Electrosynthesis of zirconia, zinc and iron supported HY zeolite-based catalysts for enhanced photodecolorization of dyes
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Date
2013
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Publisher
Universiti Teknologi Malaysia
Abstract
A facile one-pot electrosynthesis method of Zr, Zn, and Fe nanoparticles supported on HY zeolite to form single (ZrO2/HY, ZnO/HY, Fe2O3/HY), double (ZrO2 -ZnO/HY, ZrO2 -Fe2 O3 /HY, ZnO-Fe2 O3 /HY), and triple (ZrO2 -ZnO - Fe2O3/HY) catalysts was studied. The catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), Brunauer- Emmett-Teller (BET), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), 29 Si and 27 Al magic angle spin nuclear magnetic resonance (2 9 Si and 27Al MAS NMR), X-ray photoelectron spectroscopy (XPS), and inductive coupled plasma-mass spectrometry (ICP-MS). A dealumination accompanied by isomorphous substitution of related metal ions was found to have occurred in the framework of aluminosilicate HY during the electrolysis, to form a new active species (Si-O-M), which indeed affects the photocatalytic activity toward methylene blue (MB) decolorization. A 10 mg L-1 MB was completely decolorized when using 0.38 g L-1 (single and triple metal) and 0.60 g L-1 (double metal) of 1 wt% metal/HY catalysts at pH 11 under light irradiation. The modification of catalysts has allowed the use of ultraviolet (UV) to visible light and also shortened the contact time from 6 to 1-2 h. According to biological oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC) analyses, nearly complete mineralization of MB was achieved. The catalysts were still stable after five cycles with just a small decrement (<10%) of decolorization percentage without any ions leaching. The degradation followed pseudo first-order kinetic rationalized Langmuir-Hinshelwood model. The dye adsorption is the controlling step of the process for all of the catalysts except for ZrO2 /HY and ZnO/HY, in which the reaction occurred in the bulk solution and at the surface of the catalyst. Response surface methodology (RSM) shows good significance of findings (confidence level, CL = 95%) with very low probability values (<0.0001) and a high coefficient of determination (R ). Good activity towards decolorization of other synthetic dyes such as Congo red (93.4%), methyl orange (85.3%), and simulated dyes (100%) promises the catalysts to be used in textiles industry wastewater treatment and also other applications
Description
Thesis (PhD. (Chemical Engineering))
Keywords
Dyes and dyeing—Chemistry, Textile chemistry—Research, Sewage—Purification—Color removal