超高温堆肥腐殖酸与Cd(Ⅱ)高效络合机制2DCOS分析

Insight into Efficient Complexation Mechanism of Cd(Ⅱ)to Hyperthermophilic Compost-Derived Humic Acids by Two Dimensional Correlation Analyses

超高温堆肥工艺是一种新颖的污泥资源化利用技术,相比于高温堆肥工艺,具有发酵温度更高、腐殖化过程更快、堆肥产物质量更好等优势。然而,超高温堆肥产物作为调理剂在重金属污染土壤修复过程中的应用效果和优势仍有待明确。采用激发-发射矩阵荧光光谱-平行因子分析(EEM-PARAFAC)和傅里叶变换红外-二维相关光谱(FTIR-2DCOS)方法对比分析了超高温堆肥(HTC)、高温堆肥(TC)和污泥(SS)样品中提取的腐殖酸(HAs)与Cd(Ⅱ)的络合性能及相关反应机制。采用EEM-PARAFAC从HTC,TC和SS样品提取的HAs中鉴定出腐殖酸C1(Ex/Em=270,350/470)、类腐殖质物质C2(Ex/Em=270,325/470)和类蛋白质物质C3(Ex/Em=225,275/330)等3种组分,不同样品中不同组分的含量存在显著差异。进一步采用Ryan-Weber荧光猝灭模型对不同样品中HAs及HAs的各组分与Cd(Ⅱ)发生络合反应的荧光猝灭效应进行拟合,发现来源于HTC的HAs及其组分C1和C2对Cd(Ⅱ)络合稳定性和络合容量(LogKCd=5.72~5.95,CCCd=0.977~0.990)明显优于TC(LogKCd=5.62~5.67,CCCd=0.807~0.823)和SS(LogKCd=4.79~5.29,CCCd=0.476~0.581),表明HTC比TC和SS中HAs具有更好的Cd(Ⅱ)络合能力,而不同样品HAs中组分C1和C2是决定HAs与Cd(Ⅱ)络合性能的重要因素。采用FTIR-2DCOS对HAs与Cd(Ⅱ)发生络合反应时官能团变化顺序进行分析,发现HTC的HAs中羧基是与Cd(Ⅱ)发生络合时响应最为灵敏的官能团。由此推测,超高温堆肥通过促进堆肥腐殖化进程使羧基等不饱和基团含量增加是HTC的HAs与Cd(Ⅱ)具有更高效络合能力的另一关键因素。总之,样品HAs中相对高的腐熟程度以及羧基等官能团对Cd(Ⅱ)络合的高灵敏度是导致HTC络合Cd(Ⅱ)能力优于TC和SS的主要原因。EEM-PARAFAC和FTIR-2DCOS的结合,为定量表征堆肥中HAs与重金属络合性能及解析络合机制提供有力支撑,也为超高温堆肥产品应用于镉污染土壤修复研究提供了科学依据。

Compared with conventional thermophilic composting,hyperthermophilic composting as a novel technology for the treatment of sewage sludge,has the advantages of higher fermentation temperature,faster humification process and better quality of composting products.However,the application effect of hyperthermophilic compost as the conditioner in the remediation of heavy metal contaminated soil remains unclear.In this study,excitation-emission matrix spectra coupled with parallel factor(EEM-PARAFAC)and Fourier transform infrared spectra coupled with two-dimensional correlation spectroscopy(FTIR-2 DCOS)analyses were applied to compare the binding performances of Cd(Ⅱ)to hyperthermophilic compost(HTC)-,thermophilic compost(TC)-,sewage sludge(SS)-derived humic acid(HAs).Three components including humic acid(C1,Ex/Em=270,350/470),humic-like substance(C2,Ex/Em=270,325/470),and protein-like substance(C3,Ex/Em=2250,275/330)were identified from HAs by EEM-PARAFAC,The content of three components from HTC,TC and SS were found to be different.Ryan-Weber fluorescence quenching model was used to fit the fluorescence quenching effect of Cd(Ⅱ)binding to HAs as well as C1 and C2 for different samples.The higher complexing capacity and stability constants of the complexation of Cd(Ⅱ)with HAs,C1 and C2 derived from HTC(LogKCd=5.72~5.95,CCCd=0.977~0.990)than TC(LogKCd=5.62~5.67,CCCd=0.807~0.823)and SS(LogKCd=4.79~5.29,CCCd=0.476~0.581)indicated that HTC-derived HAs presented better complexation ability than other HAs,and the C1 and C2 components in HAs could be important for determining the complexation ability of Cd(Ⅱ)with HAs derived from HTC.FTIR-2 DCOS was used to figure out the contribution of the response of functional groups to Cd(Ⅱ)binding to the complexation ability of HAs derived from different samples.Compared with SS-and TC-derived HAs,carboxyl was the most sensitive group to Cd(Ⅱ)addition in HTC-derived HAs.Due to the higher humification degree,as well as the faster response of carboxyl to Cd(Ⅱ)binding with HAs,HTC-derived HAs have the greater complexation ability than both TC-and SS-derived HAs.EEM-PARAFAC integrated with FTIR-2 DCOS offers a unique insight into understanding the correlation between HAs and functional groups during the Cd(Ⅱ)binding process,and also provides a theoretical basis for the application of HTC as the conditioner in the remediation of Cd(Ⅱ)contaminated soil.