An experimental approach to assess the rock weathering and its implications on carbon mineralisation and metal behavior

This experimental study focused on rock weathering to understand the geochemical processes involved in the host rock matrix and the water at different time intervals. In this study, five different tanks were designed in the laboratory, consisting of montmorillonite clay (T1), coarse peridotite and clay (T2), finer peridotite and clay (T3), peridotite (T4) and only lake water as a control (T5). The T1-T4 tanks were allowed to react with natural lake water in a laboratory setup for eight weeks. During the experiment, weekly measurements were taken for physical parameters, major ions, and trace metals in water. The results show that increasing pH and HCO 3 - initiates the rock weathering by acquiring CO 2 directly from the air at the early stage of the experiment. Subsequently, precipitation of carbonate minerals, resulting from the removal of Ca 2+ and Mg 2+ from the liquid in the later stages of the experiment. Principal component analysis also confirms the early dissolution of minerals as a carbon source, followed by enhanced weathering leads to the precipitation of carbonate minerals. Based on solid chemistry, experiments with clay (T1) and peridotite (T4) enhance mineral precipitation, whereas a mixture of rocks (T2 and T3) supports mineral dissolution. T1 exhibits a high adsorption capacity for Fe and Ni, attributed to both ion exchange and surface complexation. In these experiments, carbonates would nucleate preferentially on or within clay-rich aggregates, where Ca 2+ , Mg 2+ and HCO 3 - are concentrated at the grain-water interface via cation exchange and surface complexation, thereby enhancing early crystal growth.