Synthesis and Testing of Zeolite from Industrial-Waste Coal Fly Ash as Sorbent For Water Adsorption from Ethanol Solution

Abstract

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•Al₂O_3•1.68SiO_2•1.8H₂O) and faujasite-Na (Na₂Al₂Si_2.4O_8.8•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.