Controllable Doping of Mn into Ni0.075-xMnxAl0.025(OH)2(CO3)0.0125·yH2O for Efficient Adsorption of Fluoride Ions

Ararso N Wagassa; Lemma T Tufa; Jaebeom Lee; Enyew A Zereffa; Tofik A Shifa

doi:10.1002/gch2.202300018

Controllable Doping of Mn into Ni_0.075-xMn_xAl_0.025(OH)₂(CO₃)_0.0125·yH₂O for Efficient Adsorption of Fluoride Ions

Glob Chall. 2023 Apr 6;7(6):2300018. doi: 10.1002/gch2.202300018. eCollection 2023 Jun.

Authors

Ararso N Wagassa¹, Lemma T Tufa^{1

2}, Jaebeom Lee³, Enyew A Zereffa¹, Tofik A Shifa⁴

Affiliations

¹ Department of Applied Chemistry Adama Science and Technology University P.O. Box 1888 Adama Ethiopia.
² Institute of Material Chemistry Chungnam National University Deajeon 34134 South Korea.
³ Department of Chemistry Chungnam National University Deajeon 34134 South Korea.
⁴ Department of Molecular Science and Nanosystem Ca' Foscari University of Venice Via Torino 155 Venezia Mestre 30172 Italy.

Abstract

Here, the structural, optical, and adsorptive behaviors of Ni_0.075-xMn_xAl_0.025(OH)₂(CO₃)_0.0125·yH₂O (Ni-Mn/Al) layered double hydroxides (LDHs) are investigated to capture fluoride from aqueous media. The 2D mesoporous plate-like Ni-Mn/Al LDHs are successfully prepared via a co-precipitation method. The molar ratio of divalent to trivalent cations is maintained at 3:1 and the pH at 10. The X-ray diffraction (XRD) results confirm that the samples consist of pure LDH phases with a basal spacing of 7.66 to 7.72 Å, corresponding to the (003) planes at 2θ of 11.47^o and the average crystallite sizes of 4.13 to 8.67 nm. The plate-like Mn-doped Ni-Al LDH consists of many superimposed nanosheets with a size of 9.99 nm. Energy-dispersive X-ray and X-ray photoelectron spectroscopies confirm the incorporation of Mn²⁺ into the Ni-Al LDH. UV-vis diffuse reflectance spectroscopy results indicate that incorporating Mn²⁺ into LDH enhances its interaction with light. The experimental data from the batch fluoride adsorption studies are subjected to kinetic models such as pseudo-first order and pseudo-second order. The kinetics of fluoride retention on Ni-Mn/Al LDH obey the pseudo-second-order model. The Temkin equation well describes the equilibrium adsorption of fluoride. The results from the thermodynamic studies also indicate that fluoride adsorption is exothermic and spontaneous.

Keywords: adsorption; aqueous fluoride ions; characterization; layered double hydroxides.