Abstract
The pursuit of improved water purification technology has motivated extensive research on novel membrane materials to be carried out. In this paper, one-dimensional carboxylated carbon nanotubes (CNTs) were intercalated into the interlayer space of layered double hydroxide (LDH) to form a composite membrane for water purification. The CNTs/LDH laminates were deposited on the surface of the hydrolyzed polyacrylonitrile (PAN) ultrafiltration membrane through a vacuum-assisted assembly strategy. Based on the characterization of the morphology and structure of the CNTs/LDH composite membrane, it was found that the intercalation of CNT created more mass transfer channels for water molecules. Moreover, the permeance of the CNTs/LDH membrane was improved by more than 50% due to the low friction and rapid flow of water molecules in the CNT tubes. Additionally, the influence of preparation conditions on the separation performance was investigated using Evans blue (EB). Optimized fabrication conditions were given (the concentration of CoAl-LDH was 0.1 g/L and the weight ratio of CNTs was 2 wt.%). Next, the separation performances of the prepared CNTs/LDH composite membrane were evaluated using both single and mixed dye solutions. The results showed that the composite membrane obtained possessed a retention of 98% with a permeance of 2600 kg/(m2·h·MPa) for EB, which was improved by 36% compared with the pristine LDH composite membrane. Moreover, the stability of the CNTs/LDH composite membrane was investigated in 100 h with no obvious permeance drop (less than 13%), which exhibited its great potential in water purification.
Highlights
A carbon nanotubes (CNTs)-intercalated CoAl-layered double hydroxide (LDH) composite membrane was prepared via vacuum-assisted assembly for use in water purification
CNTs were intercalated in CoAlLDH nanosheets via electrostatic interaction and the obtained laminates were fabricated to form a composite membrane via vacuum-assisted assembly
With the assistance of the X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterization of the membrane morphologies and components, CNTs were observed to be successfully intercalated in LDH nanosheets
Summary
The search to improve the quality of water resources has motivated researchers to develop versatile wastewater treatment techniques. Adsorption, reductive and oxidative processes, phytoremediation, and membrane separation are some of the main techniques used for the removal of organic pollutants [1]. Among these techniques, membrane separation has attracted a great deal of attention, especially for the removal of small organic molecules and high-valence inorganic salts [2–5]. Studies of membranes have aided in the development of various research fields, including wastewater treatment [6–9], the pharmaceutical industry [10–12], food processing [13,14], and bioengineering [15,16]. Both steric hindrance and the electrostatic repulsion effect determine the specific performance of a membrane [17]. The interaction of both mechanisms requires the ingenious design of the membrane structure; the corresponding membrane materials are vital for the construction of separation layers [18–20]
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