Zeolites and superporous hydrogels-based hybrid composites as solid desiccants to capture water vapors from humid air

This work reports the synthesis and use of zeolites based super-porous hydrogel composites (SPHCs) as solid polymer desiccants to capture water vapors from moist air. The SPHCs were composed of super-porous hydrogels (SPHs) of acrylic acid and methacrylamide (i.e. P(AA-co-MAM)-SPHs) as polymer matrix and AQSOA type zeolites, i.e. AQSOA-Z01, AQSOA-Z02 and AQSOA-Z05 zeolites as reinforcing materials. Different structural and morphological properties of SPHCs were characterized using techniques like XRD, SEM, FTIR and TGA-DTG. Desiccant properties of P(AA-co-MAM)-SPH and SPHCs were explored in terms of adsorption isotherm and kinetics. All the desiccants exhibited type-III adsorption isotherm, suggesting water vapors’ adsorption via capillary condensation mechanism and correlated well with GAB and FHH isotherm models. P(AA-co-MAM)-SPH exhibited maximum adsorption capacity of 0.72 g_w/g_ads. However, after reinforcing different zeolites, adsorption capacity increased to 0.80, 0.84 and 0.91 g_w/g_ads in SPHC/AQSOA-Z01, SPHC/AQSOA-Z02 and SPHC/AQSOA-Z05, respectively at 90% relative humidity and 25 °C. Further, the adsorption kinetics data correlated well with linear driving force and intraparticle diffusion models and the adsorption equilibrium was achieved much quicker at 70% relative humidity as compared to 90% relative humidity. SPHCs showed much better re-use efficiency as compared to parental SPH, therefore, reinforcement of zeolites improved the re-use efficiency of P(AA-co-MAM)-SPH.