THE EFFECTS OF NATURAL ZEOLITE ON AMMONIA REMOVAL
Ammonia and heavy metal cations pose serious health and environmental risks. Studies have determined that natural clinoptilolite zeolite is selective for these cations, meaning that it will absorb and bind them in its honeycomb structure even in the presence of larger amounts of competing cations (Mumpton, 1999). In addition, zeolite forms strong bonds with ammonia and heavy metals that are difficult to break. This prevents leaching of contaminants into the environment.
Surface water, ground water, and wastewater contain many pollutants, including inorganic and organic compounds, that are hazardous to humans, animals, and plants. One of the most potent pollutants is ammonia because it contributes to accelerated eutrophication of lakes and rivers, dissolved oxygen depletion, and fish toxicity (Wang & Peng, 2010).
The main mechanism that accounts for the adsorption of ammonium ion onto natural zeolites is ion exchange (Wang & Peng, 2010). The adsorption capacity of clinoptilolite is between 2 – 30 mg NH4+/g. Scientists have also found that some treatments, including the exhaustion and regeneration cycle, increase adsorption capacity. Essentially this means that zeolite can be reused time and time again, and that its capacity to remove ammonia increases over time.
Bolan et al. (2003) tested the effect of clinoptilolite on the removal of ammonium from wastewater streams. Prior to application, the mineral was treated with alkali solutions and the cation-exchange capacity increased by up to 74 percent; zeolite held up to 18.7–20.1 mg NH4+/g. After zeolite minerals were cation-loaded, the mineral could be regenerated and reused by leaching ammonium ions with 0.5 M of hydrogen chloride. The leaching process did not impact zeolite’s adsorption capacity and the minerals remained effective after 12 regeneration cycles (Bolan et al., 2003).
Jorgensen and Weatherley (2006) examined the use of clinoptilolite as a cationic exchanger for the purpose of removing ammonia from wastewaters. The results indicated that clinoptilolite had a significant increase in performance after cycles of exhaustion and regeneration; regenerated clinoptilolite showed a maximum adsorption capacity of 450 bed volumes (Jorgensen & Weatherley, 2006). Again, the results demonstrate that zeolite is not only capable of removing ammonia from wastewaters, it can also be reused time and time again.