Synthesis of smart ZnO@Mg(OH) 2 core - shell nanocomposite and its application for methylene blue photocatalytic degradation: Life cycle sustainability assessment and techno-economics

While several studies have developed photocatalysts for textile dye degradation, there is still a research gap in demonstrating the associated techno-economic, environmental, and potential impacts. Hence, this study focuses on developing an innovative photocatalytic material for persulfate-assisted methylene blue (MB) degradation, followed by designing an up -scale photocatalytic system, estimating the wastewater treatment unit price, and identifying the process life cycle. A ZnO@Mg(OH) 2 core -shell nanocomposite was synthesized and characterized, depicting 2.77 eV band -gap energy, 64.0 % crystallinity index, and 145 nm particle size, with 21.7 nm pore radius, 0.418 cm 3 /g pore volume, and 38.603 m 2 /g. The MB removal efficiency exceeded 90 % at 60 mg-MB/L, 658 mg/L catalyst dosage, pH of 3.2, and 1468 mg/L oxidant level within 90 min. These experimental data were involved in designing a ZnO@Mg(OH) 2 nanocomposite synthesis process for treating 10 m 3 /d of dye -laden wastewater, giving capital expenditure and operating cost of 2.7 and 4.0 USD/m 3 , respectively. The life cycle analysis (LCA) boundary included inputs (energy, catalyst material, textile wastewater, and chemicals), and outputs (treated effluent and exhausted catalyst material). The LCA results depicted that the as -prepared photocatalyst should be appropriately disposed of because it affects the "Terrestrial ecotoxicity potential " mid -point category and "Natural resources " end -point environmental impact criterion.