Preparation and characterization of double metal-silica sorbent for gas filtration
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Preparation and characterization of double metal-silica sorbent for gas filtration Ebenezer Twumasi Afriyie · Peter Norberg · Christer Sjöström · Mikael Forslund
Received: 13 December 2010 / Accepted: 22 August 2012 / Published online: 6 September 2012 © Springer Science+Business Media, LLC 2012
Abstract This paper presents the preparation of a porous (Mg, Ca) silicate structure, which could be employed as sorbent filter media. The sorbents have been prepared using sodium silicate precipitated with various ratios of magnesium and calcium salts. The sorbents obtained were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD) and nitrogen physisorption isotherm. Further, the applicability and performance of the sorbent impregnate with potassium hydroxide for removal of sulphur dioxide (SO2 ) has been demonstrated. From the isotherms, specific surface area, pore diameter and volume of pores were estimated. Results show that the chemical composition and textural properties of the resultant sorbents were highly dependent on Mg/Ca molar ratio. It was found that sorbents made with 68 mol% Mg and 32 mol% Ca (PSSMgCa-68/32); and 75 mol% Mg and 25 mol% Ca (PSSMgCa-75/25) exhibited even higher specific surface area and pore volume than the sorbents containing a single metal. The Mg/Ca-silica sorbents obtained contains interconnected bimodal porosity with large portions being mesopores of varied sizes. The pore size distribution (PSD) results further indicate that PSS-MgCa-68/32 sorbent exhibits wide PSD of interconnected pores in the size range of 1 to 32 nm while PSS-MgCa-50/50 and PSS-MgCa-75/25 exhibits narrow PSD of 1 to 5 nm. Using SO2 as model contaminate gas, it was shown that the dynamic adsorption performance of the PSS-MgCa-sorbents impregnated with 8 wt% KOH exhibits SO2 uptake, with impregnated PSS-MgCa-68/32 showing better performance. This shows that the materials prepared can be used as adsorbent for gas filtration. E. Twumasi Afriyie () · P. Norberg · C. Sjöström · M. Forslund Materials Technology, KTH Research School, University of Gävle, Gävle, Sweden e-mail: [email protected]
Keywords Mg/Ca-silica sorbent · Gas filtration · Characterization · Textural properties · Impregnate Mg/Ca-silica sorbents Abbreviations dmes maximum mesopores size distribution dmic maximum micropores size distribution NLDFT Nonlocal Density Functional Theory p/p ◦ Relative pressure PSD Pore Size Distribution SBET Specific Surface area obtained via Brunauer-Emmet-Teller-equation Smes Mesoporous surface area obtained via t-plot Smic Micropore surface area obtained via t-plot Vmes Mesoporous pore volume obtained via t-plot Vmic Microporous pore volume obtained via t-plot Vtot Total pore volume XRD X-Ray-Diffraction
1 Introduction In the current industrial society, the atmospheric concentrations of gases such as CO2 , CO, CH4 , and N2 O (greenhouse gases), NOx , SO2 and H2 S have, for various reasons, attracted attention. These gases are believed to be a major contributor of acid rain, global warming an
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