The literature describes that the affinity of graphene oxides towards alkaline earth metals presents a positive correlation with their ionic radius (for example, Klímová et al. (2016) and Sófer et al. (2014). Why does that happen?

The main results of the articles cited above are summarized below:

q (mmol/g): 0,17 (Be), 0.19 (Mg), 0.19 (Ca), 0.54 (Sr), 1.52 (Ba) (Klímová et al. (2016)

wt. % in GO: 0.11 (Mg), 0.26 (Ca), 0.54 (Sr), 2.19 (Ba) (Sofer et al. (2014).

KLÍMOVÁ, K.; PUMERA, M.; LUXA, J.; JANKOVSKÝ, O.; SEDMIDUBSKÝ, D.; MATěJKOVÁ, S.; SOFER, Z. Graphene Oxide Sorption Capacity toward Elements over the Whole Periodic Table: a comparative study. The Journal of Physical Chemistry C, v. 120, n. 42, p. 24203-24212, 14 out. 2016. American Chemical Society (ACS). http://dx.doi.org/10.1021/acs.jpcc.6b08088.

SOFER, Z.; WANG, L.; KLÍMOVÁ, K.; PUMERA, M. Highly selective uptake of Ba2+ and Sr2+ ions by graphene oxide from mixtures of IIA elements. Rsc Adv., v. 4, n. 51, p. 26673-26676, 2014. Royal Society of Chemistry (RSC). http://dx.doi.org/10.1039/c4ra02640c.

Thanks in advance!

  • $\begingroup$ The articles you reference are behind paywalls and so not available to many on this site, Please summarise in more detail the content of the articles in the question. In particular please quantify "greater ability" - what precisely do you mean by that? $\endgroup$
    – Ian Bush
    Sep 25, 2022 at 19:37
  • $\begingroup$ @IanBush, thanks for the reply. I'll summarise the main results obtained by the paper with the amount of each alkaline earth metal adsorbed by GO: q (mmol/g): 0,17 (Be), 0.19 (Mg), 0.19 (Ca), 0.54 (Sr), 1.52 (Ba) (Klímová et al. (2016) / wt. % in GO: 0.11 (Mg), 0.26 (Ca), 0.54 (Sr), 2.19 (Ba) (Sofer et al. (2014). I used the term "ability" in the sense of having greater affinity, which means that GO better adsorbed species presenting greater ionic radius. $\endgroup$ Sep 25, 2022 at 19:47
  • $\begingroup$ Perhaps because coordination sites have limited mobility - bigger cation can access more of them? $\endgroup$
    – Mithoron
    Sep 25, 2022 at 20:03


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