چكيده به لاتين
Two novel positively charged hybrid nanofiltration (NF) membranes were fabricated by incorporation of hyperbranched Polyethyleneimine (HPEI) and Triethylenetetramine (TETA) modified multiwall carbon nanotubes (MWCNT) into Polyethersulfone (PES) matrix. First response surface methodology (RSM) was employed to optimize the fabrication of PES NF membranes via phase inversion. The Box–Behnken design matrix was also applied to develop predictive regression models, minimize the number of experiments, and investigate the effects of parameters on the PES NF membrane. Then positively charged HPEI-MWCNT/PES and TETA-MWCNT/ PES hybrid NF membranes were prepared and evaluated in terms of morphology, surface properties, thermal and mechanical stabilities, nanofiltration performance and antifouling property. The best HPEI-MWCNT/PES hybrid membrane with loading of 0.6 % of nanoparticles, showed mean pore size and molecular weight cut off (MWCO) of 0.81 nm and 600 Da, respectively. This hybrid membrane pure water flux (PWF) was 75.70 L/m2 h which shows 109 % improvement compared to the neat PES. Also in the best nanoparticles loading ratio of 0.4 wt.% of TETA-MWCNT/PES hybrid membrane, the fabricated membrane exhibits a pore diameter of 0.73 nm, a MWCO of 570 Da and a PWF of 84.35 L/m2 h which shows 130% improvement compared to the neat PES. Regarding salts rejection, both hybrid membranes follow the order R (MgCl2)>R (MgSO4)>R (Na2SO4)>R (NaCl) which confirms positively charge nature of the membranes. Effects of pressure, temperature, feed concentration and feed pH on separation performance of the both membranes were also investigated. The hybrid HPEI-MWCNT/PES membrane represented superior performance for heavy metals removal in rejection order of Zn (99.06 %) > Mg (97.36 %) > Cd (96.72 %) > Cu (95.84 %) > Ca (95.25 %) > Ni (94.63 %) > Pb (93.39 %), indicating domination of Donnan exclusion mechanism. Furthermore, the hybrid TETA-MWCNT/PES membrane demonstrated effective rejection for two cationic dyes i.e. Rhodamine B (99.23%) and Crystal violet (98.43%) and acceptable rejection for two anionic dyes i.e. Indigo carmine (87.12%) and Orange G (82.13%). In addition to the improvements in their mechanical and thermal stabilities, antifouling nature of the both hybrid membranes enhanced as well due to lower surface roughness and higher hydrophilicity.
