Coupled kinetics of ferrihydrite transformation and As(V) sequestration under the effect of humic acids: A mechanistic and quantitative study
Coupled kinetics of ferrihydrite transformation and As(V) sequestration under the effect of humic acids: A mechanistic and quantitative study
复制标题
腐殖酸作用下水铁矿转化和 As(V) 封存的耦合动力学：机理和定量研究
DOI：
10.1021/acs.est.8b03492
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发表时间：
2018
影响因子：
11.4
通讯作者：
Shi Zhenqing
中科院分区：
文献类型：
--
作者：
Hu Shiwen;Lu Yang;Peng Lanfang;Wang Pei;Zhu Mengqiang;Dohnalkova Alice C;Chen Hong;Lin Zhang;Dang Zhi;Shi Zhenqing
在自然环境中，As(V)的固存/释放动力学通常伴随着动态的Fe矿物转化，而这一过程又受到天然有机质（NOM）存在的影响。以往的研究主要集中在As(V)和Fe矿物之间的相互作用。然而，对As(V) -Fe矿物- nom体系中耦合动力学过程的机理和定量认识尚缺乏。在本研究中，我们研究了腐植酸（HA）对铁水合物向赤铁矿/针铁矿转化和As(V)在铁矿物上固存耦合动力学的影响。利用像差校正扫描透射电子显微镜、化学萃取、搅拌流动动力学实验和x射线吸收光谱研究了动力学过程中时间分辨As(V)和HA与Fe矿物的相互作用。基于实验结果，我们建立了铁矿物转化过程中As(V)命运的机理动力学模型。我们的研究结果表明，铁矿物中As(V)形态的变化速率与铁水合物的转化速率是耦合的，并且由于吸附在铁矿物上的HA的存在，整体反应速度减慢。我们的动力学模型能够解释铁矿物组成、溶液化学和As(V)形态的变化，这对预测As(V)在环境中的行为具有重要的环境意义。
In natural environments, kinetics of As(V) sequestration/release is usually coupled with dynamic Fe mineral transformation, which is further influenced by the presence of natural organic matter (NOM). Previous work mainly focused on the interactions between As(V) and Fe minerals. However, there is a lack of both mechanistic and quantitative understanding on the coupled kinetic processes in the As(V)–Fe mineral–NOM system. In this study, we investigated the effect of humic acids (HA) on the coupled kinetics of ferrihydrite transformation into hematite/goethite and sequestration of As(V) on Fe minerals. Time-resolved As(V) and HA interactions with Fe minerals during the kinetic processes were studied using aberration-corrected scanning transmission electron microscopy, chemical extractions, stirred-flow kinetic experiments, and X-ray absorption spectroscopy. Based on the experimental results, we developed a mechanistic kinetics model for As(V) fate during Fe mineral transformation. Our results demonstrated that the rates of As(V) speciation changes within Fe minerals were coupled with ferrihydrite transformation rates, and the overall reactions were slowed down by the presence of HA that sorbed on Fe minerals. Our kinetics model is able to account for variations of Fe mineral compositions, solution chemistry, and As(V) speciation, which has significant environmental implications for predicting As(V) behavior in the environment.