Background and purpose: Nitrate is probably the most widespread groundwater contaminant in the world, due to its high water solubility. It imposes a serious threat to human health and contributes to eutrophication. The objectives of this study were set to explore how the factors of ultraviolet light and ionic strength could influence the nano zero valent iron (NZVI) system for nitrate removal. Material and methods: In this study, response surface methodology was employed for the design and analysis of experiments .Experiments were carried out as per Box–Behnken) BBD) surface statistical design with four input parameters namely NZVI dose (0.5–2g/L), initial concentration (50–150mg/L), contact time (15–60min), and ionic strength (1000-5000μmho/cm). All experiments were performed in the presence and absence of UV irradiation. Results: The Maximum reduction efficiency for experiments in the presence and absence of UV irradiation was 85.3% and 91.6% in nano zero valent iron dose 2g/L, initial concentration 100mg/L, Contact time 60, and ionic strength 3000μmho/cm. The proposed model was essentially in accordance with the experimental case with correlation coefficient R2 = 0.9992, 0.9946 and Adj-R2 = 0.9982, 0.9884, respectively. Conclusion: Removal efficiency of nitrate increased with increase in time and NZVI dosage. In contrast, it decreased when ionic strength and initial concentration increased. Also, UV irradiation accelerated the removal of nitrate.

Keywords: Box–Behnken design, nitrate, ionic strength, nano zero valent iron, ultraviolet light

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