Investigation of effective parameters in the removal of phosphate and iron contaminants by modified natural zeolite; Kinetic and thermodynamic study of adsorption

Clinoptilolite is a natural zeolite which is prone to use in the removal of contaminants due to its abundance, cheapness, suitable specific surface area and surface functional groups. In this research, the removal of iron and phosphate ions in aqueous solution has been investigated using natural clinoptilolite zeolite. The amount of removal of these contaminants has been investigated by the adsorbent in conditions such as the type of corrective method, the concentration of adsorbent to the contaminant, contact time and different pH. Modification of the adsorbent with acidic solutions results in the removal of 87% of iron at pH = 6.2 and D/C = 40, and 91% of phosphate at pH = 5.4 and D/C = 40. The ratio of adsorbent concentration to pollutant and pH have also been investigated as important factors in this study. Examination of different adsorption isotherm models showed that Langmuir model is suitable for phosphate with the maximum adsorption capacity of 62.25 mg/g and Freundlich model is suitable for iron with the maximum adsorption capacity of 48.35 mg/g. The present study showed that clinoptilolite can be used as an effective and inexpensive adsorbent to remove iron and phosphate from aqueous solutions.