چكيده به لاتين
A novel and reliable interfacial reaction (IR) was developed to fabricate positively-charged thin film composite (TFC) membranes for water softening applications, employing low-pressure nanofiltration (NF) system. TFC selective layer was applied and crosslinked on a carboxylated polyether sulfone (CPES) porous substrate. Polyethyleneimine (PEI) and hyperbranched PEI (HPEI) polycations were utilized as polycations during TFC NF membrane fabrication. The membranes were firstly characterized prior to investigating impacts of polycations concentration, crosslinker concentration, reaction time, reaction temperature, pH and NaCl concentration on water permeability (WP) and salt rejection. Results of substrate characterization indicated that the addition of CPES tends to the formation of a negatively-charged membrane with a finger-like structure that increased water flux from 171 L. m-2 h-1 (LMH) to 248 (LMH). Moreover, to assess the rejection performance of the prepared membranes, WP and salts rejection were measured at IR temperature, IR time, crosslinking time, polycation concentration, crosslinker concentration, pH and NaCl concentration of 60 oC, 2h, 30 min, 1.0 wt. %, 0.5 wt. %, 11.7 and 2.5 M, respectively. The results of NaOH and NaCl addition to the polycation solution during the IR and rejection layer formation showed that OH- could provide more reliable membrane performances compared to when Cl- was utilized. 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 and moreover, the membrane maintained excellent chloride resistance during 1week of exposure to chloride acide. By acrrue results designed the RO unit with a NF membrane prefiltration with ROSA software and showed this unit can reduced energy consumption by 3 times.
Keywords: Nanofiltration, Desalination, positively charged membrane, thin film composite.
