ГОДИШНИК НА МИННО-ГЕОЛОЖКИЯ УНИВЕРСИТЕТ “СВ. ИВАН РИЛСКИ”, Том 56, Св. II, Добив и преработка на минерални суровини, 2013
ANNUAL OF THE UNIVERSITY OF MINING AND GEOLOGY “ST. IVAN RILSKI”, Vol. 56, Part ІI, Mining and Mineral processing, 2013
EVALUATION OF ACTIVATED CARBON „NORIT CA1“ SORPTION AS A METHOD FOR
HEAVY METAL IONS REMOVAL FROM WASTEWATER
Georgi Nikolov, Gospodinka Gicheva
University of Mining and Geology “St. Ivan Rilski”, 1700 Sofia, e_gospodinka@yahoo.com
ABSTRACT. The Heavy metal pollution is one of the most serious problems concerning environment. Release of heavy metals is contributed mainly to mining
industry thus making it a major concern to industrially developed countries. Heavy metals pose a great hazard to human health due to their acute and chronic toxicity,
tendency for bioaccumulation and carcinogenicity. One of the industrially used methods for the removal of the ions from wastewater is the process of sorption. Here
we present the investigation of sorption capacity of activated carbon Norit CA1 toward Cd(II) and Zn(II) as a method for their removal from wastewater. The effect of
pH of the media was studied as a way to evaluate the optimal conditions for water treatment process.
ОЦЕНКА НА СОРБЦИЯТА ВЪРХУ АКТИВЕН ВЪГЛЕН „NORIT CA1“ КАТО МЕТОД ЗА ПРЕЧИСТВАНЕ НА ОТПАДНИ
ВОДИ ОТ ЙОНИ НА ТЕЖКИ МЕТАЛИ
Георги Николов, Господинка Гичева
Минно-геоложки университет “Св. Иван Рилски”, 1700 София, e_gospodinka@yahoo.com
РЕЗЮМЕ. Замърсяването с тежки метали е един от най-сериозните проблеми засягащи околната среда. То се отдава главно на минната индустрия и
поради тази причина е основен проблем в развитите страни. Тежките метали представляват сериозна заплаха за човешкото здраве поради тяхната остра
и хронична токсичност, канцерогенност, както и склонността им към биоакумулиране. Един от най-разпространените методите за отстраняване на йони от
отпадни води е процеса сорбция. В това изследване е определен сорбционният капацитет на активен въглен Norit CA1 спрямо йони на Cd(II) and Zn(II),
като метод за тяхнотот отстраняване от отпадни води. Изследвана е и зависимостта от и йонната сила на средата, за да се оценят оптималните условия за
пречистване на замърсените води.
Ключови думи: тежки метали, сорбция, активен въглен
Introduction
been developed – photocatalysis (Lazar et al., 2012; Nakata,
K. et al., 2012). Although there are a large number of research
papers in the past ten years regarding the advantages and the
prospects of this method it is still not employed as an
industrially applied water treatment process.
Heavy metal pollution is one of the most pressing problems
presenting a challenge in engineering a cost effective as well
as efficient process for their removal from contaminated
waters. Pollution with heavy metals is a problem emerging in
industrially developed countries with well pronounced mining
industry. Heavy metals are usually a waste accompanying the
process of metal extraction, mineral processing, metal plating.
Although there isn’t a uniform (unanimous) definition of heavy
metal it is usually associated with elements with metallic
properties and high atomic weight. Heavy metal ions are well
known for their toxicity, both acute and chronic as well as their
carcinogenicity. Their release in environment can pose a
serious health hazard due to their tendency for
bioaccumulation and biomagnification (Paulino et al., 2006;
Borba et al., 2006; Oyaro et al., 2007).
Each of the above listed methods has its advantages and
disadvantages regarding their cost, efficiency and selectivity
towards heavy metal removal from wastewaters. Adsorption as
a process for water purification is probably one the most widely
applied worldwide due to its cost efficiency, versatility and high
removal efficiency. Different types of adsorbents have been
applied for water purification – both synthetic and naturally
occurring. Amongst the ones that have attracted the attention
of researchers due to their excellent qualities are zeolites (ElKamash et al., 2005; Kocaoba et al., 2007; Jamil et al., 2010; ),
activated carbon (Kang et al., 2008), clays (kaolinite and
montmorillonite: Bhattacharyya et al., 2008) as well as
polymer-based materials (Liu et al., 2010; Kiani et al., 2011;
Ma et al., 2012). Activated carbon is meso- and microporous
material obtained mainly from wood and coal. It can be
activated by chemical or physical methods and depending on
that the properties of activated carbon can vary significantly.
The origin and the type of activation determine the specific
area, pore size and volume, as well surface functionality. It is
one of the most widely used sorbent due to his high sorption
capacity combined with its versatility and cost efficiency.
A lot of methods for heavy metal ions removal were
developed including chemical precipitation (Huisman et al.,
2006), ion-exchange (Petruzzelli et al., 1995), membrane
filtration (Shaalan et al., 2001; Landaburu-Aguirre et al., 2009),
reverse osmosis (Mohsen-Nia et al., 2007; Muthukrishnan et
al., 2008), dialysis (Mohammadi et al., 2005), adsorption (;
Mohan et al., 2006; Liang et al., 2010; Liu et al., 2011),
electrochemical methods (Roundhill et al., 2002) and etc.
Recently a promising new method for a water treatment has
135
Experimental part
metal ion removal. In that case the predominant is electrostatic
interaction between the functional groups on surface of AC and
the metal ion. Norit CA1 is referred as so called L carbons (low
temperature activation), which is associated with the formation
of acidic groups on their surface and negative zeta potential as
well as their ability to adsorb metal ions (Corapcioglu et al.,
1987). This interaction is dependent on the pH of the media,
ionic strength and temperature.
Chemicals. Activated charcoal Norit® CA1 was purchased
from Sigma-Alrdich and used as obtained (without any further
treatment). Cd(CH3COO)2, KCl, CH3COONa, Zn(NO3)2.6H2O
(purum) were obtained by Valerus, Bulgaria.
Solutions. Solutions of heavy metal ions were prepared by
dissolving the heavy metal ion containing compound in media
with different pH in order to obtain a solution of heavy metal ion
at different pH with concentration 0.2 M (mol/l) to use as a
starting solution, respectively. The selected buffer solutions
used in our experiments were with pH value of 2.7 (KCl/HCl),
4.8 (AcOH/ NaOH) and 0.1 M ionic strength and distilled water
(pH 6.5) and natural water (pH 7.8). Concentration of Cd2+ and
Zn2+ ion in the experiments were determined by
complexonometric titration.
Here is presented the pH and ionic strength dependence of
the adsorption of Cd(II) and Zn(II) ions onto Norit CA1. Four
different pH media with two different ionic strength were tested.
The results from obtained from adsorption of the metal ions
were processed using the linear form of Freundlich isotherm,
where q is the mass concentration of the adsorbed metal ion
per mass of sorbent (q) and its concentration in the solution at
equilibrium (CM).
Material characterization. The surface morphology of the
activated carbon was revealed by scanning electron
microscopy SEM (JEOL JSM-6390) – Figure 1. The analysis of
the specific surface was conducted by the express method
(Klyachko-Gurvich) with N2 sorption at low temperature. It has
been determined to be 980 m2/g.
Usually parameter K (intercept) is associated with the sorption
capacity of the material while 1/n (slope) is connected to the
sorption rate.
Fig. 1. SEM image of activate carbon of Norit® CA1
Fig. 2. Linear plot of Freundlich isotherms for adsorption of Cd(II) ions
onto Norit CA1 at different pH values
log( q) 
1
log CM  log K
n
(1)
As it is shown on Figure 2 the adsorption capacity of Cd(II)
ions onto Norit CA1 is practically not affected by the pH media
(with slight exception of pH 7.8-mineral water). The parameters
K and 1/n are the same for the pH 2.7; 4.8 and 6.5, meaning
that Cd(II) are adsorbed with the same rate and amount onto
Norit CA1 at that conditions.
Adsorption onto Norit CA1. The adsorption isotherms were
studied under static conditions in series of six samples. Exact
amount of Norit CA1 was placed in each of the six vials and
then a solutions of heavy metal ions (Zn(II) and Cd(II)) with
increasing concentration (from 0.001 to 0.01 M) were added in
the vials with the activated carbon present and then the vials
were closed. After 24 hours at room temperature the samples
where filtered to remove AC and the equilibrium concentration
of the metal ions after the adsorption was determined by
complexonometric
titration
with
EDTA
(ethylenediaminetetraacetic acid) as a titrant and metal
indicator xylenol orange. In order to investigate the effect of pH
and ionic strength of the media all other parameters (variables)
in the experiments were kept constant.
Results and discussions
Norit CA1 is chemically activated carbon (with phosphoric
acid) with highly developed surface. Depending on the method
of activation there can be a different type of functional groups
on the activated carbon surface. This is of significant
importance when one uses the activated carbon (AC) for heavy
Fig. 3. Linear plot of Freundlich isotherms for adsorption of Zn(II) ions
onto Norit CA1 at different pH values
136
Conclusions
Here on Figure 3 is shown the corresponding dependence of
the adsorption of Zn(II) ions onto Norit CA1 at different pH.
One can see from it that there is no apparent effect of pH onto
adsorption properties of Zn(II) onto the AC. They are practically
indiscernible.
Activated carbon is one the most widely applied sorbent for
water and wastewater treatment. That is due to its high
sorption capacity, chemical resistance and versatility. It can be
successfully applied for removal of both organic and inorganic
substances (pollutants).
By comparing the results obtained from the linear plots of
Freundlich isotherms for adsorption of Cd(II) and Zn(II) ions
(Figure 2 and Figure 3) onto Norit CA1 one can summarize
that there is not any well pronounced dependence of the
adsorption from pH media, both for Cd and Zn ions. This can
be attributed to the chemical modification of activated carbon
with phosphoric acid. That allowed the formation of a surfaced
with relatively strong acidic groups that doesn’t affect from pH
of the media in a tangible way. That makes Norit CA1 a very
attractive choice when one needs to remove heavy metal ions,
because it gives the opportunity to adsorb the same amount of
metal ions regardless of pH of the media.
The experiments conducted in this research revealed that
activated carbon Norit CA1 is very suitable for heavy metal
ions removal from waters and wastewaters. The results has
shown that there is not any significant decrease of adsorption
capacity at different pH media. That makes Norit CA1 useful
for wastewater treatment since the low pH will affect much the
adsorption of heavy metal ions onto surface of the activated
carbon. The other fact that recommends it is versatility – it was
shown that adsorption capacity of Zn(II) ions was as high as
the Cd(II) ions. This leads us to believe that it can remove a
large number of different metal ions from polluted waters with
the same efficiency.
There is no significant difference in the adsorption capacity
and rate regarding Zn(II) and Cd(II) ions. This means that Norit
CA1 is not selective adsorbent, at least not in respect these
two metal ions. But this fact also makes it a versatile adsorbent
for different types of substances.
Overall activated carbon (in this particular case Norit CA1)
has shown excellent adsorption properties to the tested heavy
metal ions, one of his major advantages being the nonpronounced pH dependence as well as its versatility.
The fact that adsorption in this case is mainly due to the
electrostatic interaction between metal ions and AC surface
makes it preferable to establish the effect and the ionic
strength dependence since it is expected to be one of the
parameters which will influence the adsorption capacity.
Acknowledgements
The authors thank to project MTF-120/ 07.07.2013 of UMG
“St. Ivan Rilski” for the financial support and to IPC-BAS for
SEM images of Norit CA1.
On Figure 4 data are presented for adsorption of Cd(II) and
Zn(II) ions onto Norit CA1 ot pH=4.8 and ionic strength – 0.1M
and 0.01 M. Here can see the way that adsorption is affected
by ionic strength of the media. In the case of Cd(II) ions when
we increase the ionic strength from 0.01M to 0.1M the
adsorption capacity and rate does not change significant which
is also the case of Zn (II) ions adsorption. Overall we can
observe from Figure 4 that ases as expected while the
adsorption rate (slope) does not change significantly. In the
case of we observe that Zn(II) ions have higher adsorption
capacity onto Norit CA1 than Cd(II) at the same other
conditions.
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