A Novel Environmental Route to Ambient Pressure Dried Thermal Insulating Silica Aerogel via Recycled Coal Gangue

Abstract

Coal gangue, one of the main hazardous emissions of purifying coal from coalmine industry, is rich in silica and alumina. However, the recycling of the waste is normally restricted by less efficient techniques and low attractive output; the utilization of such waste is still staying lower than 15%. In this work, the silica aerogel materials were synthesized by using a precursor extracted from recycled silicon-rich coal gangue, followed by a single-step surface silylation and ambient pressure drying. A low density (~0.19 g/cm3) nanostructured aerogel with a 3D open porous microstructure and high surface area (~690 m2/g) was synthesized, which presents a superior thermal insulation performance (~26.5 mW·m−1·K−1of a plane packed of 4-5 mm granules which was confirmed by transient hot-wire method). This study offers a new facile route to the synthesis of insulating aerogel material by recycling solid waste coal gangue and presents a potential cost reduction of industrial production of silica aerogels.

Fabrication and application of porous materials made from coal gangue: A review

“…In addition to the aforementioned classic micro-and mesoporous materials, other high value-added porous products, such as aerogels, 50,51,132,133 porous carbon materials, 55,134,135 gangue-biochar composite materials, 136 and C/SiO x composite materials, 137 can also be prepared by using CG as the raw material.…”

“…Due to the high content of SiO 2 in CG (approximately 40-70 wt%), silica is often extracted from CG, and aerogel is then prepared by other processes. At present, silica aerogel 50,133 and silica-alumina aerogel 51,132 are most often prepared. Zhu et al 50 pre-pared granular silica aerogel materials by extracting silica from recycled silicon-rich CG through one-step hydrophobic and atmospheric drying.…”

“…At present, silica aerogel 50,133 and silica–alumina aerogel 51,132 are most often prepared. Zhu et al 50 .…”

Advanced Fabrication of Lightweight Aerogels from Fly Ash for Thermal Insulation

“…With increasing FA content from 3.0 to 5.0 wt.%, the porosity of FA aerogels decreases causing the efficiency of gas-phase conduction to decrease, and thus, their thermal conductivity increases from 0.040 to 0.047 W/m.K. Moreover, the thermal conductivity of our FA aerogels is comparable to some commercial insulation materials such as mineral wool (0.030 -0.040 W/m.K), fiberglass (0.033 -0.044 W/m.K), expanded polystyrene (0.030 -0.040 W/m.K) and other silica aerogels from gold mine (above 0.2 W/m.K), coal gangue (0.026 W/m.K), and dislodged sludge (0.030 -0.087 W/m.K) [11][12][13][14] . It can be claimed that the aerogels from FA are a promising candidate for practical heat insulation applications.…”

Ambient-Dried Silica Aerogel Powders Derived from Coal Gangue by Using One-Pot Method

“…A yield of 68.04% for SiO 2 can be achieved by this method. P. Zhu et al [15] offered an environmental route to synthesize insulating aerogel material by recycling solid waste coal gangue; the SiO 2 aerogel prepared by this route exhibits a typical 3D open porous microstructure with high surface area (690 m 2 /g) and superior thermal insulation performance (0.0265 W•m −1 •K −1 ). Overall, there are a few reports on the preparation of silica aerogels from coal gangue, but no detailed analysis and systematic characterization of such materials have been performed.…”