Development of Cassava Starch–Biochar Metal Organic Framework Mixed Matrix Membranes for Sustainable CO₂/CH₄ Separation

The increase in carbon dioxide (CO₂) concentration in natural gas and biogas reduces fuel quality and affects gas processing efficiency. It also contributes to environmental problems. Conventional separation methods such as chemical absorption and cryogenic distillation require high energy and are expensive to operate. These methods may also cause environmental concerns. This study focuses on the development of a sustainable mixed matrix membrane (MMM) for the separation of carbon dioxide and methane (CO₂/CH₄). The membrane is made from cassava starch, biochar, and metal–organic frameworks (MOFs). Cassava starch is used as the main polymer material. It is biodegradable, widely available in Nigeria, and low in cost. Biochar is produced from agricultural waste and added as a carbon filler. It improves the strength of the membrane and increases gas adsorption. MOFs are added because they have well-defined microporous structures. These structures improve gas separation by increasing permeability and selectivity. The membranes are prepared using the solution casting method. Different compositions of cassava starch, biochar, and MOFs are used to produce several membrane samples. The membranes are analysed using standard laboratory techniques. Scanning electron microscopy (SEM) is used to study the surface structure. Fourier transform infrared spectroscopy (FTIR) is used to identify chemical bonds. X-ray diffraction (XRD) is used to determine crystallinity. Thermogravimetric analysis (TGA) is used to assess thermal stability. Gas permeation tests are carried out to measure CO₂ permeability, CH₄ permeability, and CO₂/CH₄ selectivity under controlled conditions. The results show that the addition of biochar and MOFs increases membrane porosity. It also improves gas transport and CO₂ adsorption. The optimized membrane shows higher CO₂ permeability and better CO₂/CH₄ selectivity than membranes made from cassava starch alone. The use of cassava starch and biochar makes the membrane more environmentally friendly and cost-effective. These materials are renewable and readily available. This study shows that cassava starch–biochar–MOF mixed matrix membranes can be used for natural gas upgrading and biogas purification. The membrane system provides a more energy-efficient and sustainable alternative to conventional gas separation methods.