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）已在工业和市政废水处理中广泛使用。用UF处理废水的好处之一，例如：电化学氧化，生物处理或芬顿氧化，有可能在废水中收回固体并将滤液作为过程或清洁水回收滤液。但是，由于膜结垢，渗透性的通量随着过滤时间而下降，导致UF效率降低，膜寿命较短，清洁频率较高，从而增加了更高的操作成本。因此，对膜结垢的控制在膜过滤中非常重要。已经研究了几种膜污染控制技术，例如：饲料凝血和絮凝，进料的化学/物理特性的改变，膜表面修饰和嫁接以增加膜亲水性。但是，由于膜结垢的复杂性质，尚无单一技术对所有膜过程有效。各种行业都使用超声波清洁各种材料的表面，例如：半导体晶片，塑料，陶瓷和金属零件。超声可以诱导液体中气泡的形成。气泡塌陷会产生冲击波，局部高温，高压和高流体速度（微型射流），这可以提供有效的手段以从膜表面去除颗粒。陶瓷，PVDF，PTFE和PES膜的超声清洁已在从28 kHz到100 kHz的各种超声频率下进行了研究。但是，在这些研究中使用了污染膜的离线超声清洁。离线清洁的主要缺点是膜过程的停机时间，类似于化学清洁。此外，大多数研究人员在研究中使用了死端过滤。这将限制其数据和发现的应用到跨流过滤，这是行业中膜过滤最常用的操作模式。通过超声控制与过滤过程同时应用的结垢控制机制尚不完全了解。因此，提出了有关超声辅助结垢控制的研究。这将阐明对超声在膜表面上的去除和/或破裂颗粒的去除和/或破裂的作用以及最佳条件以进行结垢控制。对于工业应用，结垢控制应便宜。因此，将进行在线综合超声污染控制的开发，以避免流程停机时间。此外，超声引起的气泡以及微射流和微流将改变流体动力学和粒子膜相互作用，这些相互作用在膜结垢中起关键作用。据我们所知，这尚未得到研究。因此，将通过超声检查在流场改变下进行结垢机制，以促进膜结垢控制的进步。