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- Conflict of Interest
- In relation to this article, we declare that there is no conflict of interest.
- Publication history
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Received October 18, 2025
Accepted May 4, 2026
Available online August 25, 2026
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This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits
unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Effi cient Extraction of Dichromate Anions Using TOPO in Multi-Dropped Liquid Membrane
https://doi.org/10.1007/s11814-026-00741-z
Abstract
This study presents the sequential extraction of dichromate (Cr2O7
2−) anions using a continuous multi-dropped liquid
membrane (MDLM) system. Trioctylphosphine oxide (TOPO) dissolved in kerosene was employed as the mobile carrier
in the organic phase. To determine the optimal operational conditions, both chemical variables (e.g., donor phase acid type,
acceptor phase composition, and carrier concentration) and physical parameters (e.g., temperature, phase volume ratios,
flow rate, and reactor frit porosity) were systematically investigated. Unlike earlier studies, this work uniquely emphasizes
the critical influence of the reactor’s hydrodynamic and physical design on overall mass transfer efficiency. Kinetic
evaluations confirmed that the dichromate transport strictly adheres to consecutive first-order irreversible reaction kinetics,
enabling the precise calculation of fundamental kinetic parameters (k1, k2, tmax, Rmax
m , Jmaxd , Jmaxa ). Furthermore, the activation energy of the process was determined to be 14.60 kJ·mol−1
(3.49 kcal·mol−1), demonstrating that the extraction is fundamentally a diffusion-controlled mechanism. Under the optimized physicochemical conditions, the MDLM system achieved a maximum overall dichromate extraction efficiency of 96.31%.

