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Recently, a research team at the Indian Institute of Technology (IIT) Mandi has developed a new method for efficient removal of heavy metals from water
Background:
- Several methods like chemical precipitation, ion exchange, adsorption, membrane filtration, reverse osmosis, solvent extraction, and electrochemical treatment have been used to remove heavy metals from contaminated water.
- Many of these methods suffer from high capital and operational costs.
- Therefore, adsorption is one of the best-suited methods, due to its high efficiency, low-cost, and ease of operation.
About the Research:
- A research team has developed a fibrous membrane filter using a biopolymer-based material that helps to separate out the heavy metals from water samples.
- These membranes contain adsorbents materials that attract and hold the metals.
- These adsorbents contain a large amount of a biopolymer, Chitosan, derived from crab shells that is mixed with a well-known polymer, Nylon.
- Funding of Research:The study was funded by the Ministry of Mines, Government of India.
Process Used:
- The researchers have used a process called “solution blowing”, while regular fibre-based adsorbents are produced through a method called “melt blowing”.
- It is a special technique for manufacturing material with very fine fibers, down to 0.5 μm (in range of micrometers).
- The fibers are elongated by blowing hot air at high speed concentrically along the fibers.
- It starts from dissolving the polymer in solvent, e.g. cellulose in ionic liquid.
- The solution is pumped through a spin nozzle where air is blown at high speed concentrically.
- Solution blowing produces fibres that are nanometres in diameter, a hundred thousand times thinner than a single human hair. Finer than those produced through the process of Melt Blowing. This increases the surface area of fibers tremendously, resulting in better adsorption of heavy metals.
- This method also enables blending of higher concentration of natural polymers like chitosan and lignin with synthetic polymers like Nylon.
Advantages:
- Higher Metal Removal Efficiency: The normal absorbent fibres bind to the target metal only at their surface, in their nanofiber membranes.
- The biopolymer-based material adsorption was seen to happen at the sub-surface scale as well, which translates to higher metal removal efficiency.
- Reuse of Membrane: The membranes could be reused at least eight times before there was considerable reduction in the efficiency of metal adsorption.
- Recovery of Adsorbed Metal: The adsorbed metal in a metal-hydroxyl nitrate form can be easily recovered. It is a value-addition to the membrane filter.
- Industrial Production: The researchers have provided a method to produce fibre-based adsorbents at large scale for handling larger volumes of metal-contaminated water.
- Environmentally Efficient: Using the solution blowing technique could replace the synthetic polymers with natural polymers.
- It will be a welcome move in this era of environmental consciousness.
SOURCE: DTE
