Since the development of advanced sound absorption material is highly critical in noise control applications, anechoic coatings, and acoustic metamaterials, both fabrication technology and structure design are significant in the achievement of broadband and strong absorption performance in the low sound frequency range. In this work, the silicone rubber resonance absorption sheet with periodic cavities is prepared via inserting cylindrical steel strips with different diameters into the non-vulcanized colloid. Effects of size and arrangement of cavities on the sound absorption properties, as well as the corresponding mechanical properties, are investigated and discussed. Results indicate that periodic pattern designs could further improve the low-frequency sound absorption performance of silicone rubber foams, and increasing the cavity diameter could significantly improve the sound absorption efficiency of the prepared samples in the middle- and low-frequency range from 125 to 2000 Hz. Particularly, increasing the number of the layered cavities could also improve the sound absorption efficiency. The consumption of sound energy in the prepared silicone rubber resonance sheet is discussed, which could be attributed to the synergistic effect in different spatial scales.

Polyaniline-based composites are potential candidates for the treatment of anionic azo dyes from an aqueous solution. However, the related adsorption mechanisms are not clearly delineated. Here, polyaniline/ montmorillonite (PANI/MMT) nanocomposite was synthesized by incorporating polyaniline (PANI) into the interlayers of montmorillonite (MMT). The nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Results indicated that polymerization of the aniline monomer within the MMT gallery led to an expansion of basal spacing of the silicate layers. The prepared PANI/MMT nanocomposite was subsequently used for the removal of anionic azo dye Reactive Green 19 (RG19) from aqueous solutions. The adsorption of RG19 onto the PANI/MMT nanocomposite was consistent with the pseudo-second order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity was found to be 46.88 mg/g at 25 °C, according to the linear regression analysis of the Langmuir isotherm. Thermodynamic parameters (ΔH° = −12.35 kJ/mol, ΔS° = −28.40 J/mol/K) revealed the spontaneous, exothermic, and enthalpy-driven nature of adsorption. Additionally, FTIR and X-ray photoelectron spectroscopy (XPS) analyses confirmed that the mechanism for adsorption of RG19 onto PANI/MMT nanocomposite involved hydrogen bonding and π-π interactions between the RG19 dye and adsorbent.

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