Sunshine, seaweed help to break down dye waste

The researchers have developed a photocatalyst using titanium dioxide doped with red seaweed polymer carrageenan to degrade the dyes. With this photocatalyst, scientists have been able to completely degrade three industrial dyes — methyl orange, methylene blue and reactive black-5 — in the presence of sunlight.

Details:

• Titanium dioxide has conventionally been used for photocatalytic degradation of industrial dyes, but it takes a long time to degrade dyes. So the researchers doped titanium dioxide nanoparticles with sulphur and carbon by treating it with carrageenan.
• The nanocomposite was found to behave as an excellent photocatalyst that helped degrade industrial dyes quickly in a single-step process. The energy required to activate the catalyst is less when it is doped and this makes the dye degradation faster. Visible light is mainly responsible for degradation.

Significance of nanocomposites:

The nanocomposites are thermally stable and can be reused up to six times with the degradation efficiency remaining at over 97%. The nanocomposite photocatalyst can safely and completely treat harmful dyes in an eco-friendly and cost-effective manner.

Background:

Despite stringent environmental regulations, a comprehensive method of treating industrial dye is not available. The methods available are expensive and do not completely break down the dye molecules to non-toxic constituents but merely concentrate the contaminants. Annually, more than 500 tonnes of non-degradable textile colour wastes are being disposed of in natural streams without adequate treatments.

Way ahead:

The researchers are planning to conduct studies during winter to assess the photocatalyst’s ability to break down the dyes when bright sunlight is not available.