Dynamic Light Scattering Technology Determination The Hamaker Constant Of Soil Colloids

Soil colloids, organic colloids and colloidal organic and inorganic compound, are concentrated in the size of several tens to thousands of mesoscopic nano-scale range. They are having a material foundation soil fertility and ecological functions, the interaction between the soil colloidal particles profound impact on the vast majority of the microscopic processes in soil and macro phenomenon. The interaction between the soil colloidal particles followed charged colloidal particle surface electric double layer theory and DLVO theory, according DLVO theory, the interaction of charged colloidal particles is the result of van der Waals attraction and electrostatic repulsion interaction. The Van der Waals force is an important interaction between colloidal particles dominance, so the study Van der Waals force and intensity in the way of soil colloidal particles interactions facilitates understanding of the mechanism of soil particles and dispersed cohesion. The Van der Waals force Pvdw(λ)(atm) can be calculated by the following formula: for the effective Hamaker constant, λ is the distance between the particles. So, just know that the Hamaker constant, Van der Waals force strength can be theoretically calculated. Therefore, in the study of the interaction between soil particles, Hamaker constant soil particles will be an important parameter. However, for Hamaker constant soil colloids is still no effective measuring method and technology, nor Hamaker constant soil colloids been measured. Therefore, it is necessary to measure the Hamaker constant of soil colloids. The study first establish a new theories and new methods that dynamic light scattering measure the Hamaker constant for soil colloids.Light scattering technique has been widely used in the study of polymer materials, colloidal chemistry and nano-materials, etc., it is an important tool for studying nanomaterials and mechanism of interaction between colloidal particles. Jia Ming Yun has a light scattering technique successfully introduced into the complex natural soil VI colloid aggregation experimental study, the aggregation kinetics can be monitored through the variation of average effective hydrodynamic diameters of aggregates changing with aggregation time. Based on the existing dynamic light scattering process of soil colloid aggregation method. Determination of single colloidal mineral montmorillonite(model system) of the Hamaker constant.Based on a new method thati dynamic light scattering measure the Hamaker constant of soil colloids. Then constant charge soil colloids and purple-based variable charge mainly of yellow soil colloids,the real soil colloids by a variety of natural minerals used as research material, Determination the Hamaker constant for complex soil colloid. Analysis of van der Waals attraction and strength of three soils colloids, further study of soil particle aggregation and dispersion mechanism. The main conclusions are as follows:1.This study Initially established a new theory and method for determination of Hamaker constant of soil colloids by Dynamic Light Scattering Technology.2.With this method measurement 2:1type clay mineral montmorillonite colloids Hamaker constant of 6.5×10-20 J; The Hamaker constant of constant charge mainly of purple soil colloid is 7.5×10-20J; The Hamaker constant of variable charge mainly of yellow soil colloids is 5.3×10-19 J. According to available literature, Hamaker constant value of most of the material is 10-19 ~ 10-20 J, the Hamaker constant value of three soil colloids measured in this study in line with the theoretical value(the order of 10-19 ~ 10-20J),it shows effective Hamaker constant of soil colloids measured is reasonable.Since the soil composition of matter is very complex, so the Hamaker constant of soils that determined by this method is the apparent mean Hamaker constant of soil various substances.3.Measured the Hamaker constant of yellow soil colloids>Hamaker constant of purple soil colloids>Hamaker constant montmorillonite colloids. Hamaker constant of yellow soil colloids is 7.1 times the purple soil colloids and is 8.2 times montmorillonite colloids. The Hamaker constant yellow soil colloids far greater than the purple soil colloids and colloidal montmorillonite.Based Determination Hamaker constant, so as to arrive, At some point in the distance of colloidal particles, the Van der Waals force that two yellow earth colloidal particles is 7.1 times between two purple soil colloidal particles is 8.2 times montmorillonite colloid. The Van der Waals force between the yellow earth colloidal particles much larger than the van der Waals attraction between purple soil colloidal particles and montmorillonite colloidal particles.4.Dynamic light scattering technique can be determined Hamaker constant single mineral soil colloids, The method is also applicable to the determination of other multi-colloidal dispersion Hamaker constant, It can be determined Hamaker constant of dispersion soil colloids.5.The critical coagulation concentration(CCC) Li+ montmorillonite colloidal system in this experiment was 42.5 mmol/L, the critical coagulation concentration Li+(CCC) purple soil system is 332.1 mmol/L, the critical coagulation concentration Li+(CCC) yellow earth colloidal system is 332.1 mmol/L. Under Li+ electrolytes, yellow soil colloids(CCC) <montmorillonite colloids(CCC) <purple soil colloids(CCC). Electrolyte Li Cl for yellow soil colloid coagulation ability>for montmorillonite colloid coagulation ability>for purple soil colloid coagulation ability. Yellow soil and purple soil colloids colloids Li+ critical coagulation concentration(CCC) in the big difference, Since Hamaker constant of yellow soil colloids is big, Large van der Waals attraction between the particles, the smaller the height of potential energy, easier coagulation. Yellow earth colloidal dispersion than the purple soil colloids and colloidal stability of montmorillonite is even worse, When the system as long as the addition of low concentrations of electrolytes to reduce electrostatic repulsion, Exclusion barrier becomes small, yellow colloidal undergoing rapid coagulation. The electrolyte concentration in the same, The Van der Waals attractive purple soil colloids is smaller than the yellow soil colloids, electrostatic repulsion dominant, The total potential energy large, colloidal aggregation does not occur.6.Purple soil colloids are more stable than the yellow earth colloidal suspension, These differences between in stability of the two soil colloid suspension, since these two substances are colloidal different characteristics cause different Hamaker constant caused.7.Although theoretically measured colloid Hamaker constant by dynamic light scattering should have certain advantages. However, because there is no standard method of measuring Hamaker constant, Intensive verification of the method is difficult to achieve. Therefore, the use of dynamic light scattering test substance Hamaker constant, its reliability is also more research is needed to confirm, This article only presents a new determination Hamaker constant technical possibilities.