Adsorption performance of sulfonamide-modified metal-organic frameworks (MOFs) for Co(II) in aqueous solution

Efficient treatment of cobalt ions from mining wastewater and effluents from nuclear facilities is critical for environmental protection. A zeolite imidazole frameworks (ZIFs), which belong to a metal-organic frameworks (MOFs), was successfully synthesized and functionalized with sulfonamide to obtain a ZIF-90-SO₂HN₂ with high-efficiency adsorption of cobalt ions. The synthesized material was characterized by scanning electron microscopy, thermogravimetric analysis, N₂ adsorption-desorption, X-ray diffraction and Fourier transform infrared spectroscopy. The adsorption performance of ZIF-90-SO₂HN₂ for Co(II) in simulated wastewater was studied. The synthesized ZIF-90-SO₂HN₂ has a maximum adsorption capacity of about 122.85 mg g^-1 for Co(II) under the conditions of pH = 6.72 and T = 303 K with an initial solution concentration of 250 mg L^-1. The adsorption equilibrium time is about 120 min. ZIF-90-SO₂HN₂ exhibits selective adsorption of Co(II) and Ni(II) in multi-metal ion solution. Thermodynamic and kinetic analysis reflects that the adsorption process of Co(II) by ZIF-90-SO₂HN₂ is spontaneous and endothermic, which is consistent with pseudo-second-order chemisorption and Langmuir monolayer adsorption. (author)