Calcined Chitosan-Supported Layered Double Hydroxides: An Efficient and Recyclable Adsorbent for the Removal of Fluoride from an Aqueous Solution

Abstract

In this work, calcined chitosan-supported layered double hydroxides (CSLDO) were synthesized through a co-precipitation method that restrained the particles’ aggregation of LDHs and exhibited huge specific surface areas, which can enhance the fluoride adsorption capacity. CSLDOs were characterized by physical and chemical methods and used for fluoride adsorption in an aqueous solution. The results indicated that the nanoparticles were constructed first and then assembled to form a porous and layered structure, and chitosan-supported layered double hydroxides (CSLDHs) calcined at 400 °C (CSLDO400) showed the highest specific surface area of 116.98 m2·g−1 and the largest pore volume of 0.411 cm3·g−1. CSLDO400 exhibited excellent adsorption performance at a wide pH range from 5 to 9 for fluoride. The adsorption kinetics indicated that the adsorption reached equilibrium after 120 min, and followed a pseudo-first-order model. It agreed well with the Langmuir isotherm with maximum adsorption amounts of 27.56 mg·g−1. The adsorption of fluoride ions was spontaneous and endothermic. Furthermore, CSLDO400 showed a high stability for fluoride removal; it could still achieve 68% removal for fluoride after repeating five times of adsorption–desorption cycles. This study demonstrated that CSLDO400 is a promising functional material to remove fluoride from surface/ground water.

Effects on the Mechanical Properties of Nacre-Like Bio-Hybrid Membranes with Inter-Penetrating Petal Structure Based on Magadiite

“…Besides, to prepare one kind of nacre-like material with excellent mechanical properties, the choice of inorganic layered materials congregated with CS is very important [20]. Supported by different technology, Chen et al [21] inserted different proportions of cationic biopolymer chitosan and quaternate hemicellulose in montmorillonite (MMT) to get compact and robust nanocomposite films with a nacre-like structure and multifunctional characteristics.…”

Synthesis of Chitosan-Polyvinyl Alcohol Biopolymers to Eliminate Fluorides from Water

“…The existing chitosan in the beads, of both materials, maintains the protonated amino groups along the chain and this facilitates the electrostatic interaction between the polymer chains and the negative charge of the fluoride [20]. The adsorption capacity with the Ch-PVA-TPP material was not significant, concerning the other materials (Ch-PVA-5EGDE, Ch-PVA-7EGDE and Ch-PVA-NaOH-TPP), this could possibly be because the cross-linking material occupied the active sites of chitosan beads [19]. Likewise, it was observed that the hydrogel of Ch-PVA-NaOH-TPP showed greater absorption of fluoride at pH 5, followed by pH 7 and pH 6.…”

“…A convenient pore classification, was originally proposed by Dubinin in 1992 and, subsequently, officially adopted by the International Union of Pure and Applied Chemistry (IUPAC). This classification is based on the properties that the different pores have according to their dimension in the adsorption processes and are manifested in the adsorption isotherms, according to this consideration the analyzed material can be classified as mesoporous [19,37].…”

“…However, the high cost and poor efficiency of these methods designed to reduce the concentration of fluoride in water have made them infeasible [3,[8][9][10][11][12][13]. The fluoride removal process based on the adsorption of biomaterials: alumina, minerals, and metal oxides, clays, metal ion nanoparticles [6,[14][15][16][17], polypyrrole, chitosan and chitin [18][19][20][21][22], has been widely accepted due to its capacity for the removal of fluorides in water. The adsorption has peculiar advantages such as low cost, simplicity of design and operation, large sorbent availability, ability to treat a pollutant at a high concentration, insensitivity to toxic substances, and high effectiveness [6].…”

Synthesis and Study of an Efficient Metal-Organic Framework Adsorbent (MIL-96(Al)) for Fluoride Removal from Water

“…Excessive fluoride in natural water is predominantly caused by the discharge of fluoride-rich wastewater effluent or surface water washing of fluoridecontaining ore over long periods [1,2]. Excessive fluoride in the human body can mineralize calcium hydroxyphosphate to calcium fluorophosphate, which causes a significant change in the fluoride-phosphorus ratio resulting in spurs, periosteal hyperplasia, osteoporosis, osteosclerosis, and bone deformation [3,4]. Long-term intake of high-fluoride food by children will result in enamel hypoplasia, tooth damage, and fluoride deposition, causing a series of deformities in the bones [5,6].…”