Waste Biomass Valorisation for the Development of Sustainable Cellulosic Aerogels and their Sound Absorption Properties

Abstract

Novel and more sustainable sound absorbing materials are produced through the valorization of waste biomass sources by following circular economy principles. Cellulosic nanocrystals (CNC) were extracted from Posidonia oceanica dead leaves, spent barely grains, and kale stems using a simplified purification protocol. These nanocrystals are used to prepare cellulosic aerogels, evaluating the effect of three parameters, namely, concentration (0.5–4%), CaCl2 and poly(lactic acid) (PLA) incorporation (hybrid aerogels), on their sound absorption properties. Aerogels from 4% suspensions show the highest sound absorption, outperforming benchmark rockwool and polyester—two modern commonly‐used sound absorbers. Moreover, PLA coating also improves the sound absorption performance of the most aerogels. CNC from KS aerogels are selected as the optimum at both high (500–6000 Hz) and low (100–1500 Hz) frequency ranges. Overall, these results represent a new proof‐of‐concept of waste biomass conversion to high‐performance cellulosic aerogels that have excellent sound absorbing properties.

Effects of Freeze-Drying Processes on the Acoustic Absorption Performance of Sustainable Cellulose Nanocrystal Aerogels

“…Moreover, it can be seen from the DTG curve that the typical decomposition of d-CNCA occurs at a relatively high temperature (322.8 • C). This pyrolysis temperature is higher than that of c-CNCA (Figure 4b) as well as that of several reported cellulosic aerogels developed from Posidonia oceanica (below 300 • C) [16] and Kenaf core [20] biomass. The ordered porous structures of cellulose aerogels fabricated through unidirectional freezing demonstrated a higher thermal conductivity than disordered structures [30].…”

“…Briefly, the good thermal stability (working temperature above 200 • C) of d-CNCA is sufficient to meet the application requirements under normal conditions. aerogels developed from Posidonia oceanica (below 300 °C) [16] and Kenaf core [20] biomass. The ordered porous structures of cellulose aerogels fabricated through unidirectional freezing demonstrated a higher thermal conductivity than disordered structures [30].…”

“…Due to their unique physical properties, such as ultra-high porosity, ultra-low density, and Gels 2024, 10, 141 2 of 13 sound propagation speed, aerogels are also excellent acoustic absorption materials to efficiently suppress noise [1,12,13]. Cellulose aerogels, as a new type of bio-based porous material, not only inherit the superior porous structures of traditional aerogels, but also possess extremely high sustainable value, showing good prospect in the field of noise reduction [14][15][16].…”

“…Hence, the design and regulation of the pore structures of cellulose aerogels play an important role in optimizing their acoustic absorption performance. It has been reported that the porous characteristics of cellulose aerogels can be effectively regulated through cellulose content [17][18][19], amounts and types of crosslinker or aging agent [16,19,20], intensity of hydrogen bonds [21], drying processes, etc. In particular, controlling their physical properties (e.g., porosity, density, and aperture) with the aid of different drying principles appears to be a convenient approach to efficiently regulate porosity features.…”