M.S. Berber-Mendoza

Removal of ammonium from aqueous solution by ion exchange on natural and modified chabazite.

The ammonium exchange capacity of a natural chabazite was studied in this work. The XRD analysis of the zeolite sample revealed that the main zeolitic phase was chabazite. The textural properties were determined by the N(2)-BET method and the surface morphology and charge were examined using a scanning electron microscope and a zetameter, respectively. The ion exchange equilibrium data were obtained in a batch adsorber and the Langmuir isotherm fitted plausibly well the equilibrium data. The effects of the temperature and pH on the ammonium exchange capacity of chabazite were investigated and the capacity increased augmenting the temperature from 15 to 35 °C and pH from 3 to 6. The natural chabazite was modified by a hydrothermal treatment using NaCl and KCl solutions and it was found that the modification influenced the ammonium exchange capacity of the chabazite. The ammonium capacity of natural chabazite was compared with that of a natural clinoptilolite and it was concluded that the chabazite capacity was 1.43 times higher than that of clinoptilolite.

Competitive Adsorption of Heavy Metals from Aqueous Solution onto Oxidized Activated Carbon Fiber

In this study, the competitive adsorption of Ni(II)–Pb(II) and Ni(II)–Zn(II) on oxidized activated carbon fiber (ACF-Ox) from aqueous solutions was studied. The experimental competitive adsorption data were interpreted by the following multicomponent adsorption isotherms: non-modified, extended, and modified Langmuir; non-modified and modified Redlich-Peterson; extended Freundlich; and Sheindorf-Rebuhn-Sheintuch. The extended Freundlich multicomponent isotherm best fitted the adsorption data for both systems Ni(II)–Pb(II) and Ni(II)–Zn(II) onto ACF-Ox. The single metal adsorption on ACF-Ox showed that the Ni(II) adsorption capacity was 1.12 times greater than that of Zn(II); however, in the competitive adsorption, the Zn(II) presented an intense antagonism to the adsorption of Ni(II) and Ni(II) to Zn(II) too. The single-adsorption isotherms of Pb(II) and Ni(II) on ACF-Ox revealed that the selectivity of Pb(II) towards ACF-Ox was slightly higher than that of the Ni(II). Nevertheless, in the competitive adsorption, the affinity of Pb(II) towards the ACF-Ox was far greater than that of the Ni(II).