Cation-exchanged nano-zeolite 13X for water vapor adsorption from air

Around 13 sextillions (1021) liters of water exist in the atmosphere which is considered as a recyclable natural source to resolve the water crisis in dry areas of the world [1]. Because of their certain average pore diameters, zeolites adsorb water molecules in preference to other gases while restricting larger molecules. Moreover, exchangeable compensation cations such as Li+, K+, Ba2+, Mg2+, and Ca2+ can be added to the zeolite structure which is expected each one shows a great attraction to link with water molecules [2]. This study concerns the synthesis of nano-zeolite 13X and its modification by a hygroscopic salt (magnesium chloride) to investigate its water vapor adsorption capacity. At first, nano-zeolite 13X with gel formula of 5.5 Na2O:1.0 Al2O3:4.0 SiO2:190 H2O was synthesized by microwave heating of precursors as sodium aluminate, sodium silicate, NaOH and distilled water at 90 °C for several hours. The final white product was characterized using techniques as XRD, FT-IR, SEM, and EDX. Then, 2g of nano-zeolite was shaken with different solutions of magnesium chloride (10 to 50 wt%) for 24 hours and calcined at 300 °C for 2 hours. A set-up was designed to measure the adsorbed content of water by the adsorbent. Airstreams with different initial humidity passed through a column containing adsorbent and the measurement of input and output humidity was continued until saturation happened. According to the obtained data of the adsorption diagram, with 14.6 g/m3 absolute humidity, this adsorbent could adsorb 131% water of its own weight in one minute.