In this paper, the retarding effect of a green additive, citric acid, towards calcium carbonate scale deposition is studied. Scale formation is one of the most common causes of malfunctions in process equipment. This is the reason it is crucial to retard scale precipitation, that is, in order to reduce economic damages. With this additive in the solution, experimental runs have been carried out in supersaturation conditions in terms of concentration of calcium carbonate at equilibrium, with a supersaturation ratio ranging from 16 to 280, at 25°C. Three different concentrations of citric acid have been investigated (0.520 × 10⁻³, 1.041 × 10⁻³ and 1.561 × 10⁻³ M) in a laboratory scale plant. Comparing results obtained in terms of induction time with previous experimental runs, performed without additives, citric acid has shown its significant capacity to retard calcium carbonate precipitation, by increasing induction time values. This behaviour is enhanced by raising the additive concentration in solution up to a specific threshold value, beyond which no benefit in terms of calcium scale inhibition is gained. Furthermore, interfacial tension has been computed without and with citric acid at 0.520 × 10⁻³ and 1.041 × 10⁻³ M, as a function of the different concentration amounts investigated. The values obtained are in good agreement with data reported in the literature.

中文翻译：

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柠檬酸作为绿色添加剂可延缓工艺设备上的碳酸钙垢

在本文中，研究了绿色添加剂柠檬酸对碳酸钙垢沉积的阻滞作用。结垢是过程设备故障的最常见原因之一。这就是延缓水垢沉淀至关重要的原因，即为了减少经济损失。在溶液中使用这种添加剂时，已经在过饱和条件下进行了实验，以平衡状态下碳酸钙的浓度进行了试验，在25°C下的过饱和比为16至280。三种不同浓度的柠檬酸已被研究（0.520×10 ^-3，1.041×10 ^-3和1.561×10 ^-3M）在实验室规模的工厂中。将在诱导时间方面的结果与以前的实验操作（不添加添加剂）进行比较，柠檬酸已显示出通过增加诱导时间值来抑制碳酸钙沉淀的显着能力。通过将溶液中的添加剂浓度提高到特定阈值，可以增强此行为，超过该阈值就无法获得抑制钙垢的益处。此外，已经计算了柠檬酸在0.520×10 ^-3和1.041×10 ^-3 M下的界面张力与不同浓度的函数。获得的值与文献报道的数据高度吻合。