All-Lignin Polyelectrolyte Multilayers as Renewable and Biodegradable Nanofiltration Membranes

High Resolution Image Download MS PowerPoint Slide Polyelectrolyte multilayers have proven to be versatile materials for the fabrication of nanofiltration membranes with a wide range of properties and applications. A problem of these membranes is that they are made of nonrenewable and nonbiodegradable fossil resources, rendering them unsustainable for the future. To solve this, we present lignin as a renewable and biodegradable alternative for the fabrication of polyelectrolyte multilayer membranes (PEMMs). Here, lignosulfonate was used as a polyanion in combination with modified Kraft lignin as a polycation in a layer-by-layer self-assembly process to coat hollow fiber support membranes to obtain so-called all-lignin PEMMs. The PEMMs showed loose nanofiltration properties (molecular weight cutoff > 1 kDa, MgSO 4 retention 20%) that could easily be fine-tuned by changing the ionic strength of the coating solutions. Furthermore, the lignin PEMMs have excellent stability in saline solutions of up to 5 M NaCl and were stable in a pH range from 1 to 11. Additionally, the lignin retained its biodegradable properties in the presence of laccase enzymes after forming a PEMM. Our results indicate that lignins are a suitable candidate for replacing fossil-based polyelectrolytes for the fabrication of chemically stable, renewable, and biodegradable PEMMs.