Title:A Mini Review on the Application of Chitosan Composites for the
Adsorption of Fluoride from Aqueous Solution
Volume: 12
Issue: 3
Author(s): Clint Sutherland*, Beverly Chittoo and Abdel Islam
Affiliation:
- Project Management and Civil Infrastructure Systems, University of Trinidad and Tobago, W.I., Trinidad
Keywords:
Chitosan composites, adsorption, kinetics, equilibrium, fluoride, adsorption mechanism.
Abstract:
Background: Exploration into the development of cost-effective and eco-friendly adsorbents
for the removal of fluoride continues to be unabated. The modification of chitosan through the
development of composites and derivatives has shown great promise over the past decade.
These modifications aim to overcome the limitation of chitosan, such as separability and adsorption
capacity.
Objectives: The objective of this study is to review various modifications to chitosan for defluoridation,
the resulting adsorption capacities, operational parameters that appreciably influence the fullscale
application of adsorption systems and, where reported, the mechanisms that influenced the adsorption
process.
Results and Discussion: Among the adsorbents reviewed, most of the processes were best modelled
by the Langmuir isotherm and the pseudo-second order model. Chitosan composites were able to
achieve significantly higher F- adsorption capacities and compared well to other adsorbents in the
literature. Gamma degraded chitosan-Fe(III) beads, 10%-Lanthanum-incorporated chitosan beads
and neodymium-modified chitosan were found to easily achieve the WHO drinking water limit of
1.5 mg/L. In all instances, the reactions were spontaneous and endothermic. Fluoride adsorption
was shown to increase from the acidic region to near neutral pH followed by a decrease into the alkaline
range.
Conclusion: The presence of competing ions is a major operational parameter for full-scale adsorption
applications. The presence of carbonate and bicarbonate ions has been a consistent hindrance in
reported studies. Thus, future investigations are warranted in this area.