Thioether-Functionalized Vegetable Oils: Metal-Absorbing Biobased Ligands

Abstract

Vegetable oils containing thioether groups have been synthesized and used to effectively remove heavy metal ions from aqueous solution. The use of thioether-functionalized corn oil (TF-corn oil) and thioether-functionalized canola oil (TF-canola oil) were both effective in the extraction of Ag+ from a 600 ppm aqueous silver nitrate solution. The TF-corn oil reduced the observed silver in solution to a level below the detection limit, whereas the TF-canola oil was only able to remove slightly over 50% of the concentration. A study of the absorption rate is also reported, where both the TF-corn oil and the TF-canola oil removed the Ag+ rapidly, at nearly the same rate. Preliminary results suggest that the efficacy and capacity of silver removal relates directly to the fatty acid composition of the oil precursor.

Thioether‐Functionalized Corn Oil Biosorbents for the Removal of Mercury and Silver Ions from Aqueous Solutions

“…Equilibrium data for the separation of Ag + ions from an aqueous solution by adding thioether‐functionalized vegetable oils were reported earlier (Murray et al, ). These results were obtained by mixing oil and aqueous phases continuously by a magnetic stir bar for 11 days.…”

“…The second 4.00 mL solution was mixed with 0.2013 g TFCO to run the separation experiment. Experience from the earlier study (Murray et al, ) showed that agitation of the oil‐aqueous mixture sometimes caused the formation of an emulsion that made the ongoing analysis of the M n + concentration in the aqueous phase problematic. Therefore, the mixed contents in the present experiments were agitated for 60 s at 3200 rpm using a Vortex Genie 2 mixer from Fisher Scientific (Waltham, MA, USA).…”

“…Therefore, the kinetics of Ag + adsorption from aqueous solution by TFCO were modeled by applying the rate equation: where q [ t ] refers to the Ag + concentration adsorbed at time ( t ) and k 2 (kg [mg min] −1 ) is the rate constant. The constant q e was inferred from the equilibrium data reported in the previous study (Murray et al, ). Plotting 1/ q [ t ] vs. 1/ t yields a straight line where k 2 is inferred from the slope () and the intercept (1/ q e ) obtained from linear‐regression analysis.…”

“…Earlier studies (Murray, Bantchev, Doll, Dunn, & Ascherl, , ; Murray, Bantchev, Dunn, Ascherl, & Doll, ) are thought to be the first reports demonstrating the efficient removal of Ag + ions from aqueous solution after contact with thioether‐functionalized corn oil (TFCO). The one‐step addition of butanethiol to the fatty‐acid double bonds in corn oil is shown in Scheme .…”

“…The product ( II ) features one or two thioether pendant groups attached at locations formerly hosting the double bonds. Similar functionalization of canola oil, which is mainly composed of TAG‐bound oleic acid groups, was less effective than the TFCO in removing Ag + from an aqueous solution (Murray et al, , ).…”