Water chemistry in coal preparation:Effect of water chemistry properties on interparticle interaction

Water chemistry properties of coal slime water have an important influence on the interparticle interaction in coal preparation plant.Coal particles and impurity particles should be fully dispersed in the flotation process,and the clarification process of coal slime water requires particles to be effective coagulated.In order to solve the problem of the contradiction between the dispersion-coagulation state of particles required in the flotation process and clarification process,as well as the contradiction between the required water chemistry environment,the effect of water chemistry properties on the inter-particle interaction behavior between coal and kaolinite particles were studied at the micro level by Zeta potential distribution and atomic force microscope.Research on the influence of metal ions on the Zeta potential distribution of particles shows that Ca2+ can narrow the Zeta potential distributions of coal or kaolinite particles,causing particles homogeneous coagulation.When Ca2+ concentration increases from 1 mmol/L to 5 mmol/L,the Zeta potential distribution of the mixed coal-kaolinite changes from two peaks to one peak,indicating that coal and kaolinite particles coagulate.Therefore,Ca2+ can promote the homogeneous and heterogeneous coagulation of coal and kaolinite particles,while Na+has little effect on the coagulation of particles.The direct force measurement between particles was carried out using atomic force microscope.The repulsive force and interaction range between coal and kaolinite particles gradually decrease with the increase of concentration of Ca2+,and the particles are more and more prone to coagulation.When Ca2+ concentration increases to 5 mmol/L,an attractive force appears between the coal and kaolinite particles.However,Na+has no obvious effect on the interaction force between particles.The test results of interparticle forces under different pH conditions show that the interaction between coal and kaolinite changes from repulsion to attraction with the decrease of pH value.It is found that there is strong hydrophobic attraction between coal particles by measuring the force between two coal particles.It is also shown that coal particles are prone to homogeneous coagulation.Therefore,it is necessary to focus on the coagulation of coal-clay particles and clay-clay particles in the clarification process of coal slime water.The research can provide a theoretical guidance for the regulation of water chemistry properties in the flotation and clarification process,and is helpful to realize the efficient flotation and clarification cycle of coal slime water.