Removal of Cr(III) from tannery wastewater using Citrus aurantium (grapefruit peel) as biosorbent

Tanneries that use Cr(III) in their processes are among the industries that can cause environmen-tal contamination by this heavy metal. Therefore, the use of grapefruit peel (GP) as a novel bio-sorbent for removal was investigated Cr(III) GP was treated with water grapefruit peel (WGP) and methanol grapefruit peel (MGP), considering parameters such as pH, contact time and initial concentration of Cr and evaluating their effect on biosorption. The adsorption capacity at a pH of 2.74 for WGP and MGP achieved 85.75% and 96.60%, respectively. Freundlich model indicated an adsorption favorable heterogeneous chemical process. The kinetic study indicated that Cr removal is due to simultaneous physicochemical processes. The analysis of attenuated total reflectance -Fou-rier-transform infrared spectroscopy showed the presence of pectin, lignin and cellulose that helps adsorption due to the participation of their functional groups. X-ray diffraction and scanning elec-tron microscopy-energy-dispersive X-ray spectroscopy analysis found that the adsorption of Cr on the surface caused significant changes in the network parameter, which confirmed that there is an ions substitution between Ca and Cr at the biosorbent surface.