Study of the Biosorption of Cr(III) in Solution Using Orange Peel (Citrus sinensis) and Pineapple Crown (Ananas comosus L.)

At present, human activity is the main source of water pollution. The tanning industry is a primary source of water contamination with Cr(III), which can cause various diseases if ingested. A circular economy approach proposes an effective, low-cost solution. The utilization of waste from the food industry is used for the removal of Cr(III) through biosorption. This study evaluated the adsorption capacity of orange peel (OP) and pineapple crown (PC) pretreated with H2O2 and NaOH was evaluated under different operating conditions. The physicochemical properties of the biosorbents were characterized using techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results show that treatment with NaOH at 60 °C obtained an adsorption capacity of 61.63 mg/g and 64.19 mg/g for OP and PC, respectively. The combined biosorbents resulted in an approximately 50% increase in the adsorption capacity of Cr(III) compared to individual biosorbents. The isotherms that best fit the experimental data were Sips and Redlich–Peterson (RP) models, suggesting heterogeneous adsorption behavior in biosorbents. Thermodynamic parameters indicated that biosorption process was spontaneous and endothermic.