Sustainable Melamine–Lignin Microspheres Composite Sponge for Superhydrophobic Surface Characteristics

Addressing marine oil spill pollution using superhydrophobic materials is low-cost, versatile, and highly reusable, which remains a significant challenge. Lotus leaves exhibit remarkable superhydrophobicity due to their surface micro/nano hierarchical structures. Inspired by this biomimetic mechanism, we fractionated black liquor lignin using lactic acid, obtaining lignin fraction with uniform molecular weight (PDI = 1.07), which was subsequently grafted with hexadecyltrimethoxysilane (HDTMS) to reduce surface energy. Through a facile self-assembly approach, monodisperse lignin microspheres with uniform size distribution were successfully immobilized onto the three-dimensional network of melamine resin sponges, leading to the fabrication of a novel superhydrophobic porous composite material based on lignin-incorporated melamine resin sponge architecture. The as-fabricated superhydrophobic melamine resin sponge (LMS3H-MRSs) exhibited remarkable separation efficiency (> 98%) for diverse oil-water mixtures, outstanding durability by maintaining superhydrophobicity after 50 cycles of oil-water separation, and efficient continuous oil-water separation performance. Notably, LMS3H-MRSs demonstrated excellent emulsion separation efficiency and maintained high separation efficiency even after 100 consecutive separation cycles. Furthermore, LMS3H-MRSs exhibited remarkable mechanical durability, high selectivity, and excellent chemical resistance to both acidic and alkaline environments. These superior characteristics make the prepared LMS3H-MRSs as a highly promising candidate for practical oil-water separation.