Assessment of Zr Metal–Organic Frameworks (UiO-66) for the Adsorption of <i>p</i> -arsanilic Acid from Natural and Drinking Water

The organoarsenical compounds, such as <i>p</i>-arsanilic acid (<i>p</i>-ASA) and roxarsone (ROX), are commonly used as veterinary drugs to control intestinal parasites in poultry and swine farms. Because of this, environmental contamination by organoarsenical compounds can occur, primarily affecting water sources, which has raised widespread concern. Metal-organic frameworks (MOFs) are emerging as promising materials for water purification because of their varied crystal structures, extensive surface areas, adjustable pore sizes, and excellent chemical stability. In this study, a zirconium-based MOF (UiO-66) was synthesized, and its structural properties were analyzed using XRD, SEM, TGA, NMR, and BET surface area measurements. The performance of Zr-MOF was evaluated for removing the organoarsenical compound (<i>p</i>-ASA) from natural and drinking water. Batch adsorption experiments were carried out to assess the effects of pH, adsorption time, analyte concentration, and potential interferences. The adsorption efficiency did not significantly change across the pH range of 4-8. The isotherm studies showed that the adsorption mechanism was best described by the Langmuir model (<i>R</i> ² 0.9880), with a maximum adsorption capacity of 542.6 mg g^-1. This indicates the presence of uniform adsorption sites and the formation of a monolayer. The adsorption kinetics studies revealed that the Avrami model fitted the data well (<i>R</i> ² 0.9971), suggesting a complex adsorption mechanism primarily based on physisorption (<i>k</i> _AV 1.33). The proposed method demonstrates that UiO-66 is highly effective at removing <i>p</i>-ASA from natural and drinking water, even in the presence of coexisting ions, providing a sustainable approach to remediating contaminated water sources.