Novel Grafted/Crosslinked Cellulose Acetate Membrane with N-isopropylacrylamide/N,N-methylenebisacrylamide for Water Desalination

Abstract

Shaker ebrahim 2 ✉ this work aims to prepare new types of grafted and crosslinked cellulose acetate (cA) reverse osmosis (Ro) membranes by phase inversion technique. the grafting and/or crosslinking processes of the pristine cA-Ro membrane were conducted using N-isopropylacrylamide (n-ipAAm) and N,Nmethylene bisacrylamide (MBAAm), respectively. the grafting/crosslinking mechanism onto the cA-Ro membrane surface was proposed. Atomic force microscope (AfM) images of the pure cA-Ro and 0.1 wt% N-IPAAm-grafted CA-RO membranes revealed that the surface roughness was 42.99 nm and 11.6 nm, respectively. Scanning electron microscopy (SEM) images of the 0.1 wt% grafted/crosslinked membrane indicated the finger-like macrovoids structure. It was observed that the contact angle of the pristine CA-RO membrane was 66.28° and declined to 49.7° for 0.1 wt % N-IPAAm-grafted CA-RO membrane. The salt rejection of the pristine CA-RO membrane was 93.7% and increased to 98.9% for the grafted 0.1 wt % N-IPAAm/CA-RO membrane. The optimum grafted/crosslinked composition was 0.1 wt %/ 0.013 wt % which produced the salt rejection and water flux of 94% and 3.2 L/m 2 h at low pressure, respectively. it was concluded that both the grafting and crosslinking processes enhanced the performance of the cA-Ro membranes. The RO membranes process is one of the most reliable, efficient and cost-effective water desalination techniques to meet the demand and indigence of the fresh water 1-3. The most common polymeric materials used in RO membrane manufacture are either cellulose acetate (CA) or polysulfone coated with dense layer of polyamide thin film 4-7. Surface functionalization enables the RO membranes to have a better water quality, stability and permeability and consequently reducing RO operational costs and energy consumption. The surface properties of RO membranes, including hydrophilicity, water permeability, salt rejection, water flux, and surface roughness are the main parameters which determine water affinity and the interactions mechanism with salts 8. Surface modification techniques such as grafting by hydrophilic molecules have been made to improve the membrane performance 9,10. Different types of the graft polymerization of monomers onto cellulose were carried out by radical, ionic and ring opening or living radical polymerizations 11-15. The modification of the membrane surfaces can be carried out by "grafting-from" and "grafting to" approaches. In the grafting-to method end-functionalized polymer molecules bind with complementary functional groups located on the surface to produce tethered chains. However, this method is rarely to be used in the membrane modification because of the low density of grafted polymer chains. The grafting from technique uses the polymerization initiated from the substrate surface by attached initiating groups. Molecules of a monomer penetrate through the already grafted polymer layer easily and significant grafted amounts can be reached. This technique is commonly used for the preparation of thick grafted l...

Hydroxyapatite integrated with cellulose acetate/polyetherimide composite membrane for biomedical applications

“…There are other cross sections that have an asymmetric structure and show channels or micro‐voids. The results shows that hydroxyapatite nanoparticles are an efficient pore former, forming distinct micro‐voids and increasing the hydrophilic character of the material 45,57 …”

“…The results shows that hydroxyapatite nanoparticles are an efficient pore former, forming distinct micro-voids and increasing the hydrophilic character of the material. 45,57…”

Cellulose acetate/polyvinylidene fluoride based mixed matrix membranes impregnated with UiO-66 nano-MOF for reverse osmosis desalination

“…4c, the surface of the pristine CA membrane has a dense, groovy, and thin top selective layer, that is supported on a thick, porous sublayer. The sublayer is characterized by a tear or finger like structure supported on a sponge like pore structure (Elkony et al 2020;Ali et al 2021).As shown in Fig. 4b, the bottom surface of the pristine membrane contains pinholes as a result to the solvent-nonsolvent exchange across the interface (Morsy et al 2016).…”

“…The bulk membrane modification, such as the usage of multiple polymeric blends and impregnation of organic or inorganic particles. The other approach is by enhancing the membrane surface, for instance, grafting hydrophilic monomers to the membrane surface or introducing polar groups to alter the membrane chemical structure (El-Ghaffar et al 2020;Elessawy et al 2020;Elkady et al 2020;Elkony et al 2020;Batool et al 2021).…”

Effect of cellulose acetate/cellulose triacetate ratio on reverse osmosis blend membrane performance

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