Inhibitory Effects of Polysaccharides on the Dolomitization Reaction of Calcite at 200 °C

Abstract

This study investigates the impact of dissolved carboxymethyl cellulose (CMC) and agar on the dolomitization reaction of calcite at 200 °C. Previous studies have suggested that CMC and agar promote dolomite precipitation at room temperature. However, this study found that their decomposition products hinder the reaction at 200 °C, with uncertainty about their role at other temperatures. The inhibitory effect of the decomposition products could be attributed to their adsorption onto calcite surfaces, which hinders their dissolution. This results in a longer reaction induction period and replacement period. Regression analysis demonstrates that the 0.1 g/L agar and 0.2 g/L CMC series decrease the cation ordering rate of dolomite produced from synthetic calcite when compared with series without polysaccharides. In contrast, the 0.1 g/L CMC series shows a slight increase in the cation ordering rate compared with series without polysaccharides. The findings of this study suggest a notable potential impact of the decomposition products of polysaccharides on the ordering of dolomite, although it is uncertain whether they inhibit this ordering process. The inhibitory effect observed in the decomposition products of CMC and agar could also exist in the decomposition products of the extracellular polymeric substances (EPS) and bacteria cell walls found in sedimentary rocks during burial diagenesis. Therefore, further research is necessary to understand the role of EPS and bacteria cell walls in dolomitization, since their impact is not always predictable.