Synthesis and thermal insulation performance of silica aerogel from recycled coal gangue by means of ambient pressure drying

Abstract

Silica aerogel materials are well recognized for their superinsulation performance and are regarded as one of the hot candidates to revolutionize building insulation. To date, high production cost related to exorbitant precursors as well as cumbrous multi-step hydrophobization process has often narrowed the field of applications. In this work, granular silica aerogel materials were synthesized by extracting SiO₂ from recycled rich silicon coal gangue, followed by one-step hydrophobization and ambient pressure drying. Lightweight (about 0.16 g/cm³) and nanostructural aerogels were obtained through this route. They exhibit a 3D open porous microstructure with around 600 cm²/g surface area and 20 nm of the average pore diameter, thermal conductivity of 4-5 mm packed granules is 20-25 mW/(m·K), which was proved by both guarded hot plate and hot-wire transient methods. This study offers a new facile route for the synthesis of silica aerogel from recycled solid waste coal gangue and suggests a method, which may lead to a cost reduction in terms of industrial production.

Keywords

silica aerogel / coal gangue / thermal insulation / one-step hydrophobization

References

[1] Pierre A, Rigacci A. SiO₂ Aerogels, in Aerogels Handbook [M]. M A Aegerter, N Leventis, and M M Koebel, Editors. New York: Springer, 2011

[2] Baetens R J B, Gustavsen A. Aerogel Insulation for Building Applications: A State-of-the-art Review [J]. Energ. Buildings, 2011, 43(4): 761-769.

[3] Soleimani Dorcheh A, Abbasi MH. Silica Aerogel; Synthesis, Properties and Characterization [J]. J. Mater. Process. Technol., 2008, 199(1-3): 10-26.

[4] Wang L, Zhao S. Synthesis and Characteristics of Mesoporous Silica Aerogels with One-step Solvent Exchange/Surface Modification [J]. J. Wuhan Univ. Technol. -Mater. Sci. Ed., 2009, 24(4): 613-618.

[5] Bhagat S D, Kim Y H, Ahn Y S, et al. Rapid Synthesis of Water-glass Based Aerogels by In-situ Surface Modification of the Hydrogels [J]. Appl. Surf. Sci., 2007, 253(6): 3231-3236.

[6] Venkateswara R A, Nilsen E, Einarsrud M A. Effect of Precursors, Methylation Agents and Solvents on the Physicochemical Properties of Silica Aerogels Prepared by Atmospheric Pressure Drying Method [J]. J. Non-Cryst. Solids, 2001, 296(3): 165-171.

[7] Venkateswara R A, Bhagat S D. Synthesis and Physical Properties of TEOS-based Silica Aerogels Prepared by Two Step (acid-base) Sol-gel Process [J]. Solid State Sci., 2004, 6(9): 945-952.

[8] Dong L, Li Y, Yan J, et al. Efficient Extraction of SiO₂ and Al2O₃ from Coal Gangue by Means of Acidic Leaching [J]. Adv. Mater. Res., 2014, 878(2): 149-156.

[9] Hou C, Wang S, Xie X. Study on Melting Available Silicone from Coal Gangue [J]. J. Coal Sci. Eng. China, 2009, 15(4): 426-429.

[10] Zhu J, Cai H, Dang N. Study of Synthesis of SiO₂ Aerogel from Coal Gangue at an Ambient Pressure [J]. Adv. Mater. Res., 2014, 997(3): 614-617.

[11] Xu G, Li S, Pan X, et al. Study on Preparation of Amorphous Nanosilica from Coal Gangue [C]. Materials for Renewable Energy & Environment (ICMREE), 2011 International Conference, 2011

[12] Chen FQ, Li F, Chen RM, et al. Method for Preparing Silica through Coal Gangue Aluminum Extraction Waste Slag [P]. China Patents CN103420386A, 2013

[13] Jia R, Zhao X. Waterglass Fabricated from Coal Gangue [P]. Chinese Patents CN102583417 A, 2012

[14] Shi F, Wang L J. Rapid Synthesis of Silica Aerogels via a New Ambient Pressure Drying Process [J]. J.Dalian Uni. Technol., 2006, 46(2): 241-245.

[15] Stahl T, Brunner S, Zimmermann M, et al. Thermo-hygric Properties of a Newly Developed Aerogel Based Insulation Rendering for both Exterior and Interior Applications [J]. Energ. Buildings, 2012, 44(0): 114-117.

[16] Karaipekli A, Sari A, Kaygusuz K. Thermal Conductivity Improvement of Stearic Acid using Expanded Graphite and Carbon Fiber for Energy Storage Applications [J]. Renewable Energy, 2007, 32(13): 2 201-2 210.

[17] Frusteri F, Leonardi V, Vasta S, et al. Thermal Conductivity Measurement of a PCM Based Storage System Containing Carbon Fibers [J]. Appl. Therm. Eng., 2005, 25(11-12): 1623-1633.

[18] Neugebauer A, Chen K, Tang A, et al. Thermal Conductivity and Characterization of Compacted, Granular Silica Aerogel [J]. Energ. Buildings, 2014, 79(0): 47-57.

[19] Wagh P B, Begag R, Pajonk G M, et al. Comparison of Some Physical Properties of Silica Aerogel Monoliths Synthesized by Different Precursors [J]. Mater. Chem. Phy., 1999, 57(3): 214-218.