Study On The Influence Of Compound Reagents On The Sedimentation And Dehydration Characteristics Of Montmorillonit

Coal washing is an important way of clean and efficient utilization of coal resources.The treatment of coal slime water in coal preparation plant not only affects the separation index of coal preparation plant,but also determines whether the coal preparation plant can produce normally to a certain extent.Montmorillonite is a clay mineral that has a significant impact on the sedimentation of coal slime water.Its surface charging and hydration characteristics hinder the aggregation between particles,keep the suspension dispersed,and worsen the sedimentation of coal slime water.The study on the influence of reagents on the settling behavior of montmorillonite in coal slime water and its dehydration characteristics is of great significance for the efficient treatment of coal slurry water containing montmorillonite.The test results show that adding inorganic coagulant into montmorillonite suspension can obtain small supernatant turbidity,and the sedimentation effect of Al³⁺,Ca²⁺and Mg²⁺is better than that of Na⁺,K⁺.Adding organic flocculant and hydrophobic modifier can accelerate the sedimentation rate of montmorillonite and obtain a smaller volume of compressed layer.Inorganic coagulant and hydrophobic modifier are more conducive to promote the filtration and dehydration of montmorillonite,and the amount of organic flocculant PAM exceeding a certain range will hinder the filtration and dehydration of montmorillonite.Compared with a single agent,the combination of CaCl₂and PAM is more conducive to the sedimentation of montmorillonite,while CaCl₂and CTAB are more conducive to the filtration and dehydration of montmorillonite.Under the combined action of CaCl₂,PAM and a small amount of CTAB,a faster sedimentation rate（1.86 cm/min）and a faster filtration rate(1.56 ml·（dm²s）^-1)can be obtained.The mechanism analysis shows that the inorganic coagulant can reduce the absolute value of zeta potential on the surface of montmorillonite and compress the thickness of its electric double layer.Among them,Mg²⁺,Ca²⁺and Al³⁺carry more positive charges than Na⁺,K⁺,and neutralize more surface charges of montmorillonite.The effect is relatively good;Hydrophobic modifier can increase the surface contact angle of montmorillonite and enhance its hydrophobicity;Organic flocculants adsorb montmorillonite particles and promote montmorillonite agglomeration mainly through their bridging effect.Compared with a single agent,the combination of CaCl₂and CTAB can make the absolute value of zeta potential on the surface of montmorillonite smaller,while the combination of CaCl₂and PAM can make the floc size of montmorillonite larger,which are beneficial to montmorillonite sedimentation and dehydration.Under the combined action of CaCl₂,PAM and a small amount of CTAB,CTAB significantly increased the surface hydrophobicity of montmorillonite,and PAM significantly increased the floc size,CaCl₂mainly reduces the surface electronegativity.The combination of the three agents has a synergistic effect,which is conducive to promoting montmorillonite sedimentation and filtration dehydration.The influence law of reagents on the settlement of montmorillonite is consistent with that of coal slime water containing montmorillonite,which shows that in the settlement process of coal slime water containing montmorillonite,montmorillonite particles have the main influence on the settlement characteristics.The research results have certain guiding significance for the treatment of coal slime water containing montmorillonite.