Determination of acid mine drainage potential of Görgü (Malatya) zinc-lead ore tailings

Görgü (Malatya) zinc-lead deposit is one of the important metallic ore deposits exploited in Turkey. The ore is beneficiated by gravimetric and flotation methods and the tailings are stored in waste piles or waste ponds. The chemical and mineralogical analyzes of the samples obtained from the fresh waste piles were performed and AMD potential of the tailings was determined by static AMD tests. Pyrite, the most important mineral in AMD generation, was added to the tailings at certain ratios and its effect the AMD generation was investigated. Since the ore tailings cause changes in the properties of water with time as a result of contact with water and air, water analyzes were also carried out. The pH, electrical conductivity and metal ion concentrations of the medium prepared with tailings and water like tailing ponds, were measured in the course of time. The geochemical changes in the tailings were determined by carrying chemical and mineralogical analyzes on the remained tailings after the tests. Chemical and mineralogical analyzes showed that the raw tailings contains high amount of carbonates, but very low amount of pyritic (or sulphitic) sulfur. The paste pH test of the tailings was measured as 8.01 and was found to be too high to generate AMD. Standard ABA and modified ABA tests were performed and Net Neutralization Potential (NNP) values were calculated as 641.25 and 242.031 kg CaCO3/ton, respectively. Since NNP >> 10, it was concluded that the tailings do not have AMD generation potential. B.C. Research Initial test results showed that the acid consumption of the tailings (372.89 kg H2SO4/ton ore) was much higher than the acid production (4.56 kg H2SO4/ton ore). At the end of NAG test, pH was measured as 8.77 and it was concluded that the tailings could not produce net acid since pH was higher than 4 (or 7). In the static tests performed in plastic containers, the pH and electrical conductivity of the medium were measured at regular intervals, and their changes with time were detected. It was observed that the medium was basic and the pH did not change regularly, but it decreased to 8.0 in the 17th week. It was observed that the electrical conductivity of the medium increased with time and reached 7500 µS/cm from 1500 µS/cm. The results show that the medium was not acidic, but some metal ions reported into the medium due to dissolution. When the concentrations of metal ions in the medium were evaluated, it was found that dissolution of some minerals took place with time, but there was no regular change in the concentration. The results indicated that dissolution and precipitation reactions took place simultenaously in the medium. When the XRD analyzes of the raw tailings and the remained tailings were compared, it was seen that there was no significant changes in the main peaks and it was concluded that the alteration of the minerals was low under these working conditions. It was found that the results obtained from static AMD tests and container tests were compatible.