How mercury emissions from industry can be greatly reduced

Date:
July 4, 2023
Source:
Chalmers University of Technology
Summary:
Sulphuric acid is the world's most used chemical. It is an important
reagent used in many industries and it is used in the manufacture of
everything from paper, pharmaceuticals and cosmetics to batteries,
detergents and fertilizers. It is therefore a worldwide challenge
that sulphuric acid often contains one of the most toxic substances
- - mercury. Researchers have now developed a method that can reduce
the levels of mercury in sulphuric acid by more than 90 per cent --
even from low levels.


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FULL STORY ========================================================================== Sulphuric acid is the world's most used chemical. It is an important
reagent used in many industries and it is used in the manufacture of
everything from paper, pharmaceuticals and cosmetics to batteries,
detergents and fertilisers.

It is therefore a worldwide challenge that sulphuric acid often contains
one of the most toxic substances -- mercury. Researchers at Chalmers
University of Technology, Sweden, have now developed a method that can
reduce the levels of mercury in sulphuric acid by more than 90 per cent --
even from low levels.

"Until now, there has been no viable method for purifying finished
sulphuric acid at all. With such a radical reduction in the mercury
content, we come well below the current limit values. Such pure high
quality sulphuric acid is in high demand in industrial applications
and an important step in reducing environmental impact," says research
leader Bjo"rn Wickman, Associate Professor at the Department of Physics
at Chalmers.

Sulphuric acid is produced either from sulphur from the petroleum
industry or as a by-product in the mining industry's smelters. In the
latter case, mercury, which is naturally present in the ore, can end up
in the finished products.

Also recycled streams in the smelters can contain mercury.

Toxic emissions that affect all life on Earth Mercury dispersal is a
worldwide problem, as the substance is volatile and can be dispersed
by air over large areas. This toxic heavy metal is then washed into
streams and lakes when it rains. It is stored in the soil, water and
living organisms, impacting the entire food chain. It can damage the
brains and central nervous systems of humans and animals.

According to a report from the United Nations Environment Programme
(UNEP), emissions of mercury to the atmosphere increased by an estimated
20 per cent from 2010 to 2015. In 2015, about 2,200 tonnes of mercury
were emitted into the air as a result of human activities such as cement manufacture, small-scale gold mining, coal burning, metal production
and other manufacturing industries.

In addition, an estimated 1,800 tonnes of mercury ended up in the soil and water in that same year. According to the report, mercury concentrations
in the atmosphere may have increased by 450 per cent in the last century.

"Any and all ways we can reduce mercury emissions are good, because any
mercury that is emitted accumulates in the environment and continues to
pose a health threat for thousands of years," says Wickman.

Captures the metal using electrochemistry Five years ago, his research
team at Chalmers presented a pioneering method for removing mercury from
water using electrochemical processes. The method is based on a metal
electrode taking up the toxic metal and forming an alloy. The mercury can
then be safely removed, and the electrode reused. Now the researchers
have taken this technology one step further, and in a new study they
have shown how mercury can be removed from concentrated sulphuric acid.

The experiments with sulphuric acid were done in collaboration with
mining and metals refining company Boliden and the company Atium, a
spin-off from the Chalmers School of Entrepreneurship with the aim of
bringing the removal of mercury from water and chemicals to market. The researchers now hope to be able to move forward with their partners and
develop a type of reactor through which sulphuric acid can flow and be
purified at the same time.

Potential to reduce costs and environmental impact Today, mercury is
mostly removed at an earlier stage -- from the concentrates and recycled streams at the smelter before sulphuric acid is produced. This is an established process, but leaves trace amounts of mercury into final
products.

"Purifying the sulphuric acid as well prevents additional mercury
emissions, while allowing industry to operate more cost-effectively and
produce a high- purity, non-toxic product. The next step will be to scale
up the method into a pilot process that is closer to real-world volumes
of thousands of tonnes," says Vera Roth, doctoral student at Chalmers
and first author of the recently published article in the journal ACS
ES&T Engineering.

Hoping for lower limit values According to the Statista database, the
worldwide market volume for sulphuric acid amounts to around 260 million
tonnes per year. By 2029, this figure is expected to rise to 314 million tonnes. The lower the mercury content of the sulphuric acid, the more
valuable it is. Sulphuric acid for commercial purposes is considered to be
of acceptable quality when its mercury content is below 0.30 milligrams
per kilogram. If the content is below 0.08 milligrams per kilogram, the sulphuric acid is considered to have a high purity. With the new method,
the researchers have reduced the level of mercury to 0.02 milligrams
per kilogram of sulphuric acid in their pilot study.

"The limit values for how much mercury sulphuric acid may contain
are based on the technology available today. With the new method for
purifying sulphuric acid, our hope is that the legislation around the
limit values will be tightened in a global perspective where mercury
levels are generally much higher," says Wickman.

Caption: Sulphuric acid is an important industrial chemical, but it often contains one of the world's most toxic substances: the volatile heavy
metal mercury, which can pollute both the air and water. Researchers
at Chalmers University of Technology have shown that it is possible
to reduce the levels of mercury in sulphuric acid by more than 90 per
cent -- even from low levels. The study was conducted in collaboration
with the spin-off company Atium and mining and metals refining company
Boliden. Image:Boliden/Unsplash, Nazrin Babashova More information about
the method and the study
* The purification method removes mercury from the sulphuric acid by
ionising the mercury and its ions forming an alloy with another
metal. An electrode with a platinum surface binds the mercury
to itself electrochemically. It then takes up the toxic mercury
and forms an alloy of the two metals. It is then possible to
remove the mercury and regenerate the electrode in a controlled
way. This means that the electrode can be reused, and the toxic
substance can be safely disposed of. The process is also highly
energy-efficient. In an episode of the program UR Samtiden from
the Swedish Educational Broadcasting Company (UR), Bjo"rn Wickman
demonstrates how the method works for removing mercury from water.

* The article Mercury Removal from Concentrated Sulfuric Acid by
Electrochemical Alloy Formation on Platinum is published in
the scientific journal ACS ES&T Engineering and was authored
by Vera Roth, Julia Ja"rlebark, Alexander Ahrnens, Jens Nyberg,
Justin Salminen, Teodora Retegan Vollmer and Bjo"rn Wickman. The
authors are active at the Department of Physics and the Department
of Chemistry and Chemical Engineering at Chalmers University of
Technology, at Atium, and at Boliden.

* Sulphuric acid is the world's most used chemical. It is an important
reagent used in many industries and it is used in the manufacture
of everything from chemicals, paper, pharmaceuticals and cosmetics
to batteries, detergents and fertilisers. It is an ingredient also
for many recycling processes contributing into circular economy
and extractive metallurgy.

* The experiments in the study were performed in a lab environment,
in a 50
millilitre beaker and subsequently in a 20 litre reactor. The
next step will be to scale up the method into a pilot project
that is closer to the actual volumes that are usual in industrial
applications.

* The research was funded by Formas and by the strategic innovation
programme Swedish Mining Innovation -- a joint venture involving
Vinnova, Formas and the Swedish Energy Agency.

More about heavy metals in the environment
* Heavy metals in water and watercourses are an enormous environmental
problem that affects the health of millions of people
worldwide. Heavy metals are toxic to all living organisms and
accumulate in the food chain. According to the World Health
Organization, mercury is one of the most harmful substances to
human health. Among other things, it affects our nervous system
and the brain's development. The substance is therefore especially
dangerous for children and foetuses.

* Today, there are strict regulations governing the handling of
toxic heavy
metals to prevent their dispersal in the natural
environment. However, there are plenty of places that have already
been contaminated or are affected by the deposition of airborne
mercury that may have come from other countries. As a result,
there are areas in our natural environment where the amounts of
heavy metals have reached toxic concentrations. For example, high
levels of mercury in freshwater fish is a well-known environmental
problem. Even in Sweden heavy metal pollution is a serious problem,
and the fish in the majority of the lakes contain more mercury
than the limit value. In industries where heavy metals are used,
as well as in recycling, wastewater treatment and decontamination,
there is a great need for new and better methods for removing
toxic heavy metals from water.

* RELATED_TOPICS
o Matter_&_Energy
# Inorganic_Chemistry # Chemistry # Energy_and_Resources
o Earth_&_Climate
# Environmental_Science # Hazardous_Waste # Acid_Rain
o Science_&_Society
# Environmental_Policies # Resource_Shortage #
World_Development
* RELATED_TERMS
o Acid o Mercury_(element) o Mercury_poisoning o
Hydrochloric_acid o Acid_rain o Fatty_acid o Citric_acid o Lead

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========================================================================== Journal Reference:
1. Vera Roth, Julia Ja"rlebark, Alexander Ahrnens, Jens Nyberg, Justin
Salminen, Teodora Retegan Vollmer, Bjo"rn Wickman. Mercury Removal
from Concentrated Sulfuric Acid by Electrochemical Alloy Formation
on Platinum. ACS ES&T Engineering, 2023; 3 (6): 823 DOI: 10.1021/
acsestengg.2c00417 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230704110915.htm

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