Study on spectral characteristics of fulvic acid in the process of mixed composting of bioleach deep dehydrated sludge and rice straw

Abstract

Bioleaching deep dewatered sludge was used as main material and rice straw was used as conditioner for mixed composting. UV-vis spectroscopy (UV-vis) and three-dimensional fluorescence spectrum (3D-EEM) were used to study the structural characteristics and component content evolution of fulvic acid (FA) during composting. UV-vis results show that the spectral parameters SUVA254 and SUVA280 show an increasing trend. E253/E203 and E253/E220 increased at the end of the compost. Emission fluorescence spectrum shows that substances with low conjugation degree were degraded to generate humus-like substances. In the synchronous fluorescence spectrum, the intensity of the fluorescence peak near 280nm gradually decreases and the intensity of the fluorescence peak near 400nm gradually increases. Combined with the parallel factor (PARAFAC) model to analyze three-dimensional fluorescence spectrum, FA was resolved into three components: microbial short-wavelength humic acid substances, long-wavelength humic acid substances and tryptophan-like substances.