Valorization of Juncus effusus pith into fully biobased and underwater superoleophobic columns for efficient oily wastewater treatment and dye removal

The disposal of oily wastewater and dye wastewater poses significant threats to aquatic ecosystems. Developing sustainable, efficient, and low-cost materials for the simultaneous treatment of these pollutants remains a challenge. In this study, we report a novel strategy for fabricating a fully biobased separation column using Juncus effusus pith, an abundant and renewable natural resource. Unlike conventional methods that rely on complex synthesis or hazardous chemical modifiers, the hydrophobic-to-hydrophilic transition of the pith was achieved through a one-step, reagent-free boiling water treatment (BWT). This green activation strategy exposed abundant hydrophilic groups on the surface, endowing the material with superhydrophilicity (water contact angle, 0°) and underwater superoleophobicity (under water oil contact angle, >151.3°). The as-prepared column, compressed into a cylindrical shape, possessed an interconnected porous network. It demonstrated excellent performance in gravity-driven separation, achieving efficiencies exceeding 99.6% for various oil/water mixtures (including surfactant-stabilized emulsions) and effective removal of organic dyes (e.g., Methylene Blue, Rhodamine B). The column operated without external pressure, driven solely by gravity, and exhibited outstanding anti-fouling properties and reusability. This work highlights a simple, green, and sustainable approach to convert natural biomass into high-performance environmental remediation materials, aligning well with the principles of a circular bioeconomy.