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Separation Processes
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🍳separation processes review

14.1 Advanced materials for separation processes

Citation:

Advanced materials like Metal-Organic Frameworks, Covalent Organic Frameworks, and Zeolitic Imidazolate Frameworks are revolutionizing separation processes. These materials offer tunable pore sizes, high surface areas, and enhanced stability, making them ideal for various applications.

These frameworks outperform traditional materials in selectivity, capacity, stability, and versatility. Case studies showcase their effectiveness in gas separation, liquid-liquid extraction, and adsorption processes, demonstrating improved performance in real-world applications.

Advanced Materials for Separation Processes

Properties of advanced framework materials

  • Metal-Organic Frameworks (MOFs) feature crystalline porous structures composed of metal ions or clusters coordinated with organic ligands enabling high surface area and tunable pore size for gas storage and separation (H2, CO2), catalysis, and drug delivery applications
  • Covalent Organic Frameworks (COFs) comprise crystalline porous polymers formed by light elements (C, H, O, N, B) linked via covalent bonds creating highly ordered structures with uniform pore sizes utilized in gas separation and storage (CH4, CO2), catalysis, and optoelectronics
  • Zeolitic Imidazolate Frameworks (ZIFs) represent a subset of MOFs exhibiting zeolite-like topologies composed of metal ions coordinated with imidazolate linkers providing exceptional thermal and chemical stability for gas separation (CO2, H2), catalysis, and sensing applications

Advantages over traditional materials

  • Selectivity achieved through tunable pore size and chemistry enables specific molecule separation enhancing shape and size selectivity (CO2/N2, H2/CH4) and improving molecular recognition capabilities
  • Capacity increased due to higher surface area compared to traditional adsorbents (activated carbon, zeolites) resulting in greater adsorption capacity per unit volume reducing equipment size and operational costs
  • Stability enhanced by greater thermal resistance for high-temperature applications (500-600°C), improved chemical resistance in harsh environments (acidic, basic), and enhanced mechanical strength for prolonged use
  • Versatility provided by tailorable structures for specific separation needs and multifunctional properties combining separation and catalysis capabilities (one-pot reactions)

Case studies in separation processes

  • Gas Separation:

    1. CO2 capture using amine-functionalized MOFs achieving high selectivity and capacity
    2. Hydrogen purification with ZIF-8 membranes demonstrating excellent H2/CO2 separation factor
    3. Methane/nitrogen separation using flexible MOFs exhibiting unique "gate-opening" behavior
  • Liquid-Liquid Extraction:

    • Removal of organic pollutants (pharmaceuticals, dyes) from water using COFs with high adsorption capacity and recyclability
    • Rare earth element extraction with functionalized MOFs showing improved selectivity over traditional extractants
    • Oil-water separation using hydrophobic ZIFs demonstrating high flux and separation efficiency
  • Adsorption:

    • Desulfurization of fuels using Cu-BTC MOF achieving lower sulfur content than conventional adsorbents
    • Removal of heavy metals (Pb, Cd, Hg) from wastewater with COF-based adsorbents showing high uptake and selectivity
    • Volatile organic compound (VOC) capture using ZIF-derived carbon materials demonstrating enhanced adsorption capacity and stability