State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China; Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China; Department of Civil and Environmental Engineering, Rice University, 6100 Main Street, Houston, TX 77005, United States.
Department of Civil and Environmental Engineering, Rice University, 6100 Main Street, Houston, TX 77005, United States; Research Institute of Petroleum Processing, SINOPEC, Beijing, China.
Water Res. 2022 Oct 15;225:119166. doi: 10.1016/j.watres.2022.119166. Epub 2022 Sep 24.
Water desalination using membrane technology is one of the main technologies to resolve water pollution and scarcity issues. In the membrane treatment process, mineral scale deposition and fouling is a severe challenge that can lead to filtration efficiency decrease, permeate quality compromise, and even membrane damage. Multiple methods have been developed to resolve this problem, such as scale inhibitor addition, product recovery ratio adjustment, periodic membrane surface flushing. The performance of these methods largely depends on the ability to accurately predict the kinetics of mineral scale deposition and fouling with or without inhibitors. Gypsum is one of the most common and troublesome inorganic mineral scales in membrane systems, however, no mechanistic model is available to accurately predict the induction time of gypsum crystallization and inhibition. In this study, a new gypsum crystallization and inhibition model based on the classical nucleation theory and a Langmuir type adsorption isotherm has been developed. Through this model, it is believed that gypsum nucleation may gradually transit from homogeneous to heterogeneous nucleation when the gypsum saturation index (SI) decreases. Such transition is represented by a gradual decrease of surface tension at smaller SI values. This model assumes that the adsorption of inhibitors onto the gypsum nucleus can increase the nucleus superficial surface tension and prolong the induction time. Using the new model, this study accurately predicted the gypsum crystallization induction times with or without nine commonly used scale inhibitors over wide ranges of temperature (25-90 °C), SI (0.04-0.96), and background NaCl concentration (0-6 mol/L). The fitted affinity constants between scale inhibitors and gypsum show a good correlation with those between the same inhibitors and barite, indicating a similar inhibition mechanism via adsorption. Furthermore, by incorporating this model with the two-phase mineral deposition model our group developed previously, this study accurately predicts the gypsum deposition time on the membrane material surfaces reported in the literature. We believe that the model developed in this study can not only accurately predict the gypsum crystallization induction time with or without scale inhibitors, elucidate the gypsum crystallization and inhibition mechanisms, but also optimize the mineral scale control in the membrane filtration system.
利用膜技术进行海水淡化是解决水污染和水资源短缺问题的主要技术之一。在膜处理过程中，矿物结垢和污垢沉积是一个严重的挑战，会导致过滤效率降低、渗透质量受损，甚至膜损坏。已经开发出多种方法来解决这个问题，例如添加阻垢剂、调整产品回收率、定期冲洗膜表面。这些方法的性能在很大程度上取决于是否能够准确预测有无抑制剂存在时矿物结垢和污垢沉积的动力学。石膏是膜系统中最常见和最麻烦的无机矿物垢之一，然而，目前还没有能够准确预测石膏结晶诱导时间和抑制作用的机理模型。在这项研究中，开发了一种基于经典成核理论和朗缪尔型吸附等温线的新的石膏结晶和抑制模型。通过该模型，认为当石膏过饱和度指数（SI）降低时，石膏成核可能逐渐从均相成核转变为异相成核。这种转变由较小 SI 值下表面张力的逐渐降低来表示。该模型假设抑制剂在石膏核上的吸附可以增加核的表面张力并延长诱导时间。利用该模型，研究人员在很宽的温度（25-90°C）、SI（0.04-0.96）和背景 NaCl 浓度（0-6mol/L）范围内，准确预测了有无九种常用阻垢剂存在时的石膏结晶诱导时间。拟合得到的阻垢剂与石膏之间的亲和常数与相同阻垢剂与重晶石之间的亲和常数具有很好的相关性，表明它们通过吸附具有相似的抑制机制。此外，通过将该模型与本研究组先前开发的两相矿物沉积模型相结合，研究人员准确预测了文献中报道的膜材料表面上的石膏沉积时间。研究人员认为，本研究中开发的模型不仅可以准确预测有无阻垢剂存在时的石膏结晶诱导时间，阐明石膏结晶和抑制机制，还可以优化膜过滤系统中的矿物结垢控制。
