Fluoride and lead abatement from synthetic and industrial wastewaters using magnetic biochar composite of walnut shell/CuFe2O4/MIL-101(Al).

In this investigation, walnut shell biochar (WSB) was amended by CuFe2O4 magnetic nanoparticles and MIL-101(Al) to improve its adsorption properties for fluoride (F-) and lead (Pb2+) abatement from synthetic and real wastewater. Characterization outcomes showed that modification significantly improved the feature and magnetic properties of WSB, increasing its area to 229.62 m2/g and enabling easy separation using a magnet. Adsorption experiments under optimal conditions (pH 5-6, 25 °C, 40 min contact time) demonstrated high removal efficiencies for both ions. Thermodynamic outcomes approved that the sorption was spontaneous and exothermic, with lower temperatures being more favorable. The uptake followed a pseudo-second-order model, controlled by chemical interactions, while equilibrium studies showed that F- adsorption by WSB and WSB/CuFe2O4 fitted the Langmuir model, whereas Pb2+ adsorption using all desired adsorbents and F- adsorption by WSB/CuFe2O4/MIL-101(Al) followed the Freundlich model. The value of the K1 parameter for the adsorption of F- and Pb2+ ions was determined to be 0.114 and 0.119 min-1, respectively, which indicates that the WSB/CuFe2O4/MIL-101(Al) magnetic composite has a higher adsorption rate compared to other samples. The maximum adsorption capacity for F- ion using WSB sample, WSB/CuFe2O4 magnetic composite and WSB/CuFe2O4/MIL-101(Al) magnetic composite was determined to be 16.68, 22.60 and 39.32 mg/g, respectively. However, the maximum adsorption capacity for Pb2+ ion using WSB sample, WSB/CuFe2O4 magnetic composite and WSB/CuFe2O4/MIL-101(Al) magnetic composite was determined to be 23.13, 36.12 and 70.93 mg/g, respectively. The magnetic composite demonstrated high efficiency in real wastewater treatment, removing 86 % lead from battery wastewater and 84 % fluoride from aluminum wastewater, and significantly reducing other elements. Additionally, reusability tests demonstrated that WSB/CuFe2O4/MIL-101(Al) magnetic composite remained effective for up to six cycles, highlighting its potential as a stable and efficient composite for wastewater purification.