Simultaneous degradation of sulfamethazine and reduction of Cr(VI) by flexible self-supporting Fe-Cu-Al2O3 nanofibrous membranes as heterogeneous catalysts: Insights into synergistic effects and mechanisms

The co-existence of sulfamethazine (SMT) and heavy metal Cr(VI) may alter their migration and conversion laws and even their biological toxicity owing to their different physicochemical properties, greatly aggravating their environmental risks and elevating the difficulty of remediation. Herein, a novel flexible self-supporting Fe-Cu-Al2O3 nanofibrous membrane (1Fe-2Cu-Al2O3-800) was synthesized via a sol–gel method with the combination of electrospinning serving as a heterogeneous catalyst for simultaneous SMT degradation and Cr(VI) removal. Copper and iron elements were highly dispersed in the alumina nanofibrous matrix in the form of Fe(III), Cu(I), and Cu(II) species. There exists a wide applicable range of environmental pH for the 1Fe-2Cu-Al2O3-800/H2O2 system, exhibiting excellent catalytic selectivity and recycling performance. The surfaced-bound hydroxyl radicals activated by reductive Cu(I) species were the main active species of SMT degradation. Meanwhile, anionic Cr(VI) was rapidly adsorbed on 1Fe-2Cu-Al2O3-800 through electrostatic interaction, and then directly reduced to Cr(III) by adjacent reductive ≡Cu(I) species and subsequently incorporated into iron oxide to constitute a stable Fe-Cr(III) complex. Moreover, the degradation kinetics results showed that Fe(II)/Fe(III) cycle in the 1Fe-2Cu-Al2O3-800/H2O2 system could mediate Cr(III)/Cr(VI) cycle to prominently accelerate the SMT degradation through Haber-Weiss-type reaction, thereby having a synergistic effect. Overall, this work would provide new insights and a feasible strategy for the remediation of organic–inorganic composite pollutions, including SMT and Cr(VI).