When concentrations of pollutants present a threat to the environment or human health, remediation action are necessary (Misaelides, 2011). This process consists of two approaches: the extraction of pollutants from soil and water as well as the reduction of their mobility (Misaelides, 2011).
While several products have been utilized for these purposes, the use of zeolite is a low-cost solution that provides a high sorption capacity with the ability to adjust the pH of soil and water systems. The application of natural zeolites to remediation processes is based on their ion exchange properties.
The main mechanism that accounts for the adsorption of chemicals and heavy metal ions 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. This finding can point to a cost savings in remediation programs without sacrificing product performance.
Myroslav et al. (2006) conducted a study regarding the sorption of heavy metals (nickel, copper, lead, and cadmium) by raw and pretreated clinoptilolite. The results indicate that fine fractions of clinoptilolite sorb higher amounts of metal due to higher mineral cleavage. Researchers concluded that clinoptilolite adsorbs heavy metal concentrations and is a particularly favorable application for low initial concentrations of metal.
A study by Motsi et al. (2009) studied the adsorption behavior of natural zeolite to determine its applicability in treating acid mine drainage containing lead, copper, zinc and magnesium. Researchers examined the rate of adsorption and the uptake at equilibrium in single and multi-component solutions. The results showed rapid uptake during the first 40 minutes, corresponding to an 80 percent total removal (Motsi et al., 2009).
Following this initial uptake, the rate of absorption decreased. However, the overall results demonstrated that natural zeolite has significant potential as an alternative, low cost material in the treatment of acid mine drainage (Motsi et al., 2009).
A study by Erdem et al. (2004) used a clinoptilolite application to remove metal concentrations from industrial wastewater. The batch method was employed and researchers used metal concentrations in a solution ranging from 100 – 400 mg/l. The results indicated that natural zeolites can be used effectively to remove metal cations from wastewater. Researchers also concluded that based on adsorption capacity, natural zeolite provides a substitute for the use of activated carbon as an adsorbent based on availability and low costs (Erdem et al., 2004).
A study by Fullen et al. (2011) examined the remediation of oil spills using natural zeolite. Various sand- clinoptilolite mixes were tested in terms of their ability to adsorb engine oil. Adsorption increased with clinoptilolite amount.
Researchers also found that it was possible to burn the oil-sand-zeolite mix and reuse the ignited mix for further oil adsorption. The findings indicated that sand-zeolite mixes can effectively adsorb terrestrial oil spills and remediate oil-contaminated soils (Fullen et al., 2011).