Insight into Efficient Complexation Mechanism of Cd(Ⅱ) to Hyperthermophilic Compost-Derived Humic Acids by Two Dimensional Correlation Analyses
WEN Ping1, 2, TANG Jia2, CAI Xi-xi1, 2, LIU Xiao-ming2, YU Zhen2*, LÜ Jian1, ZHOU Shun-gui1, 2
1. Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
2. Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, Guangzhou 510650, China
Abstract: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-2DCOS) 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-2DCOS 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-2DCOS 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.
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