with different ions and the fact that electrical charge of
biomass surface, governs sorbates adsorption.
For example,
the isoelectric point (pI) of microalgae Chlorella is about
3, while Spirulina pI = 2.8–3.5 [19].
In lower pH, positively
charged groups (e.g., amine group) attract anions and repulse
cations, while in higher pH negatively charged groups (e.g.,
carboxyl) act conversely.
Typical changes of ionization state
of functional groups on the surface of microalgae cell wall
depending on pH are shown in Figure 1, along with the listing
of functional groups (under the red arrow) and their forms
in pH = 5, for which the highest model parameters from
quantitative and kinetic examination have been obtained
[20].
In present work, dried biomass of commercially available
Spirulina sp.
(lyophilisate) and cultivated under laboratory
conditions Spirulina maxima were investigated for
supplementation with microelement ions: Cu(II), Co(II),
Mn(II), and Zn(II), which are important in livestock feeding.
Biosorption experiments were performed in both singleand
multicomponent systems, under previously evaluated
conditions. Four analytical methods were used to assess the
composition of natural and loaded biomass surface, as well
as to verify the biosorption mechanism, in exchange, posited
on the basis of earlier studies.
The major binding sites were
identified along with their concentrations, and thus total
capacity of both examined biosorbents might be estimated.
Based on changes observed in elemental composition of the
Spirulina surface after biosorption experiments, the affinity
sequence of microelement cations was determined for
single- andmultimetal systems separately.
Theapplicability of
microalgal biomaterials to feed supplementationwas assessed
due to resultant of all conducted tests.