Utilising automated mineralogy and accelerated static tests to enhance kinetic testing evaluations

Three waste materials (A, B and D) were subjected to kinetic column leach tests to determine their acid forming characteristics. To improve predictions of their behaviour from the outset and to enhance the understanding of the water chemistry data collected over 156 weeks, column feed materials were characterised using automated mineralogy and a new accelerated static geochemical test. Initial measurements of the bulk mineralogy confirmed an abundance of magnesite and dolomite in Type A with trace pyrite (0.2 wt. %) identified however only 12% of this was liberated. Type B contained far less carbonate and was instead dominated by albite, magnesiohomblende and chlorite with minor pyrite (1.15%) again observed (with 12.5% liberated). Type D contained the highest pyrite (1.3 wt. %; 10% liberated) which was notably coarser (p80 of 550 μm) with the remainder comprising albite, actinolite, chlorite and tremolite and no carbonates. Accelerated static testing classified Types A, B and D as non-acid forming (NAF). Each waste type was predicted to be NAF in the kinetic trials which was observed. This study highlights that undertaking detailed column-feed characterisation allows behaviour of materials during kinetic trials to be predicted with a better understanding of mineral weathering and water chemistry afforded.