Contrasting abiotic As(III) immobilization by undissolved and dissolved fractions of biochar in Ca2+-Rich groundwater under anoxic conditions
Contrasting abiotic As(III) immobilization by undissolved and dissolved fractions of biochar in Ca2+-Rich groundwater under anoxic conditions
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缺氧条件下富含 Ca2 地下水中生物炭的未溶解和溶解部分对非生物 As(III) 的固定对比
DOI：
10.1016/j.watres.2020.116106
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发表时间：
2020
期刊：
影响因子：
12.8
通讯作者：
John C. Crittenden
中科院分区：
文献类型：
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作者：
Delai Zhong;Zezhou Zhao;Yi Jiang;Xiao Yang;Linling Wang;Jing Chen;Chung-Yu Guan;Yanrong Zhang;Daniel C.W. Tsang;John C. Crittenden
工程黑碳（生物炭）可以通过其广泛的工程应用（例如，地下水/土壤的就地修复），它可以参与地球化学过程，可能会改变砷（As（III））等微量污染物的命运。在这里，我们研究了还原生物炭（以下分别表示为rUBC和rDBC）的未溶解和溶解部分对As（III）的固定化在无/有Ca 2+（50 mM）在pH 11.5缺氧条件下的影响。虽然rUBC和rDBC单独都不能固定As（III），但在Ca 2+存在下，rUBC和rDBC协同作用明显固定As（III），24 h内的效率分别为73.1%和89.6%。在rUBC/Ca 2 +/As（III）系统中，rUBC通过其残留的氧化还原活性部分（例如醌式C双键O和持久性自由基）将As（III）完全氧化为As（V），从而促进新生成的As（V）沉淀，Ca 2+吸附在rUBC表面上。与此相反，rDBC诱导原位富集的Ca 2+在新生rDBC衍生的絮体与主要的非氧化和轻微的氧化沉淀的As（III）通过三元rDBC-Ca-As络合。该三元复合物是由Ca 2+桥接的相互作用之间的物种和含氧官能团的rDBC，证明了FTIR结果和Ca 2+阻碍As（III）氧化。絮凝体的产生物理上捕获了少量的As物种，特别是As（III）。Ca 2+浓度（0-100 mM）和溶液pH（10.0-12.5）的增加都增强了As（III）的表观固定。这项研究提供了新的见解的环境影响的两个减少生物炭馏分释放到典型的富钙含水层的命运和运输的As物种。
Engineered black carbon (biochar) can be introduced into groundwater through its extensive engineered applications (e.g.,in-situremediation of groundwater/soils), which can participate in geochemical processes that may alter the fate of trace contaminants such as arsenic (As(III)). Here we examined the impacts of the undissolved and dissolved fractions of reduced biochar (hereafter denoted as rUBC and rDBC, respectively) on the As(III) immobilization in the absence/presence of Ca2+(50 mM) at pH 11.5 under anoxic conditions. While neither rUBC nor rDBC alone was capable of immobilizing As(III), the apparent As(III) immobilization by rUBC and rDBC synergistically occurred in the presence of Ca2+, with an efficiency of 73.1% and 89.6% within 24 h, respectively. In the rUBC/Ca2+/As(III) system, rUBC enabled full oxidation of As(III) to As(V) by its residual redox-active moieties such as quinoid Cdouble bondO and persistent free radicals, thereby facilitating precipitation of the newly generated As(V) with Ca2+adsorbed onto the rUBC’s surface. In contrast, rDBC inducedin-situlocal enrichment of Ca2+in the nascent rDBC-derived flocs with predominant non-oxidative and slight oxidative precipitation of As(III) via ternary rDBC-Ca-As complexation. This ternary complex was created by Ca2+-bridging interactions between As species and oxygen-containing functional groups of rDBC, as evidenced by the FTIR results and the Ca2+-impeded As(III) oxidation. The generation of the flocs physically trapped a small amount of As species particularly As(III). Both the increases in Ca2+concentration (0–100 mM) and solution pH (10.0–12.5) enhanced the apparent As(III) immobilization. This study provides new insights into the environmental impacts of two reduced biochar fractions released into typical Ca2+-rich aquifers on the fate and transport of As species.