Background and purpose: Nitrate is one of the most common chemical pollutants in groundwater in the world. Adsorption has been considered as an effective and efficient method of removing pollutants, particularly nitrate from aqueous solutions and so the aim of this study was to magnetization of the carbon nanotubes with zero-valent iron and using it as an adsorbent for the removal of nitrate from aquatic environments. Materials and methods: In this study, reduction method for converting divalent iron into zero-valent iron and co-precipitation method for iron particles deposition on carbon nanotubes was used. Characteristics of absorbent were analyzed by SEM (structural equation modelling), XRD (X-ray powder diffraction), and VSM (value stream mapping) techniques. In this study, the effect of the pH, contact time, mixer speed, temperature, adsorbent dosage and the concentration of nitrate was investigated by one factor at the time method and then was optimized. Results: The pH equal to 3, 60 min contact time, 200 rpm stirring speed and 1 g/l absorbent was obtained as the optimum conditions in the adsorption of nitrate. Investigating the isothermandkinetic models showed that the experimental data correlate to the Langmuir adsorption isotherm model (R2 > 0.997) and pseudo-second order kinetic (R2 > 0.993). The reaction thermodynamic study also expressed endothermic and spontaneous reaction. Conclusion: In optimal conditions, carbon nanotubes modified by zero-valent iron has well potential to quickly and effectively remove nitrate and simply be separated from the solution by the magnet due to its magnetic property.

Keywords: Nitrate, carbon nanotubes, zero-valent iron, magnetic separation, adsorption

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