Rapid and Scalable Synthesis of a Vanillin-Based Organogelator and Its Durable Composite for a Comprehensive Remediation of Crude-Oil Spillages

Phase-selective organogelators (PSOGs) that have immense potential in effective oil/water separation, antifouling coating, ice-repellent coating, and so on are often synthesized by following complex and multistep synthesis procedures that involve additional and tedious purification steps. On the other side, a comprehensive, selective, environmentally friendly, and energy-efficient separation of different and complex forms of oil spillages (e.g., floating oil or oil-in-water emulsions) from contaminated aqueous phase is challenging to achieve based on earlier-reported PSOGs and their composites. Here, vanillin, a naturally abundant molecule, is unprecedentedly exploited to synthesize a purified PSOG (with a yield of 97%) by adopting a catalyst-free, single-step, and rapid (<2 min) synthesis process under ambient conditions. The Schiffs base reaction between the aldehyde group of vanillin and the primary amine group of octadecylamine provided the desired and purified PSOG-without demanding any additional purification processes (e.g., column chromatography). The appropriate coexistence of the imine linkage, hydrocarbon tail, and hydroxyl group in the vanillin-derived organogelator (VDOG) played an important role in achieving a self-standing organogel that sustained similar to 60 times the external load of its weight-without having any noticeable physical deformation. Further, an appropriate and facile integration of the synthesized VDOG with a commercially available biodegradable porous and spongy matrix (i.e., polyurethane sponge) allowed us to develop an oil-selective absorbent with (1) enhanced water repellency (140 degrees) and (2) superior oil-absorption capacity (i.e., 55.2 times its own weight). Such composite material remained durable for repetitive (at least for 50 cycles) and distillation-free separation/recovery of crude oil at practically relevant severe and diverse settings. Thereafter, the synthesized VDOG was successfully and unprecedentedly extended to demonstrate rapid, facile, and efficient separation of surfactant-stabilized oil-in-water emulsions.

Automated summary

PSOGs synthesized from vanillin using a catalyst-free, single-step process showed high purity and excellent load-bearing capacity; the integration of VDOG with a biodegradable polyurethane sponge resulted in an oil-selective absorbent with enhanced water repellency and superior oil-absorption capacity; the synthesized VDOG was successfully extended to efficiently separate surfactant-stabilized oil-in-water emulsions.