Modeling of ammonia removal from wastewater using air stripping/modified clinoptilolite: reusability, optimization, isotherm, kinetic, and equilibrium studies
2022
Fathi, R. | Mohammadi, P. | Hosseini, S. A. | Yosefvand, F. | Norouzi, H.
Excess chemical and natural fertilizer could create eutrophication of surface waters and then depletion of the quality of water. The present study aimed to survey the removal efficiency of ammonia from aqueous solution using modified clinoptilolite and air stripping process and optimization of variables by response surface methodology. Clinoptilolite was obtained from Semnan (Northeast of Iran) and modified with sodium chloride (to create an adsorbent uniform) and ferric chloride (due to three valent of iron) as an efficient and simple method. The modified clinoptilolite was characterized by scanning electron microscopy, X-ray diffractometer, X-ray fluorescence, and Fourier transform infrared spectroscopy. Employing modified clinoptilolite as an adsorbent for ammonia removal showed that by increasing adsorbent dose, contact time, and pH and decreasing initial ammonia concentration, ammonia removal efficiency has been increased. In the optimum condition, modified clinoptilolite was able to adsorb ammonia as high as 86.04% at an adsorbent dose of 1 g/L, pH of 5, a contact time of 3.7 h, and an initial ammonia concentration of 13.27 mg/L. Also, the sorption capacity of ammonia at the optimum condition of air stripping was 96.14%. This process can properly treat the effluent of stabilization ponds as real wastewater (about 70% for ammonium removal), and the order of reduction effect for cations includes K⁺ > Ca²⁺ > Na⁺ > Mg²⁺, respectively. The findings showed that ammonia removal followed the Freundlich isotherm and intraparticle diffusion kinetic model. According to the obtained results, as an effective and reusable adsorbent, modified clinoptilolite can be appropriately employed for ammonia removal from wastewater.
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