Zeolitic Imidazolate Framework (ZIF) based Mixed Matrix Membranes for Organic Solvent Resistant Nanofiltration

Abstract

The hazardous organic solvents wasted by the industries such as toluene, hexane, chloroform are producing acute problems for the environment. The efficient recovery and re-use of chemicals (solvents & catalysts) in industrial processes provides a pathway to reduce pollution and cost of processing leading to reduction in product cost. Membrane technology is a potential alternative to the conventional industrial separation processes due to its low energy consumption and reduced environmental impact. Solvent-resistant nanofiltration (SRNF) is used as a separation process for product recovery in organic media. There is a rapid increase in SRNF application. Both polymeric and inorganic materials are used for the fabrication of membranes for SRNF applications. Mixed matrix membranes, combining the advantageous properties of polymers and inorganic fillers, are a new class of membrane materials. Such membranes not only exhibit high rejection but they have also high thermal and solvent stability which is excellent considering the working conditions and parameters in practical and industrial applications. Among the fillers used for the synthesis of mixed matrix membranes, Zeolitic Imidazolate Frameworks have shown promising results due to their very high surface areas and better affinity with polymer matrix. The objective of this work is to synthesize Zeolitic Imidazolate Framework (ZIF) based Mixed Matrix Membranes for Organic Solvent Resistant Nanofiltration to boost the separation capability and stability of membrane in organic solvents removal. Zeolitic Imidazolate Framework-8 (ZIF-8) was selected as filler for MMMs to enhance the separation performance. ZIF-8 was prepared at lab scale and was characterized by different techniques to determine its morphology, thermal stability, surface area and pore volume etc. Membranes synthesis was done by preparing PI supports followed by the coating of poly dimethoxy silane (PDMS) layer containing different percentage loadings of ZIF-8. Finally these membranes were tested by passing a feed solution, having Congo red dye (solute) and IPA (organic solvent), to check the performance of membrane for SRNF application. The results showed that the increased in the percentage of ZIF-8 in PDMS lead to increase in the solvent X permeability as well as the rejection of Congo red dye from solution. Membrane swelling tests were performed in toluene and IPA with the conclusion that filler amount has inverse relation with membrane swelling.