Abstract Gas separation membranes are the best approach for the separation of carbon dioxide from gas mixture and the prevention of its adverse environmental effects. The mixed matrix membranes that are produced with the addition of inorganic fillers into polymer matrixes are excellent choices for CO2 separation. With this in mind, in the present research, the mixed matrix membranes based on polyurethane and chitosan-modified alumina nanoparticles were prepared and eva‎luated. For this purpose, first, polyurethane based on poly(tetramethylene ether)glycol (PTMG) polyol, isophorone diisocyanate (IPDI), and butanediamine (BDA) chain extender were synthesized. Meanwhile, chitosan chains were attached to alumina nanoparticles in the presence of [3-(2, 3-epoxypropoxy) propyl] trimethoxysilane (EPO). Then, mixed matrix membranes with different amount of nanoparticles were prepared. Different analyses including FTIR, EDX, XRD, SEM, and so on were performed on the surface-modified nanoparticles and mixed matrix membranes. FTIR, EDX and XRD analyses of chitosan-modified nanoparticles showed the presence of chitosan characteristic peaks in the spectrum of modified nanoparticles. SEM images revealed that chitosan-modified nanoparticles are completely spherical and have an average diameter of 98 nm. FTIR results of mixed matrix membranes confirmed that the increase of nanoparticle content to 5% increases the phase separation by 15% compared to pure PU, however further increase of nanoparticles decreases the phase separation. SEM images of mixed matrix membranes showed that membranes are dense and the nanoparticles are well dispersed in polymer matrix up to 9 %, however with the further increase of nanoparticles, the nanoparticles agglomeration and structural defects appeared in the samples. EDX results confirmed the inhomogeneous dispersion of nanoparticles and nanoparticle agglomeration in sample with 12 % nanoparticles. DSC curves showed that the addition of nanoparticles to PU increases the glass transition temperature of the PU matrix. TGA results confirmed that the addition of 9 % nanoparticles to PU increases the thermal stability of the polymer. Gas permeability and selectivity results revealed that increasing the nanoparticle content decreases the permeability of N2, O2 and CH4, while increases the permeability of CO2. In addition, increasing the nanoparticle content increases the CO2/N2 and CO2/CH4 selectivity. Increasing nanoparticles to 9% increases the CO2 permeability, CO2/N2 selectivity, and CO2/CH4 selectivity by 31, 48, and 42%, respectively. Amongst the mixed matrix membrane, the one with 9% nanoparticles with permeability and CO2/N2 selectivity of 77 barrer and 25, respectively approaches more to Robeson upper bound and has the best gas separation performance. Key Words: Carbon dioxide separation, mixed matrix membrane, polyurethane, alumina nanoparticles, chitosan

افسانه فخار , طيبه بهزاد

احمد محب , سهيل ضرغامي