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Stabilization of Cd 2+ /Cr 3+ During Aqueous Fe(II)‐Induced Recrystallization of Al‐Substituted Goethite
Author(s) -
Liu Chengshuai,
Chen Manjia,
Li Fangbai,
Tao Liang,
Lin Jun,
Gao Ting,
Tong Hui,
Liu Yuhui,
Long Shengqiao,
Wu Fei,
Xia Yafei
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2018.05.0169
Subject(s) - goethite , recrystallization (geology) , ionic radius , aqueous solution , chemistry , ion exchange , metal , ionic bonding , mössbauer spectroscopy , inorganic chemistry , ion , nuclear chemistry , crystallography , adsorption , geology , paleontology , organic chemistry
Core Ideas Recrystallization of Al‐goethites affected mobility of heavy metals in soils. Co‐existing Cd 2+ /Cr 3+ decreased the Fe atom exchange rates between Fe 2+ aq and Al‐goethites. Fe 2+ aq ‐induced recrystallization of Al‐goethites stabilized Cd 2+ and Cr 3+ . More Cr 3+ are stabilized due to its similar ionic radius with Fe 3+ and Al 3+ . Cd 2+ ions more active than Cr 3+ considering iron mineral activity in soils. The aqueous Fe 2+ (Fe 2+ aq )–induced recrystallization of iron minerals is an important geochemical process with critical effects on the environmental behavior of metal pollutants in soils. However, the effects of different heavy metals with distinctive physicochemical properties on the Fe 2+ aq –induced recrystallization of iron minerals and the different stabilization behaviors of these heavy metals remain unclear. This study examined the effects of Cd 2+ and Cr 3+ on the Fe 2+ aq –induced recrystallization of Al‐substituted goethites and the simultaneous stabilization of Cd 2+ /Cr 3+ ions by the recrystallized Al‐substituted goethites. Results from stable Fe isotopic tracer experiments and Mössbauer characterization show that Fe atoms were exchanged between Fe 2+ aq and structural Fe(III) in Al‐substituted goethites with coexisting Cd 2+ /Cr 3+ , although both Cd 2+ and Cr 3+ decreased the exchange rates. During the Fe atom exchange, Al‐substituted goethites were recrystallized and a portion of Cd 2+ /Cr 3+ ions were stabilized by the resulting goethite products. Compared with Cd 2+ , more Cr 3+ ions were immobilized by the recrystallized Al‐substituted goethites due to the lower hydrolysis constant of Cr 3+ than Cd 2+ , as well as the closer ionic radius of Cr 3+ with Fe 3+ and Al 3+ . Al‐goethites with higher Al contents further decreased the Fe atom exchange rates while increasing the amounts of immobilized metal ions when in the presence of Cd 2+ or Cr 3+ . The findings of the present study suggest that the physicochemical properties of metal ions play critical roles in affecting their environmental behavior and fates during Fe 2+ aq –induced recrystallization of iron minerals in soils.