Enhancing tetramethylammonium hydroxide degradation in anaerobic digestion: Neglected role of iron-based conductive materials in regulating degradation pathway.

The rapid expansion of TFT-LCD industry led to significant environmental challenges due to the highly corrosive and ecotoxic tetramethylammonium hydroxide (TMAH). This study explores a previously unrecognized role of iron-based conductive materials - nano magnetite (Fe₃O₄) and nano zero-valent iron (ZVI) - in enhancing TMAH degradation and regulating degradation pathways in anaerobic digestion systems. Results show these materials significantly enhance degradation efficiency as TMAH concentration increases. At the highest TMAH level (10 g/L), while the control group achieved only 78.41 % degradation efficiency, Fe₃O₄ and ZVI groups reached efficiencies of 97.36 % and 94.96 %, with methane yields increased by 89.00 % and 97.21 %. Mechanistic exploration revealed these materials promoted secretion of charged functional groups into extracellular polymeric substances that effectively shielded microbes from TMAH toxicity. Additionally, they stimulated flavin and riboflavin production, enhancing interspecies electron transfer rates by up to 46.14-fold for Fe₃O₄ and 9.00-fold for ZVI. Microbial and metagenomic analyses further uncovered these materials induced a shift in TMAH degradation from methylotrophic methanogenesis to syntrophic metabolism, facilitating a more efficient breakdown of TMAH through direct interspecies electron transfer. These findings unravel the effects of iron-based conductive materials in regulating degradation pathways, offering a promising approach to addressing environmental challenges posed by TFT-LCD industry.