As indicated, HA was removed based on
the amount of CaCO3. The removal of HA reached the highest level
of 56% with 2.0 g of CaCO3 after which it remained as constant. The
removal amount was found to be 1.4 mg of HA per gram of CaCO3.
The amount of adsorption could be strongly influenced by the pH
of solution and the electrostatic interactions play a role in
controlling the amount of HA adsorption [39]. At neutral pH,
the CaCO3 particles are neutral or slightly positively charged. Thus,
a high adsorption affinity of the negatively charged HA was
observed.