Against the backdrop of the global transition towards green, low-carbon development and the deepening adoption of sustainable principles, industries such as chemicals, pharmaceuticals, and food processing are imposing higher demands for efficient and environmentally friendly separation technologies. Organic solvent nanofiltration (OSN) technology, as a key process for achieving molecular-level precision separation, is progressively expanding from traditional fossil-based materials to bio-based material systems. The introduction of biomass raw materials such as chitosan not only provides a new material selection perspective for OSN membrane technology but also opens up innovative pathways in structural design, performance regulation, and application scenarios. This article aims to explore the research progress and future directions of bio-based OSN membranes from new perspectives on technological development.
In terms of structural design, the development of bio-based OSN membranes demonstrates a paradigm shift from "passive compositing" to "active construction." In traditional composite membrane fabrication, the phenomenon of pore penetration often leads to an inherent conflict between mass transfer resistance and interlayer adhesion. Recently, researchers have proposed a "root-like structure" construction strategy based on the principle of interfacial instability, inspired by the formation mechanism of plant root systems. This technology leverages the synergistic effect of reaction and diffusion between alkaline pre-wetting and acidic casting solutions to form a slender, continuous chitosan fiber network within the substrate. This biomimetic structure not only significantly enhances interlayer bonding strength but also effectively preserves the mass transfer channels of the substrate, increasing pure water permeability nearly threefold. This approach offers a new perspective for resolving the structural design and performance balance issues in composite membranes.
In the regulation of the separation layer, research on bio-based OSN membranes is evolving from "single modification" to "systematic reconstruction." Early studies primarily focused on enhancing membrane stability through crosslinking or blending, whereas current technological advancements emphasize the systematic reconstruction of intermolecular interaction networks. For instance, introducing PVA to construct a weak hydrogen bonding system can moderately increase free volume while maintaining rejection performance. Further modification with -PGA achieves a transition from hydrogen bond-dominated to electrostatic force-dominated molecular interaction mechanisms. This reconstruction of interaction types not only significantly increases the free volume fraction to 5.37% but also induces fundamental changes in molecular chain conformation, ultimately leading to an order-of-magnitude improvement in solvent flux while maintaining efficient rejection of macromolecular solutes. This systematic regulation strategy at the molecular level provides a new technical pathway for breaking the traditional "trade-off" effect in membrane materials.
In summary, bio-based organic solvent nanofiltration membrane technology is advancing from material substitution to deeper levels of structural innovation and mechanism reconstruction. The construction of root-like structures offers new solutions to the structural contradictions of composite membranes, while the systematic reconstruction of intermolecular interactions opens new avenues for overcoming performance bottlenecks. With the deepening implementation of green chemical principles and the continuous optimization of manufacturing processes, bio-based OSN membranes are expected to play an increasingly important role in pharmaceuticals, food refining, and green solvent recovery. In the future, through interdisciplinary integration and industry-academia-research collaboration, bio-based OSN membrane technology will provide more competitive solutions for the greening and efficiency enhancement of chemical separation processes, driving the industry toward sustainable development goals.
