电场对污泥堆肥富里酸结构特征的影响

为了研究电场对污泥堆肥富里酸结构特征及电子转移能力(ETC)的影响,以市政污泥和米糠为原料,设置施加5V的直流电场(T1)和不施加电场(CK)的两个堆肥进行对比实验.通过三维荧光-平行因子分析(EEM-PARAFAC)、紫外可见光谱(UV-vis)、傅里叶红外光谱(FTIR)结合二维相关光谱(2DCOS)分析堆肥过程中富里酸结构和组成变化.通过电化学方法测定了堆肥富里酸的电子接受能力(EAC)和电子供给能力(EDC).结果表明,类色氨酸、类富里酸和类胡敏酸是堆肥FA的主要组分,随着堆肥的进行,FA中类色氨酸物质减少,类富里酸和类胡敏酸含量增加,电场能够促进FA在堆肥过程中类色氨酸的降解和类胡敏酸的形成,提高了FA的芳香性、分子量和腐殖化程度.电化学分析结果表明,FA的ETC呈现先增后减的趋势.相比CK处理,施加电场降低了FA的EDC,但同时增强了其EAC,使得堆肥后期的FA具有更强的ETC.结果将有助于进一步了解污泥堆肥过程中FA的形成过程及其氧化还原特性.

Effect of electric field on structure of fulvic acid during sludge composting

Fulvic acid (FA) is an important component of compost-derived humic substances, and its structure and electron transfer capacity are vital factors causing environmental effects. In order to investigate the influence of electric field on structural characteristics and electron transfer capacity (ETC) of FA that was formed during sludge composting, municipal sludge and rice bran were applied as raw materials, and two composting experiments, i.e.,one with a 5V direct current electric field and the other with no electric field (CK),were set up. Excitation-emission matrix florescence spectra coupled with parallel factor analysis, ultraviolet and visible spectroscopy, and Fourier transform infrared spectroscopy combined with two-dimensional correlation analysis were employed to investigate the evolution of the structure and composition of FA during composting. In addition, electrochemical methods was applied to determine the electron accepting capacities (EAC) and electron donating capacities (EDC) of the compost-derived FA. The results revealed that the major components of compost-derived FA were tryptophane-like, fulvic-like, and humic-like substances. Tryptophane-like substances in FA decreased during composting, whereas fulvic-like and humic-like substances increased during the process. Notably, the electric field promoted the degradation of tryptophan-like substances and the formation of humic-like substances, which inceased the aromatic degree, molecular weight, and humification of the FA. Results obtained from electrochemical analysis showed that the ETC of compost-derided FA increased initially and then decreased, Compared to the CK treatment, electric field application enhanced the EAC of compost-derided FA, though it reduced the EDC of FA, resulting the ETC of the FA from the later stage of composing was the highest. These results facilitated to elucidate the formation process of the FA and its redox properties during sludge composting.