Key Influencing Factors In The Process Of Mud Settlement Of Bauxite Tailings

Mineral resources are one of the important means of production in industrial production.With the development of science and technology and the accelerating process of global industrialization,the demand for mineral resources is also increasing day by day.Tailings slurry is a companion produced in the process of mine washing,which has the characteristics of many clay particles and fine particles,and contains a large number of clay colloids,which leads to the engineering characteristics of difficult dewatering and settling.At present,more methods are used to build tailings reservoir for storage treatment.However,the increasing discharge of slime and the long-term accumulation of slime will bring a huge burden to the ecological environment,so there is an urgent need to accelerate the settlement and consolidation rate of tailings mud and change the existing disposal methods of tailings mud.The key to solve the above problems is to explain the key factors affecting the settlement of tailings mud under different conditions and the mechanism of soil-water interaction in the process of settlement.In this paper,sedimentation tests of Pingguo aluminum slime in Baise,Guangxi were carried out under the action of different initial moisture content,environmental temperature and cationic species and concentrations.The microstructure and composition changes of Pingguo aluminum slime were studied by scanning electron microscope,nuclear magnetic resonance analyzer and micro-electrophoresis instrument,so as to provide a theoretical basis for the research and development of new flocculant and the comprehensive utilization of tailings.The main results are as follows:(1)Pingguo aluminum slime has different settlement types in different water content,which are sedimentary settlement and consolidation settlement respectively.The experimental results show that the slime sedimentation occurs when the initial water content is more than400%.Consolidation settlement occurs when the initial moisture content is less than 400%.With the decrease of moisture content,the sedimentary settlement will gradually change into consolidation settlement.The increase of initial water content of slime will lead to the increase of flocculation rate and the shortening of flocculation time,and the settling stability time T_c is highly correlated with the ratio of initial water content to liquid limit water content(w₀/w _L).(2)Through the free sedimentation test of slime in different environments,it is found that the increase of temperature accelerates the Brownian motion between slime particles and shortens its flocculation time.And the increase of temperature leads to the increase of the dynamic viscosity coefficient of clay suspension and hinders the settlement of flocs,which leads to little change in flocculation rate and time.With the increase of temperature,the dielectric constant decreases,which leads to the decrease of settlement stable void ratio.(3)The tailings mud contains a large amount of kaolinite which is easily changed by p H.In the slime sedimentation tests of different p H,the edge charge occurs with the change of p H,resulting in different changes of flocculation rate,settling stable void ratio and Zeta potential on both sides of the isoelectric point.(4)In sodium chloride and calcium chloride solution,the increase of ion concentration weakens the repulsive potential energy between slimes,which leads to the decrease of flocculation rate and settling stable void ratio.However,in ferric chloride solution,the increase of ion concentration reduces the Coulomb attraction between particles,weakens the original macropore edge-plane arrangement structure,and finally leads to the decrease of settling stable void ratio and flocculation rate.(5)The existence of cations makes the adsorbed water of the particles change into free water,which leads to the change of the transverse relaxation time T₂ corresponding to the peak value of NMR signal of slime.In Fe Cl₃ solution,part of Fe(OH)₃ colloid and polyhydroxyl polymer are produced by hydrolysis,which enhances the stability of slime suspension and the compactness of flocs.