Ceramic water filter achieves 99.8% dye removal at tap-water pressure

Conventional ceramic membranes for water treatment share an uncomfortable trade-off: achieving fine-enough pores to filter nanoscale contaminants typically requires high pressure, high temperature manufacturing, and multiple coating steps that introduce defects. Researchers at the Korea Institute of Materials Science (KIMS) have found a way around each of these problems simultaneously.

Their new membrane removes more than 99.8% of dyes from contaminated wastewater while operating at just 2 bar of pressure, roughly equivalent to household tap water. It also selectively allows salt ions to pass through, enabling not just purification but resource recovery. The results were published in Desalination (October 2025) and the Journal of Membrane Science (February 2026).

The crack problem

Ceramic membranes work by forcing water through precisely sized pores while blocking larger contaminants. The membranes are built in layers: a coarse, porous substrate provides structural support, while progressively finer layers on top do the actual filtering. Conventionally, each layer is coated and sintered separately at high temperatures, often around 1,300 degrees Celsius.

This multi-step process creates a problem. Each coating-and-firing cycle introduces surface roughness, and that roughness generates microcracks in the thin separation layer on top. Those cracks become highways for contaminants, undermining the very precision the membrane is designed to provide. It is a bit like building a fine-mesh screen on top of a bumpy surface and watching it tear at every ridge.

Firing everything at once

Dr. Hong-Ju Lee and Dr. In-Hyuk Song tackled this by developing two linked innovations. The first is a mutual doping technique, in which particles from different membrane layers are mixed at their interfaces to enhance bonding. The second is a co-sintering process that fires all layers simultaneously rather than sequentially.

Together, these approaches reduced the required sintering temperature from approximately 1,300 degrees Celsius to about 1,000 degrees, a drop of roughly 300 degrees. Despite the lower temperature, the interparticle bonding was actually stronger, producing a denser ceramic structure. Most importantly, the surface roughness dropped from 24.49 nanometers to 11.74 nanometers, a reduction of more than half. At that smoothness, the separation layer can be applied without the microcracks that plague conventional membranes.

Filtering dyes while passing salt

On this ultra-smooth substrate, the team coated a zirconia-based loose nanofiltration layer using an eco-friendly aqueous sol they developed in-house. The resulting membrane works through two mechanisms simultaneously: size exclusion, where pores are small enough to physically block dye molecules, and electrostatic repulsion, where surface charges on the membrane repel charged contaminants.

This dual mechanism allows the membrane to remove more than 99.8% of dyes from wastewater while letting smaller salt ions pass through at a pressure of just 2 bar. Conventional nanofiltration membranes typically require around 10 bar to operate, five times more pressure and proportionally more energy.

The ability to separate dyes from salts is particularly valuable for the textile industry, where dyeing wastewater contains both. Rather than treating the entire waste stream as a disposal problem, this membrane enables selective recovery of clean water and potentially reusable salt solutions.

Durability in harsh conditions

Ceramic membranes hold an inherent advantage over polymer-based alternatives in extreme environments. They resist chemical degradation, tolerate high temperatures, and can be cleaned aggressively without deteriorating. The KIMS membrane demonstrated strong flux recovery, meaning its water throughput could be restored after fouling, a practical requirement for industrial applications where membranes encounter complex waste streams.

From laboratory to scale-up

The technology has been demonstrated at laboratory scale, and the research team reports that domestic and international patents have been filed. The next phase involves scaling up to large-area membranes suitable for industrial water treatment plants. Pilot-scale demonstrations and technology transfer to commercial partners are planned.

Whether the co-sintering approach and mutual doping technique maintain their advantages at larger scales remains to be confirmed. Manufacturing consistency, cost per unit area, and long-term performance under continuous industrial operation are all factors that laboratory results cannot fully predict. The ceramic membrane market for water treatment is currently dominated by manufacturers in Europe and Japan, and the KIMS team sees their work as an opportunity to compete in this space.

The research was supported by the National Research Foundation of Korea and the Korea Institute for Advancement of Technology.