Double Polyamide Layers with CaCO₃ Nanoparticles as Scaffolds for High Performance Nanofiltration Membranes

Abstract

Nanofiltration (NF) membranes commonly with a single polyamide (PA) barrier layer play a significant role in the fields of separation and purification. Herein, an NF membrane with double PA layers was successfully fabricated through interfacial polymerization (IP) of a diamine with trimesoyl chloride, and CaCO3 nanoparticles were used as scaffolds. The upper PA layer grounded on the nano-CaCO3 aggregates was incomplete with multidefects. Trimesoyl chloride solution could permeate through the multidefect PA layer to continue IP reaction with diamine underneath the multidefect PA layer to form a bottom defect-free PA layer. The double PA layers almost fitted together, and additional nanovoids were left after removing nano-CaCO3 particles by HCl. The NF membranes with double PA layers exhibited a high water permeance of 34.1 L·m–2·h–1·bar–1, 3.4-fold that of the control sample without sacrificing selectivity. This was attributed to the enhancement of the hydrophilicity and effective filtration area and decrease in PA layer thickness, as well as additional nanovoids to reduce transport resistance. The antifouling performance of the NF membrane was found to be superior to that of the control sample possibly because the upper thin PA layer as a protective layer reduced the contamination to the separation layer.

Highly Permeable and Fouling-Resistant Polyamide Nanofiltration Membranes with Embedded Boron Nitride Nanosheets for the Purification of Water

“…As can be seen in Figure e, the enhanced permeance of TFN membranes is caused by the reduced thickness of the PA film, advanced effective membrane area, and enlarged pore size. First, the thinner PA selective layer could shorten the pathway and decrease the mass-transfer resistance of the water molecules through NF membranes, resulting in a promotion of permeance . Second, the increases in roughness and hydrophilicity could also enhance the effective membrane area, promoting more water molecules to be transported through the membrane.…”

“…First, the thinner PA selective layer could shorten the pathway and decrease the mass-transfer resistance of the water molecules through NF membranes, resulting in a promotion of permeance. 42 Second, the increases in roughness and hydrophilicity could also enhance the effective membrane area, promoting more water molecules to be transported through the membrane. In addition, the loose PA network can increase the number of transport sites for water molecules.…”