carbon-based-nanostructure-to-remove-heavy-metals-from-water

Context:

Recently a carbon-based nanostructure has been created by researchers at IIT Bombay to remove heavy metals such as arsenic, chromium, cadmium and mercury from wastewater with very high efficiency. 

About the experiment:

  • Marigold carbon-based nanostructure is obtained through a single-step process of chemical vapour deposition followed by removing the silica template.
  • The carbon-based nanostructure that the team fabricated shows 80-90?sorption efficiency for all the four heavy metals studied.


How does it purify water?

  • When the water containing the heavy metals comes in contact with the nanostructure, the majority of adsorption first takes place in the micropores
  • Since the heavy metals chemically react and bind to the surface of the nanostructure, they do not leach back into the water. They can be recovered by treating the nanostructure with mild acid (hydrochloric acid and nitric acid).

Features of the nano structure:

  • Very high adsorption efficiency: its hydrophilic [water-loving nature] nature that allows for extensive and rapid interaction between the heavy metal-containing water and the carbon nanostructure.
  • Unlike activated carbon, the surface area of nanostructure is easily accessible for heavy metals. 
  • No electricity is required for the nanostructure to remove heavy metals from water as it allows for gravity-driven purification of the water. 
  • The nanostructures can be recycled and reused multiple times. 
  • The carbon nanostructure is able to absorb the heavy metals in the wide range of pH conditions — pH 2 to 13. 

 

Nanostructures 

Nanostructures are structures that range between 1 nm (molecular scale) and 100 nm in at least one dimension. Most are synthetic and can be engineered to a wide range of physical properties. 

Uses: Nanocomposite carbon-based substrates are a large group of materials promising for medicine and various biotechnologies, for hard tissue implantation, constructing biosensors and biostimulators or micropatterned surfaces for creation of cell microarrays for advanced genomics and proteomics.

Absorption vs. Adsorption

Absorption is the process in which a fluid is dissolved by a liquid or a solid (absorbent). Adsorption is the process in which atoms, ions or molecules from a substance (it could be gas, liquid or dissolved solid) adhere to a surface of the adsorbent.

About heavy metals

The term heavy metal refers to any metallic chemical element that has a relatively high density and is toxic or poisonous at low concentrations. Examples of heavy metals include mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), thallium (Tl), and lead (Pb).