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Effect of Sodium Hypochlorite Disinfection on Polyvinylidene Fluoride Membranes in Microplastic Ultrafiltration
Summary
Researchers studied how sodium hypochlorite disinfection, commonly used in water treatment plants, affects the ability of ultrafiltration membranes to remove microplastics. They found that while pre-chlorination improved water flow through the membrane, it significantly reduced the microplastic removal rate from 36.6% to 22.6%. The study also showed that prolonged chlorine exposure damaged the membrane structure, raising concerns about the long-term effectiveness of this approach.
With the widespread use of plastic products, microplastic (MP) pollution has become an important factor threatening the water environment and human health. Ultrafiltration (UF) technology, based on organic polymer membranes, is a common method to remove MPs in water treatment processes, offering high removal efficiency and scalability. However, in water treatment plants (WTPs), oxidation pretreatment is often applied before UF, and the presence of oxidants can affect membrane performance. In this study, we constructed a polyvinylidene fluoride (PVDF) ultrafiltration membrane for a gravity filtration system to investigate the impact of sodium hypochlorite oxidation pretreatment on the removal of polystyrene (PS) MPs under gravity filtration. As a result, pre-chlorination reduced PS microplastic deposition on membranes by improving flux stability (15.1%) but significantly decreased the removal rate (from 36.6% to 22.6%). Pre-oxidation facilitated a shift in fouling behavior toward intermediate blocking while reducing standard blocking and enhancing irreversible fouling recovery. However, continuous chlorine exposure increased membrane porosity and pore size, substituted fluorine with chlorine, and led to organic carbon leaching, indicating pre-oxidation jeopardizes membrane stability and separation performance. These findings provide insights into the development of novel strategies aimed at enhancing the efficiency and sustainability of membrane treatment processes in WTPs.
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