نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم و مهندسی محیط زیست، دانشکده علوم محیطی، دانشگاه حکیم سبزواری، سبزوار
2 گروه علوم و مهندسی محیط زیست، دانشکده علوم محیطی، دانشگاه حکیم سبزواری، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Due to participation in the process of eutrophication, nitrate has caused a lot of damage to the environment. In this research, Clinoptilolite nanozeolite granules modified by hexadecyltrimethylammonium bromide surfactant named HD-Clinoptilolite were synthesized. The clinoptilolite zeolite of Sabzevar region was converted into nanozeolite by ball mill and then its granules were prepared. In this study, a continuous reactor with a fixed bed equipped with a peristaltic pump has been used to provide the necessary flow to remove nitrate from polluted water. For adsorption process, a continuous flow reactor with a diameter of 3 cm and a height of 54 cm, for investigation of pH parameters, flow intensity, initial concentration, and column height have been fabricated. A Uv-vis Array spectrophotometer was used to measure nitrate. Also, Thomas, Bohart-Adams, and Yoon-Nelson models have been used to predict column behavior. According to the results, with increasing nitrate concentration, the adsorption capacity increased from 3.16 to 95.21 due to the increased presence of nitrate ions. Also, with increasing pH and column height, the adsorption capacity increased, while with increasing flow intensity, the adsorption capacity decreased due to the reduction of contact time. The highest adsorption capacity occurred at a concentration of 200, pH equal to 8 and a column height of 54 cm. At a column height of 54 cm, the adsorption capacity is equal to 91.26 mg/g. The results indicate that the clinoptilolite nanozeolite granules modified with ammonium bromide ligand has the ability to remove nitrate from drinking water to a high extent.
کلیدواژه‌ها [English]
Synthesis of clinoptilolite nanozeolite granules modified with ammonium bromide ligand to investigate the efficiency of nitrate removal from water in a continuous reactor
EXTENDED ABSTRACT
Nitrate is one of the most common chemical pollutants in underground water in the world. Factors such as nitrate fertilizers are the most important source of nitrate pollution in surface and underground waters (Atabati et al. 2022). The disposal of untreated urban and industrial wastewaters into surface and underground waters and the discharge of waste water treatment plants and the excessive use of nitrogenous fertilizers in agriculture have caused an increase in the concentration of nitrates in water environments. Today, there are various methods for water purification that can be used in this field (Zolfaghari et al., 2011; Zolfaghari and Kargar, 2019). Among the methods that have been used so far to remove nitrate from water resources, we can mention chemical reduction, surface adsorption, ion exchange, sedimentation, membrane-based separation, denitrification, chemical precipitation, and reverse osmosis. Natural zeolite adsorbent has fine pores and consists of aluminosilicate. Also, high ion exchange capability, high efficiency, quick and complete removal of pollutants, easy access, and low cost are other features that make this adsorbent one of the best adsorbents for nitrate removal from water sources.
In this research, Clinoptilolite nanozeolite granules modified by hexadecyltrimethylammonium bromide surfactant named HD-Clinoptilolite were synthesized. For this purpose, natural clinoptilolite zeolite from Sabzevar region was first prepared and Ball mill was used to reduce the size of zeolite particles to nano dimensions. In this study, a continuous reactor with a fixed bed equipped with a peristaltic pump has been used to provide the necessary flow to remove nitrate from polluted water. For adsorption process, a continuous flow reactor with a diameter of 3 cm and a height of 54 cm, for investigation of pH parameters, flow intensity, initial concentration, and column height have been fabricated. A Uv-vis Array spectrophotometer was used to measure nitrate. To determine the chemical composition of zeolite from X-Ray Fluorescence (XRF), to check the crystal structure from X-Ray Diffraction (XRD), to determine the size of nanoparticles from Transmission Electron Microscopy (TEM), and to detect the functionalization of zeolite with surfactant from Fourier-transform infrared spectroscopy (FTIR) method was used.
The images obtained from the electron microscope show that the nano zeolite particles are in the range of 50 to 400 nm. The results showed that with the increase in nitrate concentration, the adsorption capacity increases from 3.16 to 21.95 (more than 30 times) due to the increase in the presence of nitrate ions. The results show that by increasing the height of the column containing nanozeolite adsorbent, the adsorption capacity increases from 54.04 to 63.38 mg/g. As the height increases, the contact time between nitrate and zeolite and the number of available active sites increase. The highest adsorption capacity occurred at a concentration of 200, pH equal to 8 and a column height of 54 cm. At a column height of 54 cm, the adsorption capacity was equal to 91.26 mg/g.
The results indicate that the clinoptilolite nanozeolite granules modified with ammonium bromide ligand has the ability to remove nitrate from drinking water to a high extent. It is suggested that this study be done on a larger scale and in fluidize bed columns to compare the results.
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