Column Adsorption Studies for the Removal of Ammonium Using Na-Zeolite-Based Geopolymers

Abstract

The aim of this study was to examine the removal of ammonium ions from a synthetic model solution by using Na-zeolite-based geopolymers. Na-zeolite (=analcime) is a residue from mining industry. Three adsorbents were prepared from Na-zeolite using different production steps and metakaolin as a blending agent. These novel adsorbents were investigated in a fixed-bed column system where the effects of different flow rates with the initial ammonium concentration of 40 mg/L were studied. The Thomas, Bohart–Adams and Yoon–Nelson breakthrough curve models fitted well with the experimental data with a high R2 value. After adsorption experiments, adsorbents were regenerated using a mixture of 0.2 M NaCl and 0.1 M NaOH as a regeneration agent; after that, adsorbents were reutilised for ammonium ion adsorption for three adsorption–regeneration cycles. The results of the experiment indicate that all the prepared analcime-based geopolymers are suitable adsorbents for the removal of ammonium ions and that capacity remains nearly constant for two of them during two adsorption–regeneration cycles.

Testing Zeolite and Palygorskite as a Potential Medium for Ammonium Recovery and Brewery Wastewater Treatment

“…The pH value of the solution is a key parameter for the removal of several pollutants, including ammonium [41,43]. Electrostatic interactions between adsorbents and adsorbate ions are strongly pH dependent [42,46]. The influence of pH on adsorption was evaluated though batch experiments for both adsorbents.…”

“…In addition, according to Layva-Ramos et al [48] and Genethliou et al [39], the ammonium ion NH 4 + is the predominant species at pH lower than 7, while at greater pH (alkaline) the NH 4 + -NH 3 equilibria shifts towards NH 3 . Sundhararasu et al [46] also avoided alkaline pH in their adsorption experiments with zeolite, since NH 4 + ions tend to evaporate as ammonia in high pH values. In addition, at pH values above 8, NH 4…”

“…These findings are in absolute agreement with the results of the current study (Figure 6). et al [46] also avoided alkaline pH in their adsorption experiments with zeolite, since NH4 + ions tend to evaporate as ammonia in high pH values. In addition, at pH values above 8, NH4 + is neutralized by hydroxyl groups, while below 6, H + and NH4 + compete against each other for adsorption on available active sites of the adsorbent [41,49].…”