Enhancing dye adsorption performance of sporopollenin through Thymssol-Menthol-based deep eutectic Solvent...

Dye pollution from industrial wastewater, including that from the batik industry, threatens aquatic ecosystems and water resources. Adsorption is a cost-effective and sustainable method for dye remediation. This study focused on synthesizing thymol-menthol-based deep eutectic solvent functionalized sporopollenin (T:M@DES-Sp) as a new adsorbent for Rhodamine B (RB) remediation. The synthesized adsorbent material showed O-H and C-H stretching peaks at 3311 cm^-1 and 2924 cm^-1, respectively. The contact angle measurement was less than 90°, indicating a hydrophilic surface, and the thermogram showed a major weight loss in the temperature range of 120-185 °C, which is attributed to the simultaneous decomposition of thymol and menthol in a single step. The modification of Sp with DES markedly improved the adsorption performance, increasing RB dye uptake by nearly fourfold compared to Sp, underscoring the effectiveness of DES functionalization for dye removal from aqueous media. The adsorption of RB dye using T:M@DES-Sp is a spontaneous process, with ΔG° ranging from -2.39 to -0.64 kJ/mol, while ΔH° is -28.27 kJ/mol, indicating an exothermic process. T:M@DES-Sp achieved good removal efficiency for RB dye in both synthetic and real samples and demonstrated good reusability performance for up to six cycles. Moreover, its disposal after the adsorption process is nontoxic to the environment, as Pisum sativum showed 100% germination, comparable to that in freshwater. Hence, this study provides an eco-friendly and efficient solution for dye removal, supporting Sustainable Development Goal (SDG) 6 by improving water quality and promoting sustainable industrial practices.