Struvite and ethylenediaminedisuccinic acid (EDDS) enhance electrokinetic-biological permeable reactive barrier removal of copper and lead from contaminated loess

Lin Wang; Wen-Chieh Cheng; Zhong-Fei Xue; Md Mizanur Rahman; Yi-Xin Xie

doi:10.1016/j.jenvman.2024.121100

Struvite and ethylenediaminedisuccinic acid (EDDS) enhance electrokinetic-biological permeable reactive barrier removal of copper and lead from contaminated loess

J Environ Manage. 2024 May 13:360:121100. doi: 10.1016/j.jenvman.2024.121100. Online ahead of print.

Authors

Lin Wang¹, Wen-Chieh Cheng², Zhong-Fei Xue³, Md Mizanur Rahman⁴, Yi-Xin Xie⁵

Affiliations

¹ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: wanglin@xauat.edu.cn.
² School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: w-c.cheng@xauat.edu.cn.
³ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: xuezhongfei@xauat.edu.cn.
⁴ Professor in Geotechnical Engineering, UniSA, STEM, ScaRCE, University of South Australia, SA 5000, Australia. Electronic address: mizanur.rahman@unisa.edu.au.
⁵ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: xieyixin@xauat.edu.cn.

PMID: 38744205
DOI: 10.1016/j.jenvman.2024.121100

Abstract

Removal of heavy metals using the electrokinetic (EK) remediation technology is restricted by soils containing a fraction of clay particles above 12%. Furthermore, it is also affected by hydroxide precipitation (focusing phenomenon) close to the cathode. A modified EK reactor containing a permeable reactive barrier (PRB) was proposed herein where the enzyme-induced carbonate precipitation (EICP) treatment was incorporated into the PRB. Despite that, NH₄⁺-N pollution induced by the urea hydrolysis resulting from the EICP treatment causes serious threats to surrounding environments and human health. There were four types of tests applied to the present work, including CP, TS1, TS2, and TS3 tests. CP test neglected the bio-PRB, while TS1 test considered the bio-PRB. TS2 test based on TS1 test tackled NH₄⁺-N pollution using the struvite precipitation technology. TS3 test based on TS2 test applied EDDS to enhance the removal of Cu and Pb. In CP test, the removal efficiency applied to Cu and Pb removals was as low as approximately 10%, presumably due to the focusing phenomenon. The removal efficiency was elevated to approximately 24% when the bio-PRB and the electrolyte reservoir were involved in TS1 test. TS2 test indicated that the rate of struvite precipitation was 40 times faster than the ureolysis rate, meaning that the struvite precipitate had sequestered NH₄⁺ before it started threatening surrounding environments. The chelation between Cu²⁺ and EDDS took place when EDDS played a part in TS3 test. It made Cu²⁺ negatively surface charged by transforming Cu²⁺ into EDDSCu^2-. The chelation caused those left in S4 and S4 to migrate toward the bio-PRB, whereas it also caused those left in S1 and S2 to migrate toward the anode. Due to this reason, the fraction of Cu²⁺ removed by the bio-PRB and the electrolyte reservoir is raised to 32% and 26% respectively, and the fraction of remaining Cu was reduced to 41%. Also, the removal efficiency applied to Pb removal was raised to 50%. Results demonstrate the potential of struvite and EDDS-assisted EK-PRB technology as a cleanup method for Cu- and Pb-contaminated loess.

Keywords: Biological permeable reactive barrier; Electrokinetic remediation; Environmental-friendly surfactant; Enzyme-induced carbonate precipitation; NH(4)(+)-N pollution.