ABSTRACT
Here, the structural, optical, and adsorptive behaviors of Ni0.075-xMnxAl0.025(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 11.47o 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.
ABSTRACT
Zinc oxide is one of the novel metal oxides utilized for diverse applications. The sol-gel and unintended self-propagation procedures were applied to synthesize the porous and high surface area ZnO-based metal oxide nanocomposite. The p-type manganese(III) oxide was successfully coupled with n-type ZnO. The physical property characterization results revealed the surface area, porosity, and charge transfer capability improvement on the poly(vinyl alcohol) (PVA)-aided binary nanocomposite (PVA-ZnO/Mn2O3), compared to ZnO. The XRD patterns and TEM image analysis validated the nanometer size range for the materials (15-60 nm). The SEM micrographs and BET spectral details have confirmed the porous nature of the PVA-ZnO/Mn2O3 nanocomposite. The supporting results were obtained from the HRTEM (IFFT) and SAED pattern analyses. The EDX and HRTEM analyses were used for the confirmation of elemental composition and reality of the PVA-ZnO/Mn2O3 composite, respectively. The presence of the improved charge transfer property for PVA-ZnO/Mn2O3, compared to ZnO, was evidenced from acid orange-8 dye degradation. The highest zone of inhibition (14 mm) was recorded on Escherichia coli bacteria for the uncalcined PVA-ZnO/Mn2O3 nanocomposite compared to PVA, yet, less zone of inhibition compared to the calcined PVA-ZnO/Mn2O3 nanocomposite. The authors recommend the formation of the couple between metal oxides by electrochemical technique analyses as a future work.
