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European Journal of Applied Sciences – Vol. 12, No. 3
Publication Date: June 25, 2024
DOI:10.14738/aivp.123.16868
Kouadio, L. M., Coulibaly, Z., Kedi, A. B. B., Coulibaly, V., & Sei, J. (2024). Capacity of Two Clays to Clean Up Water from An Illegal
Gold Mining Site. European Journal of Applied Sciences, Vol - 12(3). 266-277.
Services for Science and Education – United Kingdom
Capacity of Two Clays to Clean Up Water from An Illegal Gold
Mining Site
Kouadio, Lucas Moses
Nangui Abrogoua University, Abidjan, Côte d’Ivoire
Coulibaly, Zié
Felix Houphouët Boigny University, Abidjan, Côte d’Ivoire
Kedi, Atolé Brice Bienvenu
Jean Lorougnon Guédé University, Daloa, Côte d’Ivoire
Coulibaly, Vamoussa
Felix Houphouët Boigny University, Abidjan, Côte d’Ivoire
Sei, Joseph
Felix Houphouët Boigny University, Abidjan, Côte d’Ivoire
ABSTRACT
The intensive development of illegal gold mining, with the uncontrolled use of
chemicals, has a strong impact on the environment in Côte d'Ivoire. This study
aims to clean up contaminated water from the illegal gold mining site of
Angamankro in the Daoukro department using two clays from Ivory Coast. To
achieve this goal, physicochemical parameters such as pH, conductivity, turbidity
and metal contents in water were measured. The levels of most of the metals
studied in wastewater are higher than their various limit values recommended by
the WHO. In order to depollute the water, adsorption treatment on Bingerville
(BIN) and Katiola (KAT) clays were used. The treatment of wastewater with clays
showed a significant reduction in metal contents. The elimination of different
metals in water has decreased in the direction Cu >Hg > Zn> Mn > Ni > Co > Cd > Cr
> As > Pb. KAT clay adsorbs metals better than BIN clay. This greater adsorption
capacity that KAT clay possesses is due to its mineralogical composition (20.14%
smectite) and its greater surface properties.
Keywords: Illegal gold mining, adsorption, metals, clay
INTRODUCTION
Pollution is a major problem for the environment and public health that attracts the attention
of the scientific community. This pollution is very often caused by different anthropogenic
sources such as mining activity, the metallurgical and steel industry, fertilizers and pesticides
applied in soil cultivation, incinerators and waste incineration ashes, medical waste, city
recycling centers, emissions from factories and internal combustion engines, sewer effluents
and sewage sludge, etc. These different activities are responsible for the release of certain
dangerous chemical compounds that are poorly or non-biodegradable such as hydrocarbons,
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Kouadio, L. M., Coulibaly, Z., Kedi, A. B. B., Coulibaly, V., & Sei, J. (2024). Capacity of Two Clays to Clean Up Water from An Illegal Gold Mining Site.
European Journal of Applied Sciences, Vol - 12(3). 266-277.
URL: http://dx.doi.org/10.14738/aivp.123.16868
phenolic compounds, heavy metals, dyes, insecticides, etc. Among these anthropogenic
sources, it appears that the mining industry is the main source of heavy metals in the
environment [1]. Côte d’Ivoire is not on the fringes of the phenomenon of environmental
pollution. Illegal gold mining, which has grown and affects most regions of Côte d’Ivoire, is the
one that pollutes the most [2, 3]. Localities housing illegal gold mining sites such as Kong 2
(Yakassé Attobrou department), Degbézéré (Bouaflé department) and Aboisso are
contaminated by heavy metals. Most of the rivers of Côte d'Ivoire are polluted due to gold
panning, these are the Cavally, the Sassandra, the Bandama and the N'zi [4, 5]. Numerous
studies have found metal levels above the limit values set by the WHO in the surface waters of
several localities hosting illegal gold panning sites in Côte d'Ivoire [6, 7]. Consequently, this
surface water is unfit for consumption due to this contamination. However, the populations of
these localities impacted by illegal gold panning very often use this contaminated water for
their various needs. In this context, it is necessary to depollute these waters. Among the
decontamination techniques, the adsorption of pollutants by less expensive adsorbents,
available and easily used such as clays, constitutes a great interest [8]. Due to their sheet
structure and their interesting adsorbent properties linked to their large specific surface area
and their cation exchange capacities, clays are used in the depollution of contaminated
solutions as adsorbents [9, 10]. In addition, several studies have shown that Côte d'Ivoire has
numerous clay sites with interesting adsorbent properties [11]. Following the above, the
objective of this work is to depollute water from a gold panning site using two clays from
Ivory Coast.
MATERIALS AND METHODS
Materials
Water Sample:
The water sample for this study comes from the illegal gold panning site of Angamakro at
7°29'54'' north longitude and 5°10'30'' west latitude in the Daoukro department (Fig. 1).
Fig1: Location of the illegal gold panning site of Angamankro
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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 3, June-2024
Clay Materials
The clays used in this study are referenced BIN and KAT (Fig. 2). BIN clay was extracted at
5°18' north latitude and 3°50' west longitude in Bregbo in the town of Bingerville belonging
to the Autonomous District of Abidjan. As for KAT clay, it comes from the town of Katiola in
the Hambol region in the north of Ivory Coast at 8°08’ north latitude and 5°06’ west longitude.
The main characteristics of these clays are grouped in Table 1 (Mineralogical composition,
specific surface area and cation exchange capacity) below.
Fig2: Images of BIN (a) and KAT (b) clay samples
Table 1: Mineralogical composition and physicochemical properties of BIN and KAT
clays [11]
Sample % Kaolinite % Illite % Smectite % Quartz % Goethite CEC (meq/100g) SBET (m2
/g)
BIN 52.21 6.23 - 17.50 15.71 6.2 31.7
KAT 48.08 3.55 20.14 6.11 16.86 35.47 48.5
Methods
Sampling:
Water sampling was carried out using half-liter (500mL) capacity glass bottles. These bottles
were first rinsed well with 10% hydrochloric acid, then twice with distilled water. The
samples were taken with hands protected by sterile gloves to avoid any contamination. A
composite water sample was formed from the same volume of three water samples from
different points in the watercourse (Fig. 3).
Fig3: Water sample from the Angamankro gold panning site
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Kouadio, L. M., Coulibaly, Z., Kedi, A. B. B., Coulibaly, V., & Sei, J. (2024). Capacity of Two Clays to Clean Up Water from An Illegal Gold Mining Site.
European Journal of Applied Sciences, Vol - 12(3). 266-277.
URL: http://dx.doi.org/10.14738/aivp.123.16868
The formed sample was collected in a glass bottle labeled AE1. The sample taken was
immediately stored in a cooler with ice and taken to the laboratory. Before analysis, the water
sample was stored at 4°C in a refrigerator to avoid any damage.
Analysis of the Water Sample:
Parameters measured include pH, conductivity, turbidity and trace metal element
concentrations. The pH of the water was measured using a HANNA HI 2211 type pH meter.
The conductivity was determined using a HANNA HI98192 “EC/TDS/NaCl/Resistivity”
conductivity meter. A HANNA HI98713 type turbidimeter was used to determine the
turbidity. The metals in the water were measured using an optical emission spectrometer
coupled to an inductively coupled plasma (ICP-OES) of the Perkin Elmer Optima 2100 DV
type. The metals analyzed are: mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), copper
(Cu), nickel (Ni), zinc (Zn), chromium (Cr), cobalt (Co) and manganese (Mn).
Adsorption Reaction:
Part of the water sample taken from the gold panning site was treated with each of the two
clays (BIN and KAT). A mass of 1.25 g of clay is brought into contact with 125 mL of liquid
samples from the gold panning site in a beaker with a capacity of 250 mL. The clay to liquid
ratio is 10g per liter. The mixtures were stirred for 90 minutes at 600 rpm using a DWB MS- PB type magnetic stirrer. After stirring, the mixture is centrifuged at 5000 rpm for 15 min and
the supernatant is taken for the determination of chemical species at ICP-OES in order to
determine the residual contents of metallic trace elements. The elimination of chemical
species by clays is evaluated by calculating the adsorption capacity Q (Q = C0− Ct
m
V) and the
elimination percentage R (R =
C0− Ct
C0
∗ 100). Figure 4 summarizes the metal adsorption
protocol.
Fig4: Metal adsorption protocol
RESULTS
Hydrogen Potential (pH); Conductivity and Turbidity
The results of pH, conductivity and turbidity measurements, before and after treatment with
clays are shown in Figure 5. The pH of the raw sample (A1) is 6.1. After the clay treatment, the
pH increased slightly. This value increased to 6.8 after treatment with BIN clay (A1BIN) and to
7.3 for KAT clay (A1KAT). The pH of the raw sample is below the WHO standard (comprised of
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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 3, June-2024
6.5 and 8.5). Untreated water (A1) has a conductivity of 186.4 μS/Cm. After treatment, the
conductivity of A1 increased from 186.4 μS/cm to 142 μS/cm and 115.9 μS/cm respectively
with Bingerville and Katiola clays, a reduction of 24% and 38%. Before or after treatment
with clays, the conductivity values comply with the WHO standard (500 μS/cm in drinking
water) [12].
Fig5. pH, Conductivity and Turbidity of the water sample before (A1) and after treatment with
clays (A1BIN and A1KAT)
As for turbidity, the raw sample (A1) has a value greater than 1000 UNT. Clay treatment
significantly reduced the turbidity value. The turbidity increased to 202 UNT after treatment
with BIN clay and to 162 UNT with KAT clay, a reduction of more than 80% for both clays.
Despite the sharp reduction in turbidity, the values still remain above the WHO standard (5
UNT in drinking water) [12]. The reduction in turbidity is visible in Figure 6 with a darker
color for the untreated water (A1) and lighter colors for the clay-treated samples (A1BIN and
A1KAT).