Lignin-incorporated bacterial nanocellulose for proton exchange membranes in microbial fuel cells

Abstract

Microbial fuel cells (MFCs) are based on organic waste and microbes to produce electricity. Bacterial nanocellulose (BNC) can be used to produce PEMs. Incorporating Lignin (LIG) into the BNC provides more proton transport pathways and improves thermal stability. In this work, a membrane of BNC and LIG, crosslinked by citric acid (CA), was developed. Scanning electron microscopy (SEM) showed that LIG was entrapped in BNC nanofibers. Fourier transform infrared spectroscopy (FTIR) spectra of BNC/LIG membrane showed typical structural patterns of cellulose, lignin, and sulfonic groups. Thermogravimetric analysis (TGA) showed that BNC/LIG membranes are thermally more stable than those of pure BNC. BNC membrane reaching ∼90% of weight loss to temperatures higher than 380 °C and after crosslinking LIG on BNC reaching ∼64% of weight loss to temperatures higher than 480 °C. The titration tests indicated good ion exchange capacity (IEC) of the BNC/LIG membrane, presenting values of 0.78 mmol g−1 compared with Nafion® (polytetrafluoroethylene) membrane appeared in the literature a range from 0.8 to 1.0 mmol g−1. The BNC/LIG membrane as PEM in an MFC presented a maximum power density of 18.5 mW m−2 after 54 h of operation. Thus, BNC/LIG membranes are promising alternative PEMs in microbial fuel cells.