Poisonous heavy metals contaminating thousands of sites nationwide threaten to enter the food chain, and there’s been no easy way to remove them. An experimental chemical bath and electrochemical filter could now extract heavy metals from the soil and leave fields safe.
When poisonous heavy metals like lead and cadmium escape from factories or mines, they can pollute the nearby soil. With no easy ways to remove these contaminants, fields must be cordoned off to prevent these toxins from entering the food chain where they threaten human and animal health.
According to the Environmental Protection Agency, heavy metals have been found at thousands of locations nationwide. While some have been cleaned up through a combination of federal, state and private efforts, the need remains for new technologies to address heavy metal contamination.
Now a research team led by Stanford materials scientist Yi Cui has invented a way to wash heavy metals from contaminated soils using a chemical process that’s a bit like brewing coffee.
As they describe June 4 in Nature Communications, the researchers started by rinsing contaminated soil with a mixture of water and a chemical that attracts heavy metals. When that mixture percolates through the soil, the chemical pulls heavy metals loose. The team members then collected this toxic brew and ran it through an electrochemical filter that captured the heavy metals out of the water. In this way they cleansed the soil of heavy metals and recycled the water and chemical mixture to percolate through more contaminated ground.
“This is a new approach to soil cleanup,” said Cui, who is a professor of materials science and engineering and photon science. “Our next step is a pilot test to make sure that what works in the lab is practical in the field, and to figure out how much this process will cost.”
So far, his team has cleansed soils contaminated with lead and cadmium, two prevalent and dangerous toxins, as well as with copper, which is only dangerous in high concentrations. Cui believes this process of chemical cleansing and electrochemical filtering will work with other dangerous heavy metals like mercury and chromium, but further lab experiments are needed to demonstrate that.
No more sacrificial plants
Cui said the project began two years ago when he and graduate student Jinwei Xu brainstormed about how to solve the basic problem: Heavy metals bind to the soil and become virtually inextricable. Today, Cui said, cleanup may involve digging up contaminated soils and sequestering them somewhere. Agricultural researchers have also developed phytoremediation techniques – growing sacrificial plants in contaminated soil to absorb heavy metals, then harvesting these crops and taking them to an extraction and disposal facility. But phytoremediation can take many years of repeated harvests.
Seeking a quick, cost-effective way to extract heavy metals from contaminated fields, the researchers tried washing toxic soil samples with plain water. They soon realized that plain water couldn’t break the chemical bond between the heavy metals and the soil. They needed some additive to pry the contaminants loose. They found the answer in a common chemical known by its initials: EDTA.
In retrospect, EDTA was the obvious choice because this same chemical is used to treat patients poisoned with lead or mercury. Negatively charged EDTA bonds so strongly to positively charged heavy metal particles that it pulls the lead or mercury from the patient’s tissues. The researchers reasoned that, when dissolved in water, EDTA’s negative hooks would rip heavy metals loose from soils. Experiments bore this out. When EDTA-treated water percolated through contaminated soil, it carried the heavy metals away.
But the team’s job was only half done. The soil was clean, but the treated water was still toxic. They needed a way to separate the EDTA from the heavy metals in the rinse water and capture those toxins once and for all.
Isolating heavy metals
The scientists knew that EDTA remained strongly negative even after it captured a positively charged metal particle. So, the researchers built a sieve with the electrical and chemical properties to pull the negatively charged EDTA and positively charged heavy metals apart. The result was isolated heavy metals and a mixture of water and EDTA ready to purify more soil.
In addition to lead and cadmium, the researchers tested the process on copper, which is only dangerous in high concentrations. Next Cui would like to run the experiment on other heavy metals like mercury, which are so toxic they require special handling to protect the researchers. But he thinks the chemistry is so sound that he is confident of success in the lab. The bigger question is whether the process can be scaled up to treat tons of contaminated soil. The researchers have sought to patent the process through the Stanford Office of Technology Licensing and would like to find an opportunity to run a pilot project in a contaminated field.
“We really have no good remediation technology for heavy metals,” Cui said. “If this proves practical on a large scale it will be a significant advance.”
The Latest on: Heavy metals
via Google News
The Latest on: Heavy metals
- "Disillusioned" bassist Hietala leaving metal band Nightwishon January 12, 2021 at 7:14 am
The bassist and vocalist cited his own depression as well as disappointment in the music industry's corporate demands.
- Exciting times for efficient, heavy-atom-free OLEDson January 12, 2021 at 6:30 am
Organic light-emitting diode (OLED) displays are now very popular features of many mainstream products including smartphones and televisions. OLEDs have the advantages of being low cost, light, ...
- 10 Greatest Debut Albums In Metalon January 12, 2021 at 5:47 am
Hitting the ground running, Mercyful Fate's debut on Melissa was everything you could have possibly wanted in a metal release. Being a straightforward rock affair, this record introduced the world to ...
- ExOne Launches Online Calculator for Manufacturers to Quickly Compare the Cost of Metal 3D Printing for Productionon January 12, 2021 at 5:07 am
The new ExOne Production Metal Cost Calculator provides manufacturers with a per-part estimate for binder jet 3D printing a precision metal part, so the technology can easily be compared to other ...
- What covering heavy metal taught me about spotting Nazison January 12, 2021 at 4:04 am
For the uninitiated, black metal is a subgenre of heavy metal music distinguished by its aggression, over-the-top theatricality, and affinity for the occult, as well as its unfortunate history as a ...
- Marsha Zazula, metal pioneer who co-discovered Metallica and Anthrax, has diedon January 11, 2021 at 10:56 am
Marsha and Jonny Zazula co-founded a new era in heavy metal music as heads of Megaforce Records in East Brunswick, New Jersey.
- Marsha Zazula, Co-Founder of Iconic Metal Label Megaforce Records, Dies at 68on January 10, 2021 at 1:06 pm
Marsha Zazula, the co-founder of metal label Megaforce Records, has died. She was 68. "No man can ask for a partner like Marsha Zazula, someone who would stand by your side, support you, and believe ...
- Black Sabbath fans furious as ‘heavy metal expert’ Joel Dommett gets questions wrong on Michael McIntyre’s The Wheelon January 9, 2021 at 2:56 pm
Fans of Michael McIntyre’s The Wheel were left shocked as Joel Dommett managed to get most of his questions on his specialist subject of heavy metal wrong. Joel had taken his seat on The Wheel to ...
- Heavy metal loving graphic designer sets up wealth redistribution website to help Indonesians hit by COVID-19on January 9, 2021 at 2:09 pm
JAKARTA: When COVID-19 hit Indonesia in March last year, graphic designer Lody Andrian could not help but feel sorry for his friends affected by ...
- Heavy Metals Found In High Levels In Sharkson January 8, 2021 at 12:39 pm
ALARMINGLY high levels of 12 heavy metals, including mercury, have been found in the muscle tissues of large reef and tiger sharks in The Bahamas. # Researchers from the non-profit organisation ...
via Bing News