Abstract: Lime neutralization is a common method for the treatment of mine acid drainage， whereas the performance of this process is often not so good as expected due to the problems of incomplete reaction of calcium oxide and poor settling property of sludge. In order to tackle these problems， the comparison study between direct neutralization by calcium oxide and sludge reflux + calcium oxide neutralization was performed on the wastewater from a copper mine. The results show that when the calcium oxide dosage was 24 g/L， calcium oxide slaking time was 20 minutes and stirring rate was 400 r/m， the pH value of sludge could reach over 6 after 75 minutes by direct neutralization. The pH value of wastewater can also reach over 6 when wastewater was neutralized with sludge(pH>6) with reflux ratio of 40% and calcium oxide dosage of 22.0 g/L， the concentration of metal ions was greatly reduced， meeting the requirements of tailing pond storage. The sludge reflux process could not only make good use of the unreacted calcium oxide to reduce the amount of new calcium oxide， but also improve the settling property and solid content of sludge， which are good for the clarification of the backwater of tailings pond.

Key words: Mining acid drainage, Sludge reflux, Calcium oxide dosage, Settling property of sludge