Comparative Analysis of Bio-Vanillin Recovery from Bioconversion Media Using Pervaporation and Vacuum Distillation

Publisher Copyright: © 2022 by the authors.The increasing demand for natural products has led to biotechnological vanillin production, which requires the recovery of vanillin (and vanillyl alcohol at trace concentrations, as in botanical vanillin) from the bioconversion broth, free from potential contaminants: the substrate and metabolites of bioconversion. This work discusses the recovery and fractionation of bio-vanillin, from a bioconversion broth, by pervaporation and by vacuum distillation, coupled with fractionated condensation. The objective was to recover vanillin free of potential contaminants, with maximised fluxes and selectivity for vanillin against water and minimised energy consumption per mass of vanillin recovered. In vacuum distillation fractionated condensation, adding several consecutive water pulses to the feed increased the percentage of recovered vanillin. In pervaporation-fractionated condensation and vacuum distillation-fractionated condensation processes, it was possible to recover vanillin and traces of vanillyl alcohol without the presence of potential contaminants. Vacuum distillation–experiments presented higher vanillin fluxes than pervaporation fractionated condensation experiments, 2.7 ± 0.1 g·m−2 h−1 and 1.19 ± 0.01 g·m−2 h−1, respectively. However, pervaporation fractionated condensation assures a selectivity of vanillin against water of 4.5 on the pervaporation step (acting as a preconcentration step) and vacuum distillation fractionated condensation requires a higher energy consumption per mass of vanillin recovered when compared with pervaporation– fractionated condensation, 2727 KWh kgVAN−1 at 85 °C and 1361 KWh kgVAN−1 at 75 °C, respectively.publishersversionpublishe

Effect of ultrafiltration operating conditions for separation of ferulic acid from arabinoxylans in corn fibre alkaline extract

Corn fibre, a co-product of the starch industry, is rich in compounds with high added value, such as ferulic acid and arabinoxylans, which are released during alkaline extraction. This work aims to optimise an efficient separation method for the recovery of these two compounds from a corn fibre alkaline extract, allowing an efficient valorisation of this co-product. Ultrafiltration was selected as separation method, due to its potential to fractionate these compounds. In order to minimise the loss of membrane permeance, due to mass transfer limitations caused by the high arabinoxylan viscosity, the impact of relevant ultrafiltration operating parameters (membrane molecular weight cut-off, fluid dynamics conditions, transmembrane pressure, and operating temperature) were evaluated. A Nadir UP 150 membrane was found to be an adequate choice, allowing for an efficient separation of ferulic acid from arabinoxylans, with null rejection of ferulic acid, a high estimated rejection of arabinoxylans 98.0% ± 1.7%, and the highest permeance of all tested membranes. A response surface methodology (RSM) was used to infer the effect of ultrafiltration conditions (crossflow velocity, transmembrane pressure and operating temperature) on the rejection of ferulic acid, retention of arabinoxylans (assessed through apparent viscosity of the retentate stream), and permeance. Through mathematical modelling it was possible to determine that the best conditions are the highest operating temperature and initial crossflow velocity tested (66◦C and 1.06 m.s−1, respectively), and the lowest transmembrane pressure tested (0.7 bar).publishersversionpublishe

Solvent-free process for the development of photocatalytic membranes

PTDC/EAM-AMB/30989/2017.This work described a new sustainable method for the fabrication of ceramic membranes with high photocatalytic activity, through a simple sol-gel route. The photocatalytic surfaces, prepared at low temperature and under solvent-free conditions, exhibited a narrow pore size distribution and homogeneity without cracks. These surfaces have shown a highly efficient and reproducible behavior for the degradation of methylene blue. Given their characterization results, the microfiltration photocatalytic membranes produced in this study using solvent-free conditions are expected to effectively retain microorganisms, such as bacteria and fungi that could then be inactivated by photocatalysis.publishe

Novel submerged photocatalytic membrane reactor for treatment of olive mill wastewaters

POCI-01-0145-FEDER-007265A new hybrid photocatalytic membrane reactor that can easily be scaled-up was designed, assembled and used to test photocatalytic membranes developed using the sol–gel technique. Extremely high removals of total suspended solids, chemical oxygen demand, total organic carbon, phenolic and volatile compounds were obtained when the hybrid photocatalytic membrane reactor was used to treat olive mill wastewaters. The submerged photocatalytic membrane reactor proposed and the modified membranes represent a step forward towards the development of new advanced treatment technology able to cope with several water and wastewater contaminants.publishersversionpublishe

Characterisation and modelling of transient transport through dense membranes using on-line mass spectrometry

European KBBE FP7 project (262632) PTDC/MAT109973/2009Abstract: This work presents a methodology for characterising solute transport through pervaporation membranes or, more generally, through dense membranes, in the whole transient regime. A real-time characterisation of transport through dense membrane is obtained by using on-line mass spectrometry (MS) monitoring, which allows to acquire the concentration of solutes in the permeate compartment with time intervals of 2 seconds (and lower if required). Time-dependent diffusion coefficients, D(t), were calculated for the whole operation period, including the initial transient period. Based on these values it is possible to infer about the relevance of solute-membrane interactions and rearrangement of the membrane structure due to the presence of permeant solutes. Finally, based on the information acquired, a mathematical model was developed in order to obtain solute concentration profiles inside the membrane and their evolvement along time.authorsversionpublishe

Fluorescence coupled with chemometrics for simultaneous monitoring of cell concentration, cell viability and medium nitrate during production of carotenoid-rich Dunaliella salina

This work was supported by the Associate Laboratory for Green Chemistry- LAQV which is financed by national funds from FCT / MCTES ( UID/QUI/50006/2019 ); by the European FP7 KBBE project “D-Factory” (contract no. 613870); by KAUST OSR award no. OSR-2016-CPF-2907-05; grant of FCT / MCTES : SFRH/BD/108894/2015. The authors would like to thank The Marine Biological Association (Devon, UK) and NBT Ltd (Israel).Two-dimensional (2D) fluorescence spectroscopy was investigated as a monitoring tool for cultivation, harvesting, and effluent treatment of Dunaliella salina with high carotenoid concentration; aiming to improve the production process and minimise costs. Chemometric analysis, namely Principal Component Analysis (PCA) and Projection to Latent Structures (PLS), were used to build models for estimation of cellular concentration, cellular viability, and nitrate concentration in media. The estimations were based on fluorescence excitation-emission matrices (EEMs) acquired directly from algal suspensions. Cell concentration during cultivation and harvesting can be predicted by a single model capturing 92.0% of the variance, and with R2 of 0.92 and 0.97, for training and validation, respectively. Cell viability during harvesting by ultrafiltration was modelled with 79% of variance and R2 of 0.79 for training and 0.73 for validation. Nitrate concentration was successfully predicted during cultivation and permeate treatment using a single model with 81.8% of variance and R2 of 0.82 for training and 0.80 for validation. Therefore, this work demonstrates the strong potential of combining 2D fluorescence and chemometrics for monitoring different processes during microalgae production.authorsversionpublishe

Tannery effluent treatment by nanofiltration, reverse osmosis and chitosan modified membranes

UID/QUI/50006/2019The objective of this work is to develop an appropriate technology for environmentally sound membrane-based purification of a tannery effluent assuring, simultaneously, the recovery of chromium, considered as the most hazardous inorganic water pollutant extensively used in leather tanning. A comparison between the permeate fluxes obtained during treatment of a synthetic tannery effluent through nanofiltration (NF270 and NF90 membranes) and reverse osmosis (BW30 and SW30) membranes was first performed. Then, a dedicated polymeric membrane was prepared by coating chitosan (cs) on a polyethersulfone (PES) microfiltration membrane (cs-PES MFO22) support. The resulting membrane was characterized by Fourier Transforms Infrared Spectroscopy Attenuated Total Reflectance (FTIR-ATR), Emission Scanning Electronic Microscopy (SEM) to confirm the process of surface modification and cross-linking of chitosan with glutaraldehyde. This membrane was found to be highly effective for chromium removal (>99%), which was more than eight times higher in reference to monovalent cations (e.g., Na+ and K+) and more than six times higher in reference to the divalent cations (Mg2+ and Ca2+) studied. The reverse osmosis permeate conforms to local Algerian regulations regarding being discharged directly into the natural environment (in this case, Reghaia Lake) or into urban sewers linked to wastewater biological treatment stations. While the SW30 membrane proved to be the most effective for purification of the tannery effluent, the chitosan modified membrane proved to be appropriate for recovery of chromium from the reverse osmosis concentrate.publishersversionpublishe

Stability of polymeric membranes to UV exposure before and after coating with TiO2 nanoparticles

Acknowledgments: Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, Nº 2019/ 04319-9), Associate Laboratory for Green Chemistry—LAQV, Unidade de Tecnologia de Células Animais do iBET e à Paula Alves, iNOVA4Health—UIDB/Multi/04462/2020, a program financially supported by Fundação para a Ciência e Tecnologia/Ministério da Educação e Ciência, through national funds is acknowledged. Funding from INTERFACE Program, through the Innovation, Technology and Circular Economy Fund (FITEC), is also gratefully acknowledged. Funding Information: Funding: Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, Nº 2019/04319-9), Associate Laboratory for Green Chemistry—LAQV (through projects UIDB/50006/2020 and UIDP/ 50006/2020), Fundação para a Ciência e a Tecnologia through the project PTDC/EAM-AMB/30989/2017, Unidade de Tecnologia de Células Animais do iBET, iNOVA4Health—UIDB/Multi/04462/2020. Funding Information: Funda??o de Amparo ? Pesquisa do Estado de S?o Paulo (FAPESP, N? 2019/04319-9), Associate Laboratory for Green Chemistry?LAQV (through projects UIDB/50006/2020 and UIDP/ 50006/2020), Funda??o para a Ci?ncia e a Tecnologia through the project PTDC/EAM-AMB/30989/2017, Unidade de Tecnologia de C?lulas Animais do iBET, iNOVA4Health?UIDB/Multi/04462/2020. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.The combination of photocatalysis and membrane filtration in a single reactor has been proposed, since the photocatalytic treatment may degrade the pollutants retained by the membrane and reduce fouling. However, polymeric membranes can be susceptible to degradation by UV radiation and free radicals. In the present study, five commercial polymeric membranes were exposed to ultraviolet (UV) radiation before and after applying a sol–gel coating with TiO2 nanoparticles. Membrane stability was characterized by changes in hydrophilicity as well as analysis of soluble substances and nanoparticles detached into the aqueous medium, and by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectrometry (EDS) for structural, morphological, and elemental distribution analysis, respectively. The TiO2 coating conferred photocatalytic properties to the membranes and protected them during 6 h of UV radiation exposures, reducing or eliminating chemical and morphological changes, and in some cases, improving their mechanical resistance. A selected commercial nanofiltration membrane was coated with TiO2 and used in a hybrid reactor with a low-pressure UV lamp, promoting photocatalysis coupled with cross-flow filtration in order to remove 17α-ethinylestradiol spiked into an aqueous matrix, achieving an efficiency close to 100% after 180 min of combined filtration and photocatalysis, and almost 80% after 90 min.publishersversionpublishe

Monitoring of membrane processes with fluorescence molecular probes

This work discusses the use of molecular probes that change their fluorescence response in the presence of different local environmental conditions. In particular, probes able to respond to temperature and to oxygen concentration were identified and used to report the value of these parameters at a molecular scale. The development of a stable, reproducible and sensitive molecular probing system was then applied to monitor oxygen concentration at the surface of different membrane materials and also in order to obtain oxygen concentration profiles inside dense membranes. Ultimately, a temperature sensitive probe was used to measure temperature at membrane surfaces making possible its measurement locally. This technique was applied with success to experimentally measure temperature polarization in membrane distillation processes, on-line, in a non-invasive mode. Future developments of molecular probing will be also presented and discussed