Experimental Design Modeling of the Effect of Hexagonal Wurtzite-ZnO Synthesis Conditions on Its Characteristics and Performance as a Cationic and Anionic Adsorbent.

Al-Amer Al-Amer,Da’na Da’Na,Khalaf Khalaf,Hessien Hessien

doi:10.3390/molecules24213884

Abstract

Surface composite design was used to study the effect of the ZnO synthesis conditions on its adsorption of methyl orange (MO) and methylene blue (MB). The ZnO was prepared via hydrothermal treatment under different conditions including temperature (T), precursor concentration (C), pH, and reaction time (t). Models were built using four Design expert-11 software-based responses: the point of zero charge (pHzc), MO and MB removal efficiencies (RMO, RMB), MO and MB adsorption capacities (qMO, qMB), and hydrodynamic diameter of ZnO particles (Dh). ZnO was characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, UV/VIS spectroscopy, thermal gravimetric analysis (TGA), and dynamic light scattering (DLS). The formation of ZnO was confirmed by the XRD, UV, and FTIR spectra. Results showed a very high efficiency for most of the samples for adsorption of MB, and more than 90% removal efficiency was achieved by 8 samples among 33 samples. For MO, more than 90% removal efficiency was achieved by 2 samples among 33 samples. Overall, 26 of 31 samples showed higher MB adsorption capacity than that of MO. RMB was found to depend only on the synthesis temperature while RMO depends on temperature, pH, and reaction time. pHzc was found to be affected by the synthesis pH only while Dh depends on the synthesis pH and precursor concentration.

Highlights

Metal oxides have attracted huge attention recently due to their important applications in many fields
The thermal gravimetric analysis (TGA) and DTA analyses (Figure 1b) revealed that the ZnO lost about 1% of its weight when the temperature reached 104 ◦ C, which may be related to the desorption of CO2 and H2 O attached to the surface, and 2% weight loss of the total weight occurred at about 130 ◦ C, which is related to strongly bonded water
ZnO nanoparticles were synthesized via a hydrothermal technique under different conditions following surface composite design methodology

Summary

Introduction

Metal oxides have attracted huge attention recently due to their important applications in many fields. The ZnO has received great attention due to attractive characteristics including its novelty, diversity, and controlled morphologies [1], which can be used in a wide range of applications such as drug delivery and anticancer [2], antimicrobial [3,4], photocatalysis [1,5,6,7], Light-emitting diode (LEDs) [8], environmental applications [8,9], solar cells [7,10], drugs, cosmetics, antibacterial coatings for fabrics, and antibacterial packaging for food [11]. In addition to morphological structure, it is important for some applications to be able to control band gap energy for photocatalytic Molecules 2019, 24, 3884; doi:10.3390/molecules24213884 www.mdpi.com/journal/molecules

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Results

Conclusion