Cotton‐Like Micro‐Sized Magnesium Oxide High‐Efficiency Removal of Lead: Insights From Thermokinetics and Applications in Soil‐Crop‐Human Lead Ingestion Risk Control

ABSTRACT

Nano‐sized MgO with a mesoporous structure exhibited outstanding performance in the removal of contaminants from water. However, its widespread application is limited by the difficulty of recovering such fine particles and the constraints of mass production. In this study, cotton‐like micro‐sized MgO with a hierarchical micro‐nanostructure of 270.10±5.2 µm was rapidly prepared and successfully applied for lead removal and human lead ingestion risk control firstly. The results of the goodness‐of‐fit parameters from lead adsorption thermodynamics and mechanism at 298.15, 303.15, and 308.15K indicated that the Pb uptake was well‐described by the Freundlich isotherm with the maximum adsorption capacities of 618.55, 709.92, 1338.40 mg/g at 298.15, 303.15, and 308.15K at pH 5.0 with the solid‐to‐liquid ratio of 0.25 g/L, respectively. It is evident that the adsorption process follows the pseudo‐second‐order model. The average energies of adsorption E (22.36‐50 kJ/mol) in the D‐R model are above 8 kJ/mol observed, which confirms the adsorption occurs from a physically to a predominant chemical process. The adsorption is endothermic and spontaneous according to the activation energy Ea 28.84 KJ/mol, the standard free energy change ΔG ‐987.03 KJ/mol, the standard entropy change ΔS 6.60 KJ/mol/K, standard enthalpy change ΔH 1046.31 KJ/mol, respectively. The applications indicated that only a 0.008 g/kg amount of MgO can significantly reduce the migration and accumulation of lead from soil into crop grains and also substantially decrease the oral ingestion risk of corn lead exposure to the children and adults. The novelty and significance of this study confirm that the cotton‐like micro‐sized MgO will potentially serve as a higher efficiency absorbent for Pb ²⁺ removal, but also is an environmental‐friendly, sustainable remediation material to control soil lead contamination with less addition and control human lead ingestion risk in agricultural crops and food safety with no toxic effects and higher performance.