BSA adsorbs with the highest affinity onto bare silica, possibly driven by several hydrogen bonds between silanoils on particles and carbonyls on the protein, but maximal adsorption is at lowest indicating the largest area per BSA molecule occupied at maximal adsorption among those in all media and adsorbates tested (Table 2).
In the present study, maximal BSA adsorption was indeed observed when the adsorption was carried out at pH near pH(I) of the protein (i.e., at pH 5.5).
For particles made of PEG-PLA45K with different PEG Mw, a maximal reduction in protein adsorption was found for a PEG Mw of 5000 g/mole.
It can be seen that at pH 6.5, the composite containing pectin FB300 shows good Sr2+ adsorption, while at pH 8, the maximal adsorption values are inherent for nHAp/pectin FB300, nHAp/pectin APA103, and nHAp/SA.
Adsorption is found to be pH dependent with maximal adsorption at pH 8.3 decreasing with increasing and decreasing pH.
Chemical adsorption occurs usually at higher temperatures than those at which physical adsorption occurs; furthermore, chemical adsorption is ordinarily a slower process than physical adsorption and, like most chemical reactions, frequently involves an energy of activation.
Adsorption is not an absolute process.
Xm (mg g−1) is the maximal adsorption capacity, and b (L mg−1) is the empirical constant which gives the affinity of binding sites.
In the adsorption tests, the adsorption capacity was derived from the Langmuir isotherm model, and the maximal adsorption capacity of as-prepared adsorbents was 119.0 mg g−1 for Cu II) and 160.0 mg g−1 for Cd II).
The maximal adsorption capacity of SH-ePMO is lower than the capacities of mesoporous organosilicas reported in literature [12, 13].
