Plamen Georgiev, Marina Nicolova
University of Mining and Geology “St. Ivan Rilski”, 1700 Sofia; E-mail: ps_georgiev@mgu.bg
Corresponding author: ps_georgiev@mgu.bg
ABSTRACT. The aim of this study was to investigate the effect of calcium and ferrous iron ions on the removal of copper-to-copper oxalate from a model solution containing 0.0069 M Cu2+. Copper oxalate was synthesised under optimal experimental conditions (solution pH of approximately 2.5, temperature of 50 °C, and a stirring rate of 250 rpm). This was an effective process for removing copper from the model solution, and the resulting particles were larger than 200 µm and exhibited excellent filtration characteristics. In contrast, higher concentrations of calcium ions (0.036 M) and ferrous iron ions (0.045 M) decreased the selectivity and efficiency of copper removal, respectively.
Key words: copper, pregnant solutions, copper oxalate, selectivity
DOI: https://doi.org/10.58903/MPIG2657
References
Aref, R., Jantunen, N., & Virolainen, S. (2026). Recovery of high-purity cobalt oxalate from acidic effluents with solvent extraction technology. Chemical Engineering Science, 330, 23878. https://doi.org/10.1016/j.ces.2026.123878
Bohner, B., Schuszter, G., Berkesi, O., Horváth, D., & Tóth, Á. (2014). Self-organization of calcium oxalate by flow-driven precipitation. Chemical Communications, 50(33), 4289–4291. https://doi.org/10.1039/c4cc00205a
Botta, M. P., Attina, B., Ravera, M., & Gabano, E. (2025). Becoming aware of endangered and critical elements: spent batteries as metal mines. Journal of Chemical Education, 0102 (5), 2103-211. https://doi.org/10.1021/acs.jchemed.4c01535
Chen, X., Huang, K., & Wang, C. (2018). Facile synthesis of monodispersed copper oxalate flaky particles in the presence of EDTA. International Journal of Minerals, Metallurgy, and Materials, 25(7), 762–769. https://doi.org/10.1007/s12613-018-1624-5
Cheng, S., Vaughan, J., Wang, G., Ma, X., Lyu, X., & Peng, H. (2026). Slag to product: Unlocking titanium-bearing slag value via selective leaching of amorphous titanium phase. Minerals Engineering, 235, 109846. https://doi.org/10.1016/j.mineng.2025.109846
Cismasu, A. C., Michel, F. M., Tcaciuc, A. P., Tyliszczak, T., & Brown, J. G. E. (2011). Composition and structural aspects of naturally occurring ferrihydrite. Comptes Rendus. Géoscience, 343(2-3), 210–218. https://doi.org/10.1016/j.crte.2010.11.001
Gylliene, O., & Saulkaskas, M. (1995). Metal recovery from spent electroless plating solutions by oxalate precipitation. Plating & Surface Finishing, 61-63.
Gyliene, O., Saulkaskas, M., & Juskenas, R. (1997). The use of organic acids as precipitants for metal recovery from galvanic solutions. Journal of Chemical Technology & Biotechnology 70(1), 111-115. https://doi.org/10.1002/(SICI)1097-4660(199709)70:1<111::AID-JCTB691>3.0.CO;2-9
Joseph, E., Cario, S., Simon, A., Wörle, M., Mazzeo, R., Junier, P., & Job, D. (2012). Protection of metal artefacts with the formation of metal–oxalates complexes by Beauveria bassiana. Frontiers in Microbiology, 2. https://doi.org/10.3389/fmicb.2011.00270
Krajanova, V., & Lalinska-Volekova, B. (2025). Hydrometallurgical leaching experiments on selected minerals and materials by oxalic acid. Proceedings of 25 SGEM International Multidisciplinary Scientific GeoConference 2025, 29 June – 06 July 2025 – Albena, Bulgaria, pp. 319-324. https://doi.org/10.5593/sgem2025/1.1/s03.39
Korneev, A. V., Izatulina, A. R., Kuz’mina, M. A., & Frank-Kamenetskaya, O. V. (2022). Solid Solutions of Lindbergite–Glushinskite Series: Synthesis, Ionic Substitutions, Phase Transformation and Crystal Morphology. International Journal of Molecular Sciences, 23(23), 14734. https://doi.org/10.3390/ijms232314734
Lee, K. R., Kim, J., & Jang, J. G. (2017). Recovery of zinc in spent pickling solution with oxalic acid. Korean Chemical Engineering Research 55(6), 785-790. DOI:10.9713/kcer.2017.55.6.785
Lee, S. I., Kim, H. R., Park, J. K., J.K., Oh, W., Kim, J., Kim, C., Lee, J., Kim, K.-C., & Lee, B.-C. (2022). Precipitation of ferrous oxalate from ferrous ammonium sulphate in oxalic acid solution. Processes, 10(11), 2420. https://doi.org/10.3390/pr10112420
Li, X., Ma, B., Wang, C., & Chen, Y. (2024). Sustainable recovery and recycling of scrap copper and alloy resources: a review. Sustainable Materials & Technologies, 41, e01026. doi.org:1016/j.susmat.2024/e01026
Martins, L. S., Rovani, S., Botelho, A. B. J., & Espinosa, D. C. R. (2023). Sustainable approach for critical metals recovery through hydrometallurgical processing of spent batteries using organic acids. Industrial & Engineering Chemistry Research, 62(44), 18672-18682. https://doi.org/10.1021/acs.iecr.3c03048
Mustafa, L., Usman, M., Ali, S., Ali, A., & Naveed, A. (2025). Recycling technologies for extracting gallium from light-emitting diodes. Photonics, 12 (8), 808. https://doi.org/10.3390/photonics12080808
Palmieri, F., Estoppey, A., House, G. L., Lohberger, A., Bindschedler, S., Chain, P.S.G., & Junier, P. (2019). Oxalic acid, a molecule, at the crossroads of bacterial-fungal interactions. Advanced Applied Microbiology, 106, 49-77. DOI: 10.1016/bs.aambs.2018.10.001
Roy, J. J., Srinivasan, M., & Cao, B. (2021). Bioleaching as an eco-friendly approach for metal recovery from spent NMC-based lithium-ion batteries at a high pulp density. ACS Sustainable Chemistry & Engineering, 9(8), 3060-3069. https://doi.org/10.1021/acssuschemeng.0c06573
Rumble, J. (2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–188. ISBN 978-1138561632
Shlesinger, M.E., Sole, K.C., Davenport, W.G., & Alvear Flores, G.R.F. (2021). Extractive metallurgy of copper. (6th ed.). Elsevier. ISBN-13: 978-0128219034
Tita, A.M., Mends, E.A., Kar, U., Hussaini, S., & Chu, P. (2025). Leaching of Li-bearing sedimentary claystones using organic acids. Green and Smart Mining Engineering, 2(2), 156-167. https://doi.org/10.1016/j.gsme.2025.06.002
Verma, A., Kore, R., Corbin, D.R., & Shiflett, M.B. (2019). Metal recovery using oxalate chemistry: a technical review. Industrial & Engineering Chemistry Research, 58(34), 15381-15393 https://pubs.acs.org/doi/10.1021/acs.iecr.9b02598#
Wen, Y., Tribby, E.L., & Tang, Y. (2025). Intensified and selective recovery of critical metals from aqueous extracts: Fundamentals and system design. Chemical Engineering Journal, 512, 162661. https://doi.org/10.1016/j.cej.2025.162661
Werner, H., Bapat, S., Schobesberger, M., Segets, D., & Schwaminger, S. P. (2021). Calcium oxalate crystallisation: Influence of pH, energy input, and supersaturation ratio on the synthesis of artificial kidney stones. ACS Omega, 6(39), 26566–26574. https://doi.org/10.1021/acsomega.1c03938
Yang, Y., Song, W., Ferrier, J., Liu, F., Csetenyl, L., & Gadd, G.M. (2020). Biorecovery of cobalt and nickel using biomass-free supernatants from Aspergillus niger. Applied Microbiology & Biotechnology, 104, 417-425. DOI: 10.1007/s00253-019-10241-2
Ye, C., Wang, Z., & Shen, Y. (2022). Preparation of iron-copper oxalates and oxides for the oxygen evolution reaction. Journal of the Electrochemical Society, 169, 064503. DOI: 10.1149/1945-7111/ac7259
Zeng, L., Deng, S., Yang, X., & Zhang, W. (2026). Valorisation of pyrite in coal refuse into battery-grade ferrous oxalate: A sustainable pathway. Chemical Engineering Journal, 534, 174699. https://doi.org/10.1016/j.cej.2026.174699