By using polysaccharides from red seaweed, researchers have synthesized various nanocomposites that can degrade harmful industrial dyes in the presence of sunlight, making them potentially useful for treating dye-contaminated industrial wastewater1.

Textile factories use colour dyes, which can contaminate nearby water bodies. Furthermore, these dyes are toxic and some are even carcinogenic. Conventional techniques for degrading dyes are expensive and complex.

To develop simple and ecofriendly catalysts for degrading dyes, the researchers synthesized different nanocomposites by modifying titanium dioxide nanoparticles with red-seaweed polysaccharides. They then tested the efficiencies of these nanocomposites to break down three dyes — methyl orange, methylene blue and reactive black-5.

The nanocomposites degraded the dyes in the presence of ultraviolet light. The nanocomposites also degraded almost 99% of reactive black-5 within 2 hours in the presence of daylight.

A commercial titanium-dioxide-based catalyst did not induce any colour change in the dye solutions, whereas, in the presence of sunlight, the nanocomposites made methylene blue and reactive black-5 solutions completely colourless after 5 minutes and methyl orange after 20 minutes.

“The nanocomposites are thermally stable and can be reused to break down colour dyes, suggesting that they could offer an effective and low-cost way to safely dispose of harmful dyes,” says lead researcher Ramavatar Meena.