Titanium dioxide coated polyetherimide photocatalytic nanofiber membrane for water treatment

Access to clean water for human use is a growing concern across the world with the ever-increasing human population. Treatment of wastewater to produce usable water is essential to meet future clean water demand. Separation and decontamination processes using membrane technologies have been implemented worldwide. Photocatalytic membrane is an emerging technology that is capable of simultaneously separating and degrading organic pollutants (e.g., humic acid (HA) and dyes) present in aqueous solution under UV-irradiation besides microorganism disinfection. In view of this, the main objective of this work is to fabricate and characterize a new type of nanocomposite nanofiber membrane by incorporating photocatalytic nanomaterials – titanium dioxide (TiO2) into a highly porous nanofiber made of UV-resistant polyetherimide (PEI). The nanofiber membrane was fabricated via an electrospinning method using a dope solution containing 15 wt% PEI dissolved in a mixed solvent of dimethylformamide (DMF)/n-methyl-2-pyrrolidone (NMP) with ratio of 2:8. The top surface of nanofiber membrane was further modified by coating it with different TiO2 concentration (0.2 and 0.6 wt%) using electrospraying method. The properties of the TiO2-modified PEI nanofiber membranes were then analysed using scanning electron microscope (SEM), water contact angle (WCA) goniometer and tensile strength machine. Results showed that 0.2 wt% TiO2-modified PEI nanofiber displayed better behaviour by reducing WCA of unmodified nanofiber from 130.25° to 23.35° and improving water flux by 28%. Although the WCA of membrane was further reduced when a higher TiO2 amount (0.6 wt%) was used, the resultant nanofiber suffered from decreased ultimate strength and significant nanoparticles leaching. Using the best performing 0.2 wt% TiO2-modified PEI membrane, significant removal rate of Escherichia coli (99%) and humic acid (~80%) could be achieved along with 85% methylene blue degradation during photocatalytic process. The findings of this work provide an insight into the design of advanced nanocomposite nanofiber membrane for photocatalytic process

Author Correction: Chlorination disadvantages and alternative routes for biofouling control in reverse osmosis desalination

In the original version of this Review Article the affiliation and address for Lorenzo Rosa were incorrectly given as "University of Parma, Department of Information Engineering, Parma 43121, Italy"

Titanium dioxide-modified polyetherimide nanofiber membrane for water treatment

The main objective of this work is to fabricate and characterize a new type of nanocomposite nanofiber membrane by incorporating photocatalytic nanomaterials – titanium dioxide (TiO2) into a highly porous nanofiber made of UV-resistant polyetherimide (PEI). The nanofiber membrane was fabricated via an electrospinning method using a dope solution containing 15 wt% PEI dissolved in a mixed solvent of dimethylformamide (DMF)/n-methyl-2-pyrrolidone (NMP). The resultant PEI nanofiber membrane was further modified by coating its surface with TiO2 (0.2 and 0.6 wt%) using electrospraying method. The properties of the TiO2-modified PEI nanofiber membranes were then analysed using scanning electron microscope (SEM), water contact angle (WCA) goniometer and tensile strength machine. Results showed that 0.2 wt% TiO2-modified PEI nanofiber displayed better behaviour by reducing WCA of unmodified nanofiber from 130.25° to 23.35° and improving water flux by 28%. Although the WCA of membrane was further reduced when a higher TiO2 amount (0.6 wt%) was used, the resultant nanofiber suffered from decreased ultimate strength and significant nanoparticles leaching. Using the best performing 0.2% TiO2-modified PEI membrane, significant removal rate of Escherichia coli (99%) and humic acid (∼80%) could be achieved along with 85% methylene blue degradation during photocatalytic process. The findings of this work provide an insight into the design of advanced nanocomposite nanofiber membrane for photocatalytic process

Autopsy of Used Reverse Osmosis Membranes from the Largest Seawater Desalination Plant in Oman

The Barka desalination plant, commissioned in 2018, is the largest desalination plant in Oman. It has a capacity of 281 MLD with a reverse osmosis (RO) first-pass recovery rate of 46%. As part of the standard operator practice, a membrane autopsy was conducted to determine the cause of reductions in membrane performance. This study investigated fouled membranes (model No. SW30HRLE-440) from two different locations in the membrane rack. Various analytical methods were used to conduct the membrane autopsy. Field-emission scanning electron microscopy/energy-dispersive X-ray (FESEM/EDS) analyses of membrane samples showed major components of inorganic foulants. Moreover, black and salt-like crystals deposited on the membrane surface revealed significant carbon (C) components and oxygen (O), with a small amount of magnesium (Mg), chloride (Cl), sodium (Na), aluminium (Al), and calcium (Ca), respectively. A Fourier transform infrared (FTIR) analysis revealed the presence of long-chain hydrocarbons, carboxylic acids/esters, carbohydrates/polysaccharides, and inorganic foulants. Thermogravimetric analyses (TGA) of the membranes showed a high initial weight loss due to organic and inorganic fouling. X-ray photoelectron (XPS) analyses further confirmed the presence of inorganic and organic foulants on the membrane surfaces. Bacteria identification results showed the presence of Bacillus cereus and Bacillus marisflavi. This paper offers a detailed analysis of the foulants present on the reverse osmosis membrane surface and sub-surface before and after a cleaning process

Author Correction: Chlorination disadvantages and alternative routes for biofouling control in reverse osmosis desalination

In the original version of this Review Article the affiliation and address for Lorenzo Rosa were incorrectly given as “University of Parma, Department of Information Engineering, Parma 43121, Italy”