There are two methods for processing iron ore using reverse flotation: anionic collector reverse flotation and cationic collector reverse flotation.

Anionic collector reverse flotation is suitable for ores with high iron content and gangue consisting of easily floatable quartz. The pH of the pulp is adjusted to above 11 using sodium hydroxide (or a combination of sodium hydroxide and sodium carbonate). Starch and dextrin are used to suppress hematite, calcium chloride is used to activate the quartz, and then a fatty acid collector is used to collect the calcium-activated quartz. The product in the flotation cell is hematite concentrate. The advantages of this method are: variations in the composition of the iron ore and the content of slime have a relatively small impact on flotation parameters; since the product in the flotation cell is iron concentrate, it is not bound to the collector and is easy to concentrate and filter. The main disadvantages are: complex reagent formulation and high reagent consumption; and the tailings water with a pH as high as 11, if not treated, can cause pollution.

Cationic collector reverse flotation uses sodium carbonate to adjust the pH of the pulp to 8-9, and uses starch, dextrin, tannin, etc. to suppress iron minerals. Amine collectors (ether amines are the best, followed by fatty amines) are used to float quartz gangue. The advantages of this method are: (1) Flotation can be carried out under coarse grinding. As long as the monomers are ground to the point of liberation, the amine collectors can float the monomeric quartz well. (2) For ores containing hematite and magnetite, since magnetite is not easy to float, magnetic separation-flotation combined process is often used for separation. However, if cationic collectors are used to collect gangue, both hematite and magnetite are left in the tank and recovered, simplifying the process. (3) If the ore contains iron silicates, when anionic collectors are used for positive flotation, the iron silicates will be selected into the concentrate along with the hematite, reducing the quality of the concentrate. However, if cationic collectors are used for reverse flotation, they will float out together with the quartz, increasing the grade of the iron concentrate. (4) This method eliminates the need for desliming, reducing the loss of iron ore. This method is suitable for the flotation of high-grade, complex-composition iron ore. Currently, this method is often used to further process gravity and magnetic separation iron concentrates to obtain ultrapure concentrates.