Long-acting composite dust suppressant for open pit coal mine and preparation method thereof

The invention discloses a long-acting composite dust suppressant for an open pit coal mine and a preparation method thereof. The long-acting composite dust suppressant is prepared by compounding a starch-based super absorbent resin dust suppressant and a starch-based super absorbent resin dust suppressant microcapsule according to a ratio of 1:(0.2-1), wherein the dust suppressant is prepared from the following raw materials in parts by weight: 30 to 60 parts of water-soluble starch, 30 to 60 parts of methyl acrylate, 10 to 30 parts of vinyl acetate, 0.05 to 0.5 part of an initiator and 0.5 to 5 parts of a cross-linking agent. The biomass starch which is rich in source, low in cost and degradable is used as a raw material, so that the method is green and environment-friendly and has no secondary pollution; the dust suppressant is coated by adopting a microcapsule technology, so that the release rate of the dust suppressant is controlled and adjusted to a certain extent, the effective dust suppression time of