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Fabrication of aluminum-based hybrid nanocomposite for photocatalytic degradation of methylene blue dye: A techno-economic approach
* 1 , 1 , 2 , 1, 3
1  Environmental Engineering Department, Egypt-Japan University of Science and Technology (E-JUST), Alexandria, 21934, Egypt
2  Department of Chemical Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8552, Japan
3  Sanitary Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, 21544, Egypt
Academic Editor: Antoni Sánchez


Methylene blue (MB) is one of the most consumed dyes in the textile industry, imposing toxic, mutagenic, and/or carcinogenic effects on human health. The unmanaged disposal of MB-laden wastewater into the aquatic environment is associated with the loss of species and damage to habitats. Because its molecular structure contains a 6-carbon aromatic ring, nitrogen, and sulfur, MB has a non-biodegradable property. Compared with conventional biological processes, advanced oxidation technology is preferable for mineralizing MB into simple and non-toxic species. This study focuses on synthesizing aluminum-based hybrid nanocomposite (AHN) by the co-precipitation technique, followed by its application for photocatalytic degradation of MB under visible light. Material characterization revealed that AHN had an Al2O3-MgO chemical formula, with an irregular geometric shape and particle sizes in the 50-60 nm range. XRD analysis showed that AHN had a cubic crystal structure with γ-Al2O3 and crystallite size in the range of 15-34 nm. The BET surface area was 750 m2/g, with an average pore diameter of 11 nm and pore volume of 1.9 cm3/g. The AHN band gap was calculated as 5.6 eV. At an initial MB concentration of 11 mg/L, the highest removal efficiency was 72.7±3.41% at pH of 8.4 and photocatalyst dosage of 0.5 g/L within 180 min. It’s supposed that during visible light irradiation in the presence of AHN photocatalyst, there is electron transfer and formation of super-oxide (O2ˉ) and hydroxyl (OH) radicals responsible for the efficient degradation of MB dye. Another portion of MB could be removed by deposition on the synthesized AHN material, facilitating the MB photo-degradation pathway. The photodegradation reaction followed the pseudo-first-order kinetic model with (k1) of 0.0075 min-1. The electrical energy consumption was evaluated and achieved at 184 kWh/m3, equivalent to an operating cost of 16.5 USD/m3. The removal of MB by the manufactured AHN catalyst showed good agreement with other photocatalytic degradation mechanisms reported in the literature.

Keywords: photo-degradation mechanism; dye-laden solution; kinetic model; optimum operating condition; running cost