The invention discloses a method for preparing
mixed fatty acid by using waste
cooking oil and the application method of the
mixed fatty acid. The preparation method comprises: 1) the waste
cooking oil is pretreated; 2) concentrated
sulfuric acid is added into an oil layer which is then turned over and cooked and stands; the mixture is washed by hot water and stands, and the waste water at the lower layer is discharged; the obtained product is washed by water repeatedly until acidated oil with the pH value of 6-8 is obtained; 3) the acidated oil,
distilled water, sulphuric acid and a catalyst are added in a reaction vessel, heated, stirred, and hydrolyzed and then stand; the waste water at the lower layer is discharged; the mixture is washed by hot water and stands, and the waste water at the lower layer is discharged; the product is washed by water repeatedly until the discharged water is neutral; 4) the step 3 is carried out again, and crude
fatty acid can be obtained by secondary
hydrolysis; 5) the
mixed fatty acid product is obtained by thermal
dehydration and negative pressure
distillation. The method has high synthetic efficiency, low requirements for equipment as well as low investment and preparation cost; the prepared mixed
fatty acid has
high activity, strong fluidity and remarkable flotation performance when being applied to the aspect of ore dressing flotation, thereby having stronger competition strength and good application prospect.