What is coagulant aid and its application?

What is coagulant aid and its application?

Coagulant aid When the coagulant alone cannot achieve the expected effect, it is necessary to add a certain auxiliary agent to improve the coagulant effect. This agent is called a coagulant aid.

Broadly speaking, any chemical agent that cannot be used as a coagulant alone in a particular water treatment process but can be used in conjunction with a coagulant to enhance or improve the effect of coagulation and flocculation can be called a coagulant aid. Coagulants can be used to adjust or improve the coagulation conditions. For example, when the alkalinity of the raw water is insufficient, lime or sodium bicarbonate can be added; when ferrous sulfate is used as a coagulant, oxygen can be added to oxidize ferrous Fe2+ to Trivalent iron ion Fe3+ and so on. Flocculants can also be used to improve the structure of flocs, using the strong adsorption and bridging effect of polymer coagulants. Make the small and loose flocs become thick and compact. Commonly used are polyacrylamide, activated silicic acid, bone glue, sodium alginate, safflower tree, etc.

In environmental engineering or other fields, the use of flocculating agents has made certain solid particles that are difficult to separate from water to be separated from the water, but they are still emulsified or mixed in the water. In order to completely separate these particles from the water, they are added. Chemicals. The theory is: "polymer bridging", "precipitation roll sweeping" and so on.

Coagulant is used to adjust or improve the coagulation conditions, to promote the coagulation effect of the added agent or to improve the structure of the polymer material of the floc. The former such as sulfuric acid, phosphoric acid, lime, chlorine, etc. (pH can be adjusted); the latter such as polyacrylamide, activated silicic acid (or activated silica), bone glue, sodium alginate and various polyelectrolytes, which can make it compatible with Coagulants combine to produce larger, firmer and denser flocs. The density and weight of the coagulant promotes the acceleration of precipitation; it acts as a bonding bridge between the micro-flocs, so that the flocs are coarse and have a broad surface, and fully exerts the role of the adsorption coil to improve the clarification effect. In the coagulation treatment of wastewater, when the coagulant alone cannot achieve good results, the coagulant aid is often used to achieve the goal. At present, the most widely used coagulant aid is activated silicic acid, which is prepared from sodium silicate through an activation process. It is essentially an anionic inorganic polymer electrolyte and is generally used in combination with alum or ferrous salt.

Used in conjunction with a coagulant, it is a chemical agent that can quickly settle the suspended solids in the water. Mainly water-soluble organic polymers, such as galactomannans, partially hydrolyzed polyacrylamides, etc. They are mainly used in conjunction with inorganic coagulants. There are also inorganic types, such as activated silicic acid, lime and so on.