PEI-grafted graphene oxide modified phosphogypsum for the adsorption and removal of heavy metals and dyes in wastewater

In this study, due to its large surface area and strong metal chelation ability, graphene oxide (GO) and polyethyleneimine (PEI) are used as organic modifiers to functionalize inert phosphogypsum (PG) to prepare PG@GO@PEI adsorbent for effective removal of heavy metals and dyes from wastewater. The preparation of the adsorbent involved functionalizing PG with GO, followed by grafting PEI. The altered material was characterized through several methods, such as Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Patterns of powder X-ray diffraction (PXRD), to confirm successful grafting and improved surface properties. The prepared PG@GO@PEI adsorbent exhibits excellent adsorption performance for heavy metals and dyes, with removal rates close to 100%. The maximum adsorption capacity for Cr (VI) is 313.5 mg·g −1 , whereas the maximum adsorption capacities for naphthol green B (NGB) and malachite green (MG) are 425.5 mg·g −1 and 3300.9 mg·g −1 , respectively. XPS analysis revealed that Cr(VI) adsorption involved electrostatic interaction, ion exchange and chelation, while for NGB and MG adsorption, it could include electrostatic interaction, π-π interaction, and hydrogen bonding interaction. The results demonstrated that the PEI-grafted GO modification markedly improved the adsorption capacity of PG. Furthermore, an assessment using the GAPI, Complex GAPI, AGREE, and AGREEprep metrics tools demonstrates greenness of the established method and environmental sustainability. This study develop the new approach for waste PG resource utilization, alleviating the problem of environmental pollution caused by long-time storage of PG. This study also demonstrates the potential of PG@GO@PEI as a sustainable and effective adsorbent for wastewater treatment, contributing to the development of green technologies for environmental remediation.