronegativity and hydrophilicity of kaolinite surface,and increases the floc size of kaolinite,which is beneficial to the rapid sedimentation of kaolinite.