P-102: Efficacy of Silica Nanoparticles in Decreasing Nitrite Content of Water


Jebali A *, Hekmatimoghaddam SH , Dargahi M , lataei E ,

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Objective: Drinking water may be contaminated with nitrates and nitrites, which is mostly because of industrial and urban sewage spillage into the drinking water sources of cities, and also use of chemical fertilizers in rural areas. Nitrite is toxic and carcinogenic because it affects DNA and synthesized proteins, and forms methemoglobin that causes anemia and cyanosis. Infants are more vulnerable than adults because of their peculiar physical and nutritional conditions. Different approaches have been taken for reduction of the amount of nitrite in the water, including the following: demineralization by reverse osmosis or distillation, ion exchange, blending, electrodialysis, use of zeolites such as DDAC (distearyl-dimethyl-ammonium-chloride), SDBAC (stearyl- dimethyl- benzyl- ammonium-chloride) or clinoptilolite, use of metal catalysts such as palladium, use of anaerobic bioprocess, use of sulfamic acid, heterotropic and nitrite-oxidizing bacteria, and finally use of synthetic biofilters. Nanoparticles have unique physical and chemical properties due to their small size and high surface-to-volume ratio, hence having enormous applications in industry and health sciences. In this study, nanoparticles of silica (silicon dioxide) have been used for decreasing nitrites in water, and their efficacy in different incubation (reaction) times has been evaluated. Materials and Methods: In this lab trial study, different concentrations (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 mg/L) of nitrite and 0.1 g/mL of SiO2 nanoparticles (10 nm, 600 m2/g, from Lolitech, USA) were mixed, and photometric measurement of supernatant optical density was performed after 0.5, 1, 1.5, 2, 5, 10, and 24 hours, using nitrite test kit (Vaheb, Iran). For comparison with the control tubes, t-test was used for both different concentrations and different incubation times. Results: Optical densities decrease as the incubation time increases, and the lowest OD is related to 24 hours incubation, that is, nitrite is absorbed by silica nanoparticles optimally when in contact for 24 hours, and the maximum reduction is around 72%. The paired t-test on the results showed that there is a significant difference between the control group and the 24, 10, 5, 2, and 1.5 hours groups at various concentrations of nitrite (p value= 0.001). Conclusion: This is the first record that shows nitrite will be absorbed by silica nanoparticles. However, elimination of the nanoparticles in treated water and the cytotoxicity of residual nanoparticles of silica in the body should be investigated when it is anticipated that some amount of it might be taken by human and animals.