Thermal gravimetric analysis (TGA)Thermal gravimetric analysis (TGA) was used to study thepossible thermal stability and degradation processes of nano-Fe3O4 sorbent as well as the newly designed and functionalizednano-Fe3O4-DOP and nano-Fe3O4-DOP-TETA sorbents. The contentof the organic moiety loaded on the surface of magnetic nanoparticlescan be also determined from the TGA data.Fig. 1a shows the TGA-thermogram of nano-Fe3O4 and it isclearly referring to the high thermal stability of this magneticnano-material. Only one thermal degradation step was characterizedat temperature <45.51 8C and this corresponds to 0.092 mgloss of the starting mass to represent a 1.71% loss. The TGAthermogramof nano-Fe3O4-DOP is shown in Fig. 1b in which twothermal degradation steps were characterized. The first decompositionstep was identified at a temperature range of 182.15–262.57 8C and this corresponds to a loss of 0.445 mg (7.98%) fromthe starting nano-Fe3O4-DOP sorbent. The weight loss in thesecond degradation step of this sorbent corresponds to 0.125 mg(2.24%) at a temperature range of 348.41–376.64 8C. The sum ofthese two degradation steps is 10.22% and this value gives adirect evidence for the loading of DOP on the surface of nano-Fe3O4. Finally, Fig. 1c represents the TGA thermogram of nano-Fe3O4-DOP-TETA sorbent and clearly refers to a different profilethan that of the nano-Fe3O4-DOP sorbent with respect tothe temperature ranges of thermal decomposition processes.The thermogram of nano-Fe3O4-DOP-TETA sorbent refers to theexistence of three successive thermal degradation steps. The first isrelated to desorption of the surface water molecules with a 1.5%loss. The second and third steps are mainly due to the directdecomposition of the loaded organic molecules, TETA and DOP, at139.20–238.7 8C (2.5%) and 238.7–378.6 8C (9.2%), respectively.The conclusion that can be drawn from the TGA study is mainlyindicating that a high thermal stability of nano-Fe3O4 over theentire temperature range (20–600 8C), while the chemicallymodified nano-Fe3O4-DOP-TETA sorbent exhibited higher thermalstability than nano-Fe3O4-DOP in the of range 20–239 8C.
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