Modification of a natural zeolite with Fe(III) for simultaneous phosphate and ammonium removal from aqueous solutions

Abstract

BACKGROUND: The incorporation of Fe(III) was performed in a natural clinoptilolite (Z-N) for simultaneous phosphate and ammonium removal. RESULTS: The existence of hydroxyl groups (congruent to Fe-OH) in the iron zeolite (Z-Fe) enhances the phosphate uptake from 0.6 +/- 0.1 mg-P g(-1) in Z-N to 3.4 +/- 0.2 mg-P g(-1) in Z-Fe. However, the ammonium sorption capacity slightly decreases from 33 +/- 2 mg-N g(-1) in Z-N to 27 +/- 2 mg-N g(-1) in Z-Fe. The equilibrium and kinetics sorption were well explained by the Langmuir isotherm and the intraparticle diffusion model, respectively. CONCLUSIONS: Both the phosphate and ammonium uptake were slightly affected by the coexistence of competing ions. The phosphate sorption capacity of iron zeolite was decreased in the regeneration cycles. Desorption using a 1 mol L-1 NaOH solution under dynamic conditions provided higher enrichment factors for ammonium than phosphate