Nanoparticle-based remediation of chromium-contaminated water exhibits excessive effectivity

Groundwater is an important supply of ingesting water throughout the nation. Nevertheless, heavy metallic contamination in groundwater presents a big well being hazard. Researchers on the Indian Institute of Science (IISc) have developed a nanomaterial-based resolution that may successfully cut back the presence of heavy metals like chromium in groundwater.

The workforce contains researchers from the Middle for Sustainable Applied sciences (CST), Division of Civil Engineering (CiE), and Division of Instrumentation and Utilized Physics (IAP). The examine is printed within the Journal of Water Course of Engineering.

Chromium sometimes enters soil and groundwater by means of effluents from industries corresponding to leather-based tanning, electroplating, and textile manufacturing. “Heavy metals enter the atmosphere due to urbanization and sure mismanagement by industries,” says Prathima Basavaraju, Ph.D. scholar at CST and lead writer of the examine.

Most present strategies for eradicating heavy metallic contamination depend on pumping out water from the bottom, adopted by purification utilizing chemical precipitation, adsorption, ion alternate and reverse osmosis carried out at a unique location. The IISc workforce as an alternative proposes an on-site different which entails utilizing iron nanoparticles that may remediate the heavy metals.

“If the groundwater is contaminated, we are able to inject these nanoparticles into the subsurface groundwater area the place it is going to react with the chromium and immobilize it, leading to clear water,” Prathima explains.

The group first tried synthesizing nanoparticles consisting of nano zero-valent iron (nZVI). This type of iron can react with the poisonous and carcinogenic type of chromium (Cr⁶⁺) and cut back it to a much less dangerous kind (Cr³⁺), which in flip ends in co-precipitation. Nevertheless, the workforce quickly realized that the nZVI particles are likely to clump collectively, limiting their software.

To forestall clumping, the workforce turned to carboxymethyl cellulose (CMC). “We modified nZVI by coating it with CMC. It varieties a stabilizing layer round nZVI separating particular person particles,” Prathima explains. The CMC coating moreover extended the lifetime of the fabric by stopping oxidation of the iron core.

The workforce additionally boosted the reactivity of the CMC-nZVI by exposing it to sulfur-containing compounds in anoxic circumstances. This enabled the formation of a protecting iron sulfide layer on the floor, a course of referred to as sulfidation. These modifications improved the steadiness of the S-CMC-nZVI and maintained its reactivity and effectivity.

S-CMC-nZVI confirmed practically 99% effectivity at Cr⁶⁺ elimination underneath completely different circumstances corresponding to completely different pH ranges and the presence of different competing ions that is likely to be present in groundwater. The workforce examined this enhanced nanomaterial in circumstances that mimic the pure atmosphere of groundwater aquifers.

Once they pumped contaminated water by means of sand columns containing the nanomaterial, they noticed sturdy remediation exercise. Experiments have been additionally carried out on contaminated soil and sediments utilizing nZVI to immobilize the heavy metals. Scaling up experiments are nonetheless in progress.

The authors counsel that S-CMC-nZVI is a promising materials for on-site remediation of chromium-contaminated groundwater. “Locations like Bellandur lake [in Bengaluru] have a whole lot of contaminated sediments,” factors out GL Sivakumar Babu, Professor at CiE and CST, and co-author.

“The method developed may show fairly helpful in remediating contaminants corresponding to cadmium, nickel, and chromium in contaminated sediments of Bellandur lake.”