Preparation And Properties Of Zeolite-Based Humidity-Controlling Material

Humidity is an important environmental parameter, which has a close relationship withpeople’s life and prducing. Unsuitable humidity will reduce the comfort of the body and thequality of life a lot, and be harmful to industrial production and goods storage. The traditionalmaterials and equipments of controlling humidity are not intelligent, which can only absorb orrelease moisture and not be recycled, what’s more the high cost and high energy consumption,environment pollution does not meet the requirements of sustainable development strategyand building energy efficiency. The zeolite has a large number of micropores, a large rangepore size distribution, large specific surface area, good adsorption performance, nontoxic andharmless, and its mineral is plentiful and easy to obtain with low cost. Its desorption has nohysteresis which can be regenerated and has a long service life. Zeolite also has a hydrationactivity can be directly used as admixtures combined with existing building materials and it’sthe first one to be used as the humidity control material. As zeolite has a large number ofmicroporous and a wide range of pore size distribution, its amount of moisture is small and itcan not control humidity in in the specified range, thus limiting its application in terms ofhumidity. The suitable humidity for people living and working is moderate relative humidity(40-60%). The pore with3-50nanometer diamet can adsorded or desorbed water molecules,and pore is filled size by the water moleculesthe from small to large, the desorption isopposite. We need not only to improve the moisture content of zeolite, but adjust its porestructure, so it has a quantity large of mesoporous, a suitable proportion of pore size and goodconnectivity.In this paper, simple and feasible methods such as grinding, heating, acid-treatment,alkali-treatment and integrated treatment are used to modify natural zeolite; inversesuspension is used to prepare composite humidity control material of modified zeolite andsodium polyacrylate resin; humidity control block are prepared with the resulting productionand the existing cement-based building materials; the moisture absorption and desorptionmechanism and kinetics model of organic and inorganic porous humidity control materials areexplored; the moisture absorption and desorption curves are obtained by using dryer-methodand the humidity performance is evaluated by the maximum rate and moisture absorption anddesorption velocity; the surface morphology, phase structure, composition of humidity controlmaterial and the mechanical properties of the humidity control block are tested andanalyzed.The experiment results indicate that:(1)zeolite has less impurities, has large surface area, small average pore size, a large proportion of mesopore and3-7nanopore and reasonable pore size distribution, with excellentmoisture absorption and desorption performance. Being soaked in1mol/L NaOH for2hoursand heated in200℃for2hours is best modify condition, the absorption and desorption rate ofthe modified zeolite is7.92%and6.6%, which is increased by3.48fold and4.28foldcompared with unmodified zeolite.(2)composite humidity control material has the advantages of both polymer andinorganic mineral material, with high moisture absorption and desorption velocity and rate;The absorption and desorption rate of composite humidity control material is91.1%and77.43%, hysteresis rate is14%.(3) Modified zeolites and zeolite-sodium polyacrylate resin,s humidity performance hasbeen reserved as mixed with cement, and the absorption and desorption rate of humiditycontrol block is6.66%and3.62%with good mechanical properties.(4)The absorption velocity of inorganic mineral humidity material is determined byexternal diffusion velocity and its adsorption kinetics behavior in line with the model ofdiffusion kinetics, the absorption velocity of polymer humidity material is determined by theinternal diffusion rate and its adsorption kinetics behavior in line with the model of chemicalreaction kinetics; the desorption of polymer and inorganic mineral humidity control materialsare both determined by internal diffusion rate and their desorption kinetics behavior in linewith the model of chemical reaction kinetics.