Supersaturated carbon-dioxide-enhanced backwash of ceramic microfiltration membranes

IF 8.1 1区工程技术 Q1 ENGINEERING, CHEMICAL

Separation and Purification Technology Pub Date : 2025-02-04 DOI:10.1016/j.seppur.2025.131915

Weiming Qi, David A. Ladner

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Abstract

Supersaturated CO₂-enhanced backwash (SCEB) was tested as an alternative to clean-water backwash to enhance the effectiveness of foulant removal for ceramic microfiltration membranes. Air bubbles are commonly used to tangentially scour the feed side surface of micro- and ultrafiltration membranes to add scouring and loosen cake layers; this is called air-assisted backwash. Unlike air-assisted backwash, SCEB forces dissolved CO₂ and CO₂ bubbles through membrane pores. In this study, transmembrane pressure (TMP) and flux profiles during SCEB were directly analyzed to reveal the exact nucleation location. The results from constant-flux filtration show that SCEB recovered more filtration TMP compared to DI water backwash, which saves 6.5%, 2.7%, and 6.9% of the energy during lake water, activated sludge, and rendering wastewater filtration, respectively. Visualization of the membrane permeate is done for the first time, confirming that CO₂ bubbles were not formed before entering the membrane matrix. The pressure and flux profiles of SCEB itself were directly monitored. The pressure profile from constant-flux backwash was analyzed to further understand the cleaning mechanism. The results from constant-flux SCEB showed more negative pressure than DI water backwash, which means that CO₂ bubbles went through the membrane pores and created more resistance during SCEB. The visualization confirms that CO₂ bubbles nucleated inside the membrane pores rather than on the permeate side to clear the foulant blocked deep inside the membrane matrix. The behavior of CO₂ bubbles can be divided into three stages during SCEB: i) Permeate flush out, ii) Bubble concentration growth, and iii) Bubble concentration equilibrium. The last stage has the highest concentration of CO₂ bubbles, which work as pore-scrubbing entities and play an important role in better cleaning effectiveness because of the higher nucleation rate, extra shear stress, and greater lifting force.

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来源期刊

Separation and Purification Technology 工程技术-工程：化工

CiteScore

14.00

自引率

12.80%

发文量

2347

审稿时长

43 days

期刊介绍： Separation and Purification Technology is a premier journal committed to sharing innovative methods for separation and purification in chemical and environmental engineering, encompassing both homogeneous solutions and heterogeneous mixtures. Our scope includes the separation and/or purification of liquids, vapors, and gases, as well as carbon capture and separation techniques. However, it's important to note that methods solely intended for analytical purposes are not within the scope of the journal. Additionally, disciplines such as soil science, polymer science, and metallurgy fall outside the purview of Separation and Purification Technology. Join us in advancing the field of separation and purification methods for sustainable solutions in chemical and environmental engineering.