[sup.1]H-NMR spectrum of DTOF copolymer and SDTOF terpolymer resins is depicted in Fig.
SEM images of DTOF, SDTOF, and DTOF-loaded [Ni.sup.2+] and SDTOF-loaded [Ni.sup.2+] resins are shown in Fig.
Figure 4 represents the effect of solution pH on the sorption capacity of sorbents (DTOF copolymer and SDTOF terpolymer resins).
The effect of agitation period on the adsorption of Ni(II) onto DTOF copolymer and SDTOF terpolymer resins is depicted in Fig.
Figure 6 shows the effect of DTOF and SDTOF resins concentration (g [L.sup.-1]) on the adsorption capacity for Ni(II).
These experiments were performed under constant variables, pH (3.0 for DTOF resin and 4.0 for SDTOF resin), agitation period (6 hr for DTOF resin and 4 hr for SDTOF resin) and adsorbent dosage of 1 g [L.sup.-1].
where [q.sub.e] is the amount of nickel adsorbed per unit weight of the DTOF and SDTOF resins (mg [g.sup.-1]), [C.sub.e] the equilibrium concentration of nickel in solution (mg [L.sup.-1]), while k and n are the constants of Freundlich equation incorporating adsorption capacity and intensity in L x [g.sup.-1], respectively.
Based on the values of coefficient of regression ([R.sup.2]), it is possible to suggest the best isotherm model to explain the adsorption of Ni(II) onto DTOF and SDTOF resins.
In order to investigate the adsorption of Ni(II) ions onto DTOF and SDTOF resins, the following kinetic models are generally used to test experimental data.
From these results, it can be concluded that the pseudosecond-order kinetic equation provided the best model for describing the adsorption of the nickel onto DTOF and SDTOF polymer resins.
From this curve, the adsorption capacities of DTOF and SDTOF resins were found to be 94.5 and 187.8 mg [g.sup.-1], which is in good agreement with the adsorption capacity calculated using batch adsorption technique.
Various chemical reagents including HC1, HN[O.sub.3], and EDTA were used for the elution of previously adsorbed Ni(Il) onto DTOF copolymer and SDTOF terpolymer resins.