Tina Chakrabarty

Mixed‐matrix membranes (MMMs), merging the advantages of polymers and inorganic fillers, has become a preferable choice as future gas separation membrane. Owing to hierarchical structures, MMMs are suitable for high‐performance gas separation capability. Research on extended porous organic/inorganic materials also known as fillers of intrinsic nanopores (FIN_S) such as porous organic frameworks (POFs), Zeolites, metal–organic frameworks (MOFs), porous organic cages (POCs) and analogous metal–organic polyhedral (MOPs) have bloomed over the last two decades. MOFs and POFs have been proposed as good adsorbent and promising filler components for industrial gas separations, due to their prominent porosity and structural flexibility and also for MMMs with good performance in terms of permeance and selectivity. They are compatible for providing additional molecular transport channels as well as having good size‐sieving property. This review briefly outlines the innovative trends in MMMs, highlighted with different porous fillers as well as suitable polymers followed by their synthesis and their suitable application in gas separations. Finally, a state of art and challenges in the direction of actual application of MMMs in different industries are outlined in terms of inter relation and regarding the future direction and potential growth opportunities of MMMs an elaborate discussion is provided.

A major concern in membrane-based water purification system is generation of huge concentrate stream and wastage of water. A typical Reverse osmosis (RO) or Nanofiltration (NF) system generates 20–25% reject containing high amount of dissolved salts and other contaminants. Contrary to popular belief, this reject water cannot be used without removing the contaminants or cannot be discharged anywhere. Main goal of this project is to find a cheapest and green way for treatment of RO/NF reject. Algal evaporation technique was explored in laboratory scale, to find its suitability for treatment of chloride-rich membrane reject in actual scenario and based on the results obtained, a pilot plant of 48KL was established on Hooghly Met Coke division (HMC), Tata Steel. Particular species of microalgae was selected, to take up minerals from reject water. There are several types of bacteria and symbiotic algae associated with selected micro algae survive in high TDS. A unique slope roof system, connected with algae growth tank, helps in efficient evaporation of water ensuring a Zero discharge. A markedly improved performance was achieved when algal evaporation followed solar evaporation. A total evaporation of 11 L/m²/day was observed, which was almost five times faster than Solar evaporation. Graphical abstract

A novel method for the preparation of cellulose–polydimethylsiloxane (PDMS) blend membranes for organic solvent nanofiltration (OSN) and ethanol pervaporation is presented. The elegance of this approach lies in the use of trimethylsilyl cellulose (TMSC), a hydrophobic cellulose derivative, for blend membrane fabrication followed by simple hydrolysis to convert TMSC back to cellulose. The use of TMSC not only allows cellulose processing in common organic solvents, but also enables the creation of highly compatible cellulose–PDMS blend membranes. The appropriate composition of the blend membrane gave the best OSN performance with more than 10 L m⁻² h⁻¹ bar⁻¹ acetone permeance and around 750 Da molecular weight cut-off. This blend membrane can be used for OSN with any other solvents regardless of their polarity. The same membrane also showed an excellent pervaporation performance with a separation factor of 14 and a flux of 1.6 kg m⁻² h⁻¹ using a 5 wt% ethanol water mixture at room temperature. The blending of PDMS with cellulose resulted in a 100% increase of the separation factor when compared with pure PDMS. This surprising performance is a consequence of the good miscibility of the blending polymers, which can be obtained through this unique pathway. Overall, this study demonstrates a simple, efficient, and scalable method that is the only possible way reported to date to combine the superiority of cellulose and PDMS as a low-cost and stable membrane for solvent separation.

CO2 removal is necessary to mitigate the effects of global warming but it is a challenging process to separate CO2 from natural gas, biogas, and other gas streams. Development of hybrid membranes by use of polymers and metal-organic framework (MOF) particles is a viable option to overcome this challenge. A ZIF-7 nano-filler that was synthesized in our lab was embedded into a designed polymer matrix at various loadings and the performance of the mixed matrix membranes was evaluated in terms of gas permeance and selectivity. Hybrid membranes with various loadings (20, 30 and 40 wt%) were developed and tested at room temperature by a custom made time lag equipment and a jump in selectivity was observed when compared with the pristine polymer. A commercially attractive region for the selectivity CO2 over CH4 was achieved with a selectivity of 39 for 40 wt% particle loading. An increase in selectivity was observed with the increase of ZIF-7 loadings. Best performance was seen at 40% ZIF-7 loaded membrane with an ideal selectivity of 39 for CO2 over CH4. The obtained selectivity was 105% higher for CO2 over CH4 than the selectivity of the pristine polymer with a slight decrease in permeance. Morphological characterization of such developed membranes showed an excellent compatibility between the polymer and particle adhesion.