Figure 1: Structural representation of the sulphur-modification
reaction for TF-VO formation.
AgNO3, a product of Sigma Aldrich, was used to introduce
Ag contaminant in water. A stock 600 ppm aqueous solution of
AgNO3 was prepared using deionized water. Cation
extraction experiments were carried out using 20 mL of the contaminated
water for each run. First, the equilibrium liquid-liquid contact time
was determined by adding roughly 3.5 g of each of the TF oils to 20 mL
of contaminated water in masked conical flask mounted on a stirrer, all
within an enclosed dark chamber, due to the light sensitivity of silver
salts. In each case, the resulting two-phase mixture was stirred at 200
rpm for up to 10 hours. In the interim of stirring, samples were taken
after: 0.5, 1, 2, 4, 6, 8 and 10 hours, and separated. Treated water
samples were collected from the clear aqueous layer recovered after
centrifugation of the stirred oil-water mixture and Inductively Coupled
Plasma Mass Spectrometer (ICPMS-2030 Shimadzu) was used to analyze the
water samples, at 328 nm [5], while a commercial standard Ag
solution (QMX Laboratories Ltd, UK) was used for calibration.
In order to determine the respective sorption capacities, various
amounts of the vegetable oils in the range of 0.1 to 10 g, were
respectively added to 20 mL of contaminated water and brought to
equilibrium (stirred for the determined equilibrium contact
time/period). Separation and analysis of treated water were performed as
earlier stated. In this case however, normal oils were also considered.