Incorporation of Functionalized Halloysite Nanotubes (HNTs) into Thin-Film Nanocomposite (TFN) Nanofiltration Membranes for Water Softening

Abstract

Incorporating nanoparticles (NPs) into the selective layer of thin-film composite (TFC) membranes is a common approach to improve the performance of the resulting thin-film nanocomposite (TFN) membranes. The main challenge in this approach is the leaching out of NPs during membrane operation. Halloysite nanotubes (HNTs) modified with the first generation of poly(amidoamine) (PAMAM) dendrimers (G1) have shown excellent stability in the PA layer of TFN reverse-osmosis (RO) membranes. This study explores, for the first time, using these NPs to improve the properties of TFN nanofiltration (NF) membranes. Membrane performance was evaluated in a cross-flow nanofiltration (NF) system using 3000 ppm aqueous solutions of MgCl2, Na2SO4 and NaCl, respectively, as feed at 10 bar and ambient temperature. All membranes showed high rejection of Na2SO4 (around 97–98%) and low NaCl rejection, with the corresponding water fluxes greater than 100 L m−2 h−1. The rejection of MgCl2 (ranging from 82 to 90%) was less than that for Na2SO4. However, our values are much greater than those reported in the literature for other TFN membranes. The remarkable rejection of MgCl2 is attributed to positively charged HNT-G1 nanoparticles incorporated in the selective polyamide (PA) layer of the TFN membranes.

Synthesis and Characterization of Anti‐fouling Ultrafiltration Nanocomposite Membranes Integrated with S‐β Zeolite Nanoparticles for Oily Wastewater Treatment

“…The Brunauer‐Emmett‐Teller (BET) method was employed to calculate the specific surface area of a material, representing the total surface area of the pores per unit mass of the material. Conversely, the BJH method is utilized to ascertain the pore size distribution within the material [21] . The results obtained from the BET and BJH experiments for the evaluation of the surface area and pore size distribution of the nonporous nanoparticles are shown in Figure 2 and Table 1.…”

The Effect of Cu2+ and Pb2+ in the Feed Solution on the Water and Reverse Solute Fluxes in the Forward Osmosis (FO) Process Using Nanofiltration (NF) Membranes

“…A commercial PS35 ultrafiltration (UF) membrane was used as a substrate for the interfacial polymerization of two monomer solutions. The details of the synthesis protocol of TFN membranes are described elsewhere [24].…”

“…Since the initial concentration of heavy metal in the draw solution was zero, the C p was evaluated from [28]:…”

“…where: C d,f , which is the concentration of heavy metal in the draw solution at the end of the experiment, and ∆V d , which is the total volume of water permeated from the feed to the draw solution, were measured directly. The final volume of the draw solution at the end of the experiment (V d,f ) was estimated from [28]:…”

“…The TFN membranes in this study utilized modified halloysite nanotubes (HNTs) as nanoparticles. More specifically, HNTs were functionalized with the first generation of poly(amidoamine) (PAMAM) dendrimers, and the resulting nanoparticles, HNTs-G1, were dispersed in the TMC monomer solution before interfacial polymerization [24]. The observed increase in the water flux combined with a significant reduction in the reverse solute flux in the presence of heavy metal ions was attributed to their adsorption by negatively charged TFN-NF membrane surface.…”