Nanomaterial-based solution for chromium mitigation in water

By Ashwini Sakharkar 22 Sep, 2024

Collected at: https://www.techexplorist.com/nanomaterial-based-solution-chromium-mitigation-water/90114/

Groundwater is a vital source of drinking water nationwide. However, the alarming presence of heavy metal contamination poses a significant threat to public health. Excitingly, a team of researchers at the Indian Institute of Science (IISc) has pioneered a cutting-edge nanomaterial-based solution capable of effectively mitigating heavy metal pollutants, such as chromium, in groundwater.

This groundbreaking initiative involves a collaborative effort among distinguished researchers from the Centre for Sustainable Technologies (CST), the Department of Civil Engineering (CiE), and the Department of Instrumentation and Applied Physics (IAP).

Chromium often finds its way into soil and groundwater through industrial effluents from sectors like leather tanning, electroplating, and textile manufacturing.

“Heavy metals enter the environment because of urbanization and certain mismanagement by industries,” says Prathima Basavaraju, PhD student at CST and lead author of the study.

The current methods for eliminating heavy metal contamination involve extracting water from the ground and then purifying it using chemical precipitation, adsorption, ion exchange and reverse osmosis at a separate location. However, the team at IISc proposes an on-site alternative that utilizes iron nanoparticles that are capable of remediating heavy metals.

“If the groundwater is contaminated, we can inject these nanoparticles into the subsurface groundwater region where it will react with the chromium and immobilize it, resulting in clear water,” Prathima explains.

The team embarked on a mission to tackle the challenge of synthesizing nanoparticles using nano zero-valent iron (nZVI) to neutralize the toxic and carcinogenic form of chromium (Cr6+). However, they encountered a roadblock when the nZVI particles started clumping together, limiting their effectiveness.

To overcome this hurdle, the team ingeniously coated the nZVI with carboxymethyl cellulose (CMC), creating a stabilizing layer around the particles to prevent clumping. This not only extended the material’s lifespan by shielding the iron core from oxidation but also enhanced its reactivity.

Taking it a step further, the team exposed the CMC-coated nZVI to sulfur-containing compounds in anoxic conditions, leading to the formation of a protective iron sulfide layer on the surface through a process called sulphation. These strategic modifications significantly bolstered the stability, reactivity, and efficiency of the S-CMC-nZVI, paving the way for a groundbreaking solution.

The remarkable S-CMC-nZVI demonstrated an exceptional 99% efficiency in removing Cr6+ across various pH levels and in the presence of competing ions commonly found in groundwater. In simulated groundwater aquifer conditions, the nanomaterial exhibited robust remediation capabilities when contaminated water was passed through sand columns containing the material.

Additionally, experiments on contaminated soil and sediments using nZVI to immobilize heavy metals yielded promising results. The ongoing scale-up experiments further underscore the potential of S-CMC-nZVI for on-site remediation of chromium-contaminated groundwater.

“Places like Bellandur Lake [in Bengaluru] have a lot of contaminated sediments,” points out GL Sivakumar Babu, Professor at CiE and CST and co-author. “The technique developed can also prove quite useful in remediating contaminants such as cadmium, nickel, and chromium in contaminated sediments of Bellandur Lake.”

Journal reference:

1. B. Prathima, Vikram Srinivasa Raghvan, Swati Soni, Sai Siva Gorthi, Sivakumar Babu G.L. Sulfide-enhanced carboxymethyl cellulose stabilised nano zero-valent iron for chromium(VI) mitigation in water: Evidence from batch and column studies. Journal of Water Process Engineering, 2024; DOI: 10.1016/j.jwpe.2024.105832