Fixed-bed columns mathematical modeling for selective nickel and copper recovery from industrial spent acids by chelating resins

Spent acid streams generated in industry containing high concentrations of heavy metals are potential secondary sources of raw materials. Chelating resins are excellent candidates to recover valuable metals from complex mixtures at very low pH conditions. In particular, previous works reported high recoveries of nickel and copper from real industrial acids (3400 mg Cu2+ L−1, 8700 mg Ni2+ L−1 and 24000 mg Fe L−1) using commercial bis-picolyamine (BPA)-based resins. In this work, adsorption and desorption using two in-series fixed-bed columns with BPA resins have been proposed to carry out the selective and independent separation and recovery of nickel and copper. Under the selected operating conditions, it was possible to recover 90% of the copper and 80% of the nickel present in the problem solution. A mathematical model based on mass transfer was developed in order to describe the adsorption and desorption stages. Adsorption chemical reactions were modeled as equilibrium reactions, fitting to Langmuir’s and Freundlich’s isotherms for copper and nickel respectively. The chemical reactions for both metals in desorption fitted into first order reactions. Finally, the kinetic constants kde=0.81 kgdryresin L−1 h−1 for copper and kde=1.10 kgdryresin L−1 h−1 for nickel were estimated using the software Aspen Custom modeler. The predicted values agreed with the experimental data.This research was developed in the framework of the projects PID2020-115409RB-I00, PDC2021-120786-I00, TED2021-129874B-I00 and PID2021-122563OB-I00 financed by the Ministry of Science and Innovation (Spain)

Design of novel adsorption processes for the removal of arsenic from polluted groundwater employing functionalized magnetic nanoparticles

For many developing countries, groundwater is the main source for water consumption in rural and urban areas. The occurrence of arsenic in groundwater is an environmental problem due to its high toxicity. Although the removal of arsenic by different technologies has been proven, adsorption is one of the best alternatives due to its simplicity and low cost. In particular, nanoadsorbents incorporating magnetic properties are promising separation agents because of their advantageous and efficient potential recovery in a magnetic field, characteristic that is very attractive and of utmost relevance in the development of low cost technologies to provide drinking water in developing countries. In this work, Fe3O4 and Fe3O4/SiO2 magnetic nanoparticles functionalized by amino derivatives coordinated with Fe3+ were synthesized and characterized and further evaluated as adsorbents to remove arsenate from groundwater. The adsorption equilibrium of As5+ was satisfactorily described at 298 K by the Langmuir model with the following parameters: a) Fe3O4: qm=20.4±0.3 mg g-1 and KL=0.373±0.003 L mg-1 and b) Fe3O4/SiO2: qm=121±4.1 mg g-1 and KL=0.383±0.066 L mg-1. At low arsenate concentrations, 50-1000 µg L-1, the adsorption equilibrium As5+-Fe3O4/SiO2 was described by linear isotherms with equilibrium parameters KH=278.8 L g-1 in monocomponent systems and KH=1.80 L g-1 in the presence of competing ions, being carbonate and especially phosphate the main species affecting the process with contributions to the loss of efficacy around 70%. Finally, the material reuse after regeneration with NaOH 10-3 mol L-1 d was assessed under several composition scenarios reaching adsorption yields similar to those obtained with fresh materials.Financial support from the Spanish Ministry of Economy and Competitiveness under the project CTQ2012-31639 (FEDER 2007-2013) is gratefully acknowledged

In silico investigation and surmounting of lipopolysaccharide barrier in Gram-negative bacteria: how far has molecular dynamics come?

Lipopolysaccharide (LPS), a main component of the outer membrane of Gram-negative bacteria, has crucial implications on both antibiotic resistance and the overstimulation of the host innate immune system. Fighting against these global concerns calls for the molecular understanding of the barrier function and immunostimulatory ability of LPS. Molecular dynamics (MD) simulations have become an invaluable tool for uncovering important findings in LPS research. While the reach of MD simulations for investigating the immunostimulatory ability of LPS has been already outlined, little attention has been paid to the role of MD simulations for exploring its barrier function and synthesis. Herein, we give an overview about the impact of MD simulations on gaining insight into the shield role and synthesis pathway of LPS, which have attracted considerable attention to discover molecules able to surmount antibiotic resistance, either circumventing LPS defenses or disrupting its synthesis. We specifically focus on the enhanced sampling and free energy calculation methods that have been combined with MD simulations to address such research. We also highlight the use of special-purpose MD supercomputers, the importance of appropriate LPS and ions parameterization to obtain reliable results, and the complementary views that MD and wet-lab experiments provide. Thereby, this work, which covers the last five years of research, apart from outlining the phenomena and strategies that are being explored, evidences the valuable insights that are gained by MD, which may be useful to advance antibiotic design, and what the prospects of this in silico method could be in LPS research.Financial support from the Spanish Ministry of Science, Innovation and Universities under the project RTI2018-093310-B-I00 is gratefully acknowledged

Revealing the role of magnetic materials in light-driven advanced oxidation processes: enhanced degradation of contaminants and facilitated magnetic recovery

Semiconductor photocatalysis, heterogeneous photo-Fenton and heterogeneous photocatalytic persulfate activation are light-driven advanced oxidation processes (AOPs) that have attracted much attention as promising technologies in wastewater treatment. Nevertheless, their large-scale application still faces several challenges, including the need to separate the catalyst from the treated water. In this regard, composite catalysts made up of semiconductor and magnetic materials have been understood as a potential alternative since the resulting magnetic photocatalysts can be easily separated from the medium by applying an external magnetic field. Interestingly, apart from facilitating the photocatalyst retrieval, the magnetic components could also be involved in the photocatalytic process. However, while the magnetic separation ability has been widely highlighted, other functions of the magnetic constituents remain obscure. This work, which covers the last 6 years of research, provides a comprehensive review on the magnetically assisted photocatalytic degradation of organic pollutants from water. Specifically, the magnetic photocatalysts that are commonly employed for that purpose are presented and the different roles of their magnetic constituents (roughly grouped as retrieval assistance, active catalyst, conduction medium or activator) are discussed. Furthermore, the importance of designing magnetic separators for attaining the photocatalyst retrieval is also emphasized. Collectively, this study could supply an avenue for developing magnetic photocatalysts that take advantage of both roles of magnetic materials, which can contribute to accomplish a more efficient pollutant degradation.The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. Financial support from the project PID2021-122563OB-I00 funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU and Grant PLEC2021-007718 funded by MICIU/AEI/10.13039/ 501100011033 and by the European Union NextGenerationEU/ PRTR are gratefully acknowledged. CG-F also thanks the Spanish Ministry of Universities for the Margarita Salas postdoctoral fellowship (grants for the requalification of the Spanish university system for 2021–2023, University of Cantabria), funded by the European Union-NextGenerationEU

Computational modeling and fluorescence microscopy characterization of a two-phase magnetophoretic microsystem for continuous-flow blood detoxification

Magnetic beads can be functionalized to capture and separate target pathogens from blood for extracorporeal detoxification. The beads can be magnetically separated from a blood stream and collected into a coflowing buffer solution using a two-phase liquid-liquid continuous-flow microfluidic device in the presence of an external field. However, device design and process optimization, i.e. high bead recovery with minimum blood loss or dilution remain a substantial technological challenge. We introduce a CFD-based Eulerian-Lagrangian computational model that enables the rational design and optimization of such systems. The model takes into account dominant magnetic and hydrodynamic forces on the beads as well as coupled bead-fluid interactions. Fluid flow (Navier-Stokes equations) and mass transfer (Fick's law) between the coflowing fluids are solved numerically, while the magnetic force on the beads is predicted using analytical methods. The model is demonstrated via application to a prototype device and used to predict key performance metrics; degree of bead separation, flow patterns, and mass transfer, i.e. blood diffusion to the buffer phase. The impact of different process variables and parameters-flow rates, bead and magnet dimensions and fluid viscosities-on both bead recovery and blood loss or dilution is quantified for the first time. The performance of the prototype device is characterized using fluorescence microscopy and the experimental results are found to match theoretical predictions within an absolute error of 15%. While the model is demonstrated here for analysis of a detoxification device, it can be readily adapted to a broad range of magnetically-enabled microfluidic applications, e.g. bioseparation, sorting and sensing

Recovery of magnetic catalysts: advanced design for process intensification

The design of microdevices in which components with magnetic character must be separated and recovered from reactive media benefits from the advantages of microfluidics and meets the criteria for process intensification; however, there are open questions, such as the design of the most appropriate magnet arrangement, that need further research in order to increase the magnetic gradient exerted on the particles. Herein, we focus on the continuous recovery of magnetic microparticles, that can be used as support to facilitate the recovery of biocatalysts (magnetic microcatalysts, MMCs) from biological fluids. We analyze and compare the performance of two typical magnetophoretic microdevices for addressing bead recovery: (i) annular channels with a quadrupole orientation of the permanent magnets (quadrupole magnetic sorter, QMS) and (ii) the standard design, which consists of rectangular channels with a single permanent magnet to generate the magnetic field. To this end, an experimentally validated computational fluid dynamics (CFD) numerical model has been employed. Our results reveal that for devices with the same width and length, the micro QMS, in comparison to a rectangular channel, could accomplish the complete particle retrieval while (i) processing more than 4 times higher fluid velocities, treating more than 360 times higher flow rates or (ii) working with smaller particles, thus reducing by 55% the particle mass. Additionally, the parallel performance of +/-300 micro-QMSs fulfills the processing of flow rates as high as 200 L·h-1 while entirely capturing the magnetic beads. Thereby, this work shows the potential of the QMS advanced design in the intensification of the recovery of catalysts supports of magnetic character.Financial support from the Spanish Ministry of Science, Innovation and Universities under the project RTI2018- 093310-B-I00 is gratefully acknowledged. Cristina González-Fernández acknowledges the FPU (FPU18/03525) postgraduate research grants. We also wish to thank the United States National Institutes of Health (1R01HL131720-01A1, CA62349) and the United States Defense Advanced Research Projects Agency (BAA07-21) for financial assistance

Fighting against bacterial lipopolysaccharide-caused infections through molecular dynamics simulations: a review

Lipopolysaccharide (LPS) is the primary component of the outer leaflet of Gram-negative bacterial outer membranes. LPS elicits an overwhelming immune response during infection, which can lead to life-threatening sepsis or septic shock for which no suitable treatment is available so far. As a result of the worldwide expanding multidrug-resistant bacteria, the occurrence and frequency of sepsis are expected to increase; thus, there is an urge to develop novel strategies for treating bacterial infections. In this regard, gaining an in-depth understanding about the ability of LPS to both stimulate the host immune system and interact with several molecules is crucial for fighting against LPS-caused infections and allowing for the rational design of novel antisepsis drugs, vaccines and LPS sequestration and detection methods. Molecular dynamics (MD) simulations, which are understood as being a computational microscope, have proven to be of significant value to understand LPS-related phenomena, driving and optimizing experimental research studies. In this work, a comprehensive review on the methods that can be combined with MD simulations, recently applied in LPS research, is provided. We focus especially on both enhanced sampling methods, which enable the exploration of more complex systems and access to larger time scales, and free energy calculation approaches. Thereby, apart from outlining several strategies for surmounting LPS-caused infections, this work reports the current state-of-the-art of the methods applied with MD simulations for moving a step forward in the development of such strategies.Financial support from the Spanish Ministry of Science, Innovation and Universities under the project RTI2018- 093310-B-I00 is gratefully acknowledged. C.G.F. and A.B. are also thankful for the FPU (FPU18/03525) and FPI (BES-2016-077206) postgraduate research grants, respectively

Flow patterns and mass transfer performance of miscible liquid-liquid flows in various microchannels: Numerical and experimental studies

The advantages of miniaturized systems and the laminar flow regime that is present in microfluidic channels have opened a new range of applications in which the use of multiple streams with different reagents is exploited. However, further development of these microdevices needs deeper understanding on the phenomena involved in order to efficiently design such microsystems. In this work, we report the analysis of the solute mass transport performance in Y-Y-shaped microchannels as a function of the coupled influence of both the flow patterns and mass transport kinetics. With this objective, the influence of the following operation variables has been analyzed, the ratio between the residence and diffusion times (γ) and the volumetric ratio between the fluid phases (α), that was determined for three different geometric configurations. The performance of the devices was presented as the solute separation factor in the donor fluid and the concentration factor in the receiving phase. Results showed that the ratio α greatly impacts the solute concentration value reported in both phases for the same γ value, which in turn influences the solute mass flow at the channel outlets. Both the flow patterns and the concentration gradients developed inside the systems were numerically studied by using Computational Fluid Dynamics (CFD) techniques and experimentally analyzed by fluorescence microscopy with fluorescein employed as model solute. This study represents a thorough analysis of the phenomena that determine the performance of the separation of solutes between homogeneous flowing fluids in microdevices where the fluid dynamics are coupled with mass transfer phenomena and facilitates its extension to the general case where separation is enhanced by chemical reactions.Financial support from the Spanish Ministry of Economy and Competitiveness under the projects CTQ2015-72364-EXP/AEI and CTQ2015-66078-R (MINECO/FEDER) is gratefully acknowledged. Jenifer Gómez-Pastora also thanks the FPI postgraduate research grant (BES2013-064415). Cristina González-Fernández thanks the Concepción Arenal postgraduate research grant from the University of Cantabria

Magnetism and Mössbauer study of formation of multi-core γ-Fe2O3 nanoparticles

A systematic investigation of magnetic nanoparticles and the formation of a core-shell structure, consisting of multiple maghemite (γ-Fe2O3) nanoparticles as the core and silica as the shell, has been performed using various techniques. High-resolution transmission electron microscopy clearly shows isolated maghemite nanoparticles with an average diameter of 13?nm and the formation of a core-shell structure. Low temperature Mössbauer spectroscopy reveals the presence of pure maghemite nanoparticles with all vacancies at the B-sites. Isothermal magnetization and zero-field-cooled and field-cooled measurements are used for investigating the magnetic properties of the nanoparticles. The magnetization results are in good accordance with the contents of the magnetic core and the non-magnetic shell. The multiple-core γ-Fe2O3 nanoparticles show similar behavior to isolated particles of the same size.We thank the assistance by Dr. Peter Klavins at the Department of Physics, the University of California Davis, in performing the magnetization measurements. This research was partially supported by the Department of Energy, Office of Nuclear Energy, Nuclear Energy Program, under Grant No. DE-NE000070

Insights into the binding mode of lipid a to the anti-lipopolysaccharide factor ALFPm3 from penaeus monodon: an in silico study through MD simulations

The globally expanding threat of antibiotic resistance calls for the development of new strategies for abating Gram-negative bacterial infections. The use of extracorporeal blood cleansing devices with affinity sorbents to selectively capture bacterial lipopolysaccharide (LPS), which is the major constituent of Gram-negative bacterial outer membranes and the responsible agent for eliciting an exacerbated innate immune response in the host during infection, has received outstanding interest. For that purpose, molecules that bind tightly to LPS are required to functionalize the affinity sorbents. Particularly, anti-LPS factors (ALFs) are promising LPS-sequestrating molecules. Hence, in this work, molecular dynamics (MD) simulations are used to investigate the interaction mechanism and binding pose of the ALF isoform 3 from Penaeus monodon (ALFPm3), which is referred to as "AL3" for the sake of simplicity, and lipid A (LA, the component of LPS that represents its endotoxic principle). We concluded that hydrophobic interactions are responsible for AL3-LA binding and that LA binds to AL3 within the protein cavity, where it buries its aliphatic tails, whereas the negatively charged phosphate groups are exposed to the medium. AL3 residues that are key for its interaction with LA were identified, and their conservation in other ALFs (specifically Lys39 and Tyr49) was also analyzed. Additionally, based on the MD-derived results, we provide a picture of the possible AL3-LA interaction mechanism. Finally, an in vitro validation of the in silico predictions was performed. Overall, the insights gained from this work can guide the design of novel therapeutics for treating sepsis, since they may be significantly valuable for designing LPS-sequestrating molecules that could functionalize affinity sorbents to be used for extracorporeal blood detoxification.Financial support from the Spanish Ministry of Science, Innovation and Universities under the project RTI2018- 093310-B-I00 is gratefully acknowledged. C.G.F. also thanks the Spanish Ministry of Universities for the Margarita Salas postdoctoral fellowship (grants for the requalification of the Spanish university system for 2021−2023, University of Cantabria), funded by the European Union-NextGenerationEU