Constructing Positively Charged Thin-Film Nanocomposite Nanofiltration Membranes with Enhanced Performance

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.

Nanofiltration Membranes for the Removal of Heavy Metals from Aqueous Solutions: Preparations and Applications

“…Shao et al [ 69 ] formed a PEI/GO (polyethyleneimine/graphene oxide) thin film nanocomposite and used size exclusion and the Donnan effect to measure the selectivity of ions. PEI/GO.…”

“…Additionally, the use of nanoparticles at different concentrations can prevent this type of interruption. The rejection of metal ions, as depicted in Figure 8 b, can be achieved by increasing the concentration of the nanocomposite materials, which helps in the membrane separation process [ 69 , 97 , 98 ]. For Zn 2+ rejection, graphene oxide (GO) nanoparticles were incorporated into polyethyleneimine (PEI) to form a thin film nanocomposite (TFN).…”

Fabrication of High-Performance Nanofiltration Membrane Using Polydopamine and Carbon Nitride as the Interlayer

“…The surface zeta potential of membranes was characterized with a Sur-PASS electrokinetic analyzer (Anton Paar, Graz, Austria). Specifically, 1 mmol•L −1 KCl aqueous solution was used as the electrolyte, and 0.1 mol•L −1 HCl and 0.1 mol•L −1 KOH aqueous solution was used to control the pH value (3)(4)(5)(6)(7)(8)(9)(10). The gap height of the measuring cell was fixed at 100 μm and the membranes were soaked in electrolyte for at least 4 h before the measurement.…”

“…Very often, brine is heavily loaded with Mg 2+ in comparison to Li + because of their similar ionic properties, which undoubtedly makes it more difficult for recovery of lithium from the brine. Membrane separation is considered one of the most competitive separation technologies owing to its simplicity, low cost, high energy efficiency, and eco-friendliness [8,9]. Especially nanofiltration (NF), as a pressure-driven membrane separation process, has been extensively utilized in wastewater treatment and the recovery of highly-valued products [10].…”

Euler’s Numerical Method for Ions Rejection Reassessment of a Defect-Free Synthesized Nanofiltration Membrane with Ultrathin Titania Film as the Selective Layer

“…Novel NFMs have been synthesized for the first time, extremely loose or displaying excellent rejection performance, and even in some cases both at the same time. Thus, W. Shao et al recently synthesized an NFM using polyethyleneimine as the aqueous reactive monomers, and a positively charged thin-film nanocomposite NFM with enhanced performance was developed by successfully incorporating graphene oxide (GO) into the substrate active layer [17]. Other remarkable works are also reported, including that performed on organic solvent NFMs and remineralization of desalinated water [11,18,19].…”