Synthesis and Testing of Zeolite from Industrial-Waste Coal Fly Ash as Sorbent For Water Adsorption from Ethanol Solution
Keywords:Zeolite, coal fly ash, fusion, water adsorption, bioethanol.
In the present work, zeolite was prepared from industrial-waste coal fired ash (CFA) by fusion technique with and without acid-washing pretreatment under various conditions. The synthesized materials were then tested for water adsorption from bioethanol solution with an aim to produce a high purity ethanol (> 99.5%) for later utilization in gasohol production manufacturing. From our studies, it was found that the impurities (i.e., Fe2O3, TiO2, MgO, CaO, K2O and SO3) in CFA could be efficiently removed by acid-washing pretreatment. Among three different acids studied (i.e. HCl, HNO3, and H2SO4), HCl exhibited the highest pretreatment performance, while the most suitable pretreatment conditions to enhance high purity raw material (up to 85% purity) were by using 20% HCl with the acid to CFA ratio of 25 mlHCl/gCFA at 80°C for 3 h. After fusion at 550ºC with NaOH/CFA mass ratio of 2.25 and further crystallization at 90ºC for 4 h, the pretreated CFA was converted to zeolite; from which the main phases were sodium aluminum silicate hydrate (1.08Na2O•Al2O3•1.68SiO2•1.8H2O) and faujasite-Na (Na2Al2Si2.4O8.8•6.7H2O). Regarding water adsorption testing, the synthesized zeolite provided comparable adsorption performance with the commercial grade molecular sieve. Under three adsorption cycles testing at 85ºC, high ethanol purity (99.8%) could be achieved without deactivation being observed.
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