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News Article | June 19, 2017
Site: www.eurekalert.org

Materials called transition-metal carbides have remarkable properties that open new possibilities in water desalination and wastewater treatment. A KAUST team has found compounds of transition metals and carbon, known as a MXenes but pronounced "maxenes," can efficiently evaporate water using power supplied by the sun1. Renyuan Li, a Ph.D. student at KAUST, has investigated a MXene in which titanium and carbon combine with the formula Ti3C2. "This is a very exciting material," said Associate Professor Peng Wang, Li's supervisor at the KAUST Water Desalination and Reuse Center. Wang explains his excitement comes from their finding that Ti3C2 can trap the energy of sunlight to purify water by evaporation with an energy efficiency that is "state of the art." He says this clearly justifies more research toward practical applications. Other researchers had explored the ability of MXenes to act as electromagnetic shielding materials due to their ability to absorb wavelengths of electromagnetic radiation beyond the visible range. So the KAUST discovery began with a simple question. "We decided to investigate, what is the interaction with this MXene and sunlight?" Wang explained. With his group's focus on desalination technology, using the sun's energy to convert water into steam was an obvious target. The KAUST team's first observation was that Ti3C2 converts the energy of sunlight to heat with 100% efficiency. Also important, however, was that the sophisticated system developed during this research to measure light-to-heat conversion showed that various other materials, including carbon nanotubes and graphene, also achieved almost perfectly efficient conversion. "I suggest the focus of the field should now move away from finding new photothermal materials toward finding applications for the many perfect ones we now have," said Wang. To investigate MXene's possibilities in water purification, the researchers then fabricated a thin and flexible Ti3C2 membrane incorporating a polystyrene heat barrier to prevent the heat energy from escaping. This created a system that could float on water and evaporate some of the water with 84% efficiency at the illumination levels of natural sunlight. For Wang, the next challenge is how to move from this basic research finding toward practical applications. Wang hopes to break through what he calls "the 85% efficiency barrier," taking photo-thermal purification of water into new territory. In addition to maximizing the system's light-trapping capacity, the researchers want to investigate ways to capture the water vapor and yield a complete water purifying process. Wang is already in talks with one potential industrial partner.


News Article | June 19, 2017
Site: phys.org

Renyuan Li, a Ph.D. student at KAUST, has investigated a MXene in which titanium and carbon combine with the formula Ti3C2. "This is a very exciting material," said Associate Professor Peng Wang, Li's supervisor at the KAUST Water Desalination and Reuse Center. Wang explains his excitement comes from their finding that Ti3C2 can trap the energy of sunlight to purify water by evaporation with an energy efficiency that is "state of the art." He says this clearly justifies more research toward practical applications. Other researchers had explored the ability of MXenes to act as electromagnetic shielding materials due to their ability to absorb wavelengths of electromagnetic radiation beyond the visible range. So the KAUST discovery began with a simple question. "We decided to investigate, what is the interaction with this MXene and sunlight?" Wang explained. With his group's focus on desalination technology, using the sun's energy to convert water into steam was an obvious target. The KAUST team's first observation was that Ti3C2 converts the energy of sunlight to heat with 100% efficiency. Also important, however, was that the sophisticated system developed during this research to measure light-to-heat conversion showed that various other materials, including carbon nanotubes and graphene, also achieved almost perfectly efficient conversion. "I suggest the focus of the field should now move away from finding new photothermal materials toward finding applications for the many perfect ones we now have," said Wang. To investigate MXene's possibilities in water purification, the researchers then fabricated a thin and flexible Ti3C2 membrane incorporating a polystyrene heat barrier to prevent the heat energy from escaping. This created a system that could float on water and evaporate some of the water with 84% efficiency at the illumination levels of natural sunlight. For Wang, the next challenge is how to move from this basic research finding toward practical applications. Wang hopes to break through what he calls "the 85% efficiency barrier," taking photo-thermal purification of water into new territory. In addition to maximizing the system's light-trapping capacity, the researchers want to investigate ways to capture the water vapor and yield a complete water purifying process. Wang is already in talks with one potential industrial partner. Explore further: MOFs provide a better way to remove water from gas More information: Renyuan Li et al. MXene TiC: An Effective 2D Light-to-Heat Conversion Material, ACS Nano (2017). DOI: 10.1021/acsnano.6b08415


News Article | June 19, 2017
Site: www.cemag.us

Materials called transition-metal carbides have remarkable properties that open new possibilities in water desalination and wastewater treatment. A KAUST team has found compounds of transition metals and carbon, known as a MXenes but pronounced "maxenes," can efficiently evaporate water using power supplied by the sun1. Renyuan Li, a Ph.D. student at KAUST, has investigated a MXene in which titanium and carbon combine with the formula Ti3C2. "This is a very exciting material," said Associate Professor Peng Wang, Li's supervisor at the KAUST Water Desalination and Reuse Center. Wang explains his excitement comes from their finding that Ti3C2 can trap the energy of sunlight to purify water by evaporation with an energy efficiency that is "state of the art." He says this clearly justifies more research toward practical applications. Other researchers had explored the ability of MXenes to act as electromagnetic shielding materials due to their ability to absorb wavelengths of electromagnetic radiation beyond the visible range. So the KAUST discovery began with a simple question. "We decided to investigate, what is the interaction with this MXene and sunlight?" Wang explained. With his group's focus on desalination technology, using the sun's energy to convert water into steam was an obvious target. The KAUST team's first observation was that Ti3C2 converts the energy of sunlight to heat with 100% efficiency. Also important, however, was that the sophisticated system developed during this research to measure light-to-heat conversion showed that various other materials, including carbon nanotubes and graphene, also achieved almost perfectly efficient conversion. "I suggest the focus of the field should now move away from finding new photothermal materials toward finding applications for the many perfect ones we now have," said Wang. To investigate MXene's possibilities in water purification, the researchers then fabricated a thin and flexible Ti3C2 membrane incorporating a polystyrene heat barrier to prevent the heat energy from escaping. This created a system that could float on water and evaporate some of the water with 84% efficiency at the illumination levels of natural sunlight. For Wang, the next challenge is how to move from this basic research finding toward practical applications. Wang hopes to break through what he calls "the 85% efficiency barrier," taking photo-thermal purification of water into new territory. In addition to maximizing the system's light-trapping capacity, the researchers want to investigate ways to capture the water vapor and yield a complete water purifying process. Wang is already in talks with one potential industrial partner.


Ghebremichael K.,UNESCO IHE | Muchelemba E.,UNESCO IHE | Petrusevski B.,UNESCO IHE | Amy G.,Water Desalination and Reuse Center
Journal of Water Supply: Research and Technology - AQUA | Year: 2011

Electrochemically activated (ECA) water is being extensively studied and considered as an alternative to chlorine for disinfection. Some researchers claim that ECA is by and large a chlorine solution, while others claim the presence of reactive oxygen species such as ozone and hydroxyl radicals in addition to chlorine. This study compares sodium hypochlorite (NaOCl) and ECA in terms of disinfection efficacy, trihalomethanes (THMs) formation, stability and composition. The studies were carried out under different process conditions (pH 5,7 and 9, disinfectant concentrations of 2-5 mg/L and dissolved organic carbon (DOC) concentration of 2-4 mg/L). The results indicated that in the presence of low DOC (<2 mg/L) ECA showed better disinfection efficacy for Escherichia coli inactivation, formed lower THM and had better stability compared with NaOCl at both pH 5 and 7. Stability studies of stock solutions showed that over a period of 30 days, ECA decayed by only 5% while NaOCl decayed by 37.5% at temperatures of 4 °C. In a fresh ECA of 200 mg/L chlorine, about 5.3 mg/L ozone and 36.9 mg/L ClO2 were detected. The study demonstrates that ECA could be a suitable alternative to NaOCl where decentralized production and use are required. © IWA Publishing 2011.


PubMed | Imaging and Characterization Core Laboratory, Water Desalination and Reuse Center and King Abdullah University of Science and Technology
Type: Journal Article | Journal: ACS applied materials & interfaces | Year: 2016

Engineering and scaling-up new materials for better water desalination are imperative to find alternative fresh water sources to meet future demands. Herein, the fabrication of hydrophobic poly(ether imide) composite nanofiber membranes doped with novel ethylene-pentafluorophenylene-based periodic mesoporous organosilica nanoparticles is reported for enhanced and fouling resistant membrane distillation. Novel organosilica nanoparticles were homogeneously incorporated into electrospun nanofiber membranes depicting a proportional increase of hydrophobicity to the particle contents. Direct contact membrane distillation experiments on the organosilica-doped membrane with only 5% doping showed an increase of flux of 140% compared to commercial membranes. The high porosity of organosilica nanoparticles was further utilized to load the eugenol antimicrobial agent which produced a dramatic enhancement of the antibiofouling properties of the membrane of 70% after 24 h.


Le Roux J.,Water Desalination and Reuse Center | Nada N.,NOMAC | Khan M.T.,Water Desalination and Reuse Center | Croue J.-P.,Water Desalination and Reuse Center
Desalination | Year: 2015

The aim of this study was to assess the formation and the behavior of halogenated byproducts (regulated THMs and HAAs, as well as nitrogenous, brominated and iodinated DBPs including the emerging iodo-THMs) along the treatment train of full-scale desalination plants. One thermal multi-stage flash distillation (MSF) plant and two reverse osmosis (RO) plants located on the Red Sea coast of Saudi Arabia. DBPs formed during the prechlorination step were efficiently removed along the treatment processes (MSF or RO). Desalination plants fed with good seawater quality and using intermittent chlorine injection did not show high DBP formation and discharge. One RO plant with a lower raw water quality and using continuous chlorination at the intake formed more DBPs. In this plant, some non-regulated DBPs (e.g., dibromoacetonitrile and iodo-THMs) reached the product water in low concentrations (< 1.5 μg/L). Regulated THMs and HAAs were far below their maximum contamination levels set by the US Environmental Protection Agency. Substantial amounts of DBPs are disposed to the sea; low concentrations of DBPs were indeed detected in the water on shore of the desalination plants. © 2014 Elsevier B.V.


Zhang Z.,Water Desalination and Reuse Center | Yang X.,Water Desalination and Reuse Center | Hedhili M.N.,King Abdullah University of Science and Technology | Ahmed E.,Water Desalination and Reuse Center | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2014

In this article, we report that the combination of microwave heating and ethylene glycol, a mild reducing agent, can induce Ti3+ self-doping in TiO2. A hierarchical TiO2 nanotube array with the top layer serving as TiO2 photonic crystals (TiO2 NTPCs) was selected as the base photoelectrode. The self-doped TiO2 NTPCs demonstrated a 10-fold increase in visible-light photocurrent density compared to the nondoped one, and the optimized saturation photocurrent density under simulated AM 1.5G illumination was identified to be 2.5 mA cm-2 at 1.23 V versus reversible hydrogen electrode, which is comparable to the highest values ever reported for TiO2-based photoelectrodes. The significant enhancement of photoelectrochemical performance can be ascribed to the rational coupling of morphological and electronic features of the self-doped TiO 2 NTPCs: (1) the periodically morphological structure of the photonic crystal layer traps broadband visible light, (2) the electronic interband state induced from self-doping of Ti3+ can be excited in the visible-light region, and (3) the captured light by the photonic crystal layer is absorbed by the self-doped interbands. © 2013 American Chemical Society.


Karunakaran M.,King Abdullah University of Science and Technology | Nunes S.P.,Water Desalination and Reuse Center | Qiu X.,King Abdullah University of Science and Technology | Yu H.,King Abdullah University of Science and Technology | Peinemann K.-V.,King Abdullah University of Science and Technology
Journal of Membrane Science | Year: 2014

A simple and efficient approach towards the fabrication of a skinned membrane with highly ordered pores in the nanometer range is presented here. We successfully combined the self-assembly of PS-b-PEO block copolymer and water induced phase separation for the preparation of isoporous PS-b-PEO block copolymer membranes. We produced for the first time asymmetric isoporous PS-b-PEO membranes with a 100nm thin isoporous separating layer using water at room temperature as coagulant. This was possible by careful selection of the block lengths and the solvent system. FESEM, AFM and TEM measurements were employed to characterize the nanopores of membranes. The pure water fluxes were measured and the flux of membrane was exceptionally high (around 800Lm-2h-1bar-1). Protein rejection measurements were carried out for this membrane and the membrane had a retention of about 67% of BSA and 99% of γ-globulin. © 2013 Elsevier B.V.


Yu H.,King Abdullah University of Science and Technology | Qiu X.,King Abdullah University of Science and Technology | Nunes S.P.,Water Desalination and Reuse Center | Peinemann K.-V.,King Abdullah University of Science and Technology
Angewandte Chemie - International Edition | Year: 2014

The combination of nonsolvent-induced phase separation and the self-assembly of block copolymers can lead to asymmetric membranes with a thin highly ordered isoporous skin layer. The effective pore size of such membranes is usually larger than 15 nm. We reduced the pore size of these membranes by electroless gold deposition. We demonstrate that the pore sizes can be controlled precisely between 3 and 20 nm leading to a tunable sharp size discrimination in filtration processes. Besides fractionation of nanoparticles and biomaterials, controlled drug delivery is an attractive potential application. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zhang Z.,Water Desalination and Reuse Center | Zhang L.,Water Desalination and Reuse Center | Hedhili M.N.,King Abdullah University of Science and Technology | Zhang H.,Water Desalination and Reuse Center | Wang P.,Water Desalination and Reuse Center
Nano Letters | Year: 2013

A visible light responsive plasmonic photocatalytic composite material is designed by rationally selecting Au nanocrystals and assembling them with the TiO2-based photonic crystal substrate. The selection of the Au nanocrystals is so that their surface plasmonic resonance (SPR) wavelength matches the photonic band gap of the photonic crystal and thus that the SPR of the Au receives remarkable assistance from the photonic crystal substrate. The design of the composite material is expected to significantly increase the Au SPR intensity and consequently boost the hot electron injection from the Au nanocrystals into the conduction band of TiO2, leading to a considerably enhanced water splitting performance of the material under visible light. A proof-of-concept example is provided by assembling 20 nm Au nanocrystals, with a SPR peak at 556 nm, onto the photonic crystal which is seamlessly connected on TiO2 nanotube array. Under visible light illumination (>420 nm), the designed material produced a photocurrent density of ∼150 μA cm-2, which is the highest value ever reported in any plasmonic Au/TiO2 system under visible light irradiation due to the photonic crystal-assisted SPR. This work contributes to the rational design of the visible light responsive plasmonic photocatalytic composite material based on wide band gap metal oxides for photoelectrochemical applications. © 2012 American Chemical Society.

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