Effects of sulfuric acid pretreatment and liquid acids precipitation on the structure of fulvic acid extracted from peat

Abstract

To achieve high-value utilization of peat, the process of coupling methane fermentation and extraction of fulvic acid was explored and the effects of sulfuric acid pretreatment before methane fermentation and different liquid acid precipitation on the spectral characteristic of fulvic acid was studied. The fulvic acid precipitated by nitric acid has a high content and a high degree of aromatization. The highest yield of fulvic acid samples is precipitated by phosphoric acid. The fulvic acid extracted from the residues after sulfuric acid pretreatment methane fermentation descends of yield while content increase. Meanwhile, methane fermentation would consume methyl, hydroxyl, and carboxyl groups without benzene rings consumed. In addition, sulfuric acid pretreatment would promote this process and consume more functional groups to produce more methane. The research results show that coupling methane fermentation of peat and extraction of fulvic acid is feasible, and the sulfuric acid pretreatment has a significant effect to fulvic acid. To sum up, sulfuric acid pretreatment would promote methane fermentation process and degrade more fulvic acid.