Abstract
The influence of the charge compensating cation nature (Na+, Mg2+) on the water adsorption properties of LTA-type zeolites used as filler in composite materials (zeolite/polymers) was investigated. Large scale cation exchanges were performed on zeolite powder at 80 °C for 2 h using 1 M magnesium chloride (MgCl2) aqueous solutions. XRF, ICP, and EDX analyses indicate a successful cationic exchange process without the modification of the zeolite structure as shown by XRD and solid-state NMR analyses. Composite materials (granulates and molded parts) were manufactured using to extrusion and injection processes. In the case of MgA zeolite, nitrogen adsorption–desorption experiments allowed us to measure a microporous volume, unlike NaA zeolite, which is non-porous to nitrogen probe molecule. SEM and EDX analyses highlighted the homogeneous distribution of zeolite crystals into the polymer matrix. Water adsorption capacities confirmed that the trends observed in the zeolite powder samples are preserved after dragging zeolites into composite formulations. Granulates and molded parts composite samples containing the magnesium exchanged zeolite showed an increase of their water adsorption capacity up to +27% in comparison to composite samples containing the non-exchanged zeolite. The MgA composite is more promising for water decontamination applications due to its higher water adsorption properties than the NaA composite.
Highlights
Water adsorption by porous solids is important for many applications that involve the capture and release of water, such as electric dehumidifier, adsorption heat pumps (AHPs), alcohol/organic solvent dehydration, etc
Before the elaboration of the LTA-type zeolite-polymer composite, the NaA zeolite in its powder form exchanged at large scale with magnesium cations was fully characterized
X-ray Fluorescence (XRF) and Energy Dispersive X-Ray spectroscopy (EDX) analyses showed that a significant amount of the introduced Mg2+ cations were homogeneously distributed into the zeolite framework, a sign of a successful cationic exchange
Summary
Water adsorption by porous solids is important for many applications that involve the capture and release of water, such as electric dehumidifier, adsorption heat pumps (AHPs), alcohol/organic solvent dehydration, etc. One of the most promising AHPs technologies in this context is based on the evaporation and consecutive adsorption of water under specific conditions. Relative humidity is an important factor, as it affects health. A highly humid environment favors house dust mites, provides a favorable environment for fungi and harmful bacteria to grow, destroys the heat–humidity balance of human body, etc. The demand to control humidity through the development of highly efficient sorbent technology has enhanced the interest in new porous materials, especially microporous materials [9]
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