Preparation of a novel CeO₂/SiO₂ adsorbent and its adsorption behavior for fluoride ion

Abstract

The silica-based CeO 2 adsorbent (CeO 2 /SiO 2) was prepared for removing fluoride from the aqueous solution. The synthesized adsorbent was characterized by scanning electron microscope, energy dispersive spectrum, X-ray diffractometer, Fourier transform infrared spectrometer, and zeta potential measurement analyses. The adsorption batch experiments in the various experimental conditions including solution pH, contact time, initial fluoride concentration, and adsorption temperature were performed and investigated. The maximum adsorption capacity of fluoride into CeO 2 /SiO 2 was 2.441 mmol/g at pH 3 and 298 K. The adsorption kinetics and isotherms were well described by the pseudo-second-order model and the Langmuir model, respectively. The fluoride adsorption reached the equilibrium in 15 min from the aqueous solution with the initial fluoride concentration of 400 mg/l at 298 K. In the temperature range of 298-338 K, the maximum adsorption capacity of fluoride decreased from 2.441 mmol/g to 2.109 mmol/l at pH 3. The adsorption thermodynamics study revealed that this process was a spontaneous, exothermic, and entropy-driving adsorption. Furthermore, the mechanism of adsorption was identified as the anion exchange and the electrostatic interaction. The desorption efficiency of fluoride-loaded CeO 2 /SiO 2 adsorbent could reach about 95% by 0.1 mol/l NaOH.

Investigation of kinetics and adsorption isotherm for fluoride removal from aqueous solutions using mesoporous cerium–aluminum binary oxide nanomaterials

“…Metal oxides have great potential for adsorption, favorable safety, minimal water solubility, and a benecial capacity for desorption, making them suitable materials. Some of them are magnetic iron-aluminum oxide/graphene oxide nanoparticles, 21 hydrous iron oxide incorporating cerium, 3 Ce-Zr oxide nanosphere-encapsulated calcium alginate beads, 22 ironaluminum nanocomposites, 23 aluminium oxide nanoparticles, 24,25 nanoscale aluminium oxide hydroxide, 26 magnetic core-shell Ce-Ti@Fe 3 O 4 nanoparticles, 27 hydroxyapatite montmorillonite nanocomposites, 28 2-line ferrihydrite, 29 cupric oxide nanoparticles, 30 CeO 2 /SiO 2 , 31 Ce-Zn binary metal oxides, 32 and superparamagnetic zirconia nanomaterials (ZrO 2 /SiO 2 /Fe 3 O 4 ). 33 However, the removal of uoride by these materials has resulted in low adsorption capacities (i.e., as low as 0.2 mg g À1 ) with long contact duration of more than 24 hours.…”

Preparation and Application of Glutaraldehyde Cross-Linked Chitosan Coated Bentonite Clay Capsules: Chromium(vi) Removal From Aqueous Solution

“…This was explained with the equations given in Table 1, then the isotherm constants were calculated with the slopes of the curves and the y-intercept of the equations. In these equations, Ce indicated metal concentration at equilibrium (mg/L); = was the amount of adsorbed metal ion by the adsorbent (mg/g) [28,[39][40][41].…”

“…The effect of temperature on the adsorption of Cr(VI) ions was investigated and the adsorption capacity was calculated as higher at low temperatures for BC composite capsules. By using Van't Hoff equation, a graph of log Kc vs. 1/T was drawn, standard free energy (G), enthalpy (H) and entropy (S) changes were calculated [40].…”

Environmental exposure of arsenic and fluoride and their combined toxicity: A recent update

“…However, reports showed that traditional carbons could not remove As and F due to its lower adsorption capacity (Rojas‐Mayorga, Bonilla‐Petriciolet, Silvestre‐Albero, Aguayo‐Villarreal, & Mendoza‐Castillo, ; Velazquez‐Jimenez, Arcibar‐Orozco, & Rangel‐Mendez, ). Adsorbent functionalized with aluminum, cerium, lanthanum and zirconium are more capable of removing contaminants (He et al, ; Lin, Wu, Khayambashi, Wang, & Wei, ; Te, Wichitsathian, Yossapol, & Wonglertarak, ). Some special characteristics such as surface area, porosity and the presence of functional groups enhanced the adsorption properties (Arcibar‐Orozco, Josue, Rios‐Hurtado, & Rangel‐Mendez, ).…”