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Unraveling Eu(III) immobilization and cotransport risk with Bacillus subtilis from colloid aggregation, biosorption, and biomineralization.

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Title: Unraveling Eu(III) immobilization and cotransport risk with Bacillus subtilis from colloid aggregation, biosorption, and biomineralization.
Authors: Xu, Zhen1,2,3 (AUTHOR) xuz@lzu.edu.cn, Tang, Qingfeng2,3 (AUTHOR), Wang, Yanhui2,3 (AUTHOR), Chen, Yuan4 (AUTHOR), Niu, Zhiwei2,3 (AUTHOR), Pan, Duoqiang1,2,3 (AUTHOR), Wu, Wangsuo1,2,3 (AUTHOR)
Source: Chemical Engineering Journal. Dec2025, Vol. 525, pN.PAG-N.PAG. 1p.
Subjects: Bacillus subtilis, Biomineralization, Active biological transport, Colloids, Environmental remediation, pH effect, Biosorption
Abstract: The environmental fate of europium(III) [Eu(III)] is governed by competing microbial processes—immobilization through biosorption and biomineralization versus mobilization via biocolloid-facilitated transport. This study systematically investigates the role of Bacillus subtilis in mediating Eu(III) immobilization and transport risk under varying physicochemical conditions. Results showed that biocolloid aggregation was enhanced by elevated bacterial concentrations (>60 mg·L−1) and the presence of multivalent cations (Ca2+, Eu3+) through charge neutralization and ion bridging. Microbial phosphatase activity induced pH-dependent biomineralization, yielding soluble Ca P complexes under acidic conditions (pH 6.5) and crystalline hydroxyapatite under alkaline conditions (pH 9.0). Extended mineralization (120 h) promoted the crystallization of adsorbed Eu(III) into EuPO 4 , which reduced colloidal stability and increased Eu(III) retention in porous media. Column transport experiments revealed time- and concentration-dependent cotransport behavior: short-term mineralization (24 h) enhanced Eu(III) mobility, whereas prolonged reaction times or higher Eu(III) concentrations facilitated aggregation and retention. In CaCl 2 systems, acidic conditions promoted the immobilization of EuPO 4 –Ca–P aggregates, while alkaline conditions increased mobility by weakening aggregation and enhancing electrostatic repulsion. These findings indicate that Bacillus subtilis plays a dual role: initially mobilizing Eu(III) through adsorption, but ultimately immobilizing it via biomineralization, albeit with persistent migration risks. This study provides critical insights into microbial influences on radionuclide transport, informing strategies for environmental remediation and nuclear safety management. [Display omitted] • Colloids critically modulate Eu(III) immobilization pathway by B. subtilis. • B. subtilis mineralizes Eu(III) via phosphatase-generated phosphate. • pH controls biogenic calcium phosphate phase composition. • Prolonged mineralization (120 h) converts adsorbed Eu(III) into crystalline EuPO 4. • Caution needed in Eu(III) mineralization with environmental colloids. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The environmental fate of europium(III) [Eu(III)] is governed by competing microbial processes—immobilization through biosorption and biomineralization versus mobilization via biocolloid-facilitated transport. This study systematically investigates the role of Bacillus subtilis in mediating Eu(III) immobilization and transport risk under varying physicochemical conditions. Results showed that biocolloid aggregation was enhanced by elevated bacterial concentrations (>60 mg·L−1) and the presence of multivalent cations (Ca2+, Eu3+) through charge neutralization and ion bridging. Microbial phosphatase activity induced pH-dependent biomineralization, yielding soluble Ca P complexes under acidic conditions (pH 6.5) and crystalline hydroxyapatite under alkaline conditions (pH 9.0). Extended mineralization (120 h) promoted the crystallization of adsorbed Eu(III) into EuPO 4 , which reduced colloidal stability and increased Eu(III) retention in porous media. Column transport experiments revealed time- and concentration-dependent cotransport behavior: short-term mineralization (24 h) enhanced Eu(III) mobility, whereas prolonged reaction times or higher Eu(III) concentrations facilitated aggregation and retention. In CaCl 2 systems, acidic conditions promoted the immobilization of EuPO 4 –Ca–P aggregates, while alkaline conditions increased mobility by weakening aggregation and enhancing electrostatic repulsion. These findings indicate that Bacillus subtilis plays a dual role: initially mobilizing Eu(III) through adsorption, but ultimately immobilizing it via biomineralization, albeit with persistent migration risks. This study provides critical insights into microbial influences on radionuclide transport, informing strategies for environmental remediation and nuclear safety management. [Display omitted] • Colloids critically modulate Eu(III) immobilization pathway by B. subtilis. • B. subtilis mineralizes Eu(III) via phosphatase-generated phosphate. • pH controls biogenic calcium phosphate phase composition. • Prolonged mineralization (120 h) converts adsorbed Eu(III) into crystalline EuPO 4. • Caution needed in Eu(III) mineralization with environmental colloids. [ABSTRACT FROM AUTHOR]
ISSN:13858947
DOI:10.1016/j.cej.2025.170220