Measurement Study On The Particle Morphology And Interaction Forces Between Colloidal Particles

The study on flocculation of colloidal particles is one of the research highlights in the field of environmental science.Organical matter is one of major influencing factors of the flocculation.In water environment such as rivers and lakes,biological membranes exist widely on the surfaces of solid particles.The physical properties of the particles themselves will be changed by the biological membranes covered on them,including interaction forces,which will affect the flocculation process.As a result,it is so significant to study the effects of biological membranes on the flocculation processes.In this study,the interaction forces between colloidal particles were measured by Atomic Force Microscope(AFM),and the surface morphology of the particles with biological membranes were observed by Environmental Scanning Electron Microscope(ESEM).The main contents and conclusions are as follows.(1)Polystyrene colloidal microspheres with a diameter of 20 micrometers were used as the samples.Based on colloidal probe technique,a microsphere was adhered to a tipless cantilever of the AFM,and the other microsphere was adhered in the substrate.And then the interaction forces between the two particles in KCl and NaCl solutions with different concentrations were measured.(2)The observed forces were compared with the analytical results obtained by Extension DLVO(XDLVO)theory,which confirmed the validity of the experiment.The observed forces showed a good agreement with the analytical results obtained by XDLVO theory.It can be concluded that the interactions between colloidal particles could be described by XDLVO theory in a certain range.(3)Polystyrene microspheres,kaolinite particles and montmorillonite particles were cultivated in specific nutrient solutions.A certain number of days later,they were observed by ESEM,and it could be seen that flocs had been formed,and biological membranes had emerged on the surfaces of the particles.(4)The images of particles with and without membranes were respectively analyzed.The fractal dimensions were calculated,regarded as a method to implement a quantitative analysis of the effect of biological membranes on the structural properties of the particles,and the effects of biological membranes were investigated.