Cement grinding aid and method for preparing cement grinding aid from chemical waste liquid

The invention provides a cement grinding aid, which is prepared from the following ingredients in percentage by weight: 50 to 65 percent of alcohol waste liquid for glycerol production by an esterifying method or chemical waste liquid for alcohol chemical product production, 5 to 30 percent of diethanol amine, 5 to 8 percent of hydrogen peroxide, 5 to 8 percent of sodium nitrite and the balance ofwater. During the preparation, the alcohol waste liquid for glycerol production by the esterifying method is firstly added into a reaction kettle; then, a stirrer is started; the diethanol amine is added under the stirring condition; then, heating is performed to 45 to 55 DEG C; nitrous acid is added; next, heating is performed to 65 to 75 DEG C; then, the hydrogen peroxide is dripped while temperature rise is performed, wherein the dripping time is 2 to 3h; after the dripping is completed, the temperature is not higher than 100 DEG C; finally, the product in the previous step is heated to 105 to 110 DEG C; at the te