Shungite application for treatment of drinking water – is it the right choice?

Abstract

Shungite is a natural carbon containing material that is widely used in water treatment. Scientific research shows that shungite has good adsorption properties towards various organic compounds and heavy metals, as well as exhibiting antibacterial properties. Unfortunately, at the same time shungite releases various chemical elements into the water, including heavy metals. In this study changes in concentration of various heavy metals during drinking water treatment with one commercial and one non-commercial shungite sample were determined. Also sorption of Cu(II) with initial concentration of 2,500 μg/L onto shungite was investigated. The results showed that various heavy metals like nickel, copper, lead, cadmium, zinc, chromium and arsenic are leaching from shungite into water. Lead and cadmium exceeded the maximum acceptable concentration in drinking water for a few days, but nickel exceeded for up to 2 weeks. At the same time shungite showed good adsorption properties towards copper. Nevertheless, before using shungite in drinking water treatment, it would be advisable to assess the necessity and/or wash shungite with larger volumes of water for a longer period of time than is written in the instructions.

Full text

Shungite application for treatment of drinking water –is it
the right choice?
Inga Jurgelane and Janis Locs
ABSTRACT
Shungite is a natural carbon containing material that is widely used in water treatment. Scientific
research shows that shungite has good adsorption properties towards various organic compounds
and heavy metals, as well as exhibiting antibacterial properties. Unfortunately, at the same time
shungite releases various chemical elements into the water, including heavy metals. In this study
changes in concentration of various heavy metals during drinking water treatment with one
commercial and one non-commercial shungite sample were determined. Also sorption of Cu(II) with
initial concentration of 2,500 μg/L onto shungite was investigated. The results showed that various
heavy metals like nickel, copper, lead, cadmium, zinc, chromium and arsenic are leaching from
shungite into water. Lead and cadmium exceeded the maximum acceptable concentration in
drinking water for a few days, but nickel exceeded for up to 2 weeks. At the same time shungite
showed good adsorption properties towards copper. Nevertheless, before using shungite in drinking
water treatment, it would be advisable to assess the necessity and/or wash shungite with larger
volumes of water for a longer period of time than is written in the instructions.
Key words |adsorption, heavy metals, release, shungite, water treatment
HIGHLIGHTS
•Drinking water was treated with two shungite samples based on the application instructions of
the used commercial shungite sample.
•Both shungite samples released various heavy metals like nickel, copper, lead, cadmium, zinc,
chromium and arsenic.
•The released nickel exceeded the maximum acceptable concentration in drinking water up to 2
weeks but lead and cadmium for a few days.
Inga Jurgelane (corresponding author)
Janis Locs
Rudolfs Cimdins Riga Biomaterials Innovations and
Development Centre of RTU, Institute of General
Chemical Engineering, Faculty of Materials
Science and Applied Chemistry,
Riga Technical University,
Pulka 3, Riga LV-1007,
Latvia
E-mail: inga.jurgelane@rtu.lv
INTRODUCTION
Shungite is a natural mineraloid that contains non-
crystalline carbon. There are five types of shungite, classified
by carbon content. Type I shungite contains more than
98 mass% of glass-like carbon, type II contains 35–80 mass%,
type III 20–35 mass%, type IV 10–20 mass%, but type V
contains <10 mass% of carbon. Type III shungite is the
most widespread and the largest shungite deposits are
located in Karelia region, Russia (Melezhika et al. ;
Mosin & Ignatov ;Sineva ). In addition to carbon,
shungite usually contains quartz, aluminosilicates, feldspars
and carbonates. Also, various micro impurities can be found
in shungite: Fe, Ni, Cu Zn and V, mainly as sulphides,
This is an Open Access article distributed under the terms of the Creative
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89 © 2021 The Authors Journal of Water and Health |19.1 |2021
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sulphates and oxides (Charykova et al. ;Rafienko &
Belimenko ). Charykova et al. ()showed that in
addition to these micro impurities type III shungite also con-
tained Cr, Co, Pb and Mn.
There are a large number of patents on shungite appli-
cation for drinking water treatment (more than 100 results
revealed in the patent search engine https://worldwide.espa-
cenet.com with search keywords ‘shungite’and ‘drinking
water’) and a wide range of commercial shungite products
for water treatment at home are also available (Karelian
Heritage ). Information on most of these products
claims that shungite removes bad taste and odour, organic
compounds, heavy metals and bacteria and enriches water
with microelements. Indeed, studies show that shungite
has good adsorption properties towards various organic
compounds (Kalsina & Berjoza ;Sineva et al. ;
Skorobogatov et al. ) and also antibacterial properties
(Charykova et al. ). Fischer et al. ()concluded
that low-carbon shungite (total carbon content 5.4%)
could be used as an alternative adsorbent for Zn(II) removal
from water. Efremova ()showed that porous sorbent
prepared from shungite rock can adsorb Cd(II), Pb(II),
Zn(II) and Mn(II) in dynamic conditions. Nevertheless,
Charykova et al. ()showed that a large number of
chemical elements are leaching from shungite into water,
including several heavy metals like Cd, Cr, Cu, Ni, Pb and
Zn. After 3 days of shungite contact with tap water, many
elements exceeded the maximum acceptable concentration
in drinking water. The authors suggested that the increased
concentrations of some heavy metals could be the reason for
the antibacterial properties of ‘shungite water’(Charykova
et al. ). Some of the elements in large quantities are
toxic for humans, therefore in the few websites about shun-
gite it is written that it is advisable to drink just one or two
glasses of ‘shungite water’due to the presence of heavy
metals.
The aim of this study was to determine the changes in
concentration of various heavy metals (Ni, Pb, Zn, Cd, Cu,
Cr, As, Al) during the application process of drinking
water treatment with one commercial and one non-commer-
cial shungite sample. As Cu(II) can still be found in drinking
water due to corrosion of copper pipes, the sorption of arti-
ficially increased concentrations of copper ions in drinking
water was also investigated.
MATERIALS AND METHODS
Materials
Two shungite samples with particle sizes in the range of
1–3 mm were used. Sample Com is a commercial product
‘ШУНГИТ PREMIUM’for water purification at home
(ШУНГИТ PREMIUM КЛАССА ) and sample SH is
from the fields of Karelia region (Russia). For all experiments
Evian
®
natural spring water was used as model of drinking
water (in further text –water). Copper sulphate monohydrate
(98%) was purchased from Sigma-Aldrich (St. Louis, MO).
Characterization of shungite samples
Specific surface area (SSA) was determined by nitrogen gas
adsorption performed with QuadraSorb SI (Quantachrome
Instruments, Boynton Beach, Florida). SSA was calculated
according to the BET method. Before the analysis all
samples were degassed at 300 C for 3 h.
Carbon content was determined by an element analyzer
Vario Macro CHNS (Elementar Analysensysteme GmbH,
Germany).
Preparation of ‘shungite water’
The procedure was based on the application instruction
inside of the commercial shungite package. The first step
written in the instruction is to wash shungite several times
with water. Therefore, 10 g of shungite was poured in a
beaker, agitated with 200 mL of water for 2 min and then
decanted. This procedure was repeated five times. The last
decanted water was free from shungite dust particles. The
first decanted water was filtered and used for chemical
analysis (sample SH-1x and Com-1x). The procedure for
sample preparation is shown in Figure 1. The washed shun-
gite samples were mixed with 100 mL of water (shungite:
water mass ratio was 1:10) and left still. According to the
instructions, after 2–3 days the water is ready for use and
every time a certain amount of water is removed for appli-
cation, the same amount of untreated water is added to
shungite. Therefore, on the third day 50 mL of water was
removed from the container and the same amount (50 mL)
of fresh water was poured back on the shungite. This
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procedure was repeated every day for the next 14 days. The
container with shungite and water was stirred for a few
seconds once every day. The chemical analysis was per-
formed for samples removed on the 3rd, 5th, 7th, 11th and
14th day of the experiment.
Adsorption of copper
The initial concentration of Cu(II) ions in water was 2,500 μg/
L, which is slightly higher than the maximum acceptable con-
centration in drinking water (2,000 μg/L) according to the
Council Directive 98/83EC. The procedure for the adsorption
experiment was equivalent to the preparation of ‘shungite
water’described above and shown in Figure 1.Chemical
analysis was performed for samples removed on the 3rd, 5th,
7th, 11th, 14th, 17th and 21st day of the experiment.
Analysis of water and ‘shungite water’
The chemical analysis of samples was conducted at the Lat-
vian Environment, Geology and Meteorology Centre. The
concentration of Ni, Pb, Cd, As and Cr was determined
according to ISO 15586:2003 standard using an electrother-
mal atomic absorption spectrometer Varian SpectrAA 880Z
(Varian, Palo Alto, California). The concentration of Zn, Cu
and Fe was determined according to ISO 8288:1986, Ca and
Mg according to ISO 7980:2000, Al according to ISO
12020:2005 and K according to ISO 9964-3:1993 standards
using a flame atomic absorption spectrometer Varian Spec-
trAA 880 (Varian, Palo Alto, California). Only those results
equal to or higher than the quantification limit (QL) are
shown with the expanded uncertainty (±) with 95% confi-
dence level. The results which were below the method
detection limit (MDL) are marked with ‘<’. For each
element, QL and MDL can be different.
Total organic carbon (TOC) and dissolved organic
carbon (DOC) analysis were performed for water samples
after the 3rd and 5th day of contact with shungite. The
samples were prepared due to LVS EN 1484:2000 standard
and analysed with FORMACS
HT
TOC/TN Analyzer (Skalar,
Breda, The Netherlands).
RESULTS AND DISCUSSION
Release of heavy metals
Shungite SH has slightly higher carbon content but six times
lower SSA than shungite Com (Table 1) which can lead to
lower sorption properties. According to the shungite classi-
fication in Melezhika et al. (), SH belongs to type-II
but Com to type-III shungite.
The results in Table 2 show that after the first washing
(2 min of contact with shungite) the concentration of heavy
metalslikeNi,Cu,ZnandCdissignificantly increased. The
highest increase can be observed for nickel from both samples.
From these results we can conclude that these heavy metals
arereleasedinhighconcentrationsinwaterandthewashing
procedure is mandatory not just to remove the small particles
(dust), but also to get rid of heavy metals to avoid contami-
nation of the drinking water intended for consumption.
Figure 1 |Procedure of preparation of ‘shungite water’samples (1) and samples for adsorption experiments of copper (2).
Table 1 |Carbon content and SSA of shungite samples
Sample Carbon content, % SSA, m
2
/g
SH 39.3 ±0.4 1.3 ±0.1
Com 31.6 ±0.3 7.9 ±0.2
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Table 3 shows that after 3 days in contact with both
washed shungite samples, the water contained increased
levels of Ni, Cu, Pb, Cd, Zn and As, compared to pure
water (Table 2). However, only nickel, cadmium and lead
(for sample SH) exceeded the maximum acceptable concen-
tration (MAC) in drinking water (Table 4). On the 5th day of
exposure, the concentrations of released heavy metals had
decreased rapidly and were below MAC, except for nickel.
Similar results were obtained for water with increased
copper concentration after exposure to shungite (Table 5).
Here, after 3 days the water also contained increased
levels of several heavy metals (Ni, Cu, Pb, Cd, Zn and Cr),
where only cadmium and nickel exceeded MAC, but on
the 5th day of exposure only nickel exceeded MAC. Com-
pared with pure water, the increase of Ca, Mg, Na, K and
As is negligible and does not exceed MAC.
Table 4 |Maximum permissible concentrations of heavy metals (MAC)
Element
Maximum acceptable
concentration in drinking
water (Council Directive
98/83EC), μg/L
Tolerable intake level stated by
European Food Safety Authority
(EFSA)
Nickel 20 2.8 μg/kg of body weight
per day (EFSA CONTAM
)
Copper 2,000 for adults 1.3 (women) and
1.6 (men) mg/day (EFSA
NDA )
Lead 10 NA (EFSA a)
Zinc NI (5000
a
) for adults 7.5–16.3 mg/day
(depends on gender and
phytate intake) (EFSA
NDA a)
Cadmium 5 2.5 μg/kg body weight per
week (EFSA b)
Chromium 50 NA (EFSA NDA b)
Arsenic 10 NA (EFSA CONTAM )
NA, not applicable; NI, not indicated.
a
EPA (2018).
Table 5 |Concentration of heavy metals (copper not shown) in water with increased
copper concentration after exposure to shungite (elements exceeding MAC
are underlined)
Element
SH Com
3rd day 5th day 3rd day 5th day
Ni, μg/L 283 ±28 212 ±30 400 ±40 225 ±32
Pb, μg/L 2.1 ±0.2 2.8 ±0.5 3.3 ±0.3 0.8
Zn, μg/L 290 ±70 26 910 ±210 43 ±8
Cd, μg/L 7.6 ±1.7 1.5 ±0.3 10 ±2 0.9 ±0.2
Cr, μg/L 0.5 ±0.1 <0.2 0.5 ±0.1 <0.2
As, μg/L <0.2 <0.2 <0.2 <0.2
Table 2 |Chemical elements in water before and after the first washing of shungite
Element (MDL; QL) Water SH-1x Com-1x
Ni (1.2; 4), μg/L <0.9 660 ±60 175 ±16
Cu (0.3; 0.9), μg/L 0.3 36 ±535±5
Pb (0.4; 2), μg/L 0.4 1.1 1.0
Zn (10; 30), μg/L 13 153 ±29 36 ±7
Cd (0.02; 0.05), μg/L <0.007 3.5 ±0.6 1.0 ±0.2
Cr (0.2; 0.5), μg/L <0.2 0.3 0.3
As (0.2; 0.6), μg/L <0.2 0.4 0.3
Al (1; 3), mg/L <1<1<1
Ca (0.2; 0.6), mg/L 69 ±10 76 ±11 72 ±10
Mg (0.1; 0.4), mg/L 26 ±227±226±2
Fe (0.04; 0.15), mg/L <0.04 <0.04 <0.04
Na (0.2; 0.5), mg/L 5.4 ±0.3 5.9 ±0.4 5.7 ±0.3
K (0.1; 0.4), mg/L 1.0 ±0.1 1.1 ±0.1 1.3 ±0.1
Table 3 |Concentration of various metals in water after shungite treatment (elements
exceeding MAC are underlined)
Element
SH Com
3rd day 5th day 3rd day 5th day
Ni, μg/L 880 ±80 58 ±6 1700 ±150 60 ±6
Cu, μg/L 4.3 ±0.6 <0.3 33 ±4 0.8
Pb, μg/L 211 ±17 <0.5 5.0 ±0.4 1.1
Zn, μg/L 129 ±25 <10 900 ±170 <10
Cd, μg/L 5.0 ±0.9 0.022 11 ±2 0.16 ±0.04
Cr, μg/L 0.25 <0.2 <0.2 <0.2
As, μg/L 0.6 ±0.1 0.4 0.3 <0.2
Al, mg/L <1ND<1ND
Ca, mg/L 76 ±11 ND 81 ±11 ND
Mg, mg/L 31 ±2ND 38±3ND
Fe, mg/L <0.04 ND <0.04 ND
Na, mg/L 6.1 ±0.4 ND 6.1 ±0.4 ND
K, mg/L 2.5 ±0.3 ND 2.0 ±0.2 ND
ND, not determined.
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Based on the experimental procedure (Figure 1), every
day (starting from the 3rd day) 50 mL of the water exposed
to shungite was replaced with 50 mL of fresh water, there-
fore the concentration of heavy metals was diluted twice
each day. For example, in Table 3, on the 3rd day the
nickel concentration was 880 μg/L and if we assume that
during the next 2 days shungite was not releasing nickel,
the concentration on the fifth day should be 220 μg/L, but
the analysis showed four times lower concentration
(58 μg/L). The same observation was found for copper,
lead, zinc and cadmium. We believe that most likely this
could be explained by precipitation of salts due to various
anions released from shungite in the water, such as sul-
phates, sulphides and carbonates (Turkayeva et al. ;
Rafienko & Belimenko ). Another possible reason
could be shungite adsorbing back some part of the released
metals due to the fact that shungite contains and releases
organic matter that was measured as TOC and DOC
(Table 6). Organic matter and DOC forms complexes with
metal ions, thereby affecting the adsorption/desorption pro-
cess (Khokhotva & Waara ). The pH of Evian water was
7.5 and after exposure to shungite the pH of water samples
was in the range of 7.1–7.6, therefore the changes in nickel,
copper, lead, zinc and cadmium concentration cannot be
connected to precipitation due to pH. In Table 5 this rapid
concentration decrease is observed only for zinc and
cadmium.
Furthermore, the concentration of nickel in water was
determined for several weeks throughout all experiments
(Figure 2). Figure 2(a) shows the nickel concentration in
pure water after exposure to shungite and Figure 2(b)
shows the nickel concentration in the experiment with
water containing artificially added copper. If we compare
both these experiments, the released amount of nickel in
water is different for each shungite sample, especially after
the first 3 days of exposure. On the one hand this could be
affected by the inhomogeneous distribution of soluble
nickel compounds, due to the natural origin of shungite.
On the other hand, it could be connected to the presence
of additional copper (Figure 2(b)) that caused a more gra-
dual nickel release from shungite. According to the
application instructions of Com, shungite should be changed
after six months of application, meaning that every six
months for a week or two the consumer of ‘shungite
water’will be exposed to increased levels of nickel.
In Figure 2(a) and 2(b) the concentration of released
nickel from shungite Com is significantly higher than from
shungite SH after 3 days of exposure. On the 5th day the
difference is negligible, but in the following days the released
nickel from shungite Com is lower than from shungite SH.
This could be explained by the fact that shungite Com has
higher SSA than shungite SH, therefore Com releases
nickel much faster.
The recommended tolerable daily intake (TDI) of nickel
has changed over the years. In 2005, the European Food
Table 6 |TOC and DOC results
Parameter, mg/L Water
SH COM
3rd day 5th day 3rd day 5th day
TOC 0 0 1.09 ±0.09 0.89 ±0.08 1.16 ±0.09
DOC 0 0 0.69 ±0.06 0.44 ±0.04 0.65 ±0.06
Figure 2 |Nickel concentration in water samples after exposure to shungite: (a) during 2 weeks and using pure water; (b) during 3 weeks and using water with 2,500 μg/L of copper. The
red dashed line indicates the MAC of nickel in drinking water.
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Safety Authority (EFSA) Scientific Panel on Dietetic Pro-
ducts, Nutrition and Allergies released a scientific opinion
related to the tolerable upper level of nickel, where accord-
ing to scientific investigations and the lack of evidence that
Ni is essential for humans it was concluded that it is not
possible to establish the TDI for nickel (EFSA ). Two
years later, in 2007, the World Health Organization
(WHO) established the TDI at 11 μg/kg of body weight
(WHO ). In 2015 the EFSA Panel on Contaminants in
the Food Chain released a scientific opinion on the risks
of public health related to the presence of nickel in food
and drinking water where the TDI of 2.8 μg/kg of body
weight was established (EFSA CONTAM ). Based on
this, for an adult with an average weight of 70 kg the TDI
would be 196 μg and to intake such an amount of nickel
one would need to drink more than 3 litres of ‘shungite
water’with an Ni concentration of approximately 60 μg/L
(after 5 days according to data presented in Table 3), and
even more when the Ni concentration is lower. On the
other hand, the major source of Ni uptake is food –cocoa
beans and chocolate (Kruszewski et al. ), beans, seeds,
nuts, grains, vegetables, fruits and also products containing
them (EFSA CONTAM ). The amount of nickel in
foods may vary considerably from place to place, due to
the different nickel content in the soil.
The biological function of nickel in the human body is
still unclear. The highest concentrations of nickel in the
human body are found in the nucleic acids, particularly
RNA, and it is thought to be somehow involved in protein
structure or function. Nickel may play a role, as a cofactor,
in the activation of certain enzymes related to the break-
down or utilization of glucose (Kumar & Trivedi ).
The most reported effects after acute exposure to Ni
are gastrointestinal (vomiting, cramps, and diarrhea) and
neurological symptoms (giddiness, headache, and weari-
ness). Ingestion of Ni is able to elicit eczematous flare-
up reactions in the skin in Ni-sensitized individuals, but
scientific research indicates that it is unlikely that dietary
exposure to Ni would result in cancer in humans.
Although not all consumed Ni is absorbed from the gastro-
intestinal tract (1–40% from the amount ingested) (EFSA
CONTAM ),extraNiuptakebyusing‘shungite
water’inboththeshortandlongtermcancausehealth
problems.
Adsorption of copper
Despite the fact that shungite releases various heavy metals,
at the same time it adsorbs copper (Figure 3) from water.
The results in Figure 3 show that the remaining copper con-
centration slowly increases with time, where after 3 weeks
the concentration for both shungite samples was approxi-
mately 2.5 times higher than after 3 days of exposure. This
means that shungite sorption properties towards copper
decreases, removing approximately 81–87% of the initial
copper concentration after the first 3 days and 40–50% on
the 21st day of exposure to both shungite samples. The
decrease of copper concentration can also be attributed to
the precipitation of copper sulphide due to the possible sul-
phide ion release from shungite (Rafienko & Belimenko
).
As shown in Table 1, shungite SH contains higher
amounts of carbon but has lower SSA compared to shungite
Com. The obtained results show the carbon content has a
direct influence on sorption properties, because overall
shungite SH showed slightly higher sorption than Com
towards copper.
CONCLUSIONS
In the current study, drinking water treatment with shungite
was investigated. The results show that shungite samples
release various heavy metals into the water –nickel,
copper, lead, cadmium, zinc, chromium and arsenic. Lead
and cadmium is released for a short time and exceeded
MAC only after the first 3 days of exposure, but nickel is
Figure 3 |Remaining copper concentration (μg/L) in water samples during 3 weeks of
copper adsorption experiment.
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released for a much longer time and can exceed MAC up to
2 weeks. Increased specific surface area probably acceler-
ates the rate of nickel release from shungite but carbon
content in shungite promotes sorption properties.
Based on the obtained data, it would be advisable to give
careful consideration to the use of shungite for drinking
water treatment. To avoid heavy metal contamination
from shungite, prior to application and additionally to the
washing procedure written in the instructions, shungite
should be washed with a large volume of water for several
days (for example, for 5 days with shungite:water mass
ratio of 1:10 and by changing the water once a day). Also,
after the washing procedure, chemical analysis of the last
washing water should be carried out.
ACKNOWLEDGEMENT
This work was supported by the European Regional
Development Fund within the Activity 1.1.1.2 ‘Post-
doctoral Research Aid’of the Specific Aid Objective 1.1.1
‘To increase the research and innovative capacity of
scientific institutions of Latvia and the ability to attract
external financing, investing in human resources and
infrastructure’of the Operational Programme ‘Growth and
Employment’(No.1.1.1.2/VIAA/1/16/049).
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplemen-
tary Information.
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