Lead (II) is one of the most important metal ion pollutants commonly found in industrial wastewater. It is harmful to animal kingdom and prolong exposure can cause severe health trouble including cancer. Therefore, its removal to a permissible level is warranted for an eco-friendly and sustainable environment. The use of low-cost chitisan based composite material as an adsorbent can be a promising approach for Pb(II) decontamination. In this study, a novel chitosan/fluorapatite (Cs-Fap) composite has been prepared from chitosan (Cs) and fluorapatite (Fap) for the efficient removal of Pb(II) from water. Exploration of the effect of contact time, solution pH, initial Pb(II) concentration, adsorbent dosage, and the temperature was performed to understand the adsorption process. Pb(II) adsorption performance was compared among Cs, Fap and Cs-Fap composite. Pb(II) adsorption was fast and approched equlibrium in 30 min. Maximum Pb(II) adsorption was achieved at pH 4.0 for an optimum dose of 2g/L. Pb(II) adsorption kinetics data followed a pseudo-second order (PSO) model, while equilibrium isotherm data best described by Langmuir equation nicely. The maximum adsorption capacity (mg/g) follows the order: Cs-Fap (60.24) > Fap (48.31) > Cs (43.29) at pH 4.0. Thermodynamic analysis revealed that adsorption process was a feasible, endothermic and spontaneous in nature. The proposed mechanism of Pb(II) uptake involved physisorption, ion-exchange, electrostatic attraction, and surface complexation. Cs-Fap composite showed excellent regeneration capacity. After 4 (four) subsequent regeneration cycles, there was no notable loss of its adsorption capacity. The results of this study showed that the Cs-Fap composite is promising for the removal of Pb(II) and it can be used as an adsorbent for the removal of other metal ions from real environmental samples.

1. ORIGINAL PAPER
A promising chitosan/fluorapatite composite for efficient
removal of lead (II) from an aqueous solution
Rachid El KaimBillah1
& Md. Aminul Islam2
& Mahfoud Agunaou1
& Abdessadik Soufiane1
Received: 14 September 2020 /Accepted: 25 May 2021
# Saudi Society for Geosciences 2021
Abstract
Lead (II) is one of the most important metal ion pollutants commonly found in industrial wastewater. It is harmful to the animal
kingdom, and prolonged exposure can cause severe health trouble including cancer. Therefore, its removal to a permissible level
is necessary for an eco-friendly and sustainable environment. The use of low-cost chitosan-based composite material as an
adsorbent can be a promising approach for Pb(II) decontamination. In this study, a novel chitosan/fluorapatite (Cs-Fap) com-
posite has been prepared from chitosan (Cs) and fluorapatite (Fap) for the efficient removal of Pb(II) from water. Exploration of
the effect of contact time, solution pH, initial Pb(II) concentration, adsorbent dosage, and the temperature was performed to
understand the uptake process. Pb(II) adsorption performance was compared among Cs, Fap, and Cs-Fap composite. Pb(II)
adsorption was fast and approached equilibrium in 20 min. Maximum Pb(II) accumulation was achieved at pH 4.0 for an
optimum dose of 2g/L. Pb(II) adsorption kinetics data followed a pseudo-second-order (PSO) model, while equilibrium isotherm
data was best described by the Langmuir equation nicely. The maximum uptake capacity (mg/g) follows the order: Cs-Fap
(60.24) > Fap (48.31) > Cs (43.29) at pH 4.0. The thermodynamic analysis revealed (ΔG < 0, ΔS > 0, and ΔH > 0) that the
uptake process was feasible, endothermic, and spontaneous. The proposed mechanism of Pb(II) uptake involved physisorption,
ion-exchange, electrostatic attraction, surface complexation, and precipitation. The Cs-Fap composite showed an excellent
regeneration capacity up to four subsequent cycles. The results of this study showed that the Cs-Fap composite is promising
for Pb(II) uptake, and it can be utilized as an adsorbent for the uptake of other metal ions from real environmental samples.
Keywords Chitosan . Fluorapatite . Lead (II) . Adsorption . Cs-Fap composite . Langmuir . Freundlich
Introduction
The pollution of the aquatic environment by metal ions is a
major concern in recent years (Zheng et al. 2020). The problem
is acute in many developing countries due to rapid population
growth, unplanned urbanization, and industrialization (Islam
et al. 2018a, Islam 2018, Islam 2019a, 2019b, 2019c).
Lead(II) is an important toxic metal ion commonly found in
industrial wastewater (Zhang et al. 2017). Numerous applica-
tions of Pb(II) in industry and other purposes led to its enhanced
release into the environment (Islam et al. 2018b). Due to its
non-biodegradable nature, it can readily enter the food chain.
Prolonged exposure to Pb(II) can cause severe health problems
including cancer, neurological, endocrine, renal, kidney, brain,
gastrointestinal, hematological, and cardiovascular diseases
(Dewage et al. 2018; Manzoor et al. 2019; Zhang et al. 2017).
It can also cause cell division, water absorption, and balance
problems in flora and fauna (Dewage et al. 2018). The permis-
sible concentration of Pb(II) in water is approximately 10 μg /L
based on WHO (World Health Organization) and AWWA
(American Water Works Association), while the US EPA
(Environmental Protection Agency) action level is 15 μg/L
(Awual et al. 2020b; Dewage et al. 2018). It is worth noting
that Pb(II) is still found at a higher concentration than the per-
missible limit in aquifers. Therefore, the presence of trace levels
of Pb(II) in drinking water is considered highly toxic and re-
quires notable removal from water to safeguard public health.
Responsible Editor: Amjad Kallel
* Md. Aminul Islam
aminul.chem.as@aust.edu; aminulchem@gmail.com
1
Laboratory of Coordination and Analytical Chemistry, Department
of Chemistry, Faculty of Sciences, University of Chouaib Doukkali,
El Jadida, Morocco
2
Department of Arts and Sciences, Faculty of Engineering,
Ahsanullah University of Science and Technology (AUST), Tejgaon
I/A, Dhaka -1208, Bangladesh
Arabian Journal of Geosciences (2021) 14:1134
https://doi.org/10.1007/s12517-021-07473-w