Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, United States.
Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, United States.
Water Res. 2023 Nov 1;246:120701. doi: 10.1016/j.watres.2023.120701. Epub 2023 Oct 5.
Silica scaling is a major type of mineral scaling that significantly constrains the performance and efficiency of membrane desalination. While antiscalants have been commonly used to control mineral scaling formed via crystallization, there is a lack of antiscalants for silica scaling due to its unique formation mechanism of polymerization. In this study, we performed a systematic study that investigated and compared antiscalants with different functional groups and molecular weights for mitigating silica scaling in membrane distillation (MD) and reverse osmosis (RO). The efficiencies of these antiscalants were tested in both static experiments (for hindering silicic acid polymerization) as well as crossflow, dynamic MD and RO experiments (for reducing water flux decline). Our results show that antiscalants enriched with strong H-accepters and H-donors were both able to hinder silicic acid polymerization efficiently in static experiments, with their antiscaling performance being a function of both molecular functionality and weight. Although poly(ethylene glycol) (PEG) with abundant H-accepters exhibited high antiscaling efficiencies during static experiments, it displayed limited performance of mitigating silica scaling during MD and RO. Poly (ethylene glycol) diamine (PEGD), which has a PEG backbone but is terminated by two amino groups, was efficient to both hinder silicic acid polymerization and reduce water flux decline in MD and RO. Antiscalants enriched with H-donors, such as poly(ethylenimine) (PEI) and poly(amidoamine) (PAMAM), were effective of extending the water recovery of MD but conversely facilitated water flux decline of RO in the presence of supersaturated silica. Further analyses of silica scales formed on the membrane surfaces confirmed that the antiscalants interacted with silica via hydrogen bonding and showed that the presence of antiscalants governed the silica morphology. Our work indicates that discrepancy in antiscalant efficiency exists between static experiments and dynamic membrane filtration as well as between different membrane processes associated with silica scaling, providing valuable insights on the design principle and mechanisms of antiscalants tailored to silica scaling.
硅垢是一种主要的矿物结垢类型，严重限制了膜脱盐的性能和效率。虽然阻垢剂通常用于控制通过结晶形成的矿物结垢，但由于其聚合的独特形成机制，缺乏用于硅垢的阻垢剂。在这项研究中，我们进行了一项系统的研究，研究了具有不同官能团和分子量的阻垢剂在膜蒸馏（MD）和反渗透（RO）中减轻硅垢的效果。我们在静态实验（用于阻止硅酸聚合）以及错流、动态 MD 和 RO 实验（用于减少水通量下降）中测试了这些阻垢剂的效率。我们的结果表明，富含强 H-接受体和 H-供体的阻垢剂都能在静态实验中有效地阻止硅酸聚合，其阻垢性能既取决于分子功能又取决于分子量。虽然富含 H-接受体的聚乙二醇（PEG）在静态实验中表现出高阻垢效率，但在 MD 和 RO 中减轻硅垢的性能有限。具有 PEG 主链但被两个氨基端基封端的聚乙二醇二胺（PEGD）在 MD 和 RO 中既有效阻止硅酸聚合，又能减少水通量下降。富含 H-供体的阻垢剂，如聚乙烯亚胺（PEI）和聚酰胺-胺（PAMAM），能够有效地延长 MD 的水回收率，但在存在过饱和硅的情况下，反而会促进 RO 的水通量下降。对膜表面形成的硅垢的进一步分析证实，阻垢剂通过氢键与硅相互作用，并表明阻垢剂的存在控制着硅的形态。我们的工作表明，静态实验和动态膜过滤之间以及与硅垢相关的不同膜过程之间存在阻垢剂效率的差异，为针对硅垢设计阻垢剂的原理和机制提供了有价值的见解。
