Researchers pinpoint cause of membrane clogging to cut semiconductor wastewater treatment costs

Korean researchers have newly identified the cause of contamination in filtration membranes used to treat wastewater from semiconductor factories.

The National Research Foundation of Korea said Wednesday a Hankyong National University team led by Professor No Ho-jung examined fouling patterns in ceramic and polymer membranes using actual semiconductor wastewater. The team identified the mechanisms behind the different patterns of contaminant accumulation and membrane fouling for each material.

As South Korea's semiconductor production has expanded in recent years, growing volumes of wastewater have raised the importance of purification and reuse technology.

Wastewater reuse processes typically use ultrafiltration and reverse osmosis membranes for purification. But when contaminants stick to a membrane and clog it, water passes through less efficiently, requiring more frequent cleaning, driving up operating costs and destabilizing downstream processes.

Previous research has largely relied on artificial wastewater or single contaminants, falling short of fully explaining the complex fouling seen in actual semiconductor wastewater.

The research team filtered actual semiconductor wastewater for 48 hours through two representative membrane types -- an alumina ceramic membrane and a polyethersulfone, or PES, polymer hollow-fiber membrane -- comparing and analyzing their fouling behavior.

By the end of filtration, the ceramic membrane's permeate flux had dropped to about one-third that of the polymer membrane. This showed that ceramic membranes -- generally regarded as more resistant to fouling -- can undergo greater performance degradation in semiconductor wastewater from interactions between the membrane surface and contaminants.

In the process, the team identified a new "material-specific fouling pathway," in which iron ions selectively bind to aluminum hydroxide, or Al-OH, functional groups on the ceramic membrane surface, followed by additional buildup of humic substances.

"This study shows that not only membrane pore size and hydrophilicity but also the chemical interaction between wastewater components and the membrane surface are key factors determining how contaminants are captured and how permeability declines," Professor No said. "By expanding this work to selective pretreatment of major contaminants, surface modification of ceramic membranes, and optimization of operating conditions and cleaning cycles, we expect to strike a balance between contaminant removal and water productivity, improve process stability, reduce cleaning and membrane replacement costs, and contribute to expanding water recycling in the semiconductor industry."

The research was carried out with support from the Ministry of Science and ICT and the National Research Foundation of Korea's nano and materials technology development project. It was published online in Desalination, an international journal covering water treatment and separation membranes, on Aug. 19.