Iron precipitates as magnetite and siderite and sorbs via cation exchange and surface complexation on weak sites.
The acidic strength of the solids can be classified according to the following range: Ei> 100 mV (very strong sites), 0 < Ei< 100 mV (strong sites), −100 < Ei< 0 mV (weak sites), and Ei< −100 mV (very weak sites).
"Weak sites" existed in the SiC free coatings, which significantly lowered the wear performance of the coatings.
In contrast, "weak sites" are not found in the coatings with the incorporation of SiC nanoparticles, resulting in an excellent wear performance of the coatings.
The high erosion resistance was attributable to a desirable microstructure, which exhibited a favorable combination of hardness and toughness, and contained fewer weak sites for erosion attack.
Interactions between aqueous species and the solid are described by a two-layer surface complexation model [27] with two types of adsorption site being considered, ≡(s FeOH and ≡(w FeOH for strong and weak sites, respectively.
While fluoroform is good for stronger sites, weak sites can be tested by pyrrole, acetylene or its derivatives that are more sensitive, but dissociate on the most basic oxygen centers.
Here we used a value of 0.4 mol/mol Fe for weak sites concentration in the modeling of our high As/Fe molar ratio experiments and 0.2 mol/mol Fe in the modeling of Bengali sediments experiments with a lower As/Fe molar ratio.
Due to environmental control in museums (UV filtering, RH and temperature) one would expect typical degradation pathways to be those involving oxygen (thermo/photo-oxidative reactions), however due to weak sites or impurities such as metal ions present in a polymer, thermolytic initiation of degradation of some polymers (PMMA, PVC) can occur.
For example, several NK2 group sites are predicted by Stubb and few weak sites are predicted by PhyloGibbs between −9.8 to −3.8 kb region.
Consequently, although including conservation information can help in detecting weak binding sites, conservation information does apparently not give an increased sensitivity at recognizing weak sites, but an increased specificity at recognizing strong sites.
