Amidoxime surface modification of polyindole nanofiber membrane for effective removal of Cr(VI) from aqueous solution

Surface amidoxime-modified polyindole (SAMPI) nanofiber membrane was prepared by a facile method using electrospun poly(5-cyanoindole) nanofibers treated by hydroxylamine for removal of hexavalent chromium (Cr(VI)) from aqueous solution. FTIR and XPS results confirm the presence of amidoxime groups on the surface of SAMPI nanofiber membrane. The SAMPI nanofiber membrane shows higher hydrophilicity which can favor the Cr(VI) adsorption. The maximum adsorption capacities (Q (m) ) calculated from Langmuir model are 340.14, 380.23 and 404.86 mg/g at 25, 35 and 45 A degrees C, respectively. The adsorption equilibrium can be reached in the range of 20-30 min with initial solution concentration increasing from 100 to 200 mg/L, and the adsorption process can be better described using pseudo-second-order model than pseudo-first-order and intraparticle diffusion model. The isotherm data fit better to Langmuir model than Freundlich, Temkin and D-R isotherm models. The adsorption capacity can remain 81% after 10 cycle's usage, and the flux and rejection rate can keep about 84 and 86% after 5 cycle's usage, which show good durability performance. All these results indicate that the SAMPI nanofiber membrane might have potential applications in wastewater treatment for removal of Cr(VI).