Fig. 5. FTIR patterns of PABNTs (A) and PASNTs (B) before and after adsorption. (A).Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 6. (A) Effect of solution R 428 on PFOS and PFOA removal. 10 mg of adsorbent and 50 mL of 500 mg/L aqueous PFOS or PFOA solutions were used at 307 K. (■ for the adsorption of PFOS on PASNTs, for the adsorption of PFOA on PASNTs.) (B) Zeta potentials of PASNTs. (C) The possible mechanism of the adsorption of PFOS on PASNTs.Figure optionsDownload full-size imageDownload as PowerPoint slide
The effect of temperature on PFOS and PFOA adsorption to PANTs was investigated in a temperature range of 288–318 K, and the results were shown in Fig. 7. It could be observed that the adsorption amount of PFOS and PFOA onto PANTs increased as the temperature went up, which indicated the adsorption was an endothermic process. The endothermic adsorption appeared to be an uncommon behavior; however, several authors have reported endothermic adsorption of PFOS and PFOA on different types of adsorbents ,  and . The enhancement in the adsorption capacity as temeperature went up may be due to the chemical interaction between adsorbates and adsorbent, creation of some new adsorption sites or the increased rate of intraparticle diffusion adsorbates into the pores of the adsorbent at higher temperatures . Thus, the high temperature is in favor of the adsorption of PFOS and PFOA on PANTs.