Modeling of Hydrogen-Charged Notched Tensile Tests of an X70 Pipeline Steel with a Hydrogen-Informed Gurson Model.

Hydrogen can degrade the mechanical properties of steel components, which is commonly referred to as "hydrogen embrittlement" (HE). Quantifying the effect of HE on the structural integrity of components and structures remains challenging. The authors investigated an X70 pipeline steel through uncharged and hydrogen-charged (notched) tensile tests. This paper presents a combination of experimental results and numerical simulations using a micro-mechanics-inspired damage model. Four specimen geometries and three hydrogen concentrations (including uncharged) were targeted, which allowed for the construction of a fracture locus that depended on the stress triaxiality and hydrogen concentration. The multi-physical finite element model includes hydrogen diffusion and damage on the basis of the complete Gurson model. Hydrogen-Assisted degradation was implemented through an acceleration of the void nucleation process, as supported by experimental observations. The damage parameters were determined through inverse analysis, and the numerical results were in good agreement with the experimental data. The presented model couples micro-mechanical with macro-mechanical results and makes it possible to evaluate the damage evolution during hydrogen-charged mechanical tests. In particular, the well-known ductility loss due to hydrogen was captured well in the form of embrittlement indices for the different geometries and hydrogen concentrations. The limitations of the damage model regarding the stress state are discussed in this paper.

The influence of H2 partial pressure on biogenic palladium nanoparticle production assessed by single-cell ICP-mass spectrometry.

The production of biogenic palladium nanoparticles (bio-Pd NPs) is widely studied due to their high catalytic activity, which depends on the size of nanoparticles (NPs). Smaller NPs (here defined as <100 nm) are more efficient due to their higher surface/volume ratio. In this work, inductively coupled plasma-mass spectrometry (ICP-MS), flow cytometry (FCM) and transmission electron microscopy (TEM) were combined to obtain insight into the formation of these bio-Pd NPs. The precipitation of bio-Pd NPs was evaluated on a cell-per-cell basis using single-cell ICP-MS (SC-ICP-MS) combined with TEM images to assess how homogenously the particles were distributed over the cells. The results provided by SC-ICP-MS were consistent with those provided by "bulk" ICP-MS analysis and FCM. It was observed that heterogeneity in the distribution of palladium over an entire cell population is strongly dependent on the Pd2+ concentration, biomass and partial H2 pressure. The latter three parameters affected the particle size, ranging from 15.6 to 560 nm, and exerted a significant impact on the production of the bio-Pd NPs. The TEM combined with SC-ICP-MS revealed that the mass distribution for bacteria with high Pd content (144 fg Pd cell-1 ) indicated the presence of a large number of very small NPs (D50 = 15.6 nm). These results were obtained at high cell density (1 × 105 ± 3 × 104 cells µl-1 ) and H2 partial pressure (180 ml H2 ). In contrast, very large particles (D50 = 560 nm) were observed at low cell density (3 × 104 ± 10 × 102 cells µl-1 ) and H2 partial pressure (10-100 ml H2 ). The influence of the H2 partial pressure on the nanoparticle size and the possibility of size-tuned nanoparticles are presented.

Effect of Intercritical Temperature on the Microstructure and Mechanical Properties of a Ferritic-Martensitic Dual-Phase Low-Alloy Steel with Varying Nickel Content.

Dual-phase low-alloy steels combine a soft ferrite phase with a hard martensite phase to create desirable properties in terms of strength and ductility. Nickel additions to dual-phase low-alloy steels can increase the yield strength further and lower the transformation temperatures, allowing for microstructure refining. Determining the correct intercritical annealing temperature as a function of nickel content is paramount, as it defines the microstructure ratio between ferrite and martensite. Likewise, quantifying the influence of nickel on the intercritical temperature and its synergistic effect with the microstructure ratio on mechanical properties is vital to designing dual-phase steels suitable for corrosive oil and gas services as well as hydrogen transport and storage applications. In this work, we used a microstructural design to develop intercritical annealing heat treatments to obtain dual-phase ferritic-martensitic low-alloy steels. The intercritical annealing and tempering temperatures and times were targeted to achieve three different martensite volume fractions as a function of nickel content, with a nominal content varying between 0, 1, and 3-wt% Ni. Mechanical properties were characterized using tensile testing and microhardness measurements. Additionally, the microstructure was studied using scanning electron microscopy coupled with electron backscatter diffraction analysis. Tensile strength increased with increasing martensite ratio and nickel content, with a further grain refinement effect found in the 3-wt% Ni steel. The optimal heat treatment parameters for oil and gas and hydrogen transport applications are discussed.

Combined Gold Recovery and Nanoparticle Synthesis in Microbial Systems Using Fractional Factorial Design.

Green synthesis of gold nanoparticles (AuNPs) using microorganisms has been generally studied aiming for high-yield production and morphologies appropriated for various applications, such as bioremediation, (bio)sensors, and (bio)catalysis. Numerous approaches showed the individual effect of factors influencing the synthesis of AuNPs with limited analysis of the governing factors enhancing the production and desired quality of the precipitates. This study proposes a fractional-factorial design to investigate the simultaneous influence of seven environmental factors (cell concentration, temperature, anoxic/oxic conditions, pH, gold concentration, electron donor type, and bacterial species) on the recovery yield and synthesis of targeted AuNPs. Various sizes and morphologies of the AuNPs were obtained by varying the environmental factors studied. The factors with significant effects (i.e., 0.2 mM Au and pH 5) were selected according to statistical analysis for optimal removal of 88.2 ± 3.5% of gold and with the production of valuable 50 nm AuNPs, which are known for their enhanced sensitivity. Implications of the cytochrome-C on the bacterial mechanisms and the provision of electron donors via an electrochemical system are further discussed. This study helps develop gold recovery and nanoparticle synthesis methods, focusing on the determining factor(s) for efficient, low-cost, green synthesis of valuable materials.

Effect of Phosphine on Coke Formation during Steam Cracking of Propane.

In conventional steam cracking feedstocks, contaminants such as sulfur, phosphine, and heavy metal components, present in trace levels, are believed to affect coke formation on high temperature alloys. To gain an understanding of the role of phosphine coking rates on 25/35, CrNi and Al-containing reactor materials were determined in a plug flow reactor during cracking of a propane feedstock doped with ppb levels of PH3 in the presence of DMDS. The presence of phosphine decreased the asymptotic coking rates by more than 20%, while it had a smaller influence on the catalytic coking rate. The coking rate was more severely reduced for the 25/35 CrNi alloy in comparison to the Al-containing alloy. The ppm levels of phosphine did not affect the olefin yields nor the production of undesired carbon monoxide. The morphology of the coked alloys were studied using an off-line Scanning Electron Microscope with Energy Dispersive X-ray detector (SEM with EDX) images of coked coupons. Two types of coke morphology are observed, i.e., filamentous coke with DMDS as an additive and globular coke in the presence of phosphine. The effect of phosphine on the material has a positive impact on the oxide scale homogeneity of 25/35 CrNi alloy, whereas the Al-containing alloy remained unchanged.

Biological activity and antimicrobial property of Cu/a-C:H nanocomposites and nanolayered coatings on titanium substrates.

Infection associated with titanium based implants remains the most serious problem in implant surgery hence it is important to find optimal strategies to prevent infections. In the present study, we investigated the surface properties, antibacterial activity and biocompatibility of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) film containing copper nanoparticles (CuNPs) deposited on Ti discs via a gas aggregation cluster source. Three different Cu/a-C:H coatings with approximately the same amount of embedded CuNPs with and without barrier a-C:H layer were fabricated. The obtained results revealed that different structures of the produced coatings have significantly different release rates of Cu ions from the coatings into the aqueous media. This subsequently influences the antibacterial efficiency and osteoblast cell viability of the treated coatings. Coatings with the highest number of CuNPs resulted in excellent antibacterial activity exhibiting approximately 4 log reduction of E.coli and S.aureus after 24 h incubation. The cytotoxicity study revealed that after 7 day cell seeding, even the coating with the highest Cu at.% (4 at.%) showed a cell viability of Ì´90%. Consequently, the coating, formed with a properly tailored number of CuNPs and a-C:H barrier thickness offer a strong antibacterial effect without any harm to osteoblast cells.

Effect of speciation and composition on the kinetics and precipitation of arsenic sulfide from industrial metallurgical wastewater.

Precipitation of arsenic as As2S3 produces little waste sludge, has the potential for low chemical consumption and for selective metal(loid) removal. In this study, arsenic removal from acidic (pH 2), metallurgical wastewater was tested in industrially relevant conditions. Sulfides added at a S:As molar ratio of 2.5 and 5 resulted in removal of 99% and 84% of As(III) and As(V). Precipitation of As2S3 from the As(III) and industrial wastewater containing 17% As(V) was nearly instantaneous. For the synthetic As(V) solution, reduction to As(III) was the rate limiting step. At a S:As ratio of 20 and an observed removal rate (k2 = 4.8 (mol L-1) h-1), two hours were required to remove of 93% of arsenic from a 1 g As L-1 solution. In the case of As(V) in industrial samples this time lag was not observed, showing that components in the industrial wastewater affected the removal and reduction of arsenate. Speciation also affected flocculation and coagulation characteristics of As2S3 particles: As(V) reduction resulted in poor coagulation and flocculation. Selective precipitation of arsenic was possible, but depended on speciation, S:As ratio and other metals present.

Combinatorial effects of coral addition and plasma treatment on the properties of chitosan/polyethylene oxide nanofibers intended for bone tissue engineering.

Given the complex calcified nature of the fibrous bone tissue, a combinatorial approach merging specific topographical/biochemical cues was adopted to design bone tissue-engineered scaffolds. Coral having a Ca-enriched structure was added to electrospun chitosan (CS)/polyethylene oxide (PEO) nanofibers that were subjected to plasma surface modifications using a medium pressure Ar, air or N2 dielectric barrier discharge. Plasma incorporated oxygen- and nitrogen-containing functionalities onto the nanofibers surface thus enhancing their wettability. Plasma treatment enhanced the performance of osteoblasts and the interplay between plasma treatment and coral was shown to boost initial cell adhesion. The fibers capacity to trigger calcium phosphate growth was predicted via immersion in simulated body fluid. Globular carbonate apatite nanocrystals were deposited on plasma-treated CS/PEO NFs while thicker layers of flake-like nanocrystals were covering plasma-treated Coral/CS/PEO fibers without blocking the interfibrous pores. Overall, the exclusive multifaceted plasma-treated Coral/CS/PEO nanofibers are believed to revolutionize the bone tissue engineering field.

Fabrication of Microporous Coatings on Titanium Implants with Improved Mechanical, Antibacterial, and Cell-Interactive Properties.

The success of an orthopedic implant therapy depends on successful bone integration and the prevention of microbial infections. In this work, plasma electrolytic oxidation (PEO) was performed to deposit TiO2 coatings enriched with Ca, P, and Ag on titanium to improve its surface properties and antibacterial efficacy while maintaining normal biological functions and thus to enhance the performance of orthopedic implants. After PEO treatment, the surface of Ti was converted to anatase and rutile TiO2, hydroxyapatite, and calcium titanate phases. The presence of these crystalline phases was further increased with an increased Ag content in the coatings. The developed coatings also exhibited a more porous morphology with an improved surface wettability, roughness, microhardness, and frictional coefficient. In vitro antibacterial assays indicated that the Ag-doped coatings can significantly prevent the growth of both Staphylococcus aureus and Escherichia coli by releasing Ag+ ions, and the ability to prevent these bacteria was enhanced by increasing the Ag content in the coatings, resulting in a maximal 6-log reduction of E. coli and a maximal 5-log reduction of S. aureus after 24 h of incubation. Moreover, the in vitro cytocompatibility evaluation of the coatings showed that the osteoblast (MC3T3) cell integration on the PEO-based coatings was greatly improved compared to untreated Ti and no notable impact on their cytocompatibility was observed on increasing the amount of Ag in the coating. In conclusion, the coating with favorable physicochemical and mechanical properties along with controlled silver ion release can offer an excellent antibacterial performance and osteocompatibility and can thus become a prospective coating strategy to face current challenges in orthopedics.

Investigation of Ag/a-C:H Nanocomposite Coatings on Titanium for Orthopedic Applications.

One of the leading causes of failure for any bone implant is implant-associated infections. The implant-bone interface is in fact the crucial site of infection where both the microorganisms and cells compete to populate the newly introduced implant surface. Most of the work dealing with this issue has focused on the design of implant coatings capable of preventing infection while ignoring cell proliferation or vice versa. The present study is therefore focused on investigating the antibacterial and biological properties of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) matrix containing silver nanoparticles (AgNPs). a-C:H coatings with varying silver concentrations were generated directly on medical grade titanium substrates using a combination of a gas aggregation source (GAS) and a plasma-enhanced chemical vapor deposition (PE-CVD) process. The obtained results revealed that the surface silver content increased from 1.3 at % to 5.3 at % by increasing the used DC magnetron current in the GAS from 200 to 500 mA. The in vitro antibacterial assays revealed that the nanocomposites with the highest number of silver content exhibited excellent antibacterial activities resulting in a 6-log reduction of Escherichia coli and a 4-log reduction of Staphylococcus aureus after 24 h of incubation. An MTT assay, fluorescence live/dead staining, and SEM microscopy observations of MC3T3 cells seeded on the uncoated and coated Ti substrates also showed that increasing the amount of AgNPs in the nanocomposites had no notable impact on their cytocompatibility, while improved cell proliferation was especially observed for the nanocomposites possessing a low amount of AgNPs. These controllable Ag/a-C:H nanocomposites on Ti substrates, which simultaneously provide an excellent antibacterial performance and good biocompatibility, could thus have promising applications in orthopedics and other biomedical implants.

Evaluation of a Ti-Base Alloy as Steam Cracking Reactor Material.

Low-coking reactor material technologies are key for improving the performance and sustainability of steam crackers. In an attempt to appraise the coking performance of an alternative Ti-base alloy during ethane steam cracking, an experimental study was performed in a jet stirred reactor under industrially relevant conditions using thermogravimetry (Tgasphase = 1173 K, Ptot = 0.1 MPa, XC2H6 = 70%, and dilution δ = 0.33 kgH2O/kgHC). Initially, a typical pretreatment used for Fe-Ni-Cr alloys was utilized and compared with a pretreatment at increased temperature, aiming at better surface oxidation and thus suppressing coke formation. The results revealed a decrease in coking rates upon high temperature pretreatment of the Ti-base alloy, however, its coking performance was significantly worse compared to the typically used Fe-Ni-Cr alloys, and carbon oxides formation increased by a factor of 30 or more. Moreover, the analyzed coupons showed crack propagation after coking/decoking and cooling down to ambient temperature. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy indicated that the prompt and unsystematic oxidation of the surface and bulk caused observable crack initiation and propagation due to alloy brittleness. Hence, the tested Ti-base alloy cannot be considered an industrially noteworthy steam cracking reactor alloy.

Effect of Long-Term High Temperature Oxidation on the Coking Behavior of Ni-Cr Superalloys.

The service time of an industrial cracker is strongly dependent on the long-term coking behavior and microstructure stability of the reactor coil alloy. Super alloys are known to withstand temperatures up to even 1400 K. In this work, several commercially available alloys have been first exposed to a long term oxidation at 1423 K for 500 h, so-called metallurgic aging. Subsequently, their coking behavior was evaluated in situ in a thermogravimetric setup under ethane steam cracking conditions (Tgasphase = 1173 K, Ptot = 0.1 MPa, XC2H6 = 70%, continuous addition of 41 ppmw S/HC of DMDS, dilution δ = 0.33 kgH2O/kgHC) and compared with their unaged coking behavior. The tested samples were also examined using scanning electron microscopy and energy diffractive X-ray for surface and cross-section analysis. The alloys characterized by increased Cr-Ni content or the addition of Al showed improved stability against bulk oxidation and anti-coking behavior after application of metallurgic aging due to the formation of more stable oxides on the top surface.

Understanding the Interaction between a Steel Microstructure and Hydrogen.

The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels, i.e., high-strength low-alloy (HSLA), transformation-induced plasticity (TRIP) and dual phase (DP) is first studied. The highest hydrogen embrittlement resistance is obtained for HSLA steel due to the presence of Ti- and Nb-based precipitates. Generic Fe-C lab-cast alloys consisting of a single phase, i.e., ferrite, bainite, pearlite or martensite, and with carbon contents of approximately 0, 0.2 and 0.4 wt %, are further considered to simplify the microstructure. Finally, the addition of carbides is investigated in lab-cast Fe-C-X alloys by adding a ternary carbide forming element to the Fe-C alloys. To understand the H/material interaction, a comparison of the available H trapping sites, the H pick-up level and the H diffusivity with the H-induced mechanical degradation or H-induced cracking is correlated with a thorough microstructural analysis.

Metal losses in pyrometallurgical operations - A review.

Nowadays, a higher demand on a lot of metals exists, but the quantity and purity of the ores decreases. The amount of scrap, on the other hand, increases and thus, recycling becomes more important. Besides recycling, it is also necessary to improve and optimize existing processes in extractive and recycling metallurgy. One of the main difficulties of the overall-plant recovery are metal losses in slags, in both primary and secondary metal production. In general, an increased understanding of the fundamental mechanisms governing these losses could help further improve production efficiencies. This review aims to summarize and evaluate the current scientific knowledge concerning metal losses and pinpoints the knowledge gaps. First, the industrial importance and impact of metal losses in slags will be illustrated by several examples from both ferrous and non-ferrous industries. Throughout the remainder of this review, the main focus will be put on the particular issues in copper industry. In a second section, the different types of metal losses in slags will be discussed. Generally, metal losses in slags can be subdivided into two types: chemical losses and physical losses. The fundamental insights concerning the responsible mechanisms will be discussed for each type. Subsequently, an overview of the most frequently used techniques for research investigations of the losses will be given. In a fourth section, a more detailed overview will be given on the post-processing treatment of metal-containing slags, i.e. performing slag cleaning operations. The most frequently applied methods will be discussed.

Removal of Arsenic (V) from Aqueous Solutions Using Chitosan-Red Scoria and Chitosan-Pumice Blends.

In different regions across the globe, elevated arsenic contents in the groundwater constitute a major health problem. In this work, a biopolymer chitosan has been blended with volcanic rocks (red scoria and pumice) for arsenic (V) removal. The effect of three blending ratios of chitosan and volcanic rocks (1:2, 1:5 and 1:10) on arsenic removal has been studied. The optimal blending ratio was 1:5 (chitosan: volcanic rocks) with maximum adsorption capacity of 0.72 mg/g and 0.71 mg/g for chitosan: red scoria (Ch-Rs) and chitosan: pumice (Ch-Pu), respectively. The experimental adsorption data fitted well a Langmuir isotherm (R² > 0.99) and followed pseudo-second-order kinetics. The high stability of the materials and their high arsenic (V) removal efficiency (~93%) in a wide pH range (4 to 10) are useful for real field applications. Moreover, the blends could be regenerated using 0.05 M NaOH and used for several cycles without losing their original arsenic removal efficiency. The results of the study demonstrate that chitosan-volcanic rock blends should be further explored as a potential sustainable solution for removal of arsenic (V) from water.

Adsorption of As(III) versus As(V) from aqueous solutions by cerium-loaded volcanic rocks.

Contamination of drinking water with arsenic causes severe health problems in various world regions. Arsenic exists predominantly as As(III) and As(V) depending on the prevailing redox conditions of the environment. Most of the techniques developed for treating As(V) are not very effective for As(III), which is more toxic and mobile than As(V). In this study, novel cerium-loaded pumice (Ce-Pu) and red scoria (Ce-Rs) adsorbents were developed to remove both As(III) and As(V) ions from water. The Ce-Pu and Ce-Rs adsorbents were characterized using ICP-OES, EDX, and SEM. The experimental equilibrium sorption data fitted well Freundlich and Dubinin-Radushkevich (D-R) isotherms. The adsorption was very fast and reached an equilibrium within 2 h. Both Ce-Rs and Ce-Pu showed high As(III) and As(V) removal efficiency in a wide pH range between 3 and 9, which is an important asset for practical applications. The Ce-Pu and Ce-Rs adsorbents can be recycled and used up to three adsorption cycles without significant loss of their original efficiency. Accordingly, Ce-Pu and Ce-Rs seem to be suitable for removal of arsenic from aqueous systems.

Use of filtration techniques to study environmental fate of engineered metallic nanoparticles: Factors affecting filter performance.

We examined the filtration of aqueous suspensions of negatively charged (citrate-stabilized) Ag (14.5±1.1nm) and positively charged CeO2 (7.3±1.4nm) engineered nanoparticles (ENPs) via different filtration techniques such as paper filtration, micro- and ultrafiltration, and evaluated the impact of initial concentration, matrix composition, and filter type and (pre-)treatment, on nanoparticle retention. Solutions of Ag+ and Ce3+ ions were tested in the same way. Significant retention of nanoparticles was observed even for filters having considerably larger pore sizes than the ENPs size. Retention also seemingly increased with decreasing initial concentration, but generally decreased upon preconditioning of the paper or membrane filters with diluted nitric acid or 0.1M Cu(NO3)2, respectively. In ultrapure water, retention appeared to depend more on particle characteristics than on a membrane type. However, in 2mM KNO3, NaCl, or CaCl2, more significant differences in recovery were observed between different membrane materials. Additionally, background electrolytes might reduce nanoparticle or ionic retention, but could also affect their (colloidal) stability, e.g., resulting in enhanced retention of Ag ENPs and Ag+ ions in chloride-containing matrices. Results from centrifugal ultrafiltration recommend using 10kDa filters for nanoparticle removal from the solution, and suggest these filters might potentially be suitable to differentiate between (nano)particulate and dissolved species.

Platinum recovery from industrial process streams by halophilic bacteria: Influence of salt species and platinum speciation.

The increased use and criticality of platinum asks for the development of effective low-cost strategies for metal recovery from process and waste streams. Although biotechnological processes can be applied for the valorization of diluted aqueous industrial streams, investigations considering real stream conditions (e.g., high salt levels, acidic pH, metal speciation) are lacking. This study investigated the recovery of platinum by a halophilic microbial community in the presence of increased salt concentrations (10-80 g L-1), different salt matrices (phosphate salts, sea salts and NH4Cl) and a refinery process stream. The halophiles were able to recover 79-99% of the Pt at 10-80 g L-1 salts and at pH 2.3. Transmission electron microscopy suggested a positive correlation between intracellular Pt cluster size and elevated salt concentrations. Furthermore, the halophiles recovered 46-95% of the Pt-amine complex Pt[NH3]42+ from a process stream after the addition of an alternative Pt source (K2PtCl4, 0.1-1.0 g L-1 Pt). Repeated Pt-tetraamine recovery (from an industrial process stream) was obtained after concomitant addition of fresh biomass and harvesting of Pt saturated biomass. This study demonstrates how aqueous Pt streams can be transformed into Pt rich biomass, which would be an interesting feed of a precious metals refinery.

Biomass retention on electrodes rather than electrical current enhances stability in anaerobic digestion.

Anaerobic digestion (AD) is a well-established technology for energy recovery from organic waste streams. Several studies noted that inserting a bioelectrochemical system (BES) inside an anaerobic digester can increase biogas output, however the mechanism behind this was not explored and primary controls were not executed. Here, we evaluated whether a BES could stabilize AD of molasses. Lab-scale digesters were operated in the presence or absence of electrodes, in open (no applied potential) and closed circuit conditions. In the control reactors without electrodes methane production decreased to 50% of the initial rate, while it remained stable in the reactors with electrodes, indicating a stabilizing effect. After 91 days of operation, the now colonized electrodes were introduced in the failing AD reactors to evaluate their remediating capacity. This resulted in an immediate increase in CH4 production and VFA removal. Although a current was generated in the BES operated in closed circuit, no direct effect of applied potential nor current was observed. A high abundance of Methanosaeta was detected on the electrodes, however irrespective of the applied cell potential. This study demonstrated that, in addition to other studies reporting only an increase in methane production, a BES can also remediate AD systems that exhibited process failure. However, the lack of difference between current driven and open circuit systems indicates that the key impact is through biomass retention, rather than electrochemical interaction with the electrodes.

Trace organic solutes in closed-loop forward osmosis applications: influence of membrane fouling and modeling of solute build-up.

In this study, trace organics transport in closed-loop forward osmosis (FO) systems was assessed. The FO systems considered, consisted of an FO unit and a nanofiltration (NF) or reverse osmosis (RO) unit, with the draw solution circulating between both units. The rejection of trace organics by FO, NF and RO was tested. It was found that the rejection rates of FO were generally comparable with NF and lower than RO rejection rates. To assess the influence of fouling in FO on trace organics rejection, FO membranes were fouled with sodium alginate, bovine serum albumin or by biofilm growth, after which trace organics rejection was tested. A negative influence of fouling on FO rejection was found which was limited in most cases, while it was significant for some compounds such as paracetamol and naproxen, indicating specific compound-foulant interactions. The transport mechanism of trace organics in FO was tested, in order to differentiate between diffusive and convective transport. The concentration of trace organics in the final product water and the build-up of trace organics in the draw solution were modeled assuming the draw solution was reconcentrated by NF/RO and taking into account different transport mechanisms for the FO membrane and different rejection rates by NF/RO. Modeling results showed that if the FO rejection rate is lower than the RO rejection rate (as is the case for most compounds tested), the added value of the FO-RO cycle compared to RO only at steady-state was small for diffusively and negative for convectively transported trace organics. Modeling also showed that trace organics accumulate in the draw solution.