Model-Independent Description of Multicomponent Adsorption from Affinity Spectrum Statistics

Poster · ECIS 2026 — 40th Conference of the European Colloid & Interface Society

Poster presented at ECIS 2026 (Granada): a model-independent description of multicomponent adsorption to natural organic matter from the statistics (mean and covariance) of the binding affinity spectrum.

Conference · ECIS 2026 — 40th Conference of the European Colloid & Interface Society Location · Granada, Spain Dates · 6–11 September 2026 Contribution · Poster · Topic 7 – P08

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Official one-page abstract in the ECIS 2026 programme (local copy).

Summary

Multi-cation adsorption to natural organic matter can be described by an affinity spectrum — a density of binding free energies over all sites — that shows both intrinsic and electrostatically induced heterogeneity. Using multicomponent Gaussian and Frumkin spectra, together with semi-grand canonical Monte Carlo simulations of randomly distributed carboxylic and phenolic sites, the poster shows that:

• The lowest cumulants of the affinity spectrum (its mean and covariance matrix) capture most of the information contained in the binding isotherms, suggesting a model-independent way to standardize experimental binding data.
• The Frumkin isotherm reproduces the multicomponent Monte Carlo simulations for both intrinsic and electrostatic heterogeneity. Its underlying affinity spectrum has a well-defined mean and covariance and, unlike the Gaussian model, does not require the numerical evaluation of multiple integrals.

Authors

Carlos Rey-Castro^1,*, Pablo M. Blanco¹, Calin David¹, Jaume Puy¹, Pablo Lodeiro¹, Francesc Mas², Josep L. Garcés¹

¹ Department of Chemistry, Physics and Environmental and Soil Sciences & AGROTECNIO, Universitat de Lleida, Spain ² Department of Materials Science and Physical Chemistry & IQTC, Universitat de Barcelona, Spain

^* Corresponding author: carlos.rey@udl.cat

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Related work

• Gledhill, M., Gosnell, K., Humphreys, M. P., Delaigue, L., Helle, N., Zhu, K., Lodeiro, P., Rey-Castro, C., & Achterberg, E. P. (2026). Chemical controls on iron distributions across the subsurface South Pacific Ocean. Nature Communications, 17, 3533. https://doi.org/10.1038/s41467-026-72070-y
• Lodeiro, P., Rey-Castro, C., David, C., Humphreys, M. P., & Gledhill, M. (2023). Proton binding characteristics of dissolved organic matter extracted from the North Atlantic. Environmental Science & Technology, 57(50), 21136–21144. https://doi.org/10.1021/acs.est.3c01810
• Garcés, J. L., Mas, F., & Puy, J. (2006). Conditional equilibrium constants in multicomponent heterogeneous adsorption: The conditional affinity spectrum. The Journal of Chemical Physics, 124(4), 044710. https://doi.org/10.1063/1.2162876
• Garcés, J. L., Mas, F., & Puy, J. (2004). Affinity distribution functions in multicomponent heterogeneous adsorption. Analytical inversion of isotherms to obtain affinity spectra. The Journal of Chemical Physics, 120(19), 9266–9276. https://doi.org/10.1063/1.1710857
• Garcés, J. L., Mas, F., Cecília, J., Companys, E., Galceran, J., Salvador, J., & Puy, J. (2002). Complexation isotherms in metal speciation studies at trace concentration levels. Voltammetric techniques in environmental samples. Physical Chemistry Chemical Physics, 4(15), 3764–3773. https://doi.org/10.1039/b201345m

How to cite

Rey-Castro, C., Blanco, P. M., David, C., Puy, J., Lodeiro, P., Mas, F., & Garcés, J. L. (2026). Model-independent description of multicomponent adsorption from affinity spectrum statistics [Poster]. ECIS 2026 — 40th Conference of the European Colloid & Interface Society, Granada, Spain, 6–11 September 2026.

Funding

Funded by MCIN-MICIU/AEI/10.13039/501100011033/FEDER, EU, through grants PID2022-140312NB-C21 and PID2024-156219NB-C21.

License

© 2026 Carlos Rey-Castro. Shared under CC BY-NC-ND 4.0, the same licence as the rest of this website.