Table 1 shows that the adhesion of the three bacteria to SS316 is most
excellent at pH 3, decreases when pH increases to 5 and 7 and is least
at pH 7. The increase in adhesion at pH 9 is probably due to the
ionization of the functional groups (carboxyl and amino groups) on the
surface of the bacteria as pH changes.
As the pH rises from 3 to 7, the ionization of the carboxyl groups
becomes weaker and more robust. The electrostatic gravitational force
between the bacteria and the metal surface gradually increases. Still,
at pH 3, the zeta potential of the bacteria approaches 0. The thin
double electric layer (EDL) at the solid-liquid interface plays a
decisive role. Hence, the bacteria reach the SS316 surface with the
lowest adhesion barrier and thus the highest adhesion force. As the pH
rises to 9, the concentration of negatively charged
COO- in the liquid environment is more elevated and .
It combinestrostatically with the presence of Fe2+ on
the SS316 surface to produce more excellent adhesion.