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Amidst the global concerns in sustainable development and climate change mitigation, the demand for heat-insulating materials has been increasing in which the research objects mostly attracting attention are those from agricultural and industrial wastes due to their abundance. Aerogels have been studied for practical applications in construction because of their lightweight and super-porous properties as well as remarkable thermal insulation. An attempt has been made to create novel silica aerogel composites via in situ synthesis of rice husk ash-derived silica aerogels on the recycled polyethylene terephthalate (rPET) fiber framework and cost-effective ambient drying. Replacing expensive and toxic organosiloxane precursors with low-cost waste materials to synthesize the aerogel composites is a more economical, feasible, and user-friendly approach compared with the previous works. The fabricated aerogel composites exhibit characteristic features of aerogels, the low thermal conductivity of 0.040–0.056 W/(m·K), and a flame propagation speed of approx. 0.27 mm/s due to the adhesion of silica aerogels on the rPET fibers. The durability of the silica aerogel composites is enhanced with a structure of 4 layers of rPET fibers stacked on top of each other and alternating layers of silica aerogels, thus the as-fabricated aerogel composites show a high Young's modulus of 84.099 kPa and can withstand 695 times their weight. The as-fabricated silica aerogel composites having both thermal insulation and flame retardancy exhibit great potential in eco-friendly and energy-efficient design for construction purposes. [ABSTRACT FROM AUTHOR]

• Advanced fabrication of rubber aerogel via a cost effective and time saving method. • Rubber aerogel has an ultra-low density and a high porosity properties. • Rubber aerogel has a robust mechanical properties with the Young's modulus. • Rubber aerogel can be a potential material for thermal insulation applications. • Rubber aerogel can be a potential material for sound absorption applications. According to the European Waste Codes EWC 19.12.08, fibers from used tires are known as special wastes that must be burned or buried. However, these activities would pose additional risks including soil pollution, and groundwater contamination. Scientists are continually discovering more new ways to recycle these wastes in order to minimize their ecological consequences. Our effort has been also directed into this direction, and we have been able to convert rubber fibers from tire waste into aerogels, an ideal candidate for a wide range of advanced applications due to their low density, high porosity, low thermal conductivity and high sound absorption coefficient. A novel but simple and time-saving strategy to fabricate rubber aerogel from waste tire fibers, derived from car tire wastes, is reported using a freeze-drying process. The obtained rubber aerogel with a robust mechanical performance, exhibiting a Young's modulus up to 965.6 kPa and density 91 mg cm−3, can withstand a large elastic deformation without fracture. In addition, with a highly porous structure (porosity > 90 %) and an ultralight light density (20−91 mg cm−3), our rubber aerogels have a high sound absorption efficiency (noise reduction coefficient, or NRC of 0.56), and a low thermal conductivity (0.035−0.049 W m-1 K-1). These advanced rubber aerogels can be a promising candidate for thermal and acoustic insulation in cabins, vehicles, buildings, and aerospace. [ABSTRACT FROM AUTHOR]

Fly ash is waste from thermal power plants that not only has a serious impact on soil and water but also accumulates in landfills and must be treated properly. In addition, plastic waste, especially polyethylene terephthalate bottles, deteriorates for a long time, so there is an urgent need to recycle them into valuable products. To solve the environmental pollution mentioned above, a feasible zero-waste method has been developed that converts 100% of fly ash into a lightweight composite aerogel reinforced with recycled polyethylene terephthalate fiber. In this study, raw fly ash is bound to the skeleton of the fibers by a non-toxic, biodegradable xanthan gum solution as a binder, which is then lyophilized, leaving a hollow porous structure. The obtained composite aerogels display extremely low density of 0.026–0.062 g/cm3, high porosity of 96.59–98.42%, low thermal conductivity of 34–39 mW/(m·K), flexibility with Young's modulus of 3.98–20.61 kPa, and noise reduction coefficient of 0.18–0.31. Adding fly ash to the fiber framework results in a lightweight composite aerogel with higher porosity, heat, and acoustic insulation, as well as impressive compressive modulus, compared to the fly ash-free aerogels. This study provides a safe, environmentally friendly, and cost-effective solution for recycling fly ash into high-value engineering materials. [Display omitted] • Zero waste procedures have been developed to completely recycle FA into composite aerogels. • The combination of FA and rPET fibers increases the flexibility of the aerogel. • The fabricated composite aerogel is lightweight and has a porosity of over 96%. • The compressive strength of composite aerogel is 20 times higher than that of FA-free aerogel. • Composite aerogels exhibit both excellent thermal and acoustic insulation without any required modification. [ABSTRACT FROM AUTHOR]

Given the harmful effects of agricultural waste residues on the environment and the abundance of pineapple byproducts after harvest, converting pineapple waste into a high-engineering value product for practical applications is one of the solutions toward sustainable development in developing countries. For the first time, flexible cellulose aerogels from raw pineapple-leave fibers (PALF) are developed successfully by using an adhesive agent, polyvinyl alcohol (PVA), and deionized (DI) water as a solvent, followed by a freeze-drying process. The effects of the pineapple fiber (PF) concentration on the heat and acoustic insulation properties are also investigated. The PF aerogels show high porosities of nearly 99%, ultra-low densities of (0.013–0.033) g/cm3, and a microporous structure which are determined by FE-SEM, BET and XRD analysis. They have very low thermal conductivities of (0.030–0.034) W/mK, indicating their excellent suitability for heat insulation applications. Indeed, the thermal jacket using a PF aerogel as filler wrapped around a water bottle can maintain the water temperature below 0 °C for 6 h (initial temperature of −3 °C), and above 40 °C for 2.5 h (initial temperature of 90 °C). The heat insulation capacity of the thermal jacket is about three times better than that of a commercially available product. With the same thickness, the noise reduction coefficient of 2.0 wt% PF aerogel samples is greater than that of a commercial absorber Basmel, which demonstrates their potential in acoustic insulation applications. • Ultra-lightweight and highly porous pineapple fiber (PF) aerogels are developed successfully for the first time. • The PF aerogels exhibit great thermal and acoustic insulation properties. • The thermal jacket made of PF aerogels can keep water chilled within 4.5 h. • The flexibility of PF aerogels is demonstrated with low compressive moduli. [ABSTRACT FROM AUTHOR]

• A green and cost-effective method to convert sugarcane bagasse into aerogel has been developed. • Sugarcane bagasse aerogel is a promising candidate for heat insulation applications. • Sugarcane bagasse aerogel is a promising candidate for oil-spill cleaning applications. • Sugarcane bagasse aerogel is highly flexible, and can be bent without breaking. A promising and economic material for various applications, such as thermal insulation in construction building and oil clean-up in marine ecosystems, is successfully developed from the by-product of the sugarcane industry. Biodegradable sugarcane bagasse aerogels are produced using polyvinyl alcohol (PVA) binder, followed by a freeze-drying method. This environmental-friendly recycled aerogel has an ultra-low density ([0.016-0.112] g/cm3), a high porosity ([91.9–98.9]%), and a very low thermal conductivity ([0.031-0.042] W/mK). Its superhydrophobicity properties and its maximum oil absorption capacity (up to 25 g/g) are measured after coating aerogel samples with methyltrimethoxysilane (MTMS). The biodegradable aerogel has a Young's modulus of 88 K Pa and can be bent without breaking, demonstrating its high flexibility. [ABSTRACT FROM AUTHOR]