Figure 3: Comparative extraction capacities of the normal and TF
oils
Now, considering the cation removal efficiency of both the normal and TF
oils, Figure 3 gives the comparative extraction capacities of the normal
and TF oils. All normal oils were inefficient. TF-SBO was outstanding at
all concentration, attaining 100 % Ag+ removal
efficiency at a loading of 5 g per 20 mL of contaminated water. It
reduced the Ag+concentration to a value less than 0.5 ppm (the detection limit of the
analytical device). This extraction performance was maintained as the
oil loading was increased up to 10 g. TF-PO followed after with a
somewhat linear trend up to 8 g oil loading, but its extraction capacity
did not exceed 70 %. TF-PKO had the least sorption capacity of all the
TF-VOs. Considering the nature of the vegetable oils, SBO had the
highest concentration of double bonds (unsaturation) which is necessary
for thiol-ene addition reaction. Hence, TF-SBO had the highest active
sorption (TF) site concentration for heavy metal removal. The normal
oils lacked such site and TF-PO had much of it than TF-PKO. With
reference to Figure 2, the poor concentration of sorption sites in
TF-PKO, or better said, the presence of only few sites in TF-PKO could
have caused it to attain equilibrium earlier than TF-PO and TF-SBO,
since less Ag ions need to be captured to saturated the functionalized
sites. Economically speaking, the use of TF-SBO would save more oil due
to its relatively high sorption capacity – little amount was needed to
achieve the highest cation removal efficiency. Use of raw oils in this
regard only served the purpose of control experiment.