Influence of the number of regeneration cycles on the removal of ammoniacal nitrogen with zeolite clinoptilolite

The aim of this work was to investigate the influence of the number of regeneration cycles on the removal of ammoniacal nitrogen from aqueous solutions with zeolite clinoptilolite (in its sodium or homo-ionic form). In addition, the obtained results were correlated with the physicochemical properties of regenerated homo-ionic zeolites. A unifactorial experimental design, balanced with permanent effects, was applied to assess the removal of ammoniacal nitrogen with homo-ionic zeolites presenting 0–10 sodium regeneration cycles (Z0–Z10). The experimental conditions of trials were as follows: pH 7, contact time was 30 min, stirring speed was 100 rpm, in completely mixed batch reactors. Samples of natural zeolite (ZN without sodium homo-ionization) and homo-ionic zeolites (Z0–Z10) were used to determine their surface properties by using the BET-N₂ method (surface area (m²/g), pore volume (cm³/g) and pore diameter (Å)). Other determined properties were the zeta potential (by micro-electrophoresis), percentage of elements (by the X-ray disperse spectrometric method) and particle morphology by scanning electronic microscopy. The results have shown that homo-ionic zeolites had a high removal capacity of ammoniacal nitrogen; this and other properties did not change in a significant way, even after a number of regeneration cycles as high as 10.