Fast Arsenic Uptake from Natural Waters by UiO-66-NH₂: Selectivity, Kinetics and Mechanistic Insight

Amine-functionalized zirconium-based metal–organic frameworks are promising materials for selective water purification due to their highly tunable porosity and functional surface chemistry. In this work, UiO-66-NH₂ samples were synthesized at different temperatures (45–120 °C) and systematically characterized to elucidate their structure–property relationships. X-ray diffraction confirmed the formation of a highly crystalline cubic UiO-66 framework, consistent with the reference Zr–UiO-66 structure, with crystallite sizes in the range of ~24–35 nm. Nitrogen adsorption–desorption measurements confirmed a predominantly micro/mesoporous texture with a high specific surface area, which was suitable for fast mass transfer and adsorption processes. The adsorption performance of UiO-66-NH₂ was evaluated using real groundwater samples containing total 96 μg/L total arsenic. Comprehensive chemical analysis of water before and after treatment revealed a pronounced selectivity of UiO-66-NH₂ toward harmful oxoanions. Batch adsorption experiments demonstrated exceptionally fast kinetics, with arsenic concentrations reduced by more than one order of magnitude within ~10 minutes, achieving final levels well below the World Health Organization guideline value of 10 ppb. Alongside arsenic, phosphate was efficiently removed (97–99%), while the concentrations of dominant macroelements (Na⁺, K⁺) remained unchanged and only mild Ca²⁺/Mg²⁺ reduction was observed. Kinetic modeling suggests rapid surface-controlled adsorption driven by strong interactions between arsenic species and the amino-functionalized zirconium sites through electrostatic attraction, hydrogen bonding, and surface complexation.

Acknowledgement

This research was supported by the Ministry of Science, Technological Development and Innovation of the Republic of Serbia and the Ministry of Education, Science and Innovation of Montenegro, within the framework of the EUREKA project “Design and Development of Eco-Friendly Filter Media for Safe Drinking Water” (Acronym: SAFEDRINK).