Polyethylenimine/grapefruit peel hybrid biosorbent for the removal of toxic CdTe quantum dots from water

Abstract

The use of engineered nanoparticles would increase their release into wastewater treatment plants, leading to the risk of contaminating water and ultimately causing environmental and health concerns. The removal of such nanoparticles from wastewater is highly needed. In this text, the polyethyleneimine (PEI)-decorated grapefruit peel (GP) composite adsorbent was facilely prepared for this purpose, which was based on PEI grafting onto the GP through a simple one-step reaction. The as-prepared PEI–GP adsorbent was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectrometry (XPS), showing that PEI was successfully grafted onto GP. The as-prepared PEI–GP adsorbents were used for the removal of CdTe quantum dots (QDs). Batch adsorption experiments were performed to investigate the influences of pH, contact time, initial CdTe QDs concentration, ionic strength and humic acid concentration. The results show that the adsorption kinetics could be fitted well to the pseudo-second-order model and the adsorption process could be described well by the Freundlich adsorption isotherm. The ionic strength caused a significant effect on the adsorption of CdTe QDs onto the PEI–GP adsorbents due to aggregation of the CdTe QDs in the presence of salt. The presence of humic acid had a minor effect on the sequestration of CdTe QDs by the PEI–GP biosorbents. The results indicate that the PEI–GP composite can be used as a promising adsorbent for the removal of CdTe QDs from aqueous media.