چكيده به لاتين
Extracting water from air humidity is a highly efficient method for supplying drinking water, especially in dry and remote areas. Recently, the adsorption method has been considered due to its high efficiency, energy-saving and no harmful effects on the environment. The purpose of this study was to modify the structure of 13X zeolite and evaluate its performance to adsorb air humidity. For this purpose, 13X zeolite was first synthesized with the micro, meso and nanopore size and then, to increase the adsorption capacity, the ion-exchange process and the composite preparation were performed using different weight percentages of calcium chloride and magnesium chloride salts. In the second part, activated carbon firstly modified by nitric acid and sodium hydroxide to increase the number of oxygen-containing functional groups such as hydroxyl groups and thereby enhance its performance in adsorption of water vapor molecules and subsequently the composite adsorbent synthesized between micro and nano-zeolite and modified activated carbon powders. In the third part, firstly the mesoporous MCM-41 was synthesized by microwave and then nanocomposite of 13X-MCM-41 prepared by the same method and finally the ion-exchange process of nanocomposite performed using different weight percentages of calcium chloride salt. Various detection methods such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR), energy dispersive X-ray (EDX) scanning electron microscopy (SEM) and nitrogen adsorption and desorption (BET) analysis are also used to confirm the structure of the synthesized adsorbents. The saturated salt-water solution is used to produce different relative humidities, and the measuring setup is designed using two temperature and humidity sensors based on the Arduino system. The adsorption process has been performed at different relative humidities and the desorption method has been examined using three methods of the microwave, conventional furnace, and dry nitrogen. According to the obtained results at 30% relative humidity, room temperature, and atmospheric pressure, the adsorption capacity of the composite adsorbents obtained from micro, meso, nano and calcium chloride 50 wt% were 0.46, 1.00 and 1.06 gr of water while for magnesium chloride 50 wt% were 0.43, 0.99 and 0.92 gr water per gr of the adsorbent. These values for the modified activated carbon by nitric acid and sodium hydroxide were equal to 0.72 and 0.65 gr of water and composite of micro and nano-zeolite and modified activated carbons can produce 0.30 and 0.32 gr water per gr of adsorbent. Adsorption capacity values for mesoporous MCM-41, 13X-MCM-41 nanocomposite, and 13X-MCM-41 nanocomposite and calcium chloride 50 wt% were 0.23, 0.24 and 0.46 gr of water per gram of adsorbent respectively, and increasing relative humidity leads to an increase in water vapor adsorption. Finally, according to the obtained results, the composite adsorbents prepared in this study and particularly the composites of meso and nano 13X zeolites and calcium chloride 50 wt% can be used to harvest water from air humidity at industrial scale, and the desorption process could be performed with microwave or conventional furnace at temperatures below 110° C which could be considered economical and energy-efficient.
