Polyethyleneimine modified eggshell membrane as a novel biosorbent for adsorption and detoxification of Cr(VI) from water

Abstract

The polyethyleneimine (PEI) functionalized biosorbent which uses an eggshell membrane (ESM) as a model was synthesized based on the cross linking reaction between aldehydes in glutaraldehyde and functional groups such as amines and amides in ESM. The as-prepared biosorbent (PEI–ESM) strongly interacted with chromium(VI). After modification, the dynamic uptake capacity of the PEI–ESM increased by 105% compared with the control, and the maximum equilibrium adsorption capacity for Cr(VI) can reach about 160 mg g⁻¹ with an initial pH of 3.0. The Langmuir adsorption isotherm was applicable to fit the removal process. Kinetics of the Cr(VI) removal were found to follow a pseudo-second-order rate equation. The results obtained by Raman spectroscopy and X-ray photoelectron spectroscopic analysis (XPS), performed on the as-prepared biosorbent before and after Cr(VI) adsorption, suggested that some of adsorbed Cr(VI) anions were reduced to Cr(III) in Cr₂O₃ or Cr(OH)₃ during the sorption process, demonstrating that the PEI–ESM could detoxify Cr(VI). The developed biosorbent promises advantages such as low cost, high adsorption capacity, Cr(VI) detoxification, and environmental friendliness.