Eco-engineered electrospun La/Rb-MOF/chitosan–PCL nanofibrous membrane for high-performance, recyclable, and sustainable Cr(vi) removal from water

Abstract

This research presents the development of a novel electrospun nanofibrous membrane that combines chitosan (CS), polycaprolactone (PCL), and a bimetallic lanthanum–rubidium metal–organic framework (La/Rb-MOF) for the effective extraction of hexavalent chromium [Cr(VI)] from water. The La/Rb-MOF/CS–PCL membrane was created under optimized electrospinning parameters to improve both mechanical durability and adsorption capabilities. Detailed structural and surface analyses conducted through methods such as XRD, FTIR, XPS, SEM, and EDX confirmed the successful integration of La–Rb-MOF into the nanofibrous network, resulting in a porous and chemically reactive structure. Batch adsorption tests indicated that factors such as pH, adsorbent dosage, temperature, and initial Cr(VI) concentration significantly affected the removal efficiency. The adsorption kinetics were best modeled by the pseudo-second-order model, while the equilibrium data adhered to the Langmuir isotherm, achieving a maximum adsorption capacity of 449.2 mg g⁻¹ at pH 4. Thermodynamic assessments revealed that the adsorption process is spontaneous and endothermic, with the capacity for adsorption enhancing at elevated temperatures. The Box–Behnken design and response surface methodology (RSM) were utilized for optimization, identifying key parameters that influence adsorption effectiveness. Notably, the membrane exhibited excellent recyclability, sustaining a high efficiency for Cr(VI) removal even after five consecutive adsorption–desorption cycles. These results underscore the potential of the La–Rb-MOF/CS–PCL nanofibrous membrane as a durable, reusable, and eco-friendly solution for advanced water purification technologies.