Leaching behavior of mineral processing waste: comparison of batch and column investigations

In this study, a comparison of laboratory batch and column experiments on metal release profile from a mineral processing waste (MPW) is presented. Batch (equilibrium) and column (dynamic) leaching tests were conducted on ground MPW at different liquid-solid ratios (LS) to determine the mechanisms controlling metal release. Additionally, the effect of pH on metal release is also discussed. It was observed that acidic pH conditions induced dissolution of As, Zn and Cu. Negligible leaching at alkaline pH was observed. However, Se depicted amphoteric behavior with high release at low and high pH. The batch and column data showed that As and Se release increased with LS ratio, while that of Cu and Zn increased initially and tapered towards equilibrium values at high LS ratios. The results on metal release from the MPW suggested that dissolution of the metal was the controlling mechanism. Leaching profiles from the batch and column data corresponded well for most LS ratios. This is most likely due to the acidic character of the waste, minimal changes in pH during the column operation and granular structure of the waste. From a waste management perspective, low cost batch equilibrium studies in lieu of high cost column experiments can be used for decision making on its disposal only when the waste exhibits characteristics similar to the mineral processing waste.