چكيده به لاتين
The core of this research is dopamine utilization for surface modification of PES membrane to
obtain high hydrophilic and underwater oleophobic surface including with antifouling
properties for ultrafiltration of oil-in-water emulsion. First, the effects of self-polymerization
time of dopamine were evaluated. In this regard, characterization analysis including FTIR,
FESEM, EDX, AFM, water contact angle and underwater oil contact angle and also soybean
oil-in-water emulsion filtration were evaluated. Due to the polydopamine surface modification,
the pore size distribution was shifted to the smaller pores leading to change of fouling
mechanism from standard blockage model to cake filtration model. Roughness increment and
introducing hydrophilic groups improved hydrophilicity of the membranes with the
polydopamine layer so that the modified membranes showed the enhanced antifouling
properties. The values of FRR, Rt, Rir and Rr of the PES/PDA 2 ha and PES/PDA-4 h
membranes were 50.96%, 89.41%, 49.04% and 40.37% and 56.76%, 62.29%, 43.24% and
19.05%, respectively, while the corresponding values of the unmodified PES membrane were
1.77%, 98.38%, 98.23% and 0.14%. In comparison to the unmodified PES membrane, the PDA
coated membranes with 2 and 4 h self-polymerization time showed 223% and 793% water flux
increment, respectively, during oil-in-water emulsion filtration. Also, the oil rejection of the
PDA coated membranes were 98.87% and 99.12%, which were more than that of the
unmodified PES membrane (98.05%). In the next step, amine-modified MWCNTs were
utilized for surface modification of the PDA coated PES membranes. After this modification,
the average pore diameter was reduced to 12.77 nm. The FRR, Rt, Rir and Rr values of the
PES/PDA/N-MWCNTs-0.05 membrane were 95.73%, 22.35%, 4.27% and 18.08%,
respectively. The obtained results of the oil-in-water emulsion filtration showed 1086%
improvement compared to the unmodified PES membrane. Also, feed and operational
condition effects were also studied. Maximum responses were obtained at 100 ppm initial oil
concentration, 2000 ppm salinity, 2 bar trans-membrane pressure and 4 h self-polymerization
time. The long-term behavior of the PES/PDA/N-MWCNTs-0.05 membrane was monitored
via filtration of the soybean oil-in-water emulsion in two cycles within 16 h. During the first
cycle, the permeate flux was decreased from about 115 to 87 L/m2.h.bar. The obtained flux at
the end of the second cycle was about 83 L/m2.h.bar which was almost close to that obtained
at the end of the first cycle.
