Estudo granulométrico, isotérmico, cinético e termodinâmico de adsorção do agroquímico 2,4-D a partir de HDL e HTL preparados com material catódico de baterias de íons lítio obtidas em escolas municipais de Uberlândia

Abstract

In this work, the synthesis of Layered Triple Hydroxide (LTH) [Co-Mn-Al-Cl]BATTERY was carried out by leaching the cathodic material from spent lithium-ion batteries, and its adsorptive properties were compared with those of LTH [Co-Mn-Al-Cl]REFERENCE. Both prepared by the constant pH co-precipitation method at pH 8 ± 0.5. Furthermore, the influence of the granulometry of LTH [Co-Mn-Al-Cl]REFERENCE (<45 µm, <75 µm, and <90 µm) on the kinetic, isothermal, and thermodynamic properties of 2,4-D agrochemical adsorption was investigated. The major chemical elements cobalt (1.16%), manganese (2.90%), and aluminum (1.73%) were identified in the leachate solution of exhausted lithium-ion batteries by X-ray fluorescence. The X-ray diffraction patterns of LTHs [Co-Mn-Al-Cl]REFERENCE and [Co-Mn-Al-Cl]BATTERY were consistent with the hydrotalcite sheet (JCPDS 14-191), with d(003) parameter values of 7.8314 Å and 7.7651 Å, respectively. The granulometric study by Brunauer – Emmett – Teller (BET) presented surface areas of 9.119, 11.825, and 11.973 m² g-1 for the granulometries of <45 µm, <75 µm, and <90 µm, respectively. The 45 µm granulometry statistically showed the highest adsorption average (13.621 mg g-1), indicating a higher adsorption capacity of 2,4-D agrochemical by LTH [Co-Mn-Al-Cl]REFERENCE. The probability of 2,4-D agrochemical adsorption above 96% achieved a better response (81.77%) for the 45 µm granulometry. The kinetic adsorption study showed that the pseudo-second-order model fit better to the experimental data (R²=0.9945) for LDH [Co-Mn-Al-Cl]REFERENCE, indicating that under conditions of 16.5 mg L-1 of 2,4-D, pH 4, and 50 mg of LDH. Isothermal measurements at different temperatures (298, 308, 318, and 328 K) indicated that the adsorption of 2,4-D by LTHs best fit the Freundlich model, with LDH [Co-Mn-Al-Cl]REFERENCE (R² = 0.9407, 0.9272, 0.9371 and 0,9662) and LTH [Co-Mn-Al-Cl]BATTERY (R² = 0.9849, 0.9183, 0.9374 and 0.9453), respectively, indicating physiosorption. The thermodynamic study of both LDHs indicated that the adsorption was an exothermic process (ΔH ~ -5 KJ mol-1), spontaneous (ΔG < -10 KJ mol-1), and with an increase in the degree of freedom (ΔS ≥ 16 J K-1 mol-1). The IR spectra of LDHs [Co-Mn-Al-Cl]REFERENCE and [Co-Mn-Al-Cl]BATTERY after adsorption showed the presence of characteristic bands of 2,4-D and LDHs, with shifts of the carboxylate group band to lower wavenumbers, suggesting interaction between 2,4-D and the surface of the LTHs. The degradation of the adsorbed 2,4-D agrochemical by photo-peroxidation applied to LTHs [Co-Mn-Al-Cl]REFERENCE and [Co-Mn-Al-Cl]BATTERY allowed removal rates of 95.27% and 94.98% of 2,4-D, respectively. Therefore, the adsorption associated with Advanced Oxidative Process (AOP) resulted in a treatment process that allowed capturing, concentrating, and degrading the pollutant 2,4-D on the surface of the investigated LTHs.