Biodegradable carboxymethyl inulin as a scale inhibitor for calcite crystal growth: Molecular level understanding

Carboxymethyl inulin (CMI) is one of the most promising biomass materials for scale inhibition. Its potential applications as a scale inhibitor have attracted much research attention. Understanding the interactions between CMI and calcite surfaces is very important for the design of scale inhibitors. In this study, molecular dynamics simulations were carried out to investigate effects of temperature, CMI chain length, and calcite cleavage on the interactions between CMI and calcite. The results indicate that for the same mass of CMI (with different degrees of polymerization, n = 1, 3, 5), CMI exhibits different abilities in inhibiting the growth of calcite crystal in the order of CMI (n = 5) > CMI (n = 3) > CMI (n = 1) for calcite (012), (104), 11̅0, and (110) surfaces. For the calcite (012) surface, the inhibition ability is similar for CMI (n = 3) and CMI (n = 5). For the aqueous environment, comparison of the results of water effects with the results for the CMI-calcite surfaces without water showed a similar trend: the interaction between the CMI and the calcite (012) surface was greater than that of the CMI with the other calcite surfaces (104), (110), and 11̅0. However, the interactions between the CMI and the other calcite surfaces (104), (110), and 11̅0 were apparently weakened by the water environment. The results also show that temperature influences the interactions between CMI and calcite surfaces. This study provides important information for CMI potential applications as calcite inhibitor.