Development of metal-organic framework-like La-methanoate@OMS nanohybrid for the efficient adsorption of arsenate

Abstract

The presence of arsenate ions (As5+) in water at concentrations exceeding the World Health Organization's recommended limit poses serious risks to humans, animals, and the environment, necessitating efficient removal methods. In this research, a metal-organic framework-like lanthanum-methanoate (LaMe) nanohybrid was synthesized through a solvothermal synthetic process using three different organic linkers with La moieties for As5+ removal. To enhance the stability and adsorption capacity of pristine LaMe, oxygen-incorporated molybdenum disulfide (OMS) was incorporated to form a nanohybrid structure (LaMe@OMS). Among the tested linkers, La-NBDC@OMS exhibited the highest adsorption capacity, whereas La-H4TCPP@OMS demonstrated superior structural stability. The LaMe@OMS nanohybrid exhibited a maximum adsorption capacity of 2.855 mmol/g at 25 degrees C and exhibited pH-dependent performance, peaking at pH 5.0-7.0. The nanohybrid demonstrated high selectivity in the presence of common coexisting anions, except PO43- and F-. Adsorption behavior followed the Langmuir isotherm and pseudo-second-order kinetic models, while spectroscopic and thermal analyses confirmed surface interactions with As5+ and robust stability. The primary adsorption mechanism was chemisorption involving ligand exchange and electrostatic interactions. Moreover, the nanohybrid retained high efficiency over multiple adsorption-desorption cycles, confirming excellent reusability. These results highlight the LaMe@OMS nanohybrid as a promising and reusable adsorbent for efficient As5+ removal from aqueous environments.