The surface of suspended matter can be divided into hydrophilic and hydrophobic. The surface of hydrophobic particles is easy to adhere to bubbles, so air floatation can be used . Hydrophilic particles can be converted to hydrophobic after being treated with appropriate chemicals. In the air flotation method in water treatment, coagulants are commonly used to make colloidal particles agglomerate into flocs. The flocs have a network structure and are easy to trap bubbles, thereby improving the efficiency of air flotation. Furthermore, if there is a surfactant (such as detergent) in the water , it can form foam, and it also has the effect of attaching suspended particles to rise together.

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