The impregnation of ZnO onto ZSM-5 derived from red mud for photocatalytic degradation of methylene blue

Hellna Tehubijuluw,Yuly Kusumawati,Riki Subagyo,Didik Prasetyoko

doi:10.1186/s42834-021-00113-8

Abstract

Photocatalytic degradation of Methylene Blue (MB) by zinc oxide/zeolite socony mobile-5 (ZnO/ZSM-5) composites was investigated. The ZSM-5 material was synthesized from red mud by a two-step hydrothermal method to which ZnO loadings at different mass ratios were subsequently performed. Characterizations using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and scanning electron microscopy were carried out to identify the formation of ZSM-5 and ZnO/ZSM-5. ZSM-5 and ZnO/ZSM-5 have cubic microcrystallite morphologies. ZnO loading in the ZnO/ZSM-5 composites was successfully performed and confirmed by the appearance of wurtzite peaks in the XRD spectra that matched the Joint Committee on Powder Diffraction Standards data. The presence of ZnO in ZSM-5 leading resulted in a decrease in the surface area and pore size as confirming by nitrogen adsorption-desorption isotherm experiments. The band gap of the samples was measured using UV-Vis diffuse reflectance spectroscopy. The optimum photocatalytic degradation of MB was observed at a ZnO loading of 34% w/w dubbed 34-ZnO/ZSM-5. The influence of the initial concentration of MB was also investigated at 80, 90, and 100 mg L− 1 using 34-ZnO/ZSM-5 and ZSM-5. Liquid chromatography–mass spectrometry characterization was performed to analyze the degradation products.

Highlights

Red mud (RM) is a sludge-like waste generated as a byproduct of bauxite processing
The X-ray diffraction (XRD) spectra indicated that the RM consisted of SiO2 polymorph (Inorganic Crystal Structure Database (ICSD), 170,482 at 12.29; 18.30°), gibbsite (00–007-0324, at 18.28; 20.31°), boehmite (00–021-1307, at 38.38°), hematite (00–0330664, at 33.15; 35.61°), magnetite (00–019-0629, at 35.42°), goethite (01–075-5065, at 21.27; 36.72°), quartz (00–046-1045, at 20.86; 26.64°), and TiO2 anatase (00– 021-1272, at 25.28; 37.80°), where all of them matched the Joint Committee on Powder Diffraction Standards (JCPDS) and ICSD
Compared to commercial zeolite socony mobile-5 (ZSM-5) (CZSM-5), SZSM-5 was successfully synthesized in this study, as indicated by the appearance of mordenite framework inverted (MFI) peaks as the characteristic peak of ZSM-5 [29]

Summary

Introduction

To produce one ton of aluminum from bauxite processing, 1.0 to 1.8 tons of high-alkalinity RM are generated, which amount to 35–40% of total bauxite ores [1]. The disposal of large amounts of RM has caused environmental problems, such as soil and groundwater contamination, and the formation of suspensions in water. One alternative to RM utilization is its use as an adsorbent It accounts for 30% of RM utilizations, most of which are applied for wastewater treatments [18]. E.g., dye compounds, accumulate in the adsorbents, further processing of the adsorbents is necessary, which is often expensive and less effective, causing other problems [21]

Methods

Results

Conclusion