Dual function of gellan gum-infused polyurethane foam for remediation of methylene blue dye and sustainable acoustic protection

Abstract

The growing scarcity of water resources, coupled with the pressing need to alleviate the impacts of anthropogenic climate change, underscores the importance of developing sophisticated wastewater treatment systems that can deliver high-quality effluent. This study presents an innovative approach to address these interconnected issues via fabrication of modified flexible polyurethane (PU) foam adsorbent through the incorporation of varying concentrations (1–5 wt%) of gellan gum (GLG) bio-filler. The objective is to enhance the mechanical durability of the adsorbent while simultaneously tackling two critical environmental concerns; cleanup of methylene blue (MB) dye from aquatic systems and mitigation of noise pollution. The physicochemical attributes of the prepared composites were comprehensively conducted using FTIR, XRD, TGA, gel fraction analysis, rheological studies, density, stress-strain compression testing, SEM, and pore size distribution measurements. The loading capacity of the PU/GLG5 composite for MB dye was rigorously inspected under diverse experimental conditions of initial pH (e.g., 2.1–10.3), PU/GLG5 concentration (e.g., 0.5–5 g L⁻¹), MB concentration (e.g., 10–1000 mg L⁻¹), residence time (e.g., 180 min), temperature (e.g., 298–328 K), and several interfering ions (e.g., 5–45 g L⁻¹). The results demonstrated about 10.88 %, and 34.23 % improvement in the density, and compression strength of PU/GLG5, respectively, compared to the pristine foam. Moreover, the sorption process of MB onto PU/GLG5 was pH-dependent with 98.38 % efficiency under optimized pH ∼10.3. Meanwhile, kinetic studies indicated that adsorption process conformed closely to PSORE model, while isotherm data were well-correlated with the Langmuir assumption, demonstrating a maximum loading capacity of 476.19 mg g⁻¹. The adsorption process was characterized as exothermic, and the recyclability of the spent adsorbent was effectively maintained over 10th cycles, achieving above 84 % efficiency. The sorption characteristics of PU/GLG5 towards spiked tap water and wastewater were 86.8 %, and 80.4 %, respectively. Moreover, the treated wastewater became nearly colorless, achieving approximately 95 % color removal. Additionally, the COD decreased significantly from 350 mg L⁻¹ to just 26 mg L⁻¹, demonstrating the effectiveness of the PU/GLG5 sorbent in addressing wastewater contamination. Significantly, PU/GLG5 composites exhibited outstanding sound absorption performance, achieving sound absorption coefficient (SAC) up to 0.98 at high frequencies. Furthermore, the spent sorbent demonstrated enhanced SAC in the low-frequency range compared to the untreated foam. Based on the cost analysis, the total cost per kg of foam is approximately $7.01/kg, making it a highly cost-effective material for environmental applications. This research highlights the dual functionality of the developed material, contributing to the remediation of water pollution and the promotion of sustainable practices in the face of pressing global challenges.