'Holey' Nanosheets for Wastewater Dye Removal

Jul 01, 2009 feature

(PhysOrg.com) -- Researchers have discovered that extremely thin sheets of nickel oxide with hexagonally shaped holes can absorb hazardous dyes from wastewater nearly as well as the best traditional methods, but are recyclable. The research was reported recently in the journal Nanotechnology.

The group, consisting of scientists from the Colorado School of Mines and South-Central University for Nationalities, in China, compared the performance of their nickel-oxide (NiO) “nanosheets” to the absorption properties of a powdered form of NiO as well as to activated carbon, a material often used for absorption applications because it has a very large overall surface area.

In a similar way, the hexagonal holes in the NiO nanosheets also possess a high surface area. Each sheet has a polar surface, containing distinct regions of positive and negative charge.

According to Colorado School of Mines scientist Ryan Richards, one of the paper's authors, “Metal oxides like NiO have the main advantage that the absorbed material can be burned off and the NiO can be reused. Additionally, the polar surface of the NiO nanosheets may provide some advantages in adsorbing certain substrates. Methods for the recycling of activated carbon are often expensive and in this way and the carbon and the material it has absorbed must be discarded.”

Richards and his colleagues tested the absorption performance of the nanosheets and the NiO powder using three common synthetic dyes: reactive brilliant red X-3B, congo red, and fuchsin red. These dyes are used for many industrial purposes, including paper and pulp manufacturing, cloth dyeing, leather treatment, and printing.

The textile industry is a heavy user of dyes, consuming 60% of the world's supply, and experts estimate that 10 to 20 percent of water-soluble dyes are lost during the dyeing process and released into wastewater. The dyes pose a threat to environmental health on their own, but as they undergo chemical reactions in the water other toxic and hazardous intermediate compounds are created.

Various remediation methods exist, but physical absorption - using an absorbent material to “catch” and trap the dye - is the most common. Activated carbon is widely used, although many other materials have been investigated, including silica, clay, natural polymers, synthetic polymers, and various types of nanotubes.

The group prepared solution samples containing all three dyes and stirred in either powdered NiO or a small amount of nanosheets. They found that the nickel oxide nanosheets could remove, on average, two to three times as much dye as the powdered NiO. The nanosheets still do not perform as well as activated carbon - for example, the nanosheets absorbed about 71 percent of the congo red dye while the activated carbon took up 98 percent - but they have the advantage that the absorbed material can be readily burned off and the sheets reused. The sheets are also inexpensive to produce and can be created using “green” methods.

“We think that this means NiO nanosheets or similar materials could become the preferred media for dye removal in the future,” said Richards.

More information: Nanotechnology 20 (2009) 275707

Copyright 2009 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Thinnest feasible nano-membrane produced

add to favorites email to friend print save as pdf

Related Stories

New plastic is strong as steel, transparent

Oct 04, 2007

By mimicking a brick-and-mortar molecular structure found in seashells, University of Michigan researchers created a composite plastic that's as strong as steel but lighter and transparent.

Sounding out Congo Red

May 06, 2008

Brightly colored dyes such as the shimmering Congo Red commonly used in silk clothing manufacture are notoriously difficult to dispose of in an environmentally benign way.

The Dye with the Pumpkin Cuff

Jun 20, 2005

Complexation with a large cuff-shaped molecule stabilizes rhodamine dye fluorescence When irradiated, fluorescent dyes emit light at a different wavelength; for scientists and engineers, these dyes are extremely important aide ...

Recommended for you

Thinnest feasible nano-membrane produced

Apr 17, 2014

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Apr 17, 2014

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jul 01, 2009
In Confirmation class they asked me to write down and share something "holy". I chose Swiss cheese.

If only I was into physics back then, I could say "NiO nanosheets".

More news stories

'Exotic' material is like a switch when super thin

(Phys.org) —Ever-shrinking electronic devices could get down to atomic dimensions with the help of transition metal oxides, a class of materials that seems to have it all: superconductivity, magnetoresistance ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...