Adsorption Behavior of Various Forms of Arsenic in Water on UiO-66(Zr) Metal–Organic Framework and Its Impact on the Hydrosphere Environment

Metal–organic frameworks (MOFs) are effective absorbents in the extraction of arsenic pollutants from water matrices. This study systematically explored the adsorption of arsenic by UiO-66(Zr), including both inorganic arsenic, arsenite (As(III)), and arsenate (As(V)), and organic arsenic like roxarsone (ROX), p-arsanilic acid (p-ASA), and dimethylarsenic acid (DMA). UiO-66(Zr) exhibits the maximum adsorption capacity for As(V) significantly beyond that of other species, ranking as follows: As(V) ≫ p-ASA > As(III) > ROX > DMA (325.24, 189.12, 161.65, 154.99, and 126.83 mg·g^–1, respectively). According to Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results, the adsorption experiments revealed that the Zr–O–As inner-sphere coordination is the predominant chemisorption mechanism of arsenic species on UiO-66(Zr). Compared with DMA, hydrogen bonds and π–π stacking interactions strengthen the adsorption of ROX and p-ASA. Additionally, pH and coexisting anions influence adsorption and are also highly dependent on the arsenic structure. The evaluation of arsenic-contaminated groundwater cycling stability and toxicity characteristics leaching procedure (TCLP) for UiO-66(Zr) indicates that it still retains 60% efficiency after five cycles due to strong Zr–O–As coordination with minimal leaching of As and Zr. These results provide broader relevance, offering insights into the efficient, selective, and sustainable removal of arsenic species across diverse hydrosphere environments.