Tannin-coated PVA/PVP/PEI nanofibrous membrane as a highly effective adsorbent and detoxifier for Cr(VI) contamination in water

• Tannin-coated PVA/PVP/PEI membranes is prepared based on electrospinning, and the membrane has a high adsorption capacity for Cr(VI). • The maximum adsorption capacity of the adsorbent for Cr(VI) at 318 K is 695.04 mg/g. • The material can easily be separated and reduce part of the Cr(VI) to Cr(III). • The adsorbed material can be converted into Cr 2 O 3 by calcination, reducing secondary pollution. Cr(VI) pollution severely threatens the water environment and human health. One of the effective ways to solve this problem is to develop environmentally friendly and efficient adsorbents. This paper proposes a highly efficient Cr(VI) adsorbent based on tannic acid coating PVA/PVP/PEI nanofibrous membrane. The adsorbent is environment-friendly and has satisfying water stability and adsorption performance. The optimum preparation conditions, adsorption conditions, and the influence of ionic strength and coexisting ions were investigated comprehensively. Through the study of adsorption kinetics and isotherms, the adsorption of Cr(VI) on the nanofibrous membrane was found following the pseudo-second-order kinetics model, and the adsorption isotherm model following the Langmuir model. The maximum adsorption capacities were 631.97 mg/g, 667.52 mg/g, and 695.04 mg/g at 298 K, 308 K, and 318 K, respectively. After adsorption of Cr(VI), the membrane can be converted to high purity Cr 2 O 3 by calcination. The tannin-coated PVA/PVP/PEI nanofibrous membrane is a promising adsorbent because it can efficiently adsorb Cr(VI) and convert highly toxic Cr(VI) into hypotoxic Cr(III).