2.3. Heavy metal adsorption experiments
The adsorption of Pb(II) by functionalized and non-functionalized
SBA-15 was studied by a batch operation, including effects
of contact time, the solution pH, and initial metal ion concentration.
Deionized water was used in all experiments. Stock solutions
of lead were prepared from Pb(NO3)2. Batch sorption experiments
were performed at 30 C under natural pH conditions in a shaker
incubator at 150 rpm for 1 h, using 50 mL capped plastic centrifuge
tubes containing 20 mL of 200 mg/L Pb(II) solutions and 0.1 g of the
adsorbents. pH of the solution was adjusted by using 0.1 mol/L HCl
or NaOH and without adding any buffer to control the pH constantly.
After a time period of agitation, the suspensions were centrifuged at 2500 rpm for 5 min and then filtered to collect the
final solutions. Metal concentration, both in the initial and final
solutions, was determined by inductively coupled plasma atomic
emission spectroscopy (ICP-AES). The effects of those parameters
to the adsorption capacity of both functionalized and non-functionalized
SBA-15 in the experiments were investigated. Measurements
were performed in a Perkin Elmer Optima 3300 DV
spectrometer after calibration with stock solutions. The emission
lines used were according to the standard EPA method for analysis
of this metal [40]. Adsorbed heavy metal amount was determined
by difference between initial and final metal concentrations in the
solution.