LAUSR

Abstract Surface crystallization of insoluble carbonate poses a serious problem for marine equipment industries which can be seriously influenced by soluble microbial products (SMPs). In Here, the effects of SMPs secreted by sulfate-reducing bacteria on the formation of CaCO3 were investigated by monitoring the crystallization rates and crystal polymorphs and morphologies. When 8.95 mg/L of SMP was added, vaterite and calcite were formed at the initial stage. This could be partly attributed to the formation of SMP and Ca2+ complexes, which provided a nucleation site for calcite. Simultaneously, crystallization by particle attachment promoted the increase of the crystallization mass density in the early stage of crystallization. As the concentration increased to 17.90 mg/L, a larger proportion of vaterite was stabilized. However, a further increase of SMP concentration to 44.76 mg/L did not enhance the proportion of vaterite and a different morphology of elongated calcite was formed. All investigated concentrations of experiments indicate that lower concentrations of SMP promotes calcite nucleation, and higher concentrations inhibit the formation of vaterite. However, an inverse relationship still exists between the concentration of SMP and the amount of surface crystallization of calcium carbonate.