Abstract
Using polyethylenimine (PEI) as the aqueous reactive monomers, a positively charged thin-film nanocomposite (TFN) nanofiltration (NF) membrane with enhanced performance was developed by successfully incorporating graphene oxide (GO) into the active layer. The effects of GO concentrations on the surface roughness, water contact angle, water flux, salt rejection, heavy metal removals, antifouling property, and chlorine resistance of the TFN membranes were evaluated in depth. The addition of 20 ppm GO facilitated the formation of thin, smooth, and hydrophilic nanocomposite active layers. Thus, the TFN-PEI-GO-20 membrane showed the optimal water flux of 70.3 L·m−2·h−1 without a loss of salt rejection, which was 36.8% higher than the thin-film composite (TFC) blank membrane. More importantly, owing to the positively charged surfaces, both the TFC-PEI-blank and TFN-PEI-GO membranes exhibited excellent rejections toward various heavy metal ions including Zn2+, Cd2+, Cu2+, Ni2+, and Pb2+. Additionally, compared with the negatively charged polypiperazine amide NF membrane, both the TFC-PEI-blank and TFN-PEI-GO-20 membranes demonstrated superior antifouling performance toward the cationic surfactants and basic protein due to their hydrophilic, smooth, and positively charged surface. Moreover, the TFN-PEI-GO membranes presented the improved chlorine resistances with the increasing GO concentration.
Highlights
Nowadays, many industries such as mining [1], metallurgy [2], electroplating [3], and microelectronic manufacturing [4] discharge a large amount of industrial wastewater contaminated by heavy metals
PEI and trimesoyl chloride (TMC) was reduced by the introduced graphene oxide (GO), which decreased the Membrane thickness of theMorphologies active layer
The thickness of the active layer slightly decreased from 256.8 nm (TFCPEI-blank, Figure 1(a2)) to 223.3 nm (TFN-PEI-GO-40, Figure 1(c2))
Summary
Many industries such as mining [1], metallurgy [2], electroplating [3], and microelectronic manufacturing [4] discharge a large amount of industrial wastewater contaminated by heavy metals. The conventional PEI-based PA NF membrane via IP process still faces huge challenges for enhancing the permselectivity [33], antifouling ability [34], and chlorination resistance [35] To overcome these challenges, novel thin-film nanocomposite (TFN) NF membranes have been extensively studied by incorporating various nanofillers into the active layer [36,37,38]. The effects of GO concentrations on the resultant positively charged NF membranes were investigated in depth in terms of the surface roughness, water contact angle, water flux, salt rejection, heavy metal removals, antifouling property, and chlorine resistance. This novel, positively charged NF membrane demonstrated an exceptional removal of heavy metal ions with improved antifouling performance and chlorine resistance
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