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°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.