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 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 43, 2015 

A publication of 

The Italian Association 
of Chemical Engineering 
Online at www.aidic.it/cet 

Chief Editors: Sauro Pierucci, Jiří J. Klemeš 
Copyright © 2015, AIDIC Servizi S.r.l., 
ISBN 978-88-95608-34-1; ISSN 2283-9216                                                                               

 

Hazards of Mercury – Safety Perspectives and Measures 

Tauqeer Abbasa, Salman Nazir*b, Kjell Ivar Øvergårdb, Davide Mancac, M.I Abdul 
Mutaliba and Eakalak Khand 
aPetronas Ionic Liquid Center, Department of Chemical Engineering, Universiti Teknologi PETRONAS 
c,bHuman Factors Research Group, Buskerud and Vestfold University College – Postboks 4, 3199 Borre, Norway 
cPSE-Lab, CMIC Department “Giulio Natta” Politecnico di Milano – Piazza Leonardo da Vinci 32, 20133 Milano, Italy 
dDepartment of Civil and Environmental Engineering, North Dakota State University, Dept. # 2470, P.O. Box 6050, Fargo, 
ND 58108-6050, USA 
Salman.Nazir@hbv.no 

Mercury is one of the most hazardous contaminants emitted to the atmosphere due to its toxic effects on the 
environment and human health. Anthropogenic and geological sources account for 30 % and 10 % respectively, 
whereas the rest is from re-emissions. Consumption of fossil fuels for power generation and heating purposes 
is still the main source of anthropogenic emissions of mercury. The mercury emissions from industrial sources 
not only affect equipment and processes but are also a potential hazard for plant and operator’s safety. High 
reactivity and volatility of mercury make its capture rather difficult. Mercury in the atmosphere is in three primary 
forms i.e. elemental, inorganic and organic. Gaseous elemental mercury is the most common in anthropogenic 
and natural emissions to the atmosphere. The transport and deposition of atmospheric mercury depend greatly 
on whether it is elemental or oxidized. The global cycle of mercury is mainly controlled by oxidation–reduction 
reactions in the atmosphere and aquatic ecosystem that readily convert volatile Hg0 into soluble Hg2+ and vice 
versa. A small fraction of mercury is converted to methyl mercury by bacteria in anoxic environments. Exposures 
to mercury can affect the human nervous system and harm the brain, heart, kidneys, lungs, and immune system. 
The only way to reduce mercury pollution is to capture it from emission sources by effective technologies and 
safety measures. The paper highlights the mercury sources, which increase health hazards in Europe and Asia 
along and discusses the transport of mercury and viable preventive measures. The progress in mercury removal 
technologies is also discussed with their limitations. 
 

1. Introduction 

The rapid pace of industrialization and its by-products has been changing the environment due to hazardous 
waste discharges and poisonous gas fumes and smokes into the environment. All these by-products adversely 
affect terrestrial ecosystems, e.g., water, air, vegetation, forestry resources, and other forms of life (Dubey et 
al., 2003). The boom in world’s heavy industry has greatly increased the consumption of energy. Fossil fuels 
are still used to support more than 80 % of world energy consumption. However, one of the main concerns 
arisen from the use of fossil fuels is the emission of gases that are considered detrimental to the environment 
such as carbon dioxide, sulphur dioxide, nitrogen dioxide, unburned hydrocarbon etc. and heavy metals such 
as mercury etc. 
Mercury is a toxic, bio-accumulating trace metal whose emissions to the environment have increased 
significantly as a result of anthropogenic activities such as mining and fossil fuel combustion. It is released the 
environment either naturally or through human activities in three forms such as elemental (Hg0), oxidized (Hg2+) 
and particulate (Hgp). 
During the post-industrial era, combustion of fossil fuels combined with long-range, atmospheric transport have 
increased the mercury in soils and sediments by a factor of 3 to 10, and the global mercury emission into the 
atmosphere was reported to amount to 3,000 t in 2005 (Xu et al., 2015). A recent study (Lamborg et al., 2014) 

                                

 
 

 

 
   

                                                  
DOI: 10.3303/CET1543358 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Tauqeer A., Nazir S., Overgard K.I., Manca D., Mutaliba M.I.A., Khan E., 2015, Hazards of mercury  – safety 
perspectives and measures, Chemical Engineering Transactions, 43, 2143-2148  DOI: 10.3303/CET1543358

                                

 
 

 

 
   

                                                  
DOI: 10.3303/CET1543358 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Tauqeer A., Nazir S., Overgard K.I., Manca D., Mutaliba M.I.A., Khan E., 2015, Hazards of mercury  – safety 
perspectives and measures, Chemical Engineering Transactions, 43, 2143-2148  DOI: 10.3303/CET1543358

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reported that anthropogenic perturbations to the global mercury cycle have led to an approximately 150 % 
increase in the amount of mercury in thermocline waters and have tripled the mercury content of surface waters 
compared to pre-anthropogenic conditions. Most mercury forms are highly toxic for highly exposed humans, but 
even low exposure can seriously and adversely affect the central nervous system. The presence of mercury not 
only affects the environment but also has detrimental effects on industrial equipment. Mercury in natural gas is 
present predominantly as elemental mercury. 
Elemental Mercury forms an amalgam with the surface layer of the metal it contacts (Abbas et al., 2014). A very 
small amount of mercury is sufficient to destroy the aluminum heat exchangers often used in the cryogenic 
processes at LNG plants or naphtha crackers for olefin production. Moreover, mercury deposition in equipment 
poses a health and safety risk for workers involved in maintenance or inspection activities. Mercury in gas plant 
products affects downstream processes as well. 
The only way to reduce the mercury hazards is to deal with it by adopting proper safety and remove it from 
process streams efficiently. The paper highlights mercury emission sources in Europe and Asia, and provides 
an over view of health hazards and safety measures in mercury removal technologies. 

2. Mercury Sources 

Mercury is released by natural and anthropogenic sources throughout the world. Mercury emissions to the 
atmosphere from natural sources are estimated at about 80–600 t/y. According to UNEP (UNEP, 2013a), the 
flow of mercury through the environment suggests that natural sources account for about 10 % of the estimated 
5,500-8,900 t of mercury currently being emitted and re-emitted to the atmosphere from all sources. 
Anthropogenic sources of mercury emissions account for about 30 % of the total amount of mercury entering 
the atmosphere each year. 
Current anthropogenic sources, which include numerous industrial point sources, are estimated to release about 
1960 t of mercury on an annual basis (UNEP, 2013a). The major source regions are Asia and Africa (47.5 % 
and 16.8 % of the global total, respectively). The main sectors identified are artisanal and small scale gold 
mining, coal combustion, production of non-ferrous metals (including copper, lead, zinc, aluminum and large-
scale gold production), cement production, and disposal of wastes containing mercury (AMAP/UNEP, 2013). 
Figure 1 shows the mercury emission sources (2005-2010) in Europe and Asia. 
 

 

Figure 1: Mercury emissions sources in Asia and Europe data extracted from (UNEP, 2013a) 

Overall, coal burning is still the main source of mercury emissions in Asia and Europe. However, the trend 
continues to increase in Asia, but at the same time improvements are taking place in Europe. The reason of 
increasing mercury emissions in Asia is predominantly due to increasing energy demand and improvements in 
infrastructure that lead to more cement production, mainly in China and India. 
Strict regulations in Europe on mercury imports and slight shift towards renewable energy resources are the 
major factors in reduction of mercury emissions. The area coverage by Hg emissions depends on the chemical 
formulation of that substance. As Hg0 in gaseous form it can remain in the atmosphere for long periods (e.g., 
one year) and be transported over long distances. Conversely, as Hg2+ and Hgp mercury is short lived, resulting 

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European Union 2005 European Union 2010

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in localized deposition. For instance, in industrial areas of Europe, the deposition of mercury emissions from 
European sources constitutes up to 60 %, whereas in the Mediterranean area it is just 20 % or even less (Elsie 
M, 2013). 
Furthermore, the growing population and expansion of industrial sector will influence the increase of the demand 
for energy. Thus, in the near future, we can expect a growth in mercury emissions due to anthropogenic sources, 
such as power generation from coal and natural gas. 
 

3. Health Hazards of Mercury 

Mercury is mainly classified in three distinct forms in flue gases from coal power plants: (Hg0), (Hg2+) and (Hgp) 
(Pavlish et al., 2003). The Hg2+ and Hgp are soluble in water and hence they are deposited on a local and 
regional scale, whereas Hg0 is present in vapour phase that enables its transportation worldwide (Rao, 2010). 
As a result, most of mercury in the air is in the gaseous elemental phase. When mercury moves from air to water 
and land, it is generally in an oxidized gaseous or particulate form, whereas when it is re-emitted to air it has 
been converted back to gaseous elemental mercury. 
The pathways and fate of mercury in aquatic environments are important because it is in waters, sediments, 
and wetland soils. Usually, that inorganic form of mercury is converted into methyl mercury (MeHg) by sulfur 
reducing bacteria in anoxic environments. 
 MeHg bio accumulates in the bodies of aquatic animals, so people are exposed to it mainly by consuming 
contaminated fish and sea food. Recently, it was found that mercury is coming from human activities, including 
burning fossil fuels like coal. Mining for gold and coal, are deemed as the main drivers for the increase in the 
ocean’s mercury, causing the substance to increase by a factor of 3.4 in the ocean’s upper levels since the 
beginning of the Industrial Revolution (Lamborg et al., 2014).  
Mercury is a neurotoxin, and ingesting too much of it can cause developmental defects in foetuses and, at 
extreme levels, death. Typically, people ingest mercury by eating fish, with larger, predatory fish containing more 
mercury than smaller prey fish. However, the main exposure to methyl mercury is not only restricted to fish, but 
also to rice meals (Feng et al., 2007). 
Apart from MeHg, Hg0 vapors are also quite dangerous for humans if exposed to. In industrial settings such as 
chloralkali and power generation plants, workers and local residents are also likely be exposed to mercury 
through the respiratory tract (Li et al., 2009). In humans, approximately 80 % of mercury vapour (Hg0) is readily 
absorbed through the respiratory tract, but only 0.01 % by the gastrointestinal tract and to a limited extent via 
the skin (0.024 ng Hg/cm2 skin per 1 mg/m3 of Hg present in air) (Holmes et al., 2009). On one hand, when 
organic Hg vapors are absorbed, they get distributed to fat-rich tissues and their high lipophilicity enables the 
transfer across placental and blood-brain barriers. 
On the other hand, the inorganic forms of mercury allow reaching most human organs, but their reduced 
lipophilicity limits the ability to penetrate the blood-brain and placental barriers (Holmes et al., 2009).Figure 2 
shows the impact of mercury toxicity on various organs. 
New estimates suggest that between 1.5 and 2 million children in the Europe are born each year with MeHg 
exposures above the safe limit of 0.58 µg/g and 200,000 above the WHO’s recommended maximum of 2.5µg/g 
(Bellanger et al., 2013). Figure 3 shows detailed facts on the number of annual births having excess Hg levels 
in different European countries with MeHg exposure distributions. 

4. Safety measures for dealing Hg Hazards  

As aforementioned that the most efficient method of removal of Hg is to eliminate it from the source. At the same 
time, the awareness of the hazards of Hg can play an important role in the mitigation process into the 
biogeochemical cycle (UNEP, 2013b). Advanced training methods (see for instance Nazir et al. (2012)) can be 
used to improve the understanding, knowledge, and awareness of specific operators dealing with Hg. To reach 
an optimal point between investments on Hg related Hazards and overall profitability, it is essential to involve 
decision/policy makers. An overview of mercury removal methods is provided in the following section. 

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Figure 2: Impact of mercury toxicity on organ systems (modified from (Zahir et al., 2005)and (Bose-O’Reilly et 
al., 2010)) with permission from Elsevier, 2014 

 

Figure 3: Annual number of births with excess (>0.58 μg/g) Hg exposure in Europe, data extracted from 
(Bellanger et al., 2013) 

5. Mercury Removal Technologies 

As discussed above, fossil fuels are being used mostly for energy generation, thus emitting mercury to the 
atmosphere. Hg0 is mainly present in flue gases of coal power plants ((others: Hg2+ and Hgp) and natural gas 
((others: Hg2+). However in crude oil and condensate, organic mercury is mainly present. Virgin activated 

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carbon, sulfur, chloride, iodine and brominated carbons are being used to capture mercury from emission 
sources (Yang et al., 2007). Furthermore, a number of technologies and products, which meet the specifications 
for down- stream processing, are commercially available. However, not all systems are capable to treat the full 
range of mercury emissions in a single action (Mahpuzah et al., 2011). The limitations of some of mercury 
removal technologies are summarized in Table 1 (Abbas et al., 2014). 
 
Table 1: Mercury removal systems with their limitations 

Mercury Removal Systems Limitations 
Adsorption on activated carbon Low saturation loading but cheap, disposal problem and cant remove

all types of mercury in one step 
Sulfur impregnated carbon Less efficient and lose of sulfur in contact with liquid hydrocarbons 
Adsorption on molecular sieve Common sieves have low capacity; big beds 
Adsorption on metal sulphide 
impregnated on mesoporous 
Alumina 

Low resistance to both capillary condensation and liquid carry-over, 
only capable to remove elemental mercury 

Adsorption by amalgamation with a 
metal such as aluminium, silver 
Zeolites etc. 

High investment cost, lower capacities 

Oxidising solutions- potassium 
permanganate, sodium hypochlorite,
and sodium vanadate 

Regeneration problems; system contamination 

Acid absorption of mercury-acidic 
permanganate and chromic acid 

Increased corrosion, low saturations, system contamination 

Condensation and separation Poor removal efficiency, liquid contamination 

 
Abu Daabes (Abu-Daabes, 2005) synthesized and evaluated chelating adsorbents to remove oxidized mercury 
from flue gas. Moreover, it is also proven that ionic liquids, particularly solid supported ionic liquids (SSILs), can 
capture different  types of mercury in a single step more efficiently than other techniques (Mahpuzah et al., 
2011). Ji and coauthors (Ji et al., 2008) used a ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethane 
sulfonyl) imide (P14), as a coating on both a silica substrate and on a chelating adsorbent, for the capture of 
elemental mercury from flue gas at 160 °C. Fixed-bed experiments done using P14 and P14-KMnO4 ionic liquids 
coated adsorbents showed high capacity for the capture of vapor phase elemental mercury. P14-KMnO4 coated 
based adsorbents showed a capacity to capture elemental mercury greater than 7.2 mg/g due to their ability to 
oxidize Hg0 (Ji et al., 2008). Silica coated with 1-butyl 3-methyl imidazolium chloride showed 10mg/g and 38mg/g 
of adsorption capacity for Hg0 and Hg2+ respectively (Ji et al., 2008). SSILs can adsorb mercury three times 
more than other commercially available adsorbents from natural gas even without modifications of the plant 
infrastructure (Mahpuzah et al., 2011). First author found in his experiment that carbon supported ionic liquids 
are more promising than silica supported ionic liquids, it will definitely help to reduce the adsorbent cost for its 
practical application on large scale. The research is in progress to understand the mechanism of mercury 
adsorption on carbon supported ionic liquids that will help to further improve the efficiency. 

6. Conclusions 

The hazards of mercury were illustrated with help of recent literature and some statistics. In spite of the 
limitations of existing removal methods, it is necessary to integrate the safety awareness of mercury in the 
industry as well as for those who may get exposed to it. The immediate way to reduce mercury pollution is to 
capture it efficiently from anthropogenic sources especially from power plants. SSILs have proven better ability 
to remove mercury from process streams efficiently in a single step. Future studies and investigations are 
required to understand the mercury adsorption mechanism on SSILs, it will surely help researchers to come up 
with best pair of ionic liquids and solid support. 

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removal of mercury vapor from flue-gases. University of Cincinnati. 

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