Synthesis and Characterization of Zeolite A Using Bagasse Ash, as BioSilica Source for Water Hardness Removal

Abstract

Zeolite A is a synthetic sodium alumino-silicate which is important synthetic zeolites widely used for separation and adsorption in industry. However, its wide application has been constrained by availability and cost of raw materials specifically the silica sources. Therefore, in this study low cost industrial byproduct Bagasse Ash was used as a BioSilica and synthesis of zeolite A for application of water hardness removal. Na2CO3 and Al2O3 were used to replace the expensive NaAlO2 on Ethiopian market to adjust molar ratio of bagasse ash as required for zeolite A. The process parameters for the synthesis of zeolite A for water hardness removal, such as the effect of ageing time (gel formation), crystallization time and crystallization temperature were systematically studied to optimize the control variables. The composition, morphology, crystalline phase, Thermal stability and CEC of synthesized zeolite A was further characterized using Chemical Method, SEM, XRD, DTA and AAS. Finally, the performance of the synthesized zeolite A in the removal of Ca2+ and Mg2+, highly water hardness causing metal ions, was investigated. The result showed that phase-pure zeolite A can be synthesized from Bagasse Ash at reactant molar ratio, of 1.3Na2O: 0.6Al2O3 :1SiO2: xH2O, at 110°C reaction temperature, reaction time of 3h, and aging time of 3h and the synthesized zeolite efficiently removed 96.43% Ca2+ and 99.44% Mg2+ ions from synthetic very hard water. The removal of Ca2+and Mg2+ from water which occurred through precipitation and ion exchange mechanisms was seen to be more efficient comparing to the previous studies. The adsorption of Ca2+ and Mg2+ ions by the synthesized zeolite A follows Langmuir adsorption isotherm with 555.54ml/g/g and 65.78ml/g/g maximum Sorption Capacity respectively and pseudo-second- order kinetic model. In conclusion, Bagasse Ash could be one of the alternative source of Bio-Silica extraction for different purpose and the synthesized zeolite Na-A showed an excellent potential to removal of water hardness.