Fresh metal precursor solution was prepared at a desired concentration across the pH
range of 1-13 using HCl or NaOH. The initial pH values were recorded and the support
material was added to 50 ml solution at a desired surface loading (anion with 500m2
/L
and cation with 1000m2
/L). Samples were then shaken for 1 hour. After 1 hour of
contact, 10ml of each sample were filtered and final pH values were measured. A plot
was then constructed with pH final vs pH initial. Both initial and filtered final samples at
each pH were analyzed by PerkinElmer Inductively Coupled Plasma-Optical Emission
Spectrometer (ICP-OES) to determine metal concentration. The surface density, or Γ, is
calculated from the equation below.