Enhanced surface hydrophilicity of thin-film composite membranes for nanofiltration: an experimental and DFT study

Abstract

In the current study, thin-film composite (TFC) nanofiltration membranes desirable for water softening were successfully developed through interfacial polymerization using N-(2-hydroxyethyl)ethylenediamine (HEDA) as the amine monomer in the aqueous phase. The hydrophilicity of the membrane surface was greatly enhanced with the introduction of the residual hydroxyl groups during the fabrication process. The TFC membranes possessed a permeate flux of 15.8 L m(-2) h(-1) under 0.6 MPa, with a rejection of 85.9%, 73.8%, and 99.8% for Na2SO4, MgSO4 and Congo red, respectively. The interplays of the solvent, solute and polymer matrix on the separation performance were investigated by means of the solubility parameter study. Moreover, density functional theory was employed to calculate the Fukui function by the Hirshfeld charge, which gave the global and local softness values to predict the reactivity of the atomic sites in the HEDA molecule. The findings of this study support the possible forming mechanism of the barrier layer for the first time. The TFC membrane was found to be stable and displayed good separation ability over a week-long filtration process. The combined results of this work suggest that these HEDA/TMC TFC nanofiltration membranes are promising candidates for various applications, such as desalination and dye removal from wastewater.

Fabrication of a high-flux sulfonated polyamide nanofiltration membrane: Experimental and dissipative particle dynamics studies

“…Due to the increasing usage of membrane technology in water treatment processes, it is important to improve our understanding of synthetic membranes and separation mechanisms. One convenient method to achieve this objective is to employ computational techniques [25][26][27][28][29][30]. For instance, Lo et al used a quantum mechanical simulation to calculate the global/local reactivity of piperazine (PIP) and m-phenylenediamine (MPD) molecules towards trimesoyl chloride (TMC) based on density functional theory (DFT).…”

Positively Charged Nanofiltration Membrane with Dendritic Surface for Toxic Element Removal

“…Then 50 mL of n -hexane consisting of TMC 0.1% (w/v) was poured onto the amine-saturated membranes surface for 1 min. After the excessive solution was poured out, the membranes were rinsed with fresh n -hexane solution (50 mL) and then dried in an air for 3 min. , After that, a new aqueous solution (100 mL) containing different concentrations of CMPI (0.01–0.04% (w/v)), PAMAM (0.05–0.2% (w/v)) and a trace amount of NaOH (equal to CMPI) was poured onto the membranes for 10 min, allowing for chemical grafting. Finally, the obtained membranes were washed with DI water and stored wetly until they were employed.…”

“…One of the successful approaches used for removing containments from water is the membrane technique, as it offers several advantages over other common methods such as low energy consumption, simple operation, efficient separation and scalability. − The commonly used membranes can be divided into three types by surface potential, i.e., negatively charged, neutral and positively charged membranes. Among them, the positively charged membranes are more attractive since the electrostatic interactions provide an effective way to reject positively charged ions, especially heavy metal ions. − In this manner, those commonly associated anions such as chloride or sulfate could also be simultaneously removed via the Donnan effect. , …”

Preparation and modification of thin film composite membrane using a bulky dianhydride monomer

“…The mechanism of interfacial polymerization for the TFC formation consists of two stages: a fast stage and a slow growth stage. 32 In the first stage, the MPD molecules should be diffused to the reaction zone and reacted rapidly with organic phase monomers, which resulted in the creation of a thin PA layer. In the next stage, the immigration of the MPD molecules to organic phase slowed down by the polymeric layer, which resulted in the development of a second layer named ridge-andvalley morphology which formed above the first layer.…”