Nanofiltration and reverse osmosis for defluoridation: The role of inorganic carbon

Fluoride (F) concentrations above the World Health Organization (WHO) guideline value of 1.5 mg/L in drinking water can lead to serious health problems such as dental fluorosis and skeletal fluorosis. High F levels are often associated with carbonaceous (i.e. high inorganic carbon (IC)) type waters. The high fluoride concentrations in natural waters often occur in arid regions where no sufficient quantity of alternative water is readily available due to scarcity of water, consequently, treatment is the best option to provide safe drinking water. Nanofiltration (NF) and reverse osmosis (RO) are promising and appropriate membrane technologies for defluoridation due to their high fluoride removal efficiency and their ability to simultaneously remove a wide range of other inorganic and organic contaminants 1. Different ions can have various effects on F removal by NF/RO 2. IC in natural waters is present as carbonate ion (CO32-), bicarbonate ion (HCO3-), carbonic acid (H2CO3), and carbon dioxide (CO2) depending on the pH. Due to the different characteristics of these species it is important to study the impact of IC on F retention mechanisms at different pH. In this study the mechanisms of IC species impact on F retention by NF/RO has been investigated as a function of pH.Two commercial NF and RO membranes, BW30 and NF270 respectively from DOW Chemicals (USA) were used. Synthetic waters were prepared using realistic ranges of F and IC for carbonaceous waters found for example in the fluoride rich waters in Tanzania. Feed concentration of F and IC were 50 mgF/L as NaF and 500 mgC/L as NaHCO3 respectively. Visual MINTEQ software was used to predict the speciation of IC and F at various pH. Figure 1 indicates that the permeate F concentrations were high (35-47 mg/L) at pH 2 where F existed mainly as uncharged HF. At pH 8 and 11, when there was a change in speciation to F ion and the membranes were negatively charged, permeate F concentrations decreased drastically. Permeate F concentrations for the RO BW30 membrane were lower than that of the relatively open NF270. BW30 removed fluoride to meet WHO guideline value of 1.5 mg/L at pH 11 up to about 40% recovery, while NF270 did not achieve the guideline value at any pH studied. In the past, BW30 had achieved the guideline value at pH 8 but with relatively low electrical conductivity (EC) of about 2000 µS/cm. However, in the current study the high IC concentration resulted in high EC (3600 µS/cm) and high osmotic pressure. This led to a decrease in the net driving pressure thus facilitating the diffusion of F through the membrane 3. The predominant IC species at pH 2 was H2CO3. This resulted in very low feed IC concentrations (1-5 mg C/L, less than intended 500 mgC/L) at pH 2 due to degassing (H2CO3 decomposes to CO2). Monovalent HCO3- predominated at pH 8 and easily permeated the NF270 membrane. At pH 11, MINTEQ predicted divalent CO32- as the predominant IC species and permeate IC was lower than at pH 8 for the NF270. For the BW30 membrane, IC concentrations in the permeates were lower than the NF270 and impact of IC speciation was not observed. This suggests that the main retention mechanism of IC by the NF270 is charged repulsion and that of the RO BW30 membrane is size exclusion. Please click Additional Files below to see the full abstract

Comparison of Photocatalytic Membrane Reactor Types for the Degradation of an Organic Molecule by TiO₂-Coated PES Membrane

Photocatalytic membrane reactors with different configurations (design, flow modes and light sources) have been widely applied for pollutant removal. A thorough understanding of the contribution of reactor design to performance is required to be able to compare photocatalytic materials. Reactors with different flow designs are implemented for process efficiency comparisons. Several figures-of-merit, namely adapted space-time yield (STY) and photocatalytic space-time yield (PSTY), specific energy consumption (SEC) and degradation rate constants, were used to assess the performance of batch, flow-along and flow-through reactors. A fair comparison of reactor performance, considering throughput together with energy efficiency and photocatalytic activity, was only possible with the modified PSTY. When comparing the three reactors at the example of methylene blue (MB) degradation under LED irradiation, flow-through proved to be the most efficient design. PSTY1/PSTY2 values were approximately 10 times higher than both the batch and flow-along processes. The highest activity of such a reactor is attributed to its unique flow design which allowed the reaction to take place not only on the outer surface of the membrane but also within its pores. The enhancement of the mass transfer when flowing in a narrow space (220 nm in flow-through) contributes to an additional MB removal. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Investigation of the reaction kinetics of photocatalytic pollutant degradation under defined conditions with inkjet-printed TiO2_{2} films – from batch to a novel continuous-flow microreactor

Pollutants accumulating in natural and drinking water systems can cause severe effects to the environment and living organisms. Photocatalysis is a promising option to degrade such pollutants. When immobilizing the photocatalyst, additional catalyst separation steps can be avoided. Among various reactor types, the use of microreactors in photocatalysis has proven advantageous regarding process intensification. However, so far the local conditions are not well understood and described in literature and there is little quantitative understanding of the relevant phenomena. In this work, inkjet-printing was used to immobilize TiO$_{2}$ as a thin film with a precisely tuneable thickness and catalyst loading. In a batch reactor, the degradation of rhodamine B (RhB) as a model pollutant was performed for different initial concentrations and catalyst layer thicknesses. By employing the Langmuir–Hinshelwood model and a light irradiation model, the kinetic parameters were determined. The influence of the light intensity at different positions inside the immobilized photocatalyst on the reaction kinetics is quantified. RhB degradation was tested under defined operational conditions using an in-house developed continuous-flow microreactor with advanced fiber optics for precise light introduction. The models derived from batch experiments were used to simulate the degradation in the continuous-flow microreactor. Results show that the simulation allows prediction of the performance with less than 20% deviation to the experimental data. An analysis of mass transport effects on the reaction rate indicates that external mass transfer is a limiting factor in the microreactor experiment. This study further demonstrates the potential of the new reactor system (microreactor, fiber optics and printed catalyst) for detailed investigations on photocatalytic reaction kinetics

Investigation of the reaction kinetics of photocatalytic pollutant degradation under defined conditions with inkjet-printed TiO2_{2} films – from batch to a novel continuous-flow microreactor

Pollutants accumulating in natural and drinking water systems can cause severe effects to the environment and living organisms. Photocatalysis is a promising option to degrade such pollutants. When immobilizing the photocatalyst, additional catalyst separation steps can be avoided. Among various reactor types, the use of microreactors in photocatalysis has proven advantageous regarding process intensification. However, so far the local conditions are not well understood and described in literature and there is little quantitative understanding of the relevant phenomena. In this work, inkjet-printing was used to immobilize TiO$_{2}$ as a thin film with a precisely tuneable thickness and catalyst loading. In a batch reactor, the degradation of rhodamine B (RhB) as a model pollutant was performed for different initial concentrations and catalyst layer thicknesses. By employing the Langmuir–Hinshelwood model and a light irradiation model, the kinetic parameters were determined. The influence of the light intensity at different positions inside the immobilized photocatalyst on the reaction kinetics is quantified. RhB degradation was tested under defined operational conditions using an in-house developed continuous-flow microreactor with advanced fiber optics for precise light introduction. The models derived from batch experiments were used to simulate the degradation in the continuous-flow microreactor. Results show that the simulation allows prediction of the performance with less than 20% deviation to the experimental data. An analysis of mass transport effects on the reaction rate indicates that external mass transfer is a limiting factor in the microreactor experiment. This study further demonstrates the potential of the new reactor system (microreactor, fiber optics and printed catalyst) for detailed investigations on photocatalytic reaction kinetics

Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems

Over the last few years, extraordinary advances in experimental and theoretical tools have allowed us to monitor and control matter at short time and atomic scales with a high degree of precision. An appealing and challenging route toward engineering materials with tailored properties is to find ways to design or selectively manipulate materials, especially at the quantum level. To this end, having a state-of-the-art ab initio computer simulation tool that enables a reliable and accurate simulation of light-induced changes in the physical and chemical properties of complex systems is of utmost importance. The first principles real-space-based Octopus project was born with that idea in mind, i.e., to provide a unique framework that allows us to describe non-equilibrium phenomena in molecular complexes, low dimensional materials, and extended systems by accounting for electronic, ionic, and photon quantum mechanical effects within a generalized time-dependent density functional theory. This article aims to present the new features that have been implemented over the last few years, including technical developments related to performance and massive parallelism. We also describe the major theoretical developments to address ultrafast light-driven processes, such as the new theoretical framework of quantum electrodynamics density-functional formalism for the description of novel light–matter hybrid states. Those advances, and others being released soon as part of the Octopus package, will allow the scientific community to simulate and characterize spatial and time-resolved spectroscopies, ultrafast phenomena in molecules and materials, and new emergent states of matter (quantum electrodynamical-materials).This work was supported by the European Research Council (Grant No. ERC-2015-AdG694097), the Cluster of Excellence “Advanced Imaging of Matter” (AIM), Grupos Consolidados (IT1249-19), and SFB925. The Flatiron Institute is a division of the Simons Foundation. X.A., A.W., and A.C. acknowledge that part of this work was performed under the auspices of the U.S. Department of Energy at Lawrence Livermore National Laboratory under Contract No. DE-AC52-07A27344. J.J.-S. gratefully acknowledges the funding from the European Union Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant Agreement No. 795246-StrongLights. J.F. acknowledges financial support from the Deutsche Forschungsgemeinschaft (DFG Forschungsstipendium FL 997/1-1). D.A.S. acknowledges University of California, Merced start-up funding.Peer reviewe

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Recycled and desalinated water: consumers’ associations, and the influence of affect and disgust on willingness to use

Traditional water sources are increasingly coming under pressure from urbanization, population and industrial growth as well as climate variability and alternatives such as desalinated and recycled water will need to be considered in the future. However, available data indicate that consumers are apprehensive about these alternative water sources, with many reactions centered on disgust. It is not clear though, whether trait or state disgust is responsible for these disgust reactions. Secondly, the associations the public has with desalinated and recycled water are not well described, even though knowledge of these associations would provide the holistic understanding required for addressing perceptions. Using respondents from Australia and South Africa, therefore, this study investigated the associations people have with recycled and desalinated water, as well as the influence of affect, institutional trust, cultural/religious beliefs, water scarcity, and demographic variables, on willingness to use (WTU) these waters. The results show that whereas recycled water is associated with negative affect from notions of disgust, desalinated water is often thought of in terms of minerals, or as “simply water”. We also found that affect was the most significant predictor, and that state disgust as well as trait disgust influenced WTU. Together these data suggest that disgust-related rejection of is likely due to the disgust elicited by the waters rather than disgust-proneness of individuals. It is plausible, therefore, that efforts to induce positive affect through making salient positive associations e.g. NEWater in Singapore, may increase WTU

Natural Organics Removal using Membranes

Membrane processes are increasingly used in water treatment. Experiments were performed using stirred cell equipment, polymeric membranes and synthetic surface water containing natural organics, inorganic colloids and their aggregates, and cations. All processes could remove a significant amount of natural organics. Pretreatment with ferric chloride was required toachieve significant organic removal with MF and high MWCO UF. Additionally, fouling mechanisms for the three processes were investigated. Crucial parameters were aggregate characteristics (fractal structure, stability, organic-colloid interactions), solubility of organics and calcium, and hydrodynamics. In MF, fouling by pore plugging was most severe. Variations in solutionchemistry changed the aggregation state of the colloids and/or natural organic matter and dramatically affected rejection and fouling behaviour. UF membrane fouling was mainly influenced by pore adsorption and could improve natural organics rejection significantly. Coagulant addition shifted fouling mechanism from pore adsorption to cake formation. Aggregate structure wasmost significant for flux decline. In NF, rejection of natural organics involved both size and charge exclusion. Fouling wascaused by precipitation of a calcium-organic complex. Fouling could be avoided by pretreatment with metal salt coagulants.Thorough chemical characterisation of the organics used demonstrated that only size and aromaticity can be related to fouling.The study is concluded with a process comparison based on a water quality parameter and a cost comparison. Treatment costof microfiltration with chemical pretreatment was similar to that of nanofiltration at a comparable natural organics rejection

TLR Signaling-induced CD103-expressing Cells Protect Against Intestinal Inflammation

Background: Toll-like receptor (TLR) expression in patients with inflammatory bowel disease is increased when compared with healthy controls. However, the impact of TLR signaling during inflammatory bowel disease is not fully understood. Methods: In this study, we used a murine model of acute phase inflammation in bone marrow chimeric mice to investigate in which cell type TLR2/4 signal induction is important in preventing intestinal inflammation and how intestinal dendritic cells are influenced. Mice were either fed with wild-type bacteria, able to initiate the TLR2/4 signaling cascade, or with mutant strains with impaired signal induction capacity. Results: The induction of the TLR2/4 signal cascade in epithelial cells resulted in inflammation in bone marrow chimeric mice, whereas induction in hematopoietic cells had an opposed function. Furthermore, feeding of wild-type bacteria prevented disease; however, differing signal induction of bacteria had no effect on lamina propria dendritic cell activation. In contrast, functional TLR2/4 signals resulted in increased frequencies of CD103-expressing lamina propria and mesenteric lymph node dendritic cells, which were able to ameliorate disease. Conclusions: The TLR-mediated amelioration of disease, the increase in CD103-expressing cells, and the beneficial function of TLR signal induction in hematopoietic cells indicate that the increased expression of TLRs in patients with inflammatory bowel disease might result in counterregulation of the host and serve in preventing disease.</p