12:30 PM - 2:00 PM
[R4-P-02] Preliminary Study: Heating Polysaccharides' Effects on Dolomite Precipitation at Room Temperature.
Keywords:dolomite, Polysaccharides
Recent studies have shown that certain microorganisms, such as sulfate-reducing bacteria, have been observed to mediate disordered dolomite precipitation (e.g., Petrash et al., 2017). Additionally, polysaccharides like carboxymethyl cellulose (CMC), agar, and biomass can facilitate the generation of disordered dolomite at ambient temperatures (e.g., Zhang et al., 2012; 2015; 2021). However, Wei and Konishi (submitted to Minerals) discovered that CMC and agar hinder the dolomitization process at 200°C. The specific temperature below 200°C at which decomposed polysaccharides exhibit inhibitory effects remains unknown.
In our investigation, we are examining the impact of heated CMC at temperatures below 200°C on the precipitation of disordered dolomite at room temperature. The CMC solution was heated within the range of 100 to 200°C for 48 hours. Subsequently, we prepared two sets of experimental solutions containing 10 mM Ca and 50 mM Mg using the dissolved CMC solution (0.2g/L). Through the vapor diffusion method, we placed vial tubes containing the experimental solutions and a petri dish filled with ammonium hydrogen carbonate powders in a desiccator for a duration of 48 days. We utilized calcite seeds to prevent potential precipitation of aragonite and monohydrocalcite.
After the incubation period, we collected the precipitated materials and conducted X-ray diffraction analysis. Additionally, we compared these results to two sets of solutions that did not contain heated CMC for comparison. Specifically, we focused on the d104 values as the shift from 3.03Å (calcite) to 2.88Å (dolomite) occurs with increasing MgCO3 content. Our examination of the 104 reflections indicated that the d104 values of the precipitates from all experimental solutions ranged from 2.963Å to 2.982Å. Comparing these values to the control values of 2.978Å and 2.976Å, we did not observe any significant differences in the d104 values. Therefore, we were unable to confirm the catalytic effect of heated CMC at temperatures higher than 100°C for dolomite precipitation from the solution at room temperature.
In our investigation, we are examining the impact of heated CMC at temperatures below 200°C on the precipitation of disordered dolomite at room temperature. The CMC solution was heated within the range of 100 to 200°C for 48 hours. Subsequently, we prepared two sets of experimental solutions containing 10 mM Ca and 50 mM Mg using the dissolved CMC solution (0.2g/L). Through the vapor diffusion method, we placed vial tubes containing the experimental solutions and a petri dish filled with ammonium hydrogen carbonate powders in a desiccator for a duration of 48 days. We utilized calcite seeds to prevent potential precipitation of aragonite and monohydrocalcite.
After the incubation period, we collected the precipitated materials and conducted X-ray diffraction analysis. Additionally, we compared these results to two sets of solutions that did not contain heated CMC for comparison. Specifically, we focused on the d104 values as the shift from 3.03Å (calcite) to 2.88Å (dolomite) occurs with increasing MgCO3 content. Our examination of the 104 reflections indicated that the d104 values of the precipitates from all experimental solutions ranged from 2.963Å to 2.982Å. Comparing these values to the control values of 2.978Å and 2.976Å, we did not observe any significant differences in the d104 values. Therefore, we were unable to confirm the catalytic effect of heated CMC at temperatures higher than 100°C for dolomite precipitation from the solution at room temperature.