Effect of crystallite size reduction and widening of optical phonon vibration due to AC variation on ZnO/Mg composites in implementation of methylene blue degradation.

Abstract

The fashion industry's reliance on dyes contributes significantly to environmental pollution, which disturbs the ecological balance. To address this issue, we used ZnO/Mg combined with activated carbon (AC) at various concentrations (0.1 g, 0.5 g, and 1 g), which were synthesized via sol-gel and mechanical alloying processes. The analysis of X-ray diffraction shows reduced crystallite size, with d-spacing change ( $\to$ d $\leftarrow$ ) for ZnO/Mg/AC (0.5 g) and ( $\leftarrow$ d $\to$ ) for ZnO/Mg/AC (1 g), respectively. The results of the IR spectrum indicated the main vibrations is MgO and Zn-O bonds at wave numbers 673 cm^-1 and 467 cm^-1. It was found that ZnO/Mg/AC (1 g) shows high degradation performance $D\%$ : 86.15% as a consequence of reduced crystallite size: 22.67 nm, decreased skin depth: 0.002 cm, widening of optical phonon vibration ( $\Delta (\text{LO}-\text{TO})$ ): 252 cm^-1 and increased $E_{\text{g}}$ : 4.6 eV as a function AC variation. Moreover, the finding of high photocatalytic performance $\ge$  80% for 0.25 mL MB dissolved in 250 mL distilled water is obtained from all composites. Based on these results, ZnO/Mg/AC shows potential as a photocatalyst to solve the MB waste problem.