Acid Production Rules Of Waste Rocks From Dexing Copper Mine

The exploitation of mineral source has contributed to economic growth and development, while it has caused a lot of environmental problems, among these challenges acid mine drainage(AMD) is the most significant one.AMD is a wordwide problem which occurs in waste rock dumps, mine tailings impoundments, heap leach pads, mine adits, open-cuts, pit walls and other areas.It is difficult to control because of its huge amounts.The study has done work in three areas,one is to evaluate the acid generation potential of waste rocks from Dexing Copper Mine, which had been stored for 1,5,10, and 20 years, respectively. The second part is a nine month long kinetic leaching experiment,through monitoring pH,EC and other heavy metal ions Cu2+,Zn2+,Fe3+,Pb2+,SO42- and Ca2+. The third part is to carry out chemical analysis and metal ion speciation analysis before and after the experiment, according to the changes of total and each form of heave metals to infer the long-term acid production rules. Waste rock environmental pollution risk assessment was then carried out on this basis to provide a theoretical basis for acid mine drainage prevention and treatment.Static test results showed that the waste rocks of 4 different ages had acid generation potentials. Apart from the fresh waste rock with 1 year old, all other waste rocks generated acid.The results of 9-month kinetic test showed that the pH of waste rocks of the four different age categories was significantly negatively correlated with leachate conductivity. The main solutes in the leachates were F,Cu2+,Zn2+,SO42-,Ca2+ and Fe3+.In the kinetic test, the 1-year waste rock did not yet produce acid during the experimental period, but,5-year and 10-year old waste rocks produced acid persistently. The acid production rate of the 20-year old waste rocks declined. The acid production capacity was in the process of non-production-rapid production-stable production-declined production.Using BCR sequencial extraction procedure to analysis the Cu, Zn, Fe, Pb speciations in waste rocks of 4 different ages, the result indicates that the main form of Pb, Zn and Cu is residual phase,the Fe is oxidizable and residual phase.Using RAC and Igeo to evaluate the potential ecological risk of waste rocks.The RAC method is better while it may underestimate the threat of AMD from waste rocks.Using available forms of heavy metal to correct the result of RAC can more accurately assess the risk of acid waste rock.