S. A. AL-JLIL: MISWAK (SALVADORA PERSICA ROOTS): DISCOVERY OF A NEW BIOMATERIAL FOR REMOVING ...
35–39
MISWAK (SALVADORA PERSICA ROOTS): DISCOVERY OF A
NEW BIOMATERIAL FOR REMOVING HEAVY METALS FROM
WATER IN SAUDI ARABIA
MISWAK (KORENINE SALVADORA PERSICA): ODKRITJE
NOVEGA BIOMATERIALA ZA ODSTRANJEVANJE TE@KIH
KOVIN IZ VODE V SAUDSKI ARABIJI
Saad A. Aljlil
National Center for Membrane Technology (NCMT), King Abdulaziz City for Science and Technology (KACST),
P. O. Box 6086 Riyadh, Kingdom of Saudi Arabia
saljlil@kacst.edu.sa
Prejem rokopisa – received: 2015-07-01; sprejem za objavo – accepted for publication: 2015-12-17
doi:10.17222/mit.2015.183
The aim of this study was to evaluate Miswak (Salvadora Persica Roots Powder, SPRP) as a natural bio-adsorbent from Saudi
Arabia for water treatment. The adsorption capacity of the SPRP increased with an increasing concentration of heavy-metal ions
and the temperature of the experimental solution. The maximum adsorption capacity of the SPRP was 18.2 mg g–1 and
20.79 mg g–1 for lead at 25 °C and 45 °C, respectively. Of the two isotherm models (Langmuir and Freundlich), the Langmuir
model fitted the experimental data well at 45 °C, while the Freundlich model correlated well with the experimental data at
25 °C.
Keywords: Miswak (Salvadora Persica Roots), Miswak powder, lead, Langmuir, Freundlich ishotherm model, contaminated
water, adsorption capacity
Namen te {tudije je bila ocean Miswaka (prah iz korenin Salvadora Persica, SPRP) kot naravnega bioadsorbenta iz Saudske
arabije, za obdelavo vode. Zmogljivost absorpcije SPRP se pove~uje z nara{~anjem koncentracije ionov te`kih kovin in
temperature eksperimentalnih raztopin. Maksimalna zmogljivost absorpcije svinca s SPRP je bila 18,2 mg g–1 in 20,79 mg g–1
pri 25 °C oziroma pri 45 °C. Med dvema izotermnima modeloma (Langmuir in Freundlich), se je Langmuir model dobro skladal
z eksperimentalnimi podatki pri 45 °C, medtem ko je bila korelacija Freundlich modela z eksperimentalnim podatki dobra pri
25 °C.
Klju~ne besede: Miswak (korenine Salvadora Persica), Miswak prah, svinec, Langmuir, Freundlichov izometri~ni model,
kontaminirana voda, zmogljivost absorpcije
1 INTRODUCTION
Lead (Pb) is one of the toxic metals present in diffe-
rent types of waters as a pollutant. It is a potential source
of human health hazards such as heart failure, thyroid
and liver damage when its concentration in water is
above the permissible limits for various uses. Currently,
many conventional water-treatment techniques such as
membrane processes, chemical precipitation, ion-ex-
change processes and adsorption are used for the remo-
val of heavy metals such as lead. Existing technologies
for heavy metals’ removal from waters and wastewaters
are often ineffective, expensive, time consuming and
unavailable in developing countries. Therefore, the use
of Miswak (SPRP) as a low-cost adsorbent seems a
viable approach for removing the lead ions from waters
and or wastewater through an adsorption process.
Among the different water-treatment techniques, the
adsorption of heavy metal by miswak (SPRP) is con-
sidered as cheap and cost effective compared to more
expensive process such as ion exchange. Many natural
local materials such as clay, charcoal, solid waste from
water-treatment plants and different agricultural wastes
(biomaterials) are available for wastewater purification.
Saudi Arabia is one of the largest producers of Miswak
stick (roots of Sulvadora persica tree) in the world and
this is mainly used for cleaning teeth instead of using
chemically produced tooth pastes.
Many industries use aqueous solutions of heavy
metals such as lead for manufacturing batteries. Unfort-
unately, the removal of heavy metals such as Pb, Zn, Co
and Cr from aqueous solutions is both difficult and
expensive. Previously, different types of adsorbents, such
as activated carbon, activated sludge, various types of
natural clays, carbon aerogels, coirpith carbon, natural
zeolites and date-pits powder were used for water
treatment. Similarly, heavy-metal removal was achieved
by expensive ion-exchange resins (U.S. Patent No.
4,133,755). These investigators used various adsorbents,
mainly a dithiocarbamate bond-containing low-mole-
cular-weight compound, amorphous silica and activated
carbon powder, granulated with a vinyl acetate polymer
binder and clay as a thixotropic excipient for removing
heavy metals. However, Cody (U.S. Patent No.
5,667,694) used granulated materials for treating mer-
Materiali in tehnologije / Materials and technology 51 (2017) 1, 35–39 35
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967-2017) – 50 LET/50 YEARS
UDK 620.1:666.123.4:626.812 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(1)35(2017)
cury-contaminated wastewater for removing heavy
metals such as lead and the radioactive contaminants
from contaminated aqueous systems including aqueous
soil systems. They used organically modified smectite
clay or organoclay to treat these systems. This product
removes heavy-metal ions by flotation and air sparging
(U.S. Patent No. 5,256,615). According to this patent, a
granular inorganic ion exchanger was obtained by firing
at 400 °C or above, a granular molded product of a
mixture of a metal alkoxide such as Si(OMe)4 or hydro-
lyzate, a clay mineral such as sepiolite and an inorganic
ion exchanger such as antimony pentoxide having
mechanical strength and heat resistance without losing
its inherent ion exchangeability (World Patent Publica-
tion No. WO 00/72958). M. Minamisawa et al.1 investigated
the adsorption of Cd(II) and Pb(II) at pH 2–6.7 on
different biomaterials and inorganic adsorbents. They
also stated that biomaterials prepared from plant mate-
rials are promising for the development of novel and
low-cost adsorbents. Also, bio-adsorbents proved to be
potential remediation materials for the removal of heavy
metals and organic materials.2 Rice husk (RH), fly ash
and similar other low-cost (agricultural by-product) bio-
adsorbents were used for the removal of various heavy
metals and metalloids (such as Pb, Cd, Zn, Ni and As)
from both groundwater and surface water.3 In another
study, agricultural waste-based biosorbents (AWBs)
showed equal or even greater adsorption capacities com-
pared to conventional adsorbents for removing heavy
metals from contaminated waters.4 Recently, a wide
range of low-cost modified adsorbents including acti-
vated carbon, natural source adsorbents (clay, bentonite,
zeolite, etc.), biosorbents (black gram husk, sugar-beet
pectin gels, citrus peels, banana and orange peels, carrot
residues, cassava waste, algae, algal, marine green
macroalgae, etc.), and byproduct adsorbents (sawdust,
lignin, rice husk, rice husk ash, coal fly ash, Snail Shells,
Melanoides tuberculata Muller etc.) were examined for
the removal of some heavy metals from water.5,6 The
reported the highest adsorption capacities for Zn2+ were
168 mg g–1 on powdered waste sludge, 128.8 mg g–1
dried marine green macroalgae, 73.2 mg g–1 lignin,
55.82 mg g–1 cassava waste, and 52.91 mg g–1 bentonite.
Some investigators utilized Portulaca oleracea plant
biomass (dried leaves and stem) and dried leaves of
water hyacinth along with the effect of pH, contact time
and adsorpent dose on biosorption and removing some
heavy metals such as Cd, Pb, Zn and Cr from the
aqueous solutions and wastewaters.7 They reported a
maximum removal of Pb at pH of 5 with 120 min of
contact time and 3 g of adsorbent dose.
A review on the use of Sulvadora persica roots
powder (SPRP) as a bioadsorbent for the removal of
heavy metals from waters did not refer to any study relat-
ing to this material. However, in the water- or waste-
water-treatment sector dealing with polluted ground-
water, waste effluents from industrial, domestic,
agriculture, potable drinking water in the markets and
health facilities, it is imperative to remove highly toxic
heavy metals from the available water and waste
effluents for its safe reuse in agriculture and other
purposes. In Saudi Arabia, Miswak (roots of Sulvadora
persica tree) is abundant and is a cost effective bioma-
terial. Therefore, a study on the use of Miswak powder
as an adsorbent for removing heavy metals may deter-
mine it as an appropriate biomaterial substitute for
commercial activated-carbon and other adsorbents. The
main aim of this study was to explore the possibility of
using Miswak (SPRP) as a new natural biomaterial and
low-cost adsorbent for removing toxic heavy metals such
as lead from waters and wastewaters.
2 MATERIALS AND METHODS
2.1 Materials
The adsorbate is a lead-ion solution prepared from
lead (II) nitrate purified LR and supplied by VWR Inter-
national SAS 201.
Salvadora persica is a tree naturally growing in Jazan,
Saudi Arabia from which the miswak (root portion of
tree) was prepared and is commonly known as Arak tree.
The miswak samples were collected, dried, crushed and
milled to a particle size less than 125 mesh (particles
sized between about 0.125 mm to 0.25 mm). Then, the
powder was used as an adsorbent for removing heavy
metals from waters and wastewater. The inherent ion-
exchange capacity of this powder is in the pH range bet-
ween 3 and 5. For example, the miswak powder contains
many functional groups such as carboxylic groups as
found by FT-IR analysis (Table 1). As the pH of the
solution affects the charge on the functional groups,
therefore the functional groups such as carboxylate are
protonated at low pH values.8 The surface area and pore
characteristics of miswak powder as an adsorbent are
given in Table 2. The chemical analysis of miswak
powder was carried by XRF and presented in Table 3.
Table 1: Some of the main functional groups in Saudi miswak powder
Tabela 1: Nekaj glavnih funkcionalnih skupin v savdskem miswak
prahu
Observed band (cm–1) Functional group
3488- 3100
O-H
N-H
2800-2900 C-H
1600-1740
C=O
Carbonyl
1000-1200 C-O
Table 2: Surface area and pore characteristics of Saudi miswak
powder
Tabela 2: Povr{ina in zna~ilnosti por v savdskem miswak prahu
Element Miswak stick powder
BET surface area (m2 g–1) 0.6933
Pore volume ( p/po=0.97)
(cm3 g–1 ) 0.001788
Average pore width (nm) 10.3144
36 Materiali in tehnologije / Materials and technology 51 (2017) 1, 35–39
S. A. AL-JLIL: MISWAK (SALVADORA PERSICA ROOTS): DISCOVERY OF A NEW BIOMATERIAL FOR REMOVING ...
Table 3: Chemical analysis of Saudi miswak powder by XRF
Tabela 3: XRF kemijska analiza savdskega miswak prahu
Element Composition (%)
S 23.0752
Cl 11.195
K 10.02
Ca 55
Fe 0.492
Zn 0.108
Br 0.0998
The experimental set up showing the adsorption
system including a batch adsorption unit for removing
heavy metals from contaminated wastewater is presented
in Figure 1.
2.2 Equilibrium experiments
Equilibrium isotherm experiments for the miswak
powder were carried out by placing 0.25 g of powder
with 50 mL lead solution in a batch adsorption unit. The
concentration of lead ion solution ranged from 50 to 800
ppm. The particle size of the miswak powder was 0.125
mm. The equilibrium experiments were run for a total
period of 3 h to ensure that the adsorption process is in a
state of equilibrium. After termination of the experiment,
samples were collected, filtered and the concentration of
Pb was measured by atomic absorption spectroscopy.
The amount of Pb ion adsorbed on the surface of miswak
powder was calculated using the following Equation (1):
q
v C C
Me
e=
−( )0
(1)
where M is the mass of miswak powder in g, V is the
volume of the solution in liters, qe is the amount of ion
adsorbed mg g–1, Co is the initial concentration of lead
ion solution as mg/L and Ce is concentration of Pb ion at
equilibrium in mg/L. The equilibrium adsorption iso-
therm curves were prepared from the amount of lead ion
adsorbed on the surface of the miswak powder and the
Pb concentration in solution.
3 RESULTS AND DISCUSSION
3.1 Ion removal efficiency of Miswak powder
The Pb ion concentration in the solution after
treatment was less than 285.17 ppm and the removal
efficiency of Pb ion by miswak powder was more than
58.81 %.
3.2 Initial concentration vs. Pb ion adsorption
The data in Figure 2 shows that the adsorption
capacity of the sPb ion increased with increasing the
initial concentration. The maximum adsorption capacity
of the miswak powder was 18.2 mg g–1 and 20.79 mg g–1
at 25 °C and 45 °C, respectively. The process of Pb-ion
adsorption on the negative sites of the miswak powder is
due to the electrostatic attraction between these negative
sites and the lead ions. Furthermore, the formation and
number of negative sites on the surface of the miswak
powder are mainly due to the presence ofa carboxyl
group. The miswak powder has chemical functional
groups such as carboxylic acid (COOH), as shown by
FT-IR analysis (Table 1). The study’s findings agree
with many researchers who reported that the metal
uptake capacity of the root for different metals was in the
order of: Ni>Cd>Pb>Cu>Cr; stem Ni>Pb>Cu>Cd>Cr;
and leaf Ni>Cd>Cu>Pb>Cr. They also reported that Ni
adsorption was the highest in the root and its
concentration was 428.4 ng/g dry wt. Also the trend of
adsorption of the phytomass was similar for Ni and Cd,
i.e., root>leaf>stem.9–12
3.3 Temperature vs. adsorption capacity of Miswak
powder
The adsorption capacity of miswak powder increased
with increasing temperature (Figure 2), thus indicating
that the adsorption process of Pb ions on miswak powder
is an endothermic process. Therefore, the adsorption of
Pb ions on the surface of the miswak powder is favor-
able. The results agree with those of S. A. Aljlil et al.13
S. A. AL-JLIL: MISWAK (SALVADORA PERSICA ROOTS): DISCOVERY OF A NEW BIOMATERIAL FOR REMOVING ...
Materiali in tehnologije / Materials and technology 51 (2017) 1, 35–39 37
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967-2017) – 50 LET/50 YEARS
Figure 2: Equilibrium isotherm for lead ions adsorption on miswak
powder
Slika 2: Ravnote`na izoterma za adsorpcijo ionov svinca na miswak
prahu
Figure 1: Experimental setup for heavy-metal adsorption
Slika 1: Eksperimentalni sestav za adsorpcijo te`ke kovine
who reported similar behavior when increasing the
solution temperature.
4 SAUDI MISWAK STICK POWDER VS.
COMMERCIAL ADSORBENTS
The maximum adsorption capacities of miswak
powder, activated carbon and silica were taken from the
equilibrium isotherm experimental data for comparing
the ion-removal efficiency among these different
adsorbents (Table 4). The results in Table 4 indicated
that miswak powder proved to be the best bio-adsorbent
compared to other similar adsorbents. Because it seems
cheaper, has a relatively high saturation capacity, a
natural biomaterial and easily available locally.
Table 4: Comparison between miswak powder and other commer-
cially available adsorbents for the adsorption of lead ions
Tabela 4: Primerjava med miswak prahom in drugimi komercialno
dostopnimi adsorbenti za adsorpcijo ionov svinca
Adsorbent Saturation (maximum)capacity, (mg g–1)
Activated carbon 7.49
Miswak powder 18
Silica 5.15
5 ANALYSIS OF THE EQUILIBRIUM
EXPERIMENTAL RESULTS
Two types of equilibrium isotherm models were used
in this paper, i.e., the Langmuir and Freundlich models.
5.1 Langmuir isotherm model
The Langmuir isotherm model assumes that a mono-
layer of lead ions is adsorbed on the miswak powder
particles and is also used to estimate the maximum
capacity. The Langmuir isotherm Equation (2) is written
as follows:
q
KC
bCe
e
e
=
+1
(2)
The Langmuir model in the linear form is:
c
q K
b
K
C
e
e
e= +
⎛
⎝
⎜ ⎞
⎠
⎟1 (3)
The equilibrium parameters, K and b, can be deter-
mined by using the non-linear regression method with
Equation (3).
Figure 3 shows the relationship between Ce and qe at
T = 25 °C and T = 45 °C. The equilibrium constants, K
and b, were estimated using the nonlinear regression
method and are tabulated in Table 5. As shown in
Figure 3, the Langmuir model fits the experimental data
well at T = 45 °C.
Table 5: Langmuir equilibrium parameters for lead ions adsorption on
Miswak powder
Tabela 5: Parametri Langmuir ravnote`ja za adsorpcijo ionov svinca
na Miswak prahu
Temperature K (L/g) b (L/mg) R2
T = 25 °C 0.2024 0.00644 0.8895
T = 45 °C 0.3758 0.01529 0.9230
5.2 Freundlich isotherm model
The Freundlich isotherm model was applied to des-
cribe the data from equilibrium adsorption experiments
for a heterogeneous surface. The Freundlich model is
written as follows in Equation (4):
q K Ce e
n= F
1 / (4)
The equilibrium parameters, KF and n, can be cal-
culated by using the non-linear regression method with
Equation (4). The adsorption of metal ions on miswak
powder is favorable when the values of n are greater than
one14.
The Freundlich model in the linear form is:
lg( ) lg( ) lg( )q k
n
Ce F e= + ⋅
1
(5)
Figure 4 shows the relationship between Ce and qe at
T = 25 °C and T = 45 °C. The equilibrium constants were
S. A. AL-JLIL: MISWAK (SALVADORA PERSICA ROOTS): DISCOVERY OF A NEW BIOMATERIAL FOR REMOVING ...
38 Materiali in tehnologije / Materials and technology 51 (2017) 1, 35–39
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967-2017) – 50 LET/50 YEARS
Figure 4: Freundlich equilibrium isotherm for lead adsorption on
Miswak powder
Slika 4: Freundlich ravnote`na izoterma za adsorpcijo svinca na
Miswak prahu
Figure 3: Langmuir equilibrium isotherm for lead adsorption on
Miswak powder
Slika 3: Langmuir ravnote`na izoterma za adsorpcijo svinca na
Miswak prahu
estimated using the nonlinear regression method and are
tabulated in Table 6. As shown in Figure 4, the Freund-
lich model also correlates the experimental data well at
T = 25 °C.
Table 6: Freundlich equilibrium parameters for lead ions adsorption
on Miswak powder
Tabela 6: Freundlich ravnote`ni parametric za adsorpcijo ionov
svinca na Miswak prahu
Temperature K (L/g) b (L/mg) R2
T = 25 °C 0.7207 1.457 0.941
T = 45 °C 1.0690 1.862 0.720
6 CONCLUSIONS
The adsorption of lead ions on the surface of miswak
powder was studied. The study on the influence of the
initial concentrations on the adsorption capacity of the
Saudi miswak powder indicated that the saturation
capacity increased with increasing the initial solution
concentration. The maximum adsorption capacity of
miswak powder (SPRP) for lead ions was 18.2 (mg g–1)
and (0.79 (mg g–1) at 25 °C and 45 °C, respectively. The
application of Langmuir and Freundlich models showed
that this model fitted the experimental data well at T = 45
°C, while, the Freundlich model correlated the
experimental data well at T = 25 °C.
Acknowledgements
The author would like to thank King Abdulaziz City
for Science and Technology (KACST) for the support
and encouragement to carry out the study.
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