The maximum adsorption capacity is called qmax. It can be
obtained from the Langmuir isotherm and it gives us an idea of
how efficient is certain material if compared with other ones.
If we take into account previous adsorption data, the values in Table 2 are significantly higher than what obtained with
other adsorbent materials. Methylene blue has been tested with
very different materials, such as those activated carbon from
coconut shell (qmax of 0.86 mmol g−1), rice husk (1.07 mmol g−1)
or bamboo (0.44 mmol g−1) [52] while tannin rigid resin reached
1.35 mmol g−1. Regarding CTAB, qmax was 2.12 mmol g−1, radically
higher than what obtained with carbon black (1.8 mmol g−1 [53])
or expanded perlite (1.05 mmol g−1 [54]). Finally, Zn2+ was also
removed from aqueous solution by means of adsorbents such as
new nanocomposites (0.38 mmol g−1 [55]) or a large variety of carbons
(up to 0.30 mmol g−1 [56]). Instead, this work reports a qmax
level of almost 1 mmol g−1.