Study on Composite Coagulants-Flocculants Mechanism Action

Abstract

This research deals with the investigation of adsorption characteristics of different types of composite coagulants-flocculants, combined by polyaluminum chloride (aluminum oxychloride) with organic polymer. The effect of this composite coagulants-flocculants on solution's turbidity removal and characteristics of cohesion and coagulation process have been studied too. On the basis of experimental data obtained the character and mechanism of cohesion and coagulation for different types of composite coagulants-flocculants were discussed. It was stated out that the adsorption isotherm of cationic composite coagulants-flocculants conforms to Langmuir adsorption law, and it characterized by monolayer adsorption parameters, which increases their ability to neutralize electric charge. The anionic composite coagulants-flocculants enhance the adsorption value and bridging ability with the help of organic polymers, showing multilayer adsorption characteristics. It was observed specifically, that under the same conditions the flocculation rate and sedimentation rate of composite coagulants-flocculants are higher than polyaluminum chloride has. This fact was explained by the advantages of organic polymer due to its long chain which is able to form larger floc within short time. The large floc has strong attractive potential energy for tiny particles, which make the opportunity of effective collision between particles what leads to sharply increased coagulation. The influence of storage time period on composite coagulants-flocculants coagulation effectiveness has been examined. The experimental results witness that the coagulation characteristics of reagents will be reduced to some extent after long-term storage, but composite coagulants-flocculants have advantages in this aspect over polyaluminum chloride. It should be concluded that, in general, the quality of composite coagulants-flocculants in relation to their stability remained at a high level.