2.3. Characterization of adsorbent
The particle size distribution was determined by weighing the
oil palm shell according to its particle size categories. The fraction
of oil palm shell (wt.%) for each particle size category was computed
respectively.
In order to determine the pH of the adsorbent-containing water,
1.0 g of adsorbent was agitated in 20 mL of distilled water at
100 rpm for 12 h. The pH was then measured. This is similar to
the method used by Tang (2001).
The oil palm shell point of zero charge, pHpzc, was determined
using equilibrium technique (Ponnusami et al., 2008; Chen et al.,
2010). A series of NaCl solutions of 0.1 M concentration with initial
pH (pHi) ranging from 1 to 10 was prepared by adding HCl or
NaOH. A volume of 50 mL of the pH adjusted NaCl solution was
agitated with 1.0 g of adsorbent at 150 rpm for 24 h. The final pH
(pHf) was measured utilizing Mettler Toledo FG2 pH meter fitted
with LE407 gelled electrolyte electrode. A graph of pHi–pHf versus
pHi was plotted. The point at which pHi–pHf equals to zero is the value of pHpzc