Ion Exchange Efficiency of Nitrate Removal from Water 1- Equilibrium Sorption Isotherms for Nitrate on Resin Purolite A-400

In the current study, an anion exchange resin, Purolite A 400, was employed to investigate nitrate removal from aqueous solutions. For the adsorption isotherm study, 0.15 g of resin was contacted with 50 mL of NaNO3 solution at the concentrations of 5, 20, 40, 60, 80, 100, 150, and 200 mg-NO3 L-1 with two pHs of 6.5 and 7.5 at two equilibrium temperatures of 20 and 25 oC for 24 h with continuous shaking. Aadsorption characteristics of the resin for nitrate were evaluated by modeling of adsorption isotherms using Langmuir, Freundlich, Redlich - Peterson and Sips models. Based on the statistics of Chi-square test and correlation coefficient, Langmuir equation showed the best fit to the data. Sips and Redlich–Peterson equations followed Langmuir model, respectively. Freundlich equation fitted poorly to the date, though its correlation coefficient was significant. Comparison and relations among the calibrated parameters of the models showed that Sips and Redlich–Peterson equations were similar to Langmuir equation. Based on the latter equation, Purolite A-400 revealed higher (average 30 percent) bonding energy at 25 oC than 20 oC. Adsorption capacity of the resin also was 25 percent higher at pH 6.5 than pH 7.5.