Physical sciences | Chemistry
Removal of nickel and methylene blue
from aqueous solutions by steel slag as a low cost adsorbent
Van Thuan Le1, Hoang Sinh Le1, Xuan Vu Tran2,Thi Kieu Ngan Tran2,Dang Quang Vo2, Bao Chau Tran2,
Quoc Phu Ngo2, Thị Xuan Thuy Le3*
1Center for Advanced Chemistry, Institute of Research & Development, Duy Tan University
2Faculty of Environmental and Chemical Engineering, Duy Tan University
3Faculty of Environment, Da Nang University of Science and Technology
Received 3 April 2017; accepted 20 October 2017
inhaled [5, 6]. Therefore, the treatment
Nowadays, wastewater from various industries contains a large number of
harmful heavy metals and coloring agents, which have to be removed to
restore the quality of the environment. In this study, the removal of nickel
ions (Ni2+) and methylene blue (MB) from the aqueous solution using steel
slag as a low cost adsorbent was investigated. The chemical and mineralogical
compositions, as well as the surface area of slag, were analyzed by using X-ray
fluorescence spectroscopy, X-ray diffraction, and the Brunauer-Emmett-Teller
method (BET). The effect of several important parameters such as contact
time, adsorbent dose, pH, temperature, and initial adsorbate concentration on
the adsorption process was studied systematically by batch experiments. The
adsorption data were well correlated with the Langmuir isotherm model by
all samples. The maximum adsorption capacity of the raw slag samples was
36.49 mg/g for Ni2+ and increased from 0.68 to 1.98 mg/g for MB after being
acid-activated. The determined thermodynamic parameters indicate that the
adsorption of Ni2+ and MB on steel slag is spontaneous in nature, endothermic
(for Ni2+), and exothermic (for MB).
of effluent, containing heavy metal
ions, and dyes such as nickel and MB,
is necessary due to their harmful effects
on humans.
Among the various methods
currently applied for removing heavy
metals and dyes from the water industry,
adsorption is the most widely used
method due to its merits of efficiency,
economy, and simple operation [7].
Different adsorbents have been used for
the removal of MB and nickel ions from
aqueous solutions, including graphene
[8, 9], bentonite [10], activated carbon
[4], perlite [11], pumice [12], and
hydroxyapatite [13, 14]. However, these
adsorbents are relatively expensive, and
Keywords: adsorption, dye, heavy metals, low cost adsorbent, steel slag, water
this has restricted their application at
Classification number: 2.2
Steel slag is the main by-product of the
iron and steel industry. A huge amount of
It is well known that water is a
precious and irreplaceable resource for
human and animals’ life [1]. However,
water pollution of heavy metals and
dyes, which are major contributors to
the contamination of water streams, has
been a serious environmental problem
in the recent years. The increasing water
contamination by heavy metal ions and
dyes has become a significant concern
for ecological systems and public health
one of the important toxic heavy metals
that is widely used in electroplating,
printing, storage-battery industries,
silver refineries, and production of some
alloys. High concentration of nickel
causes poisoning effects like lung, nose,
bone cancers, headaches, dizziness,
nausea, cyanosis, and extreme weakness
[3]. One of the high consuming materials
in the dye industry is MB, which is the
most commonly used substance for
dying cotton, wool, and silk [4]. The MB
it is accumulated in the environment and
causes numerous ecological problems.
Therefore, determining the sustainable
usage of accumulated steel slag for
other purposes will bring economic and
environmental benefits. In the recent
years, steel slag has been reported as
potential adsorbent to remove pollutants
from waste water [15-19]. In this study,
steel slag was chosen as a low cost
adsorbent to remove nickel ions and
methylen blue dye. The main objective
of this work was to evaluate the removal
can cause eye burns, nausea, vomiting,
ability of steel slag and its activated
property, bioaccumulation, and toxicity,
diarrhea, dyspnea, tachycardia, cyanosis,
form for Ni2+ and MB under different
even at low concentrations [2]. Nickel is
methemoglobinemia, and convulsions if
experimental conditions.
*Corresponding author: Email:
December 2017 Vol.59 Number 4
Vietnam Journal of Science,
Technology and Engineering
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Physical sciences | Chemistry
Materials and methods
Materials and chemicals
initial concentrations and a certain
temperature. The pH of the solutions
was adjusted by adding 0.1 M aqueous
surface area and density of the steel
slag are 4.23 m2/g and 3.025 g/cm3,
respectively. Aqueous suspensions of
The experiment material used in this
solutions of NaOH or HCl using a pH
the slag have a high pH value (10.52)
study was electric arc furnace (EAF) steel
meter InoLab Multi 9310. To ensure
slag obtained from a steelmaking plant
homogeneous mixing, an orbital shaker
hydroxide (30.23 w%) and basic oxides
(Danang, Vietnam). The collected steel
slag was crushed and sieved to obtain
particles. Activated slag was obtained by
soaking raw crushed steel slag with 2 M
HCl for 24 hours at room temperature.
After that, the acid suspension was
filtered by vacuum filter and then, the
residue was washed with distilled water.
Finally, the sample was dried at 100˚C
for 12 hours and ground to a powder
state. Nickel sulfate hexahydrate and
methylen blue were purchased from
Merck. The reagents dimethylglyoxime
(99.00%), NaOH (99.95%), and HCl
(36.5%) were provided by Sigma
Aldrich. All other reagents used in this
study were analytical grade, and distilled
or double distilled water was used in the
preparation of all solutions.
with an agitation speed of 150 rpm was
used throughout the experiment. Then,
the samples were centrifuged at 5000
rpm for 10 min. The concentrations of
the nickel ions and the MB dye before
and after adsorption were estimated
using an UV-visible spectrophotometer
(UV-VIS Ultrospec 8000). The effect
of the adsorbent dose was conducted
using 2.5-20 g/l of adsorbent. The effect
of pH was investigated over a pH range
of 2-8. The effect of contact time was
studied under different given contact
time between 5 min and 120 min.
The percentage removal (R%) and
the amount of adsorbed nickel ion
and MB dye were calculated using the
following equations:
in it, which lead to a high capacity of the
slag to neutralize strong acidic media.
The mineralogical compositions of
slag samples were determined by the
XRD analysis, and obtained results
are given in Fig. 1. The analysis of the
diffraction patterns showed that both
slag samples are heterogeneous materials
consisting the following major crystalline
phases: larnite (Ca SiO ), wuestite
(FeO), gehlentite (Ca Al(AlSiO )),
mullite (3Al O .2SiO ), and quartz
(SiO ). Other minor constituent phases
in the analyzed samples are very difficult
to identify because of the complexity
of the diffractograms. Additionally,
XRD patterns show that the peaks of
the activated slag are more intense and
clearer compared to the raw steel slag.
Characterization of adsorbent
The chemical composition of the slag
was determined by X-ray fluorescence
spectroscopy (XRF) using a Philips PW
2404 instrument. The morphologies
of the samples were investigated by
scanning electron microscopy (SEM,
Hitachi S4800). The mineralogical
composition was analyzed by an
X-ray diffractometer Rigaku Ultima
IV (Japan), operating at 45 kV and
40 mA, using Cu-Kα radiation of λ =
0.15418 nm, 2θ ranging from 5 to 60°,
and step size 0.1o. Phase identification
was carried out by comparing the peak
positions of the diffraction patterns with
ICDD (JCPDS) standards. Surface area
of the slag was measured by the BET on
Micromeretics TriStar 3000 instrument.
Batch studies
Batch adsorption studies were
performed at different doses of adsorbent,
initial pH, contact time, concentrations
of Ni2+ and MB. For each experiments,
three replicates of the adsorbents (0.5 g)
R = . (1)
. (2)
where: C and C are the initial and
final concentrations of Ni2+ ions and
MB before and after the adsorption in
aqueous solution (mg/l); Q is the amount
of Ni2+ and MB dye adsorbed by the slag
(mg/g); V is the volume of solution (l);
m is the mass of adsorbent (g).
Results and discussions
Characterization of sorbent
The chemical and physical
characteristics of the steel slag are
presented in Table 1. The result
showed that the steel slag of this study
mainly contains calcium, iron, silicon,
magnesium, aluminum, manganese,
and phosphorus compounds. The joint
presence of calcium oxide and alumina
silicate compounds could facilitate the
provision of negatively charged sites for
This may be because some impurities in
the raw slag have been removed when it
was soaked in the acid solution.
Morphology study
Figure 2 shows the morphologies
of the slag samples before and after
adsorption, as characterized by SEM.
It can be seen from the SEM images
that there is no significant change in
morphology of the slag samples before
and after adsorption of Ni2+ and MB.
Under SEM, the slag particles showed
irregular shapes with sharp edges about
0.5 µm to 2 µm in size.
Effect of initial solution pH
The initial pH value of the adsorbate
solution is one of the most important
factors influencing the adsorption
process due to its strong effect on the
surface charge, the surface binding
sites of the adsorbent, and the degree of
ionization and species of adsorbate [21].
The effect of initial pH on the adsorption
process was studied in the range from
were mixed with 50 ml solutions of Ni2+/
cation exchange reactions with metal
2 to 8 at 25±2oC, the adsorbent dosage
MB in 150 ml conical flasks at different
ions in the aqueous solution [20]. The
of 0.5 g, contact time of 60 min, 50 ml
Vietnam Journal of Science,
Technology and Engineering
December 2017 Vol.59 Number 4