MIL-101-SO₃H: functionalized MOF for enhanced barium ion adsorption and environmental remediation

Cationic pollution from barium ions in wastewater poses environmental and health risks including cardiovascular effects and disrupted aquatic ecosystems. This study investigates the use of Metal-Organic Frameworks (MOFs), including both MIL-101(Cr) and its sulfonated derivative MIL-101-SO₃H, for efficient removal of barium ions in contaminated water sources. Sulfonation of MIL-101 at the metal center was shown to considerably increase its adsorption capacity compared to unmodified MIL-101 for barium ions, achieving 141.9 mg g^-1 for Ba²⁺ as compared to 54 mg g^-1 for MIL-101. The study deeply looked into the effects of the pH, adsorbent dosage, initial Ba²⁺ concentration, and contact time on adsorption efficiency. Approximately pH = 4 has been determined as the best for Ba²⁺ adsorption at which the sulfonated MOF gave essentially complete removal efficiencies of 99% of the barium cations. The adsorption correlated with the Langmuir model indicates a homogeneous monolayer adsorption on the surface. MIL-101-SO₃H, given the superior characteristics of its adsorptive ability compared with other materials including MIL-101, is tested with ion coexistence and retention trials. These results indicate that MIL-101-SO₃H would be an extremely efficient adsorbent for barium ion removal from wastewater that could prove beneficial for a future large-scale application in environmental remediation.