R. Malekian, J. Abedi-Koupai, S. S. Eslamian, M. Afyuni,
Volume 17, Issue 63 (6-2013)
Abstract
Nitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate contamination in surface and groundwater and increases N applications to crops. This is because negatively charged nitrate normally does not have much affinity to soil particles. To retard the movement of nitrate, materials should have high affinity for anions, which most naturally occurring minerals do not have. The cation-exchange properties of natural zeolites can be exploited to modify their surface chemistries so that other classes of compounds, particularly anions and non-polar organics are retained. In this study, the ability to remove nitrate from aqueous solutions with different Cl- concentrations using Iranian zeolite (Semnan) modified by hexadecyltrimethylammonium bromide in millimeter and nanometer particle sizes was determined and the equilibrium isotherms were characterized. The nitrate release as affected by time and ionic strength was also evaluated. It was demonstrated that SMZ is capable of adsorbing more than 60 mmol kg-1 and 80 mmol kg-1 nitrate in millimeter and nanometer sizes, respectively, and adsorbed nitrate can be easily released under different ionic strengths. The millimeter and nanometer-sized SMZ showed 26.7% to 82.3% and 37.8% to 85.5% nitrate removal efficiency, respectively. The average of nitrate released by millimeter-sized SMZ was 6.92 mmol kg-1 in deionized water while it was 14.68, 22.71, and 34.91 mmol kg-1 in releasing solutions with ionic strengths of 0.03, 0.1, and 0.3 M, respectively
S. Rezaei, M. Heidarpour, A. Aghakhani,
Volume 29, Issue 2 (7-2025)
Abstract
The growing concern for environmental protection and increasing demand for green approaches to address environmental problems have prompted researchers to explore a sustainable and reliable method for treating dyeing wastewater. One of the sustainable and reliable methods is the electrocoagulation process. In this study, a batch electrocoagulation reactor was designed to evaluate the efficiency of this process in treating dyeing wastewater. The effects of two parameters, electrode distance and retention time, on pollutant removal efficiency were investigated. Electrode distances of 2, 5, and 7 cm were tested, and retention times of 10, 15, 20, 25, and 30 minutes were examined. Results indicated that the optimal electrode distance was 5 cm and the optimal retention time was 20 minutes. Under these conditions, the removal efficiency of BOD, COD, TSS, color, and turbidity reached 83%, 85%, 98%, 98%, and 93%, respectively. The results of this research demonstrate the significant potential of the electrocoagulation system for treating dyeing wastewater.
Jahangir Abedi Koupai, Noshin Shafiee, Behrooz Mostafazadehfard, Mohammad Mehdi Matinzadeh,
Volume 30, Issue 2 (7-2026)
Abstract
One of the key factors in agricultural production is the availability of sufficient and usable nutrients for plant growth, and among these, nitrogen plays a particularly important role. The waste of nitrogen fertilizers due to the low efficiency of using fertilizers has caused environmental problems such as pollution of surface and groundwater by nitrate or ammonium. In this study, the influence of fertigation as a combination of urea, ammonium nitrate, natural zeolite of Semnan (CP), and modified zeolite by surfactant (SMZ) in the reduction of waste and manure fertilizer was evaluated. Two separate experiments with a completely randomized design with three replications were used for loam soil columns. Treatments consisted of four levels of zeolite application (0, 4, 8, and 16 g/Kg) and a fertilization level with a concentration of 60 mg per liter nitrate applied at three fertigations during six irrigations. In the first part of the study, the role of nitrogen fertilizers in fertigation as a combination of urea and ammonium nitrate (UAN) for ordinary soil was examined to reduce the concentration of nitrate and ammonium in the drainage water, and the results were compared with one of the fertigation applications. The results showed that the loss of fertilizer in the form of nitrate was reduced by 40 percent for the UAN treatment during the first period of fertigation. Since the results of the first part of the experiment showed that the concentration of ammonium nitrate does not reduce to the same level as drinking water, in the second part of the experiment, the soil amendments were used. The measured nitrate removal showed that the highest nitrate removal belonged to the soil mixed with 16 g/kg of modified zeolite in the surface layer of soil (SM16) treatment, and it was equivalent to 90 percent. The highest ammonium removal belonged to the soil mixed with 16 g/kg of natural zeolite in the surface layer of soil (CP16) treatment, and it was 85 percent. Therefore, the use of fertigation as a combination of nitrogen fertilizers with soil amendments for conditions where there is a potential for groundwater pollution by nitrate leaching is recommended.
