Electrospinning PVA/PEI/rGO Fibrous Membrane and Its Adsorption of Cr(VI) and Congo Red in Water

The heavy metal Cr(VI) and azo dye Congo Red are notorious substances in wastewater, which must be dealt with effectively. As an adsorbent for wastewater remediation, a fibrous membrane has ideal advantages, including high adsorption efficiency, facile separation, and easy recovery. This study prepared a PVA/PEI/rGO membrane by convenient mixing and electrospinning for highly efficient adsorption of Cr(VI) and Congo Red. The microfibrous membrane was characterized by SEM, TEM, Raman, XRD, and FT-IR techniques. The adsorption kinetics for Cr(VI) and Congo Red followed the pseudo-second-order kinetic model, and the adsorption isotherms obeyed the Langmuir model. The maximum adsorption capacities of the fibrous membrane for Cr(VI) at 298, 308, and 318 K were 244.99, 304.43, and 337.10 mg/g, respectively, and for Congo Red were 226.36, 314.16, and 362.63 mg/g, respectively. Moreover, the adsorbents in five cycles had satisfying adsorption performance for Cr(VI) and Congo Red. The interactions between the membrane and adsorbate were explored to disclose the adsorption mechanism. After adsorption, hypotoxic Cr(III) was detected on the membrane, originating from the reduction of Cr(VI). Furthermore, the chromium on the adsorbent could be converted to Cr2O3 by calcination, realizing Cr(VI) recovery in wastewater. This PVA/PEI/rGO membrane provided a competent adsorbent for wastewater containing Cr(VI) and Congo Red and shed light on a recovery pathway for Cr(VI).