Mineral dressing collector for poor hematite reverse flotation

The invention provides an ore-dressing agent for use in reverse flotation of lean hematite ore. The collecting agent is a potassium salt of the hydroxy fatty acid and has a chemical molecular formula of R1-C(OH)n1-C(OH)n2-COOK, wherein n1 ranges from 1 to 2, n2 ranges from 0 to 2, and R1 is preferably saturated or unsaturated hydrocarbons having 9 to 19 carbon atoms. According to a molecular design principle, the invention introduces hydroxyl functional groups to alpha positions and beta positions of a fatty acid mixture and adopts potassium hydroxide for saponification. The collecting agent has the advantages of reducing energy consumption due to preparation and use at the normal temperature, reducing use cost due to small dosage, reducing tailings grade during reverse flotation ore dressing operation by improving the technical indexes of reverse flotation, along with obvious economic effect.