Effective Antiscaling Performance of Reverse-Osmosis Membranes Made of Carbon Nanotubes and Polyamide Nanocomposites

Yoshihiro Takizawa; Shigeki Inukai; Takumi Araki; Rodolfo Cruz-Silva; Josue Ortiz-Medina; Aaron Morelos-Gomez; Syogo Tejima; Ayaka Yamanaka; Michiko Obata; Auppatham Nakaruk; Kenji Takeuchi; Takuya Hayashi; Mauricio Terrones; Morinobu Endo

doi:10.1021/acsomega.8b00601

Effective Antiscaling Performance of Reverse-Osmosis Membranes Made of Carbon Nanotubes and Polyamide Nanocomposites

ACS Omega. 2018 Jun 5;3(6):6047-6055. doi: 10.1021/acsomega.8b00601. eCollection 2018 Jun 30.

Authors

Yoshihiro Takizawa¹, Shigeki Inukai¹, Takumi Araki^{1

2}, Rodolfo Cruz-Silva^{1

1}, Josue Ortiz-Medina^{1

1}, Aaron Morelos-Gomez^{1

1}, Syogo Tejima^{1

2}, Ayaka Yamanaka^{1

2}, Michiko Obata¹, Auppatham Nakaruk¹, Kenji Takeuchi^{1

1}, Takuya Hayashi^{1

1}, Mauricio Terrones^{1

3}, Morinobu Endo^{1

1}

Affiliations

¹ Global Aqua Innovation Center and Institute of Carbon Science and Technology, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan.
² Research Organization for Information Science & Technology, 2-32-3, Kitashinagawa, Shinagawa-ku, Tokyo 140-0001, Japan.
³ Department of Physics, Department of Materials Science and Engineering, and Department of Chemistry. The Pennsylvania State University, University Park, Pennsylvania 16802, United States.

Abstract

The antiscaling properties of multiwalled carbon nanotube (MWCNT)-polyamide (PA) nanocomposite reverse-osmosis (RO) desalination membranes (MWCNT-PA membranes) were studied. An aqueous solution of calcium chloride (CaCl₂) and sodium bicarbonate (NaHCO₃) was used to precipitate in situ calcium carbonate (CaCO₃) to emulate scaling. The MWCNT contents of the studied nanocomposite membranes prepared by interfacial polymerization ranged from 0 wt % (plain PA) to 25 wt %. The inorganic antiscaling performances were compared for the MWCNT-PA membranes to laboratory-made plain and commercial PA-based RO membranes. The scaling process on the membrane surface was monitored by fluorescence microscopy after labeling the scale with a fluorescent dye. The deposited scale on the MWCNT-PA membrane was less abundant and more easily detached by the shear stress under cross-flow compared to other membranes. Molecular dynamics simulations revealed that the attraction of Ca²⁺ ions was hindered by the interfacial water layer formed on the surface of the MWCNT-PA membrane. Together, our findings revealed that the observed outstanding antiscaling performance of MWCNT-PA membranes results from (i) a smooth surface morphology, (ii) a low surface charge, and (iii) the formation of an interfacial water layer. The MWCNT-PA membranes described herein are advantageous for water treatment.