Enhancing fluoride ion removal from aqueous solutions and glass manufacturing wastewater using modified orange peel biochar magnetic composite with MIL-53

Abstract

In this study, we developed new adsorbents derived from orange peel biochar (BCOP) and enhanced them with CoFe₂O₄ magnetic nanoparticles (BCOP/CoFe₂O₄) and MIL-53(Al) (BCOP/CoFe₂O₄/MIL-53(Al)). These adsorbents were utilized to remove fluoride (FL) ions from aqueous solutions. We analyzed the properties of these adsorbents using a range of techniques, including FTIR, XRD, SEM, EDX-Map, VSM, Raman spectroscopy, and BET. Our findings indicate that the components interact effectively with one another. Specifically, the BCOP/CoFe₂O₄/MIL-53(Al) sample exhibited a specific surface area of 196.430 m²/g and a magnetic saturation value of 9.704 emu/g. The maximum FL ion adsorption capacities for BCOP, BCOP/CoFe₂O₄, and BCOP/CoFe₂O₄/MIL-53(Al) were 7.618, 16.330, and 37.320 mg/g, respectively, indicating that the modifications significantly enhanced the adsorption capacity. The optimum fluoride ion removal rates using BCOP, BCOP/CoFe₂O₄, and BCOP/CoFe₂O₄/MIL-53(Al) were 97.88%, 98.23%, and 99.06%, respectively, at adsorbent doses of 2.5, 1.5, and 0.8 g/L, contact times of 90, 70, and 50 min, pH 4, temperature 50 °C, and a FL concentration of 10 mg/L. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic, with increased randomness between the adsorbent and fluoride ions. Kinetic analyses showed that fluoride ion adsorption by BCOP/CoFe₂O₄/MIL-53(Al) followed a pseudo-second-order (PSO) model, while BCOP and BCOP/CoFe₂O₄ followed a pseudo-first-order (PFO) model. Additionally, the equilibrium data for fluoride ion adsorption on BCOP/CoFe₂O₄/MIL-53(Al) adhered to the Freundlich model, whereas the other samples conformed to the Langmuir model. The study evaluates the effectiveness of BCOP, BCOP/CoFe₂O₄, and BCOP/CoFe₂O₄/MIL-53(Al) in removing FL ions from glass manufacturing wastewater, highlighting the superior performance of the magnetic composite due to its enhanced surface area and functional groups. Notably, the adsorbents demonstrated good regenerative capabilities, maintaining high performance over multiple adsorption cycles.

Keywords: Adsorption; Biochar; Fluoride; Magnetic composite; Metal-organic framework.