Synthesis and characterization of metal–organic frameworks based on thorium for the effective removal of 2,4-dichlorophenylacetic pesticide from water: Batch adsorption and Box-Behnken Design optimization, and evaluation of reusability

Abstract

This study aimed to assess the effectiveness of thorium metal–organic frameworks (Th-MOF) as an adsorbent for the removal of the hazardous herbicide 2,4-dichlorophenylacetic (2,4-D) from aqueous solutions. The experimental results convincingly demonstrate Th-MOF's capability as an adsorbent, effectively eliminating 2,4-D from water. The material's properties were thoroughly examined using SEM, TEM, PXRD, XPS, FT-IR, and BET studies, revealing a substantial surface area of 1122.12 m2/g, indicative of its potential for high adsorption capacity. Surface charge analysis indicated a positive charge below the point of zero charge (5.2) and a negative charge above it, influencing the adsorption behavior. The study explored the impact of pH on adsorption equilibrium through batch experiments, providing insights into the environmental factors affecting the adsorption process. In summary, this research highlights Th-MOF as a promising adsorbent for 2,4-D removal, contributing valuable insights into its characteristics and performance in water treatment applications. The significance of our findings lies in the clear impact of variations in solution pH on the adsorption behavior observed in the study. We conducted a detailed investigation into the effectiveness of 2,4-dichlorophenylacetic acid (2,4-D) adsorption on Th-MOF, employing pseudo-second-order kinetic models to unravel the kinetics of the process. The Langmuir isotherm model proved to be a reliable predictor of the adsorption mechanism, highlighting a chemisorption process throughout. Intriguingly, our study revealed that the entire adsorption–desorption process was characterized by an endothermic and spontaneous nature, as indicated by the calculated thermodynamic parameters (ΔH°), (ΔS°), and (ΔG°) when utilizing Th-MOF as the adsorbent. Furthermore, the artificially synthesized Th-MOF adsorbent showcased exceptional flexibility and cyclability, successfully undergoing up to six adsorption–desorption cycles. This versatility underscores the potential practical applications of Th-MOF in water treatment processes, emphasizing its effectiveness and recyclability for sustainable environmental remediation efforts. In a scaled-down laboratory demonstration of wastewater treatment, we evaluated the efficacy of the developed adsorbent. The interaction mechanism between Th-MOF and 2,4-dichlorophenylacetic acid (2,4-D) was closely examined, considering factors like H-bonding, π-π interaction, pore filling, or electrostatic contact. The Th-MOF adsorbent demonstrated its capability for efficient water filtration and industrial wastewater management. Our study is noteworthy for pioneering the method for removing 2,4-D from wastewater samples using the Th-MOF adsorbent. Results revealed maximum 2,4-D adsorption onto Th-MOF at a pH of 4, reaching 358.3 mg.g − 1. Further exploration assessed removal efficacy from real samples and the sustained performance of the adsorbent through more than six cycles, with attention to its regeneration potential. The optimization of adsorption outcomes was achieved through the utilization of the Box-Behnken Design. This analysis underscores the practical application and sustainability of Th-MOF in addressing real-world wastewater treatment challenges.