Surface Treatment by Physical Irradiation for Antifouling, Chlorine-Resistant RO Membranes.

Reverse osmosis (RO) membranes represent a strategic tool for the development of desalination and water treatment processes. Today's global needs for clean water supplies show stressing circumstances to secure this supply, relying upon desalination and wastewater treatment and reuse, especially in Egypt and the Middle East. However, chlorine attack and fouling of polyamide layers, the active (selective) layers of RO membranes, are representing a great obstacle to seriously spreading the use of this technology. One promising way of fouling control and chlorine resistance is surface modification using grafting by plasma or vacuum ultraviolet (VUV) irradiation as a layer-by-layer assembly on polyamide membranes. Several studies have shown the effect of grafting by plasma using methacrylic acid (atmospheric pressure plasma) and showed that grafted coatings can improve PA membranes toward permeation compared with commercial ones with fouling behavior but not chlorine resistance. In this work, the techniques of layer-by-layer (LBL) assembly for previously prepared PA RO membranes (3T) using a mixed-base polymer of polysulfone and polyacrylonitrile in the presence of nanographene oxide (GO) without chemical grafting and with chemically grafted poly-methacrylic acid (3TG) were used. Membranes 3T, 3TG, a blank one (a base polymer membrane only was surface modified using VUV activation (AKT), and one with a grafted layer with polyethylene glycol (VUV-PEG) were prepared. These were then compared with polydimethylsiloxane (VUV-PDMS) and another surface modification with low-pressure plasma using acrylic acid (acryl) and hexadimethyl siloxane (GrowPLAS). The tested membranes were evaluated by short-term permeation and salt rejection experiments together with fouling behavior and chlorine resistance. A clear improvement of chlorine resistance and antifouling was observed for 3T membranes under plasma treatment, especially with the grafting with polyacrylic acid. Better antifouling and antichlorine behaviors were achieved with the vacuum UV treatment.

Development of Ag/AgX (X = Cl, I) nanoparticles toward antimicrobial, UV-protected and self-cleanable viscose fibers.

In situ synthesis of Ag/AgX nanoparticles (NPs) onto viscose fibers adds new functionalities and broadens their applications. In this study, Ag/AgX (X = Cl, I) NPs were in situ synthesized onto viscose fibers to impart brilliant colors, UV-protection, antimicrobial, self-cleaning, and photocatalytic properties. The AgX NPs were deposited on the fibers by ultrasonic irradiation, while Ag-NPs were formed by photoreduction of excess Ag+ ions under UV irradiation. The Ag/AgX NPs-loaded onto viscose fibers endowed with pale yellow for Ag/AgI and pale purple/violet for Ag/AgCl. The colored viscose fibers showed excellent antimicrobial activity against Escherichia coli (gram-negative), Staphylococcus aureus (Gram positive), and Candida Albican. The Ag/AgX/viscose fiber also showed excellent photocatalytic and self-cleaning activity toward degradation of methylene blue.

Nanocomposites based on chitosan/silver/clay for durable multi-functional properties of cotton fabrics.

The present work addresses an innovative approach for benign development of environmentally synthesis of chitosan-based nanocomposite. The synthesis involves the inclusion via interaction of AgNPs and clay with chitosan (Cs) giving rise to Cs/AgNPs and Cs/AgNPs/clay nanocomposites which when applied independently induce super functionalities. Comparison is made among the two nanocomposites with respect to their intimate association with the in depth cotton fibre-fabric surfaces and the onset of this on the multi-functionalization of cotton fabrics. It is as well to emphasize that Cs/AgNPs/clay nanocomposites prove unequivocally that its use in one-step treatment process for cotton fabrics results in imparting very appreciable good technical properties which, in turn, are reflected on all the gained functionalities of cotton fabrics. Of these functional performance properties, mention is made of cotton fabrics which exhibit high strength, uniform morphology, increased thermal stability, successful deposition of the composite on the surface of cotton fabrics, high water absorption, antimicrobial activity, flame retardant, controlled release of fragrance and UV protection. The obtained data indicate that the treatment for cotton fabrics with these nanocomposite is stable against washing even after 20 washing cycles. Based on encourage data, the environmental benign synthesis of Cs/AgNPs/clay nanocomposites is considered as a promising nanocomposite for the multifunctional finishing textiles.

Towards multifunctional cellulosic fabric: UV photo-reduction and in-situ synthesis of silver nanoparticles into cellulose fabrics.

Herein, the highly multifunctional cotton fabric surfaces were designed with excellent coloration, UV-protection function, and antimicrobial activity. These multifunctional functions were developed by in-situ synthesis of silver nanoparticles (Ag NPs) into the cotton fabric surface using a simple green one-pot "UV-reduction" method. Cotton fabrics were pretreated with non-anionic detergent, immersed into alcoholic silver nitrate solution (concentration ranging from 100 to 500ppm), squeezed to remove excess solution and then exposed to UV-irradiation (range 320-400nm) for 1h. The influence UV-irradiation on the thermal, chemical, optical and biological properties of the cotton fabric surface was discussed in details. The UV-irradiation promotes reducing of Ag+ ions and the cotton fabrics act as seed medium for Ag NPs formation by "heterogeneous nucleation". Increasing Ag+ concentration (from 100 to 500ppm) results in Ag NPs of particle size (distribution) of 50-100nm. Interestingly, the Ag NPs exhibited different localized surface Plasmon resonance properties causing a coloration of the cotton fabrics with different color shades ranging from bright to dark brown with excellent color fastness properties. The treated cotton fabrics also show high protecting functions against UV-transmission (reduction of 65%) and Escherichia coli growth (99%). The side-effects of the UV-reduction process are further investigated.