Abstract—Nitrogen loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate (NO 3 - ) levels in surface and groundwaters. Thus, it is of great interest to use inexpensive natural products that can increase the fertilizer efficiency and decrease nitrate leaching. In this study, the ability of natural Iranian zeolite clinoptilolite (Cp) and surfactant modified zeolite clinoptilolite (SMZ) to remove NH 4 + and NO 3 - , respectively, from aqueous solutions was determined. The feasibility of using Cp and SMZ as soil amendment to reduce nitrate leaching from soil using lysimeters was also investigated. Zeolite showed 10.23% to 88.42% NH 4 + removal efficiency over a wide range of initial NH 4 + concentrations. Nitrate removal efficiency by SMZ was 32.26% to 82.26%. Field study results showed that Cp and SMZ significantly (p < 0.05) reduced leachate NO 3 -N concentration compared to control. There was no significant difference between maximum and mean leachate NO 3 -N concentration of SMZ lysimeters and those of Cp lysimeters. Keywords— Ammonium removal, Leaching, Nitrate removal, Surfactant modified zeolite I. INTRODUCTION ITROGEN leaching from agricultural land is a contributor of nitrate (NO 3 - ) contamination of surface and groundwaters. This is a growing concern, especially as population growth is causing urbanization of former agricultural/horticultural lands. In semiarid and arid regions, especially areas with sandy soils, the potential of NO 3 - leaching increases due to frequent irrigations, which are needed to sustain plant growth. NO 3 - leaching is because negatively charged nitrate normally does not have much affinity for soil particle surface, and thus, does not readily sorb on soils [1]. Numerous studies have documented the adverse effects of high NO 3 levels in humans, most notably methemoglobinemia [2], stomach cancer [3], and non- Hodgkin’s Lymphoma [4]. The development of new natural products that would decrease nitrate leaching, improve fertilizer use efficiency, and increase crop yield and at the same time not pollute our environment is a challenge for agronomists and soil chemists throughout the world. Zeolites are crystalline hydrated aluminosilicates with a framework R. Malekian is with Water Engineering Department, Isfahan University of Technology, Isfahan, Iran, 84156-83111 (corresponding author. phone: +98- 311-391-5084; fax: +98-311-391-2254; e-mail: ramalekian@ yahoo.com). J. Abedi-Koupai is with Water Engineering Department, Isfahan University of Technology, Isfahan, Iran, 84156-83111 (e-mail: koupai@ cc.iut.ac.ir). S. S. Eslamian is with Water Engineering Department, Isfahan University of Technology, Isfahan, Iran, 84156-83111 (e-mail: saeid@cc.iut.ac.ir). structure containing pores occupied by water and by alkali and alkaline earth cations. Due to their high cation-exchange ability as well as to the molecular sieve properties, natural zeolites show special importance in agriculture and aquaculture [5]. Although natural raw zeolites, with their negative charge framework, have already been used as cation exchanger, they are obviously unable to use as an anion exchanger. However, the removal of anions was made possible on SMZ, prepared through the sorption of cationic surfactant, such as hexadecyltrimethylammonium (HDTMA), on the zeolite surface [6]. The maximum loading of HDTMA is about 200% of the zeolites external cation exchange capacity (ECEC). At the HDTMA sorption maximum, the surfactant molecules form bilayers on zeolite surfaces with the lower layer held by electrostatic interactions between the negatively- charged zeolite surface and the positively-charged surfactant head groups, while the upper layer is bound to the lower layer by hydrophobic forces between the surfactant tail groups in both layers [7]. Under the surfactant bilayer configuration, the zeolite reverses its surface charge, resulting in a higher affinity, sorption, and retention of negatively-charged anionic contaminants that is attributed to surface anion exchange [7, 8]. The use of surfactant-modified zeolite (SMZ), which represents a type of inexpensive anion exchanger, to remove anionic contaminants from water has been studied extensively [9, 10]. The objective of this study was to investigate the ammonium exchange on natural Iranian zeolite clinoptilolite (Cp) and nitrate exchange on natural Iranian SMZ through batch experiment. The feasibility of using Cp and SMZ as soil amendments to reduce nitrate leaching from soil was also investigated through filed experiment. II.EXPERIMENTAL METHODS The natural zeolite used in this study originated from Semnan province, Iran. Mineral identification using X-ray diffraction showed that the zeolite consisted mainly of clinoptilolite. The zeolite had the following chemical composition (in %) SiO 2 = 65.90, Al 2 O 3 = 11.20, Na 2 O = 2.10, K 2 O = 2.31, CaO = 3.20, Fe 2 O 3 = 1.25, MgO = 0.52, LOI = 11.89, and SiO 2 /Al 2 O 3 = 5.9. The particle size of zeolite was between 0.2 and 0.8 mm. The cation exchange capacity (CEC) of the zeolite was 140 cmol kg -1 as determined by the 1 M NH 4 OAc saturation method [11]. The ECEC of the zeolite was determined to be 70 mmol kg -1 using the method of Ming and Dixon [12]. Use of Zeolite and Surfactant Modified Zeolite as Ion Exchangers to Control Nitrate Leaching R. Malekian, J. Abedi-Koupai, S. S. Eslamian N World Academy of Science, Engineering and Technology International Journal of Geological and Environmental Engineering Vol:5, No:4, 2011 267 International Scholarly and Scientific Research & Innovation 5(4) 2011 scholar.waset.org/1307-6892/12522 International Science Index, Geological and Environmental Engineering Vol:5, No:4, 2011 waset.org/Publication/12522