Study On The Mechanism Of Fluid Mechanic Chemistry In Coagulation

On the basis of comprehended numbers of relative literatures, the experiment of fluid dynamic condition and the mechanism of fluid mechanic chemistry in coagulation are studied in this paper.The experiment results of fluid dynamic condition show that, the optimal fluid dynamic condition is affected by species and dose of coagulant, the turbidity of initial water and the characteristic of colloid. On the species and dose of coagulant, the optimal fluid-shear velocity of inorganic coagulant AlCl₃ is weaker than the organic coagulant PAM's, but there is no obvious difference on the optimal fluid-shear time. The more dosage of coagulant (inorganic or organic), the optimal of fluid-shear velocity and time will descend a little. On the turbidity of initial water, as the turbidity is accretion, the optimal of fluid-shear rate will fall, but the optimal of the fluid-shear time will be long. On the properties of colloid, the optimal of fluid-shear rate has no clear difference in the suspended of kaoline and humic acid, however, there is marked distinction in the optimal fluid-shear time. On the condition of suspended kaoline, with the fluid-shear time is long, the turbidity removal will be more, when the time exceeds some fixed value, the turbidity will be high. The longer of fluid-shear time is, the extent of reduction in TOC is very little. At the experiment of the relation with flow field distribution and species of coagulant, coagulant dosage, the turbidity of initial water, the characteristic of colloid, monolayer flat-blade blender produce uniform distribution second-fluid, which makes the collision frequency improve greatly, so the coagulation effect is much better than magnetic stirring.Al-Ferror complex colorimetric method illustrates that, as the fluid-shear velocity is increscent, the distribution of Al³⁺ hydrolytes will be changed. The content of Alb becomes more, and the Alc is distinct less. On the ground of"Double Hydrolysis"model and"Continuous Hydrolysis"model, the"Double and Continuous Hydrolysis"model is put, which is of fluid dynamic affecting Al³⁺ hydrolytes.The result of Zeta potential finds that, the faster of fluid-shear rate is, the higher of the Zeta potential value is. When the dosage of AlCl₃ is lower, as fluid-shear time is longer, the Zeta potential value will be high. However, when the dosage is more, fluid-shear time has a little effect on the Zeta potential. By the experimental result of fluid dynamic affecting Zeta potential, the model of fluid dynamic making the hydrated layer of colloid distortion is brought. When the fluid dynamic has the hydrated layer of colloid attenuation, even breakage, just then it will be named as"Cleave pressure".On the base of analyzing the mechanism of fluid mechanic chemistry, it definitely define fluid mechanic chemistry in coagulation, that is, appropriate fluid dynamic condition can accelerate a series of physical chemistry reaction, for example, the pervasion of coagulant, the hydrolysis of coagulant, the modification of colloid, the collision of colloid, etc, then coagulation efficiency will be perfect.