absorption of carbonyl, which confi

absorption of carbonyl, which confirmed that RS hasbeen modified by BiBB (Fig. 7b). After polymergrafting, a new absorption band located at 2238 cm-1was observed in RS-g-PSAN belonging to the CNstretching of acrylonitrile (Fig. 7c) (Rahman et al.2014). Compared with RS-g-PSAN, a new absorptionband appearing at 3215 cm-1 was assigned to thestretching vibrations of the primary amine (–NH2) inRS-g-APSAN, indicating that RS-g-PSAN reactedwith TEPA successfully (Fig. 7d). The remainingadsorption peak of 2248 cm-1 belonging to th C:Nstretching of acrylonitrile was ascribed to incompletereaction of nitrile groups with TEPA, which was inaccordance with the calculated nitrile group conversion of 16.2%.Elements characteristic of RS samples were identified by XPS (Fig. 8). Peaks attributed to C, O and Nwere observed in the pristine RS. After modified byBiBB, Br 3d absorption peak appeared at 70.1 eVindicating that a-bromoisobutyryl groups were chemically bonded on RS. No characteristic bands changedbetween RS-g-PSAN and RS-g-APSAN (Fig. 8a).Figure 8b showed that the C 1s core-level spectra ofRS-g-APSAN can be curve-fitted into three components with binding energies at 284.4, 286.1, and291.6 eV corresponding to the C–C, C:N, and O–C=O, respectively. The appearance of these absorption bands implied the successful bonding of abromoisobutyryl groups and subsequent polymergrafting of RS-g-APSAN as expected. The atomic%of C, N, O and Br was calculated and shown in Fig. 8c.Compared with RS-g-PSAN, the increasing atomicratio of N (from 6.10 to 8.85%) in RS-g-APSANcontributed to the formation of amidoxime groupsafter the nitrile group of RS-g-PSAN reacted withTEPA, which is consistent with FT-IR results.Surface structures of RS samples were identified bySEM. As shown in Fig. 9a, pristine RS presentedtypically rough surface. After initiator immobilization, the chemically bonded a-bromoisobutyrylgroups made the surface of RS-Br rougher than thatof RS, which formed microfibrils by destroyinghydrogen bonding (Fig. 9b). After polymer grafting,the accumulated PSAN brushes led to the appearanceof tiny particles on the surface of RS-g-PSAN(Fig. 9c). Compared with RS-g-PSAN, further amination processes generated more wrinkles on thesurface of RS-g-APSAN, which would contribute toachieving high adsorption of heavy metal ions(Fig. 9d).Performance evaluation of oil/water separationin the first step purificationThe absorption capacity is one of the importantparameters for evaluating oil/water separation performance (Bayat et al. 2005). In a typical absorptionprocess (Ke et al. 2014), the saturated absorptioncapacities of C18-RS-g-PS towards chloroform wasinvestigated (Fig. S2). Figure 10 showed that C18-RSg-PS demonstrated different absorption capacities fordifferent oils. The absorption performance of C18-RSg-PS for toluene, ethyl acetate, n-hexadecane, dichloromethane, and chloroform were 3.33, 5.63, 4.15, 8.35,and 4.77 g/g. As discussed above, C18-RS-g-PSdemonstrated good oil absorption performance. Forcomparison, the absorption performance of C18-RSBr towards these same oils were evaluated in