Carbon quantum dots in-situ relieve humic acids inhibition on methanogens while significantly increasing the abundance of Methanosarcinaceae

• Published in: Journal of cleaner production 2023-09, Vol.419, p.138258, Article 138258
• Main Authors: Liu, Qiang, Xu, Yuanting, Li, Yeqing, Ma, Chengjie, Chen, Shuo, Feng, Lu, Xu, Quan, Pan, Junting, Peng, Bo, Zhou, Hongjun, Xu, Chunming
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Carbon quantum dots; Humic acids; Interaction; Microbial community
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2023.138258

Monophenols form humic acids (HA) through polycondensation reaction in the anaerobic digestion (AD) process, which will inhibit AD process. Currently, metal ions are the option for in-situ relieving HA inhibition during AD, but excess metal ions are harmful to microorganisms. In this study, carbon quantum dots (CQDs, a non-metallic materials) were proposed to relieve HA inhibition in-situ. We investigated the effect of HA on AD acidification and methanation stage, and synthesized CQDs using sodium citrate (s-CQDs) and p-phenylenediamine (p-CQDs) as precursors to relieve the HA inhibition in-situ. Results showed that s-CQDs (3.0 g/L) significantly increased the cumulative CH4 yield from AD of ethanol with 1.0 g/L HA (1.9 times higher than that without s-CQDs). Microbiological analysis indicated the most dominant methanogen was Methanosarcinaceae, with richness of 89.7%. Compared to the HA inhibition system, the relative abundance of Methanosarcinaceae increased by 87.5%. The analysis of interaction mechanism between CQDs and HA indicated that s-CQDs has an in-situ binding effect to HA by reacting with -OH, CC, and -COOH. This study provided a novel means for in-situ relieving HA inhibition, and illustrated the interaction mechanism between CQDs and HA, which will guide the application in production of bioenergy. [Display omitted] •CQDs was able to relieve the HA inhibition on microorganisms in-situ.•3.0 g/L s-CQDs increased the cumulative CH4 yield of ethanol AD with 1.0 g/L HA to 350.0 ± 5.0 mL/g VS.•3.0 g/L s-CQDs significantly promoted the abundance of Methanosarcinaceae to reached 89.7%.•s-CQDs has a binding effect to HA by reacting with -OH, CC, and -COOH.