Impact of Cr(III) complexation with organic acid on its adsorption in silts and fine sands

IF 1.9 4区地球科学 Q3 WATER RESOURCES

Journal of Groundwater Science and Engineering Pub Date : 2024-12-01 DOI:10.26599/jgse.2024.9280026

Zi-xuan Zhang, Lin Wu, Xiangke Kong, Huijun Li, Le Song, Ping Wang, Yanyan Wang

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引用次数: 5

Abstract

Trivalent chromium (Cr(III)) can form stable soluble complexes with organic components, altering its adsorption properties in the water-soil environment. This increases the risk of Cr(III) migrating to deeper soils and transforming into toxic Cr(VI) due to the presence of manganese oxides in sediments. In this study, Citric Acid (CA) was selected as a representative organic ligand to prepare and characterize Cr(III)-CA complexes. The characteristics, mechanisms and environmental factors influencing the adsorption of Cr(III)-CA on porous media (silts and fine sands) were investigated in the study. The results show that Cr(III) coordinates with CA at a 1:1 molar ratio, forming stable and soluble Cr(III)-CA complexes. Compared to Cr(III) ions, the equilibrium adsorption capacity of Cr(III)-CA is an order of magnitude lower in silts and fine sands. The adsorption of Cr(III)-CA in silts and fine sands is dominated by chemical adsorption of monolayers, following the pseudo-second-order kinetic equation and the Langmuir isotherm adsorption model. Varying contents of clay minerals and iron-aluminum oxides prove to be the main causes of differences in adsorption capacity of Cr(III)-CA in silts and fine sands. Changes in solution pH affect the adsorption rate and capacity of Cr(III)-CA by altering its ionic form. The adsorption process is irreversible and only minimally influenced by ionic strength, suggesting that inner-sphere complexation serves as the dominant Cr(III)-CA adsorption mechanism.

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有机酸与Cr（III）络合对其在淤泥和细砂中吸附的影响

三价铬（Cr(III)）可与有机组分形成稳定的可溶配合物，改变其在水土环境中的吸附特性。由于沉积物中锰氧化物的存在，这增加了Cr（III）迁移到更深土壤并转化为有毒Cr（VI）的风险。本研究选择柠檬酸（CA）作为有机配体的代表，制备并表征Cr(III)-CA配合物。研究了多孔介质（淤泥和细砂）对Cr(III)-CA的吸附特性、机理及环境因素的影响。结果表明，Cr（III）与CA以1:1的摩尔比配位，形成稳定、可溶的Cr(III)-CA配合物。与Cr（III）离子相比，Cr(III)-CA在粉砂和细砂中的平衡吸附量低一个数量级。Cr(III)-CA在粉砂和细砂中的吸附主要以单分子层的化学吸附为主，符合拟二级动力学方程和Langmuir等温吸附模型。黏土矿物和铁铝氧化物含量的不同是泥沙和细砂对Cr(III)-CA吸附能力差异的主要原因。溶液pH的变化通过改变离子形态影响Cr(III)-CA的吸附速率和容量。吸附过程是不可逆的，且受离子强度的影响很小，表明球内络合是主要的Cr(III)-CA吸附机制。

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来源期刊

Journal of Groundwater Science and Engineering WATER RESOURCES-

CiteScore

2.80

自引率

9.10%

发文量

308

期刊介绍： It publishes original, innovative, and integrative research in groundwater science and engineering with a focus on hydrogeology, environmental geology, groundwater resources, agriculture and groundwater, groundwater resources and ecology, groundwater and geologic environment, groundwater circulation, groundwater pollution, groundwater exploitation and utilization, hydrogeological standards and methods, groundwater information science, climate change and groundwater. The Editorial Board is composed of more than sixty world-renowned experts and scholars, 47% of whom are foreign scientists. Up to now, the foreign authors contributed papers are from USA, Japan, Canada, Australia, Russia, Mongolia, Thailand and Vietnam.