Waterborne pathogens are a major health threat and must be eliminated to guarantee safe usage of water for potable purposes. For this purpose, a new carbon-based nanomaterial composed of single-walled carbon nanotubes (SWCNTs) and iron oxides was constructed for bacterial inactivation. Owing to its magnetic properties, the SWCNT-iron oxide nanocomposite may serve as a reusable antimicrobial agent. The nanocomposite material exhibited high antimicrobial activity against Escherichia coli. Successful reuse of the nanocomposite material was achieved by washing with calcium chloride and distilled water, which restored its performance for several successive cycles. To investigate the cytotoxicity mechanisms of the nanocomposite material, we exposed it to single-gene knockout mutant strains of E. coli. Mutants bearing shorter lipopolysaccharide (LPS) layers in the outer membrane (ΔrfaC and ΔrfaG) demonstrated an increased sensitivity in comparison to the wildtype strain, exemplified in enhanced removal by the nanocomposite material. This finding suggests that the LPS acts as a protective shield against the nanocomposite material. Inactivation of mutants impaired in specific oxidative stress defense mechanisms (ΔsodA, ΔkatG and ΔsoxS) emphasized that oxidative stress plays a significant role in the inactivation mechanism of the nanocomposite. This study sheds light on the mechanisms of bacterial inactivation by carbon-based nanomaterials and advances their potential implementation for water disinfection.

Engel Maya    Yitzhak Hadar    Belkin Shimshon    Xinglin Lu    Menachem Elimelech     Benny Chefetz   

Environmental Science: Nano

2018

This study intends to reinvent classical Fenton chemistry by enabling the Fe(II)/Fe(III) redox cycle to occur on a newly developed FeOCl nanosheet catalyst for facile hydroxyl radical (OH) generation from HOactivation. This approach overcomes challenges such as low operating pH and large sludge production that have prevented a wider use of otherwise attractive Fenton chemistry for practical water treatment, in particular, for the destruction of recalcitrant pollutants through nonselective oxidation byOH. We demonstrate that FeOCl catalysts exhibit the highest performance reported in the literature forOH production and organic pollutant destruction over a wide pH range. We further elucidate the mechanism of rapid conversion between Fe(III) and Fe(II) in FeOCl crystals based on extensive characterizations. Given the low-cost raw material and simple synthesis and regeneration, FeOCl catalysts represent a critical advance toward application of iron-based advanced oxidation in real practice.

Sun Meng    Chu Chiheng    Geng Fanglan    Xinglin Lu    Jiuhui Qu    John charles Crittenden    Menachem Elimelech     Kim Jae-Hong   

Environmental Science and Technology Letters

2018

This study systematically compares the performance of osmotic membrane bioreactor – reverse osmosis (OMBR-RO) and conventional membrane bioreactor – reverse osmosis (MBR-RO) for advanced wastewater treatment and water reuse. Both systems achieved effective removal of bulk organic matter and nutrients, and almost complete removal of all 31 trace organic contaminants investigated. They both could produce high quality water suitable for recycling applications. During OMBR-RO operation, salinity build-up in the bioreactor reduced the water flux and negatively impacted the system biological treatment by altering biomass characteristics and microbial community structure. In addition, the elevated salinity also increased soluble microbial products and extracellular polymeric substances in the mixed liquor, which induced fouling of the forward osmosis (FO) membrane. Nevertheless, microbial analysis indicated that salinity stress resulted in the development of halotolerant bacteria, consequently sustaining biodegradation in the OMBR system. By contrast, biological performance was relatively stable throughout conventional MBR-RO operation. Compared to conventional MBR-RO, the FO process effectively prevented foulants from permeating into the draw solution, thereby significantly reducing fouling of the downstream RO membrane in OMBR-RO operation. Accumulation of organic matter, including humic- and protein-like substances, as well as inorganic salts in the MBR effluent resulted in severe RO membrane fouling in conventional MBR-RO operation.

Wenhai Luo    Phan Hop V.    Ming Xie    Faisal Hai    Price William E.    Menachem Elimelech     Nghiem L.   

Water Research

2017

Chanhee Boo    Menachem Elimelech    

Nature Nanotechnology

2017

Increasing demands for energy-efficient separations in applications ranging from water purification to petroleum refining, chemicals production, and carbon capture have stimulated a vigorous search for novel, high-performance separation membranes. Synthetic membranes suffer a ubiquitous, pernicious trade-off: highly permeable membranes lack selectivity and vice versa. However, materials with both high permeability and high selectivity are beginning to emerge. For example, design features from biological membranes have been applied to break the permeability-selectivity trade-off.We review the basis for the permeability-selectivity trade-off, state-of-the-art approaches to membrane materials design to overcome the trade-off, and factors other than permeability and selectivity that govern membrane performance and, in turn, influence membrane design.

Park Ho Bum    Kamcev Jovan    Lloyd Robeson    Menachem Elimelech     Benny dean Freeman   

Science

2017

Innovation in urban water systems is required to address the increasing demand for clean water due to population growth and aggravated water stress caused by water pollution, aging infrastructure, and climate change. Advances in materials science, modular water treatment technologies, and complex systems analyses, coupled with the drive to minimize the energy and environmental footprints of cities, provide new opportunities to ensure a resilient and safe water supply. We present a vision for enhancing efficiency and resiliency of urban water systems and discuss approaches and research needs for overcoming associated implementation challenges.

Katherine Zodrow    Qilin Li    Buono Regina M.    Chen Wei    Glen Daigger    Dueñas-Osorio    Menachem Elimelech     黄霞    Guibin Jiang    Jaehong Kim    Bruce Logan    David Sedlak    Paul Westerhoff    Pedro jose Álvarez   

Environmental Science and Technology

2017

In this study, we demonstrate the potential of an osmotic membrane bioreactor (OMBR)-membrane distillation (MD) hybrid system for simultaneous wastewater reuse and seawater desalination. A stable OMBR water flux of approximately 6 L mhwas achieved when using MD to regenerate the seawater draw solution. Water production by the MD process was higher than that from OMBR to desalinate additional seawater and thus account for draw solute loss due to the reverse salt flux. Amplicon sequencing on the Miseq Illumina platform evidenced bacterial acclimatization to salinity build-up in the bioreactor, though there was a reduction in the bacterial community diversity. In particular, 18 halophilic and halotolerant bacterial genera were identified with notable abundance in the bioreactor. Thus, the effective biological treatment was maintained during OMBR-MD operation. By coupling biological treatment and two high rejection membrane processes, the OMBR-MD hybrid system could effectively remove (>90%) all 30 trace organic contaminants of significant concern investigated here and produce high quality water. Nevertheless, further study is necessary to address MD membrane fouling due to the accumulation of organic matter, particularly protein- and humic-like substances, in seawater draw solution.

Wenhai Luo    Phan Hop V.    Guoxue Li    Faisal Hai    William Price    Menachem Elimelech     Nghiem L.   

Environmental Science and Technology

2017

Wastewater nutrient recovery holds promise for more sustainable water and agricultural industries. We critically review three emerging membrane processes - forward osmosis (FO), membrane distillation (MD) and electrodialysis (ED) - that can advance wastewater nutrient recovery. Challenges associated with wastewater nutrient recovery were identified. The advantages and challenges of applying FO, MD, and ED technologies to wastewater nutrient recovery are discussed, and directions for future research and development are identified. Emphasis is given to exploration of the unique mass transfer properties of these membrane processes in the context of wastewater nutrient recovery. We highlight that hybridising these membrane processes with existing nutrient precipitation process will lead to better management of and more diverse pathways for near complete nutrient recovery in wastewater treatment facilities.

Ming Xie    Shon Ho Kyong    Stephen Gray    Menachem Elimelech    

Water Research

2016

Heterogeneous electrode materials with hierarchical architectures promise to enable considerable improvement in future energy storage devices. In this study, we report on a tailored synthetic strategy used to create heterogeneous tungsten sulfide/oxide core-shell nanofiber materials with vertically and randomly aligned thorn-bush features, and we evaluate them as potential anode materials for high-performance Na-ion batteries. The WS (2 ≤ x ≤ 3, amorphous WS and crystalline WS) nanofiber is successfully prepared by electrospinning and subsequent calcination in a reducing atmosphere. To prevent capacity degradation of the WS anodes originating from sulfur dissolution, a facile post-thermal treatment in air is applied to form an oxide passivation surface. Interestingly, WO thorn bundles are randomly grown on the nanofiber stem, resulting from the surface conversion. We elucidate the evolving morphological and structural features of the nanofibers during post-thermal treatment. The heterogeneous thorn-bush nanofiber electrodes deliver a high second discharge capacity of 791 mAh g and improved cycle performance for 100 cycles compared to the pristine WS nanofiber. We show that this hierarchical design is effective in reducing sulfur dissolution, as shown by cycling analysis with counter Na electrodes.

Wonhee Ryu    Wilson Hope    Sungwoo Sohn    Li Jinyang    Tong Xiao    Shaulsky Evyatar    Schroers Jan    Menachem Elimelech     André Taylor   

ACS Nano

2016

Innovative approaches to prevent bacterial attachment and biofilm growth on membranes are critically needed to avoid decreasing membrane performance due to biofouling. In this study, we propose the fabrication of anti-biofouling thin-film composite membranes functionalized with graphene oxide-silver nanocomposites. In our membrane modification strategy, carboxyl groups on the graphene oxide-silver nanosheets are covalently bonded to carboxyl groups on the surface of thin-film composite membranes via a crosslinking reaction. Further characterization, such as scanning electron microscopy and Raman spectroscopy, revealed the immobilization of graphene oxide-silver nanocomposites on the membrane surface. Graphene oxide-silver modified membranes exhibited an 80% inactivation rate against attached . Pseudomonas aeruginosa cells. In addition to a static antimicrobial assay, our study also provided insights on the anti-biofouling property of forward osmosis membranes during dynamic operation in a cross-flow test cell. Functionalization with graphene oxide-silver nanocomposites resulted in a promising anti-biofouling property without sacrificing the membrane intrinsic transport properties. Our results demonstrated that the use of graphene oxide-silver nanocomposites is a feasible and attractive approach for the development of anti-biofouling thin-film composite membranes.

Faria Andreia F.    Liu Caihong    Ming Xie    François Perreault    Nghiem L.    马军    Menachem Elimelech    

Journal of Membrane Science

2016