In Situ Raman Analysis of CO\u2082-Assisted Drying of Fruit-Slices

This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO\u2082) drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i) the reduction of the water from the fruit slice and (ii) the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO\u2082 into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve

Investigations on Strategic Element Recovery by an Underground Membrane Pilot Plant from <i>In-Situ</i> Extracted Bioleaching Solutions

Focusing on the selective extraction of the critical raw materials indium and germanium from real bioleaching solutions, extended studies have been carried out using Europe’s first underground hybrid membrane pilot plant (TRL6). In order to transfer former laboratory experiments to pilot scale, NF99 (Alfa Laval) was used for the evaluation of membrane permeance and ion retention. A performance test of microfiltration (MF) and nanofiltration (NF) showed high permeances with low root-mean-square deviation under feed variation (5.2% for MF, 4.7% for NF). Depending on the feed load, a significant permeance drop of up to 57% for MF (3 bar) and 26% for NF (10 bar, 1.1 m s−1) was observed. The NF retention performance showed that, without regular chemical cleaning, the selectivity between the target elements degraded. By introducing acidic-basic cleaning steps, it was possible to keep the retention behavior at an approximately constant level (In 91.0 ± 1.3%; Ge 18.2 ± 5.5%). In relation to the specified target, the best results could be achieved at low pressure (7.5 bar) and a maximum overflow velocity of 1.1 m s−1, with a retention of 88.4% for indium and 8.8% for germanium. Moreover, the investigations proved the functionality and long-term stability of the underground membrane device

Investigations on Strategic Element Recovery by an Underground Membrane Pilot Plant from In-Situ Extracted Bioleaching Solutions

Focusing on the selective extraction of the critical raw materials indium and germanium from real bioleaching solutions, extended studies have been carried out using Europe&rsquo;s first underground hybrid membrane pilot plant (TRL6). In order to transfer former laboratory experiments to pilot scale, NF99 (Alfa Laval) was used for the evaluation of membrane permeance and ion retention. A performance test of microfiltration (MF) and nanofiltration (NF) showed high permeances with low root-mean-square deviation under feed variation (5.2% for MF, 4.7% for NF). Depending on the feed load, a significant permeance drop of up to 57% for MF (3 bar) and 26% for NF (10 bar, 1.1 m s&minus;1) was observed. The NF retention performance showed that, without regular chemical cleaning, the selectivity between the target elements degraded. By introducing acidic-basic cleaning steps, it was possible to keep the retention behavior at an approximately constant level (In 91.0 &plusmn; 1.3%; Ge 18.2 &plusmn; 5.5%). In relation to the specified target, the best results could be achieved at low pressure (7.5 bar) and a maximum overflow velocity of 1.1 m s&minus;1, with a retention of 88.4% for indium and 8.8% for germanium. Moreover, the investigations proved the functionality and long-term stability of the underground membrane device

Aerogel-Lined Capillaries for Raman Signal Gain of Aqueous Mixtures

We report an experimental study on the gain of the Raman signal of aqueous mixtures and liquid water when confined in aerogel-lined capillaries of various lengths of up to 20 cm and various internal diameters between 530 and 1000 µm. The lining was made of hydrophobised silica aerogel, and the carrier capillary body consisted of fused silica or borosilicate glass. Compared to the Raman signal detected from bulk liquid water with the same Raman probe, a Raman signal 27 times as large was detected when the liquid water was confined in a 20 cm-long capillary with an internal diameter of 700 µm. In comparison with silver-lined capillaries of the same length and same internal diameter, the aerogel-lined capillaries featured a superior Raman signal gain and a longer gain stability when exposed to mixtures of water, sugar, ethanol and acetic acid

Pressure drop particle precipitation from a quasi-incompressible, ternary and liquid mixture

We found a quasi-incompressible and liquid mixture of ibuprofen, water and acetone, that enables the crystallization of ibuprofen particles by decreasing the pressure from 15MPa to ambient pressure (~0.1MPa). We measured the solubility of ibuprofen in the mixture as a function of the acetone/water-ratio for pressures of 0.1MPa, 5.5MPa and 15MPa and at 308K using the cloud point method. Based on the solubilities, binodal compositions of the ternary system were modelled using the NRTL-SAC model. The solubility of the drug in the mixture increases with increasing pressure at constant acetone/water-ratio. This pressure sensitive solubility can be exploited for the crystallization of ibuprofen particles via a pressure-drop approach. A pressure-drop from 15MPa to ambient pressure (~0.1MPa) can result in a supersaturation of up to 1.43.The project leading to this contribution has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under ERC Starting Grant agreement No. 637654 (Inhomogeneities). The ICTS “Nanbiosis”, more specifically U6 Unit, unit of the CIBER in Bioengineering, Biomaterials & Nanomedicne (CIBER-BBN), is also acknowledged for the experimental information provided. The authors acknowledge funding from the Generalitat de Catalunya through the Centres de Recerca de Catalunya (CERCA) programme and grant 2017-SGR-918, from the Ministry of Economy and Competitiveness (MINECO) of Spain through grant PID2019–105622RB-I00 (MOL4BIO).Peer reviewe

A fast and remote screening method for sub-micro-structuration in pressurized mixtures containing water and carbon dioxide

We present a fast optical screening method for the detection of sub-micro-structures nanostructuration in water-containing fluids. The optical method is based on Raman spectroscopy of the water stretching vibration. The shape of this Raman band reveals information about the development of hydrogen bonds, from which it can be extracted whether the water molecules are homogeneously distributed in the mixture, or they are heterogeneously distributed (sub-micro-structuration). The fast screening is enabled by analyzing the potentially structured ternary system CO2/acetonitrile/water between 10 and 22 MPa and at 308 K, 318 K and 328 K in continuously spilled microcapillary system (MCS). Compared to batch systems we specify the advantages of the MCS in which the operational conditions with respect to pressure, temperature and composition can be changed fast, reproducibly and across a wide range.Peer reviewe

Pressure-responsive, surfactant-free CO2‑based nanostructured fluids

Microemulsions are extensively used in advanced material and chemical processing. However, considerable amounts of surfactant are needed for their formulation, which is a drawback due to both economic and ecological reasons. Here, we describe the nanostructuration of recently discovered surfactant-free, carbon dioxide (CO2)-based microemulsion-like systems in a water/organic-solvent/CO2 pressurized ternary mixture. “Water-rich” nanodomains embedded into a “water-depleted” matrix have been observed and characterized by the combination of Raman spectroscopy, molecular dynamics simulations, and small-angle neutron scattering. These single-phase fluids show a reversible, pressure-responsive nanostructuration; the “water-rich” nanodomains at a given pressure can be instantaneously degraded/expanded by increasing/decreasing the pressure, resulting in a reversible, rapid, and homogeneous mixing/demixing of their content. This pressure-triggered responsiveness, together with other inherent features of these fluids, such as the absence of any contaminant in the ternary mixture (e.g., surfactant), their spontaneous formation, and their solvation capability (enabling the dissolution of both hydrophobic and hydrophilic molecules), make them appealing complex fluid systems to be used in molecular material processing and in chemical engineering.N.G. acknowledges the European Commission (EC) (FP7-PEOPLE-2013-Initial Training Networks (ITN) “‘NANO2FUN’” project no. 607721) for her Postdoctoral contract. A.S.B. thanks funding from the European Research Council under ERC starting grant agreement no. 637654. The authors appreciate the economical support from DGI, MINECO, Spain (Grant MAT2016-80826-R and “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV- 2015-0496)), and the Instituto de Salud Carlos III, through “Acciones CIBER”. The ICTS “Nanbiosis”, more specifically U6 Unit, is also acknowledged since some of the studies here reported have been performed there. Neutron beam time at the Institut Laue-Langevin (ILL) Grenoble, France, is acknowledged together with Dr. Thomas Sottmann, who has kindly provided the high-pressure cell used for SANS measurements. The authors acknowledge the valuable support of Julian Jonathan Schuster from FAU with respect to the processing of Raman spectra and the valuable help of David Bowyer during experiments at ILL.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe

Pressure-Responsive, Surfactant-Free CO₂‑Based Nanostructured Fluids

Microemulsions are extensively used in advanced material and chemical processing. However, considerable amounts of surfactant are needed for their formulation, which is a drawback due to both economic and ecological reasons. Here, we describe the nanostructuration of recently discovered surfactant-free, carbon dioxide (CO₂)-based microemulsion-like systems in a water/organic-solvent/CO₂ pressurized ternary mixture. “Water-rich” nanodomains embedded into a “water-depleted” matrix have been observed and characterized by the combination of Raman spectroscopy, molecular dynamics simulations, and small-angle neutron scattering. These single-phase fluids show a reversible, pressure-responsive nanostructuration; the “water-rich” nanodomains at a given pressure can be instantaneously degraded/expanded by increasing/decreasing the pressure, resulting in a reversible, rapid, and homogeneous mixing/demixing of their content. This pressure-triggered responsiveness, together with other inherent features of these fluids, such as the absence of any contaminant in the ternary mixture (<i>e</i>.<i>g</i>., surfactant), their spontaneous formation, and their solvation capability (enabling the dissolution of both hydrophobic and hydrophilic molecules), make them appealing complex fluid systems to be used in molecular material processing and in chemical engineering