Friday, September 20, 2024

Nanoparticle-based remediation of chromium-contaminated water

Indian Institute of Science (IISc)

ChromiumPR_1 — image:
SEM images of S-CMC-nZVI
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Credit: CeNSE, IISc

Groundwater is an essential source of drinking water across the country. However, heavy metal contamination in groundwater presents a significant health hazard. Researchers at the Indian Institute of Science (IISc) have developed a nanomaterial-based solution that can effectively reduce the presence of heavy metals like chromium in groundwater.

The team includes researchers from the Centre for Sustainable Technologies (CST), Department of Civil Engineering (CiE), and Department of Instrumentation and Applied Physics (IAP). The study is published in the Journal of Water Process Engineering.

Chromium typically enters soil and groundwater through effluents from industries such as leather tanning, electroplating, and textile manufacturing. “Heavy metals enter the environment because of urbanisation and certain mismanagement by industries,” says Prathima Basavaraju, PhD student at CST and lead author of the study.

Most current methods for removing heavy metal contamination rely on pumping out water from the ground, followed by purification using chemical precipitation, adsorption, ion exchange and reverse osmosis carried out at a different location. The IISc team instead proposes an on-site alternative which involves using iron nanoparticles that can remediate the 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 immobilise it, resulting in clear water,” Prathima explains.

The group first tried synthesising nanoparticles consisting of nano zero-valent iron (nZVI). This form of iron can react with the toxic and carcinogenic form of chromium (Cr6+) and reduce it to a less harmful form (Cr3+), which in turn results in co-precipitation. However, the team soon realised that the nZVI particles tend to clump together, limiting their application.

To prevent clumping, the team turned to carboxymethyl cellulose (CMC). “We modified nZVI by coating it with CMC. It forms a stabilising layer around nZVI separating individual particles,” Prathima explains. The CMC coating additionally prolonged the life of the material by preventing oxidation of the iron core. The team also boosted the reactivity of the CMC-nZVI by exposing it to sulphur-containing compounds in anoxic conditions. This enabled the formation of a protective iron sulphide layer on the surface, a process called sulphidation. These modifications improved the stability of the S-CMC-nZVI and maintained its reactivity and efficiency.

S-CMC-nZVI showed nearly 99% efficiency at Cr6+ removal under different conditions such as different pH levels and the presence of other competing ions that might be found in groundwater. The team tested this enhanced nanomaterial in conditions that mimic the natural environment of groundwater aquifers. When they pumped contaminated water through sand columns containing the nanomaterial, they observed robust remediation activity. Experiments were also conducted on contaminated soil and sediments using nZVI to immobilise the heavy metals. Scaling up experiments are still in progress.

The authors suggest that S-CMC-nZVI is a promising material 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.”

TEM images of S-CMC-nZVI

Credit

CeNSE, IISc

Journal

Journal of Water Process Engineering

DOI

10.1016/j.jwpe.2024.105832

Article Title

Sulfide-enhanced carboxymethyl cellulose stabilised nano zero-valent iron for chromium (VI) mitigation in water: Evidence from batch and column studies

African food future looks bright with blueprint for food security

University of Birmingham

Countries in Sub-Saharan Africa can secure future food supplies by unlocking the potential of their people and farming systems, a new study reveals.

Sub-Saharan Africa faces several challenges impacting agricultural productivity and food security - including climate change, inadequate infrastructure, conflict, and limited access to modern technology.

But researchers have created a blueprint for future food security across the region, which builds on assets that can be used to enhance food system resilience – these assets include abundant agricultural resources, genetic diversity, and a youthful population.

Publishing their findings in Food and Energy Security, experts from the University of Birmingham and the Ethiopian Institute of Agricultural Research, in Addis Ababa, have identified a series of key factors which will help to build food resilience.

Co-author Dr Helen Onyeaka, from the University of Birmingham, commented: “Sub-Saharan Africa faces many obstacles, but there are several drivers of food resilience that offer hope for a brighter future and greater food security across the region.

“Several key strategies will help to boost resilience. These include diversifying suppliers, empowering local farmers, promoting sustainable practices, and investing in education and training - reducing reliance on external sources and improving self-sufficiency.

“By leveraging abundant agricultural resources, genetic diversity, and a youthful population, Sub-Saharan Africa can transform its food systems and enhance self-sufficiency.”

The proposed blueprint for future food resilience creates a comprehensive approach to building resilience in the region’s food systems - focusing on local empowerment, sustainable practices, and technological integration:

Technology: Digital tools and data-driven approaches can provide valuable insight and enhance efficiency in agricultural practices.

Resilience: Boosting food system resilience including diversifying suppliers, empowering local farmers, and reducing reliance on external sources.

Education: Farmer training initiatives and educational programmes can build local capacity - equipping communities with sustainable agricultural practices.

Collaboration: Governments, NGOs, private sectors, and local communities must work together to bridge gaps in capacity and disseminate best practices.

The researchers note that obstacles including climate change, inadequate infrastructure, and limited access to resources combine with rising urbanisation and population growth to increase food insecurity. Climate variability affects crop yields and livestock production - emphasising the urgent need for adaptive strategies.

ENDS

For media enquiries please contact Press Office, University of Birmingham, tel: +44 (0)121 4142772: email: pressoffice@contacts.bham.ac.uk

Notes to editor:

The University of Birmingham is ranked amongst the world’s top 100 institutions. Its work brings people from across the world to Birmingham, including researchers, teachers and more than 8,000 international students from over 150 countries.

‘Building resilience in Sub-Saharan Africa’s food systems: Diversification, traceability, capacity building and technology for overcoming challenges’ - Solomon Abate Mekonnen, Dassalegn Daraje Jalata, and Helen Onyeaka is published in Food and Energy Security.

Journal

Food and Energy Security

Method of Research

Observational study

Subject of Research

People

Article Title

Building resilience in Sub-Saharan Africa’s food systems: Diversification, traceability, capacity building and technology for overcoming challenges’

Lake ice quality degrading as planet warms – skaters, hockey players, ice truckers on thin ice

Several studies have looked at lake ice quantity and its duration, but there is little research on the quality of the ice which directly corresponds to how safe it is to venture out on

York University

Measuring lake ice — image:
York University Postdoctural Fellow Joshua Culpepper measures a block of lake ice
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Credit: Kirill Shchapov

TORONTO, Sept. 19, 2024 – Ice may look safe for a game of pick-up hockey on the lake, but as a new study out of York University found, looks can be deceiving. Warming winters are not only affecting ice thickness and timing – when a lake freezes and thaws – but also quality, making it potentially unstable and unsafe.

When lakes and rivers freeze, there are two predominant layers of ice, what’s called white ice and black ice. White ice is generally opaque, like snow, and filled with more air bubbles and smaller ice crystals, diminishing its strength and stability, while black ice is clear and dense with few air pockets and larger ice crystals making it a lot stronger.

“Ice quality is important because of its direct implications for load bearing capacity for human safety and also how much light will transmit under ice for life under frozen lakes,” says York Professor Sapna Sharma.

The problem, says lead author and York Postdoctoral Fellow Joshua Culpepper, is that the unpredictable and warmer winter weather is creating thinner layers of black ice and sometimes a corresponding thicker layer of white ice, the unstable kind. The two combined can make for treacherous conditions for skaters, hockey players, snowmobilers, ice anglers and ice truckers.

Watch Video: https://www.youtube.com/watch?v=KclNTOl8QRE

“We know that in general, lake ice is forming later in the season and breaking up earlier, which implies an overall shorter duration of ice cover, but our study looked at what the ice is doing. How is it changing? You might get periods of time when people are on the ice and they think it's safe, but it really isn't. It's not sufficiently thick enough given the changes in the quality,” says Culpepper.

10 cm no longer the golden rule

Thickness alone is no longer a good predictor of safe ice. If there is too much white ice and not enough black ice, the ice it may not be strong enough to hold a person’s weight. It’s what the researchers are calling a dangerous combination.

“For a human to go out on the ice to skate or play, that requires about 10 centimeters or four inches of black ice…but what we're seeing and what we're predicting is that climate change is contributing to more white ice conditions,” says Sharma, who recommends people measure the ice and if there is only a thin layer of black ice to double the usual recommended thickness to at least 20 cm.

“Black ice is clear and there's no slush. You shouldn't be walking over slush,” says Sharma, she adds that it’s always best to go with someone or a group.

On thin ice

The lack of consideration for quality ice is already leading to a loss of life. In Canada last December, six people, including a couple of teens in Ontario, died within a week plunging through thin ice. Two more died in Ontario this February. In Finland, four people died from falling through weak ice in January and February alone, where the average is said to be 18 people annually. In Sweden, 16 people drowned from falling through the ice in 2014 and at least nine in 2021, for example.

The findings from a 2020 study led by Sharma found widespread drowning across the Northern Hemisphere, but surprisingly, northern Canada, the territories, had the highest drownings per capita even though it was the coldest.

“That is because of the dramatic changes in the Arctic which is warming four times faster than the rest of the globe so it's not just southern regions that are experiencing these changes in ice conditions, but also far north. What you would consider to be like extremely cold icy areas,” says Sharma.

“For a transport truck, they require 100 cm or about 42 inches of black ice. So those benchmarks on transportation are no longer viable because there is more white ice, which is approximately less than half the strength of black ice. What we’re predicting is a 95 to a 99 per cent loss in winter ice road transportation infrastructure without meaningful adaptations for ice safety.”

That could mean remote communities are at risk of not being cut off and unable to access food, supplies, medicine and the like, during the winter.

Unseasonable winter weather

For this study, Culpepper and some of his co-authors had to stop taking ice measurements in mid-February on Lake Simcoe and early March on Paint Lake in the Muskoka region because the ice cover was dangerously thin.

Changes in precipitation from unseasonably warm weather is creating a lot of the unsafe ice conditions and unpredictability. Warmer temperatures, rain and even snow can alter the strength and thickness of lake ice.

Sharma and Culpepper recommend checking the weather reports for the last month.

“Lake ice has a memory,” says Sharma. “All of the weather fluctuations are stored in the ice. If the temperature was over 0 C for a period of time, if there was rain or if there were extremely sunny conditions, all of that can affect the safety of the ice for human use. When there are freeze thaw events or temperatures are above 0 C, the ice becomes weaker, and it becomes structurally less stable.”

Underneath the ice

The diminishing quality of ice is also affecting life below, the amount of nutrients available for fish and other aquatic life, such as invertebrates, as well as phytoplankton which needs light for photosynthesis, but with more white ice, it’s blocking some of that light and compromising the health of the ecosystem.

But as Culpepper says, their study is one of only a few that looks at the quality of lake ice and yet that ice is changing dramatically. “The thing that stuck out to me first is the surprising lack of data that we have on ice quality broadly,” he says. “We were diving into what data was available, but trying to find exactly what we could work with in terms of data that's available in the Northern Hemisphere was pretty challenging.”

What’s needed, he says, is regular measurements of ice quality, including black and white ice thickness, throughout the Northern Hemisphere.

The paper, Lake ice quality in a warming world, was published today in the journal Nature Reviews Earth and Environment.

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York University is a modern, multi-campus, urban university located in Toronto, Ontario. Backed by a diverse group of students, faculty, staff, alumni and partners, we bring a uniquely global perspective to help solve societal challenges, drive positive change and prepare our students for success. York's fully bilingual Glendon Campus is home to Southern Ontario's Centre of Excellence for French Language and Bilingual Postsecondary Education. York’s campuses in Costa Rica and India offer students exceptional transnational learning opportunities and innovative programs. Together, we can make things right for our communities, our planet, and our future.

A hand can be seen through a clear block of black lake ice