Exploring Hg2+ Adsorption: Batch Experiments with Resins

2.6. Batch adsorption experiments

2.6.1. Adsorption experiments

The adsorption studies were performed in batch experiments by agitating definite amounts of the studied resin with Hg2+ aqueous solution with predetermined concentrations at varying pH values, temperatures and for deferent time intervals. For pH studies; 0.05g of the studied resin was equilibrated with 50mL 100mg/L Hg2+ solution for 3h at 300C. HCl/KCl was utilized to adjust the pH range 1-3, CH3COOH/CH3COONa was used for pH 4 and 5. For temperature effect studies, 0.05g of the resin were equilibrated with 50mL Hg2+ aqueous solution with initial concentration 50mg/L and pH 5 for 3h at 150rpm in temperature range 20-40. The kinetic studies were carried out by shacking 0.5g of the

Selectivity coefficient (βHg2+/Mn+) was computed using Eq. (3) in order to evaluate the selectivities of both ion-imprinted Hg-PMTF and non-imprinted NI-PMTF for Hg2+ ions compared to other interferring metal ions [26]. βHg2+/Mn+ = D Hg2+/DMn+ (3) where D Hg2+ and DMn+‏ are the distribution coefficient of the Hg2+ ions and the other interfering metal ions, respectively, which can be calculated according to Eq. (4).

D = [(Ci-Ce)/Ce]V/W (4)

The potential of the ion-imprinting process in improvement of Hg2+ selectivity can be evaluated using relative selectivity coefficient βr (Eq. (5)) [27, 28]. βr = βimprint / βnon-imprint (5) where βimprint and βnon-imprint are the selectivity coefficients related to both Hg-PMTF and NI-PMTF resins, respectively.

2.8. Desorption and

The main diagnostic peaks that are related to the ligand active groups and which are expected to display marked shifts or changes after coordination with Hg(II) are summarized in Table 2. As previously reported [29, 30], thiosemicarbazide and thiourea derivatives, which contain thioamide (-NH-C=S) moiety are known to display thione–thiol tautomerism in solution. The presence of v/δ(C=S) characteristic peaks at approximately 1300, 870 cm-1, absence of v/δ(C-S) peaks at about 1150, 650 cm-1 in addition to the absence of the diagnostic (S-H) peak at 2350 cm-1 and presence of only one peak at 1660 cm-1 correspond to the triazine C=N bond, revealed that thione form is the dominant one in solid state. After coordination with Hg2+, the spectrum of the complex showed an appearance of two peaks at 1150 and 650 cm-1, which are related to both stretching and bending vibrations of C-S bond, in addition a new peak at about 1665 cm-1correspond to C=N was also observed. These observations indicated that thion- thiol transformation had been performed during coordination with Hg2+. Also, the absence of S-H characteristic peak at about 2350 cm-1, gives and evidence for the deprotonation of the thiol (S-H). Moreover, the obvious shift of the triazine C=N peak at 1630 cm-1, confirms involvement of triazine