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Abstract
Nitrite is an important pollutant appearing in the large amount of wastewater from flue gas denitrification process. Its removal is essential for wastewater discharge or reuse. In this paper, we made an attempt to remove nitrite using ion exchange resin (IXR) by conducting batch experiments first, in which adsorption equilibrium and kinetics were determined. Fixed bed experiments were then carried out to investigate bed breakthrough and elution behavior. Isotherm data showed that nitrite adsorption on IXR fitted Freundlich model better than Langmuir model. Kinetic data from batch experiments were well correlated with second-order reversible kinetics model. From bed experiments, it was found that increase in flow rate and inlet concentration decreased breakthrough time, but the capacity of saturated adsorption stayed almost the same. It was also found that the capacity of adsorption decreased in the presence of other anions. Breakthrough curves under various operating conditions were well predicted by the Thomas model, and nitrite ions adsorbed in the bed could be completely eluted by using 3.0 wt% NaCl solution at flow rate of 3.0 L•h−1.
ACKNOWLEDGEMENTS
This work was supported by the Chinese Academy of Sciences under the talented program.
NOMENCLATURE
| q | = | adsorption capacity (mg) |
| C | = | concentration (mg•L−1) |
| V | = | volume (L) |
| q0 | = | Langmuir constants (mg) |
| b | = | Langmuir constants (L•mg−1) |
| kf | = | Freundlich constants |
| n | = | Freundlich constants |
| ka1 | = | the adsorption rate constant for first order (min−1) |
| kd1 | = | the desorption rate constant for first order (min−1) |
| k | = | the overall rate constant (min−1) |
| ka2 | = | the adsorption rate constant for second order (L•mg−1•min−1) |
| kd2 | = | the desorption rate constant for second order (L•mg−1•min−1) |
| m | = | mass (g) |
| M | = | the amount of nitrite ions |
| Q | = | volumetric flow rate (L•min−1) |
| KT | = | Thomas rate constant |
Greek Letters
| δ | = | water retention |
| φ | = | recovery ratio |
Subscript
| t | = | adsorption time (min) |
| 0 | = | initial time |
| e | = | equilibrium state |
| ec | = | elution |
| in | = | flow in |
| out | = | flow out |