Modelling and mechanisms of ultrasound-assisted membrane filtration

超声辅助膜过滤的建模和机制

• 批准号: RGPIN-2021-03054
• 负责人: Doan, Huu
• 金额: $ 2.04万
• 依托单位: Ryerson University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=747124
• 关键词: Modelling; mechanisms; ultrasound; assisted; membrane

Ultrafiltration (UF) has been widely used in both industrial and municipal wastewater treatment. One of the benefits of treating wastewater by UF over other processes, such as: electrochemical oxidation, biological treatment, or Fenton oxidation, is the potential to reclaim the solid in the effluent and to recycle the filtrate as process or cleaning water. However, due to membrane fouling, the permeate flux declines with filtration time, resulting in a reduced UF efficiency, shorter membrane lifetime, higher cleaning frequency, and hence, a higher operational cost. Therefore, control of membrane fouling is of great importance in membrane filtration. Several membrane-fouling control techniques have been studied, such as: feed coagulation and flocculation, alteration of chemical/physical properties of the feed, membrane surface modification and grafting to increase the membrane hydrophilicity. However, no single technique has been shown to be effective for all membrane processes due to the complicated nature of membrane fouling. Various industries have used ultrasound to clean surfaces of a variety of materials, such as: semiconductor wafers, plastics, ceramic, and metal parts. Ultrasound can induce the formation of bubbles in liquid. Bubble collapse can produce shock-wave, localized high temperature, high pressure, and high fluid velocity (micro-jet), which can provide an effective means to remove particles from the membrane surface. Ultrasonic cleaning of ceramic, PVDF, PTFE, and PES membranes has been studied at varied ultrasonic frequencies from 28 kHz to 100 kHz. However, off-line ultrasonic cleaning of fouled membranes was used in those studies. The main disadvantage of off-line cleaning is the membrane process downtime, similar to that of chemical cleaning. In addition, most researchers used dead-end filtration in their studies. This would limit the application of their data and findings to cross-flow filtration, which is the most commonly-used operational mode for membrane filtration in industries. Mechanisms of fouling control by ultrasound applied concurrently with filtration process are not fully understood. Therefore, a study on ultrasound-assisted fouling control is proposed. This would elucidate a thorough understanding of the role of ultrasound on the removal and/or breakage of fouling particles on the membrane surface and optimal conditions for fouling control. For industrial applications, fouling control should be inexpensive. The development of an on-line integrated ultrasonic fouling control will thus be carried out so as to avoid process downtime. In addition, ultrasound-induced bubbles and micro-jet and micro-streaming would alter the hydrodynamics and the particle-membrane interaction, which play a key role in membrane fouling. To our best knowledge, this has not been studied. Therefore, fouling mechanisms will be studied under flow field alteration by ultrasound, so to facilitate advancement in membrane fouling control.

超滤（UF）已广泛应用于工业和城市废水处理。与其他工艺（例如电化学氧化、生物处理或芬顿氧化）相比，超滤处理废水的好处之一是可以回收废水中的固体并将滤液作为工艺水或清洁水进行回收。然而，由于膜污染，渗透通量随着过滤时间的推移而下降，导致超滤效率降低、膜寿命缩短、清洗频率更高，从而导致运营成本更高。因此，膜污染的控制在膜过滤中具有重要意义。已经研究了几种膜污染控制技术，例如：进料混凝和絮凝、改变进料的化学/物理性质、膜表面改性和接枝以增加膜亲水性。然而，由于膜污染的复杂性，没有一种技术被证明对所有膜过程都有效。各个行业都使用超声波来清洁各种材料的表面，例如：半导体晶圆、塑料、陶瓷和金属零件。超声波可以引起液体中气泡的形成。气泡破裂可以产生冲击波、局部高温、高压和高流体速度（微射流），这可以提供去除膜表面颗粒的有效手段。陶瓷、PVDF、PTFE 和 PES 膜的超声波清洗已在 28 kHz 至 100 kHz 的不同超声波频率下进行了研究。然而，这些研究中使用了对污染膜的离线超声波清洗。离线清洗的主要缺点是膜工艺的停机时间，与化学清洗类似。此外，大多数研究人员在他们的研究中使用了死端过滤。这将限制他们的数据和研究结果在错流过滤中的应用，错流过滤是工业中最常用的膜过滤操作模式。通过与过滤过程同时应用的超声波来控制结垢的机制尚不完全清楚。因此，提出了超声辅助污垢控制的研究。这将阐明超声波在去除和/或破坏膜表面污垢颗粒方面的作用以及污垢控制的最佳条件的透彻理解。对于工业应用，污垢控制应该是便宜的。因此，将开发在线集成超声波污垢控制，以避免过程停机。此外，超声波引起的气泡、微射流和微流会改变流体动力学和颗粒-膜相互作用，这在膜污染中起着关键作用。据我们所知，尚未对此进行研究。因此，将研究超声流场改变下的污染机理，以促进膜污染控制的进展。