Influence of Zn/Fe Molar Ratio on Optical and Magnetic Properties of ZnO and ZnFe₂O₄Nanocrystal as Calcined Products of Layered Double Hydroxides

Abstract

The coprecipitation method has been used to synthesize layered double hydroxide (Zn-Fe-LDH) nanostructure at different Zn2+/Fe3+molar ratios. The structural properties of samples were studied using powder X-ray diffraction (PXRD). LDH samples were calcined at 600°C to produce mixed oxides (ZnO and ZnFe2O4). The crystallite size of mixed oxide was found in the nanometer scale (18.1 nm for ZnFe2O4and 43.3 nm for ZnO). The photocatalytic activity of the calcination products was investigated using ultraviolet-visible-near infrared (UV-VIS-NIR) diffuse reflectance spectroscopy. The magnetic properties of calcined LDHs were investigated using a vibrating sample magnetometer (VSM). The calcined samples showed a paramagnetic behavior for all Zn2+/Fe3+molar ratios. The effect of molar ratio on magnetic susceptibility of the calcined samples was also studied.

Functionalization of Wood Char for Adsorption of Organic Contaminant

“…Zn-Fe-LDH has been formed by coprecipitaion of Zn(II) and Fe(III) nitrate solution using NaOH solution. Calcination of LDH not only changes hydroxide to oxide, but also removal of anion by thermal decomposition reaction Calcination of Zn-Fe-LDH forms ZnFe-LDO or ZnFe2O4 [16]. The ZnFe-LDO/AC composite from wood char showed good adsorption of paracetamol.…”

Iron-based Layered Double Hydroxides aiming biomaterials: structure, composition, and polymer composites

“…Although much less studied than Al-LDHs, MgRFe and ZnRFe LDHs have been reported for catalysis [78,79], agriculture [80], energy conversion/storage [81,82], as adsorbents for environmental remediation in its layered phases or as oxides after calcination [83][84][85][86][87][88][89][90][91][92][93], and more rarely for organic anions loading and delivery [94]. Ironbased LDHs (Fe 3+ -LDHs) are difficult to characterize due to their quite low crystallinity and the presence of crystalline and/or amorphous impurities.…”

“…Phase segregation also tends to occur when increasing the value of the M 2+ /Fe 3+ molar ratios, combined with the application of thermal treatment. Such conditions conduct to the appearance of XRD peaks not attributed to the corresponding LDH materials and frequently, for Zn-LDHs, peaks related to Zn(OH)2 and ZnO species [84,85,88,[98][99][100][101][102][103][104][105][106][107][108]. For instance, Morimoto et al [109] investigated the effect of different aging temperature values (25,50,75,100,125, and 150 °C ) on the formation of hematite in MgRFe-Cl (R = 2, 3, and 4) samples and observed that hematite formation is favored as higher the iron content and higher the temperature; this fact was explained by the decrease of LDH dehydroxylation temperature with the increase in the iron amount.…”

“…These conditions were then applied to all members of Mg series. They were also applied for Zn series except for the temperature, since heating may lead to the formation of ZnO/Zn(OH)2 as often reported in the literature [84,85,88,[98][99][100][101][102][103][104][105][106][107][108], and the pH set to 7.5 (see Appendix B:…”

“…By simplification, the same parameters were applied for the materials composed by zinc, but without heating to avoid the formation of undesired zinc phases, such as Zn(OH)2 and/or ZnO. [85,252] Also, synthetic pH for the Zn-series was lowered to 7.5, since even an increase in one pH unity from this value conducted to the formation of only Zn(OH)2 and ZnO side phases for the material with Zn2Fe-Cl nominal composition, as shown in shows two main mass loss events. The first event, with onset temperature at 120 °C, is a combination of the release of hydration water molecules (see MS curve, m/z = 18), HABI melting (about 170 °C [268]), both endothermic, and an additional event not associated with the release of high amount of CO2 that contributed to an overall exothermic event.…”