Effect of adding carbon quantum dots to a NMP solution of cellulose acetate on the formation mechanism of ensuing membrane

Abstract

BackgroundCarbon quantum dots (CQDs) can improve membrane separation efficiency and significantly contribute to solving global problems. Investigating the influence of adding CQDs on phase separation of cellulose acetate (CA)/ N-methyl-2-pyrrolidone (NMP) solution would provide more understanding of membrane formation. MethodsCA+CQDs membrane was fabricated through non-solvent induced phase separation, using water as coagulant. Kinetic and thermodynamics behavior of polymer solution affected the phase separation mechanism. The thermodynamic behavior was observed in cloud-point curve from the ternary phase diagram of CA/NMP/water, whereas the kinetic was studied by correlating the viscosity of the dope with light transmittance experiment and optical microscope observation. Fourier transform infrared microscope measured the time of phase separation at different depths of the casting plate. Significant findingsAdding CQDs can affect both the kinetics and thermodynamic behavior CA/NMP solution. At the top of the casting plate, phase separation behavior was affected mainly by the formation of pseudo water layer, causing fast demixing rate with more porous structure. In the inner part, phase separation was facilitated by kinetic of the dope. The 1,000 ppm CQDs added CA membrane delivered the highest pure water flux of 731.90 ± 68.27 L·m−2·h−1 (1 bar).