# Iron-Based Metal–Organic Frameworks for the Removal of Different Organic and Inorganic Arsenic Species from Water: Kinetic and Adsorption Studies

## TL;DR

Iron-based metal-organic frameworks effectively remove various arsenic species from water across a wide pH range and can be reused multiple times.

## Contribution

The study introduces Fe-MOFs as efficient and reusable adsorbents for diverse arsenic species with insights into adsorption mechanisms and regeneration.

## Key findings

- Fe-MOFs show broad pH adsorption for MMA, DMAA, ASA, and arsenate, with higher effectiveness for Basolite® F300.
- Adsorption kinetics follow pseudo-second-order models, indicating chemisorption with pore diffusion as the rate-limiting step.
- Fe-MOFs can be regenerated for four cycles using acidic methanol, maintaining adsorption efficiency.

## Abstract

Basolite® F300 and synthetic nano-{Fe-BTC} MOFs, two iron-trimesate MOFs, have been investigated, demonstrating broad pH range adsorption for monomethylarsenate (MMA), cacodylic acid (DMAA), 4-aminophenylarsonate (ASA), and arsenate, while arsenite adsorption was notable at pH > 9.5. A similar uptake trend was found for both MOFs, with Basolite® F300 being the more effective given its higher porosity and greater surface area. Pseudo-second-order kinetic models were followed by MMA, DMAA, ASA, and As(V), suggesting a chemisorption mechanism with arsenic species diffusion into MOF pores as the controlling step. Equilibrium data for DMAA and ASA fit the Langmuir model whereas MMA adsorption fits the Redlich–Peterson model. The uptake of MMA, DMAA, and ASA by both Fe-MOFs is mainly attributed to their coordination with Fe(III). Aromatic units in ASA enhance adsorption through П-П stacking interactions. The competition between all arsenic species for the sorption sites of the Fe-MOFs led to an uptake decrease of 10% for MMA and ASA and higher than 30% for DMAA and As(V) with respect to the individual uptakes. The Fe-MOFs can be reused for four cycles by washing with acidic methanol. Basolite® F300 and synthetic nano-{Fe-BTC} effectively removed organic and inorganic arsenic species, exhibiting rapid adsorption, selective uptake, stability, and easy regeneration.