Qi Yongbo, Zhu Jun, Fu Qingling, Hu Hongqing, Huang Qiaoyun
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, China.
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, China.
J Environ Manage. 2017 Sep 15;200:304-311. doi: 10.1016/j.jenvman.2017.05.087. Epub 2017 Jun 3.
The sorption of Cu on humic acid (HA) from the decomposition of rice straw in the absence (Ck-HA) and presence of montmorillonite (M-HA), kaolinite (K-HA), gibbsite (Gi-HA) and goethite (Go-HA) was investigated at pH 5.0 by using batch studies combined with isothermal titration calorimetry (ITC) and atomic force microscopy (AFM). Characterization by elemental analysis and potentiometric titration showed the composition difference among these five HA. The sorption capacity and rate increased in the order: M-HA < K-HA < Gi-HA < Ck-HA < Go-HA. ITC results revealed that the sorption process was spontaneous and endothermic. The aggregation of HA particles after sorption were observed by AFM images. The influence of pH and positive correlations between the sorption capacity and the content of acidic functional groups of HA indicated that the dissociated acidic functional groups, especially the dissociation of carboxylic groups in HA played an important role in Cu sorption. Sequential desorption of sorbed Cu showed that the surface bonded fraction (97.6-99.0%) was significantly higher than the ion exchanged fraction (1.0-2.4%). Markedly positive entropies (ΔS, 94.4-104.3 J mol K) further demonstrated that Cu binding to HA by forming inner-sphere complexes. The findings of this study would promote the understanding on the environmental impact of the decomposition of organic waste from agricultural production.
通过批次研究结合等温滴定量热法（ITC）和原子力显微镜（AFM），在pH 5.0条件下研究了稻草分解产生的腐殖酸（HA）在不存在蒙脱石（Ck-HA）、存在蒙脱石（M-HA）、高岭石（K-HA）、三水铝石（Gi-HA）和针铁矿（Go-HA）时对铜的吸附情况。通过元素分析和电位滴定进行表征，结果显示这五种腐殖酸的组成存在差异。吸附容量和速率的增加顺序为：M-HA < K-HA < Gi-HA < Ck-HA < Go-HA。ITC结果表明吸附过程是自发且吸热的。通过AFM图像观察到吸附后腐殖酸颗粒的聚集情况。pH的影响以及吸附容量与腐殖酸酸性功能基团含量之间的正相关表明，解离的酸性官能团，尤其是腐殖酸中羧基的解离在铜吸附中起重要作用。对吸附的铜进行连续解吸表明，表面键合部分（97.6 - 99.0%）显著高于离子交换部分（1.0 - 2.4%）。明显为正的熵（ΔS，94.4 - 104.3 J mol K）进一步证明铜通过形成内球络合物与腐殖酸结合。本研究结果将有助于增进对农业生产有机废弃物分解对环境影响的理解。
