Rui Viegas - Academia.edu (original) (raw)

Papers by Rui Viegas

Research paper thumbnail of Through the Ion Exchange Membrane Bioreactor

Removal of heavy metals from drinking water supplies through the ion exchange membrane bioreactor

Research paper thumbnail of Pilot Studies and Cost Analysis of Hybrid Powdered Activated Carbon/Ceramic Microfiltration for Controlling Pharmaceutical Compounds and Organic Matter in Water Reclamation

Water, 2019

This paper addresses the enhanced removal of pharmaceutical compounds (PhCs), a family of contami... more This paper addresses the enhanced removal of pharmaceutical compounds (PhCs), a family of contaminants of emerging concern, and effluent organic matter (EfOM) in water reclamation by powdered activated carbon/coagulation/ceramic microfiltration (PAC/cMF). Four chemically diverse PhCs are targeted: ibuprofen (IBP), carbamazepine (CBZ), sulfamethoxazole (SMX) and atenolol (ATN). Pilot assays (100 L/(m2 h), 10 mg Fe/L) run with PhC-spiked sand-filtered secondary effluent and 15 mg/L PAC dosed in-line or to a 15-min contactor. They showed no PAC-driven membrane fouling and +15 to +18% added removal with PAC contactor, reaching significant removals of CBZ and ATN (59%–60%), SMX (50%), colour (48%), A254 (35%) and dissolved organic carbon (DOC, 28%). Earlier long-term demo tests with the same pilot proved PAC/cMF to consistently produce highly clarified (monthly median < 0.1 NTU) and bacteria-free water, regardless of the severe variations in its intake. A detailed cost analysis points...

Research paper thumbnail of TGumí, MValiente CPalet JMembrSci 256 - 2005- p150

Research paper thumbnail of Modelling of the enantio-selective extraction of propranolol in a biphasic system

Separation and Purification Technology, 2007

This work reports the study of the racemic resolution of propranolol, an amino-alcohol with prove... more This work reports the study of the racemic resolution of propranolol, an amino-alcohol with proven efficacy in the treatment of hypertension, ischemic heart disease and arrhythmia. Among all ␤-blockers, propranolol was selected, as a case study, also due to its enantiomers diverse properties. The studies performed involve an enantio-selective extraction in a biphasic system, where propranolol first reacts with boric acid in aqueous media and then complexes with a chiral di-dodecyltartrate selector present in the organic phase. Factors affecting the extraction mechanism were analysed, namely the influence of the concentrations of the tartrate complexing agent and boric acid and the pH. A comprehensive mechanism of extraction is proposed. Due to its complexity the mathematical approach developed involves the use of a hybrid model, with a deterministic component, describing the material balance equations of the reactions involved, and a neural network, which allows accounting for the variable non-selective partition of propranolol.

Research paper thumbnail of Enantioselective Separation of Propranolol by Chiral Activated Membranes

Separation Science and Technology, 2005

The employment of racemic drugs has become unattractive due to policy changes introduced by regul... more The employment of racemic drugs has become unattractive due to policy changes introduced by regulatory agencies. As a consequence, pharmaceutical industries have been forced to develop new technologies for preparing non-racemic drugs. Resolution can be performed by membrane technology due to its several advantages over traditional methods. And, in particular chiral activated membranes can be used for the enantioselective separation in continuous mode with a longer lifetime than corresponding liquid membrane systems. 2 In this work, chiral activated membranes have been tested for the enantioseparation of the racemic drug propranolol. Polysulfone (PS) based membranes have been prepared for this purpose, using N-hexadecyl-L-hydroxyproline (HHP) and L-din -dodecyltartrate (L-DDT) as chiral carriers, respectively. Kinetic experiments have been carried out using a membrane module with two rectangular channels separated by the membrane, which allows for a well-defined hydrodynamics of the feed and stripping phases. Propranolol transport across the membrane depends on its diffusion rate from the bulk solution to the membrane surface and also on the relative amount of carrier present in the membrane. Therefore, the influence of both the solute/carrier ratio and the flow rates of the feed and stripping phases on the rate of extraction and on the selectivity of the process was evaluated for both chemical systems. Modelling of kinetic experiments has been performed and mass transfer coefficients obtained for both systems were compared.

Research paper thumbnail of Removal of valeric acid from wastewaters by membrane contactors

Journal of Membrane Science, 1997

Membrane contactors, providing a non-dispersive extraction technique, were used for the removal o... more Membrane contactors, providing a non-dispersive extraction technique, were used for the removal of valeric 01-pentanoic) acid from synthetic aqueous solutions simulating an industrial wastewater from polymer manufacturing. Amberlite LA-2 (secondary amine) in toluene was chosen as the extraction system. Equilibrium conditions were determined and mechanistically modelled for different extractant concentrations allowing the further calculation of mass transfer coefficients. The influence of the hydrodynamics of both the aqueous and organic phases on the overall mass transfer coefficient, calculated through two proposed methods, was studied. The integration of extraction and backextraction was also carried out, allowing a further acid removal with lower extractant concentrations. ~(, 1997 Elsevier Science B.V.

Research paper thumbnail of Racemic resolution of propranolol in membrane contactors: Modelling and process optimisation

Journal of Membrane Science, 2007

This work reports the study of the chiral resolution of propranolol, an amino-alcohol with proven... more This work reports the study of the chiral resolution of propranolol, an amino-alcohol with proven efficacy in the treatment of hypertension, ischemic heart disease and arrhythmia. Among all β-blockers, propranolol was selected also due to the distinct properties of its enantiomers.Extraction and stripping kinetic studies were performed using a tubular module contactor, with ceramic ultrafiltration supporting membranes. Three different configurations were evaluated in terms of enantio-selectivity and enantiomeric excess of the desired enantiomer: (1) single extraction; (2) simultaneous extraction, where each enantiomer is preferentially recovered to a different extraction phase; (3) simultaneous selective extraction and stripping of a target enantiomer.The kinetic model developed, comprising an equilibrium modelling of the extraction process and differential mass balances in pseudo steady-state, fully describes the overall process. Moreover, the model allowed the optimisation of the operating conditions and enables to predict the optimum combination of module configurations in order to maximise the enantiomeric excess.

Research paper thumbnail of Hybrid modelling of the racemic resolution of propranolol in membrane contactors

Desalination, 2006

... in membrane contactors Rui MC Viegas*, João G. Crespo, Isabel M. Coelhoso CQFB/REQUIMTE – Dep... more ... in membrane contactors Rui MC Viegas*, João G. Crespo, Isabel M. Coelhoso CQFB/REQUIMTE – Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal email: rui.viegas@dq.fct.unl.pt ...

Research paper thumbnail of Removal of heavy metals from drinking water supplies through the ion exchange membrane bioreactor

Desalination, 2006

Arsenic (As) and mercury (Hg) are two highly toxic heavy metals that must be removed to very low ... more Arsenic (As) and mercury (Hg) are two highly toxic heavy metals that must be removed to very low levels in drinking water supplies. A novel treatment method for the removal of both compounds is the ion exchange membrane bioreactor (IEMB) process, which incorporates pollutant ...

Research paper thumbnail of Mass transfer correlations in membrane extraction: Analysis of Wilson-plot methodology

Journal of Membrane Science, 1998

Mass transfer correlations have been obtained for the past eight decades by the Wilson-plot metho... more Mass transfer correlations have been obtained for the past eight decades by the Wilson-plot method which has proved to be suitable for systems operating in steady-state conditions and where the only variable is the¯uid velocity. In this work, this methodology is evaluated by using a membrane extraction process with a hollow-®ber membrane contactor as a case study. Taking into consideration the currently available mathematical tools, alternative methods to obtain mass transfer correlations are proposed and discussed. The proposed one-step calculation methodology proved to be a most suitable approach, leading to a drastic reduction in the errors associated with the estimated parameters. Additionally, improvements were observed when accounting for the partition coef®cient variation.

Research paper thumbnail of Key Factors for Activated Carbon Adsorption of Pharmaceutical Compounds from Wastewaters: A Multivariate Modelling Approach

Water

Projection to Latent Structures (PLS) regression, a generalization of multiple linear regression,... more Projection to Latent Structures (PLS) regression, a generalization of multiple linear regression, is used to model two datasets (40 observed data points each) of adsorption removal of three pharmaceutical compounds (PhCs), of different therapeutic classes and physical–chemical properties (carbamazepine, diclofenac, and sulfamethoxazole), from six real secondary effluents collected from wastewater treatment plants onto different powdered activated carbons (PACs). For the PLS regression, 25 descriptors were considered: 7 descriptors related to the PhCs properties, 10 descriptors related to the wastewaters properties (8 related to the organic matrix and 2 to the inorganic matrix), and 8 descriptors related to the PACs properties. This modelling approach showed good descriptive capability, showing that hydrophobic PhC-PAC interactions play the major role in the adsorption process, with the solvation energy and log Kow being the most suitable descriptors. The results also stress the impo...

Research paper thumbnail of Hybrid Process of Adsorption/Coagulation/Ceramic MF for Removing Pesticides in Drinking Water Treatment—Inline vs. Contact Tank PAC Dosing

Membranes, 2021

Two pilot trials of powdered activated carbon (PAC)/(coagulation)/ceramic microfiltration were co... more Two pilot trials of powdered activated carbon (PAC)/(coagulation)/ceramic microfiltration were conducted to compare continuous 10–12 mg/L PAC inline dosing with 8–10 mg/L dosing to a 2 h-contact tank. Two low turbidity/low natural organic matter (NOM, total organic carbon <2 mg C/L) surface waters spiked with 7.2–10.3 µg/L total-pesticides were tested and the dosing options were compared towards operational performance, average removal of pesticides and NOM and costs. Removal differences between the two PAC dosing options depended on pesticides’ amenability to adsorption and NOM characteristics (254 nm absorbance, A254). Waters containing low A254-absorbing NOM and only pesticides amenable to adsorption showed very high removals (all pesticides ≥93%) and no significant differences between the two PAC dosing options. Waters containing higher A254-absorbing NOM and high loads of pesticides less amenable to adsorption (dimethoate, bentazone) required higher inline PAC dose. Those or...

Research paper thumbnail of Adsorption/Coagulation/Ceramic Microfiltration for Treating Challenging Waters for Drinking Water Production

Membranes

Pressurized powdered activated carbon/coagulation/ceramic microfiltration (PAC/Alum/MF) was inves... more Pressurized powdered activated carbon/coagulation/ceramic microfiltration (PAC/Alum/MF) was investigated at pilot scale for treating low turbidity and low natural organic matter (NOM) surface waters spiked with organic microcontaminants. A total of 11 trials with clarified or non-clarified waters spiked with pesticides, pharmaceutical compounds, or microcystins were conducted to assess the removal of microcontaminants, NOM (as 254 nm absorbance, A254, and dissolved organic carbon, DOC), trihalomethane formation potential (THMFP), aerobic endospores as protozoan (oo)cysts indicators, bacteriophages as viruses indicators, and regular drinking water quality parameters. PAC/(Alum)/MF achieved 75% to complete removal of total microcontaminants with 4–18 mg/L of a mesoporous PAC and 2 h contact time, with a reliable particle separation (turbidity < 0.03 NTU) and low aluminium residuals. Microcontaminants showed different amenabilities to PAC adsorption, depending on their charge, hydro...

Research paper thumbnail of Water reclamation with hybrid coagulation–ceramic microfiltration: first part of a long-term pilot study in Portugal

Journal of Water Reuse and Desalination, 2015

Sustainable water management must nowadays consider alternative water sources and the use of recl... more Sustainable water management must nowadays consider alternative water sources and the use of reclaimed water is a good candidate. Low-pressure ceramic membrane filtration is an emerging option for safe water reclamation given its high mechanical and chemical robustness with safety and operational advantages. One-year pilot studies of hybrid coagulation–ceramic filtration were developed in Portugal in two wastewater treatment plants in the Lisbon metropolitan area. The results obtained demonstrated the technology's effectiveness, reliability and efficiency towards water quality, with the hybrid process consistently producing water highly clarified (monthly median <0.1 NTU), bacteria-free and with reduced organic matter content, regardless of the strong and severe variations in its intake.

Research paper thumbnail of Modelling chlorine residual decay as influenced by temperature

Water and Environment Journal, 2015

ABSTRACT

Research paper thumbnail of How do the HSDM and Boyd’s model compare for estimating intraparticle diffusion coefficients in adsorption processes

Adsorption, 2014

Adsorption kinetics is a key-issue for a successful activated carbon selection and design of the ... more Adsorption kinetics is a key-issue for a successful activated carbon selection and design of the treatment system. Crucial predictive aspects are the determination of the diffusion coefficients and the establishment of the controlling adsorption step. Several kinetic models have been developed and two of the most frequently used, the homogeneous surface diffusion model (HSDM) and the Boyd’s model, were applied to microcystins, and particularly MC-LR adsorption. Different initial MC-LR concentrations and carbons (particle diameter, porosity), yielding diverse Biot numbers (Bi), were tested. The model outcomes were compared, namely the Boyd’s effective intraparticle diffusion coefficient (Di) with the HSDM surface diffusion coefficient (Ds), as well as the Bi and Boyd’s criteria to establish the controlling adsorption step, which constitute a novel approach. Very good HSDM fittings were achieved with a constant diffusion model (Ds independent of MC-LR surface concentration). Di was similar to Ds whenever Boyd plots intercepted the origin. The Biot limit above which it may be considered that intraparticle diffusion is the rate limiting step depended on the carbon. A lower limit was observed for smaller carbons.

Research paper thumbnail of Modelling and understanding the competitive adsorption of microcystins and tannic acid

Water Research, 2013

A predictive model integrating adsorption kinetics and competitive isotherm models (Homogeneous S... more A predictive model integrating adsorption kinetics and competitive isotherm models (Homogeneous Surface Diffusion Model, Freundlich-type and Fritz &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Schlünder isotherms) was developed to describe and understand the competing mechanism(s) and the ionic strength (IS) role on microcystins (MC) and tannic acid (TA) competitive adsorption. The developed model showed good agreement with the experimental data obtained from batch adsorption tests and isotherms conducted with MC extracts and TA model solutions (single-solute and multicomponent, IS presence and absence) using a mesoporous powdered activated carbon (PAC). Results confirm that similar size molecules such as MC and TA are strong competitors and tannin-rich waters may severely affect MC residuals in the treated water. Unlike usually considered, both direct site and pore blockage mechanisms seem relevant. Competition effects appear to be more dependent on the competitor/contaminant molar ratio than on the initial concentrations. The IS affects the extent and the mechanisms of MC-TA competitive adsorption, reducing PAC dose for safe control of MC residuals. The developed model, including a Ds analysis, is an important tool to understand the competitive adsorption of similar size adsorbates.

Research paper thumbnail of Aroma recovery by integration of sweeping gas pervaporation and liquid absorption in membrane contactors

Separation and Purification Technology, 2009

An integrated process for recovering of aroma compounds from dilute natural matrices is proposed,... more An integrated process for recovering of aroma compounds from dilute natural matrices is proposed, combining the advantages of organophilic and sweeping gas pervaporation with gas–liquid absorption in membrane contactors. This process avoids the use of vacuum conditions and condensation steps for aroma recovery. Additionally, it presents the advantage of stabilising the target aroma compounds after being captured in a liquid

Research paper thumbnail of Kinetics of phenylalanine extraction and reextraction by cationic reversed micelles using a diffusion cell

Chemical Engineering Science, 2000

ABSTRACT

Research paper thumbnail of Extraction and re-extraction of phenylalanine by cationic reversed micelles in hollow fibre contactors

Journal of membrane science, 1999

This work reports the extraction of phenylalanine with a reversed micellar system consisting of T... more This work reports the extraction of phenylalanine with a reversed micellar system consisting of TOMAC/hexanol/n-heptane using hydrophobic hollow ®bre modules. Extraction studies were performed under different hydrodynamic conditions and mass transfer correlations for the shell and tube sides were developed. The correlations were determined using a one-step calculation method and the results obtained are in agreement with the literature for the range of Reynolds numbers studied. Based on the obtained correlations and on the resistance in series model, a transport model was developed in which the phenylalanine concentration in the feed phase can be predicted during the experimental run. For the extraction process the model developed describes satisfactorily the evolution of phenylalanine concentration with time under different hydrodynamic conditions. The re-extraction process was found to be kinetically controlled due to the higher dynamic stability of reversed micelles when contacting a stripping phase with high ionic strength. The experimental results obtained were described using a kinetic model developed. Simultaneous extraction/stripping of phenylalanine was also accomplished using two hollow ®bre modules in series, using different volume phase ratios. The mass transfer process was modelled and compared with the experimental results.

Research paper thumbnail of Through the Ion Exchange Membrane Bioreactor

Removal of heavy metals from drinking water supplies through the ion exchange membrane bioreactor

Research paper thumbnail of Pilot Studies and Cost Analysis of Hybrid Powdered Activated Carbon/Ceramic Microfiltration for Controlling Pharmaceutical Compounds and Organic Matter in Water Reclamation

Water, 2019

This paper addresses the enhanced removal of pharmaceutical compounds (PhCs), a family of contami... more This paper addresses the enhanced removal of pharmaceutical compounds (PhCs), a family of contaminants of emerging concern, and effluent organic matter (EfOM) in water reclamation by powdered activated carbon/coagulation/ceramic microfiltration (PAC/cMF). Four chemically diverse PhCs are targeted: ibuprofen (IBP), carbamazepine (CBZ), sulfamethoxazole (SMX) and atenolol (ATN). Pilot assays (100 L/(m2 h), 10 mg Fe/L) run with PhC-spiked sand-filtered secondary effluent and 15 mg/L PAC dosed in-line or to a 15-min contactor. They showed no PAC-driven membrane fouling and +15 to +18% added removal with PAC contactor, reaching significant removals of CBZ and ATN (59%–60%), SMX (50%), colour (48%), A254 (35%) and dissolved organic carbon (DOC, 28%). Earlier long-term demo tests with the same pilot proved PAC/cMF to consistently produce highly clarified (monthly median < 0.1 NTU) and bacteria-free water, regardless of the severe variations in its intake. A detailed cost analysis points...

Research paper thumbnail of TGumí, MValiente CPalet JMembrSci 256 - 2005- p150

Research paper thumbnail of Modelling of the enantio-selective extraction of propranolol in a biphasic system

Separation and Purification Technology, 2007

This work reports the study of the racemic resolution of propranolol, an amino-alcohol with prove... more This work reports the study of the racemic resolution of propranolol, an amino-alcohol with proven efficacy in the treatment of hypertension, ischemic heart disease and arrhythmia. Among all ␤-blockers, propranolol was selected, as a case study, also due to its enantiomers diverse properties. The studies performed involve an enantio-selective extraction in a biphasic system, where propranolol first reacts with boric acid in aqueous media and then complexes with a chiral di-dodecyltartrate selector present in the organic phase. Factors affecting the extraction mechanism were analysed, namely the influence of the concentrations of the tartrate complexing agent and boric acid and the pH. A comprehensive mechanism of extraction is proposed. Due to its complexity the mathematical approach developed involves the use of a hybrid model, with a deterministic component, describing the material balance equations of the reactions involved, and a neural network, which allows accounting for the variable non-selective partition of propranolol.

Research paper thumbnail of Enantioselective Separation of Propranolol by Chiral Activated Membranes

Separation Science and Technology, 2005

The employment of racemic drugs has become unattractive due to policy changes introduced by regul... more The employment of racemic drugs has become unattractive due to policy changes introduced by regulatory agencies. As a consequence, pharmaceutical industries have been forced to develop new technologies for preparing non-racemic drugs. Resolution can be performed by membrane technology due to its several advantages over traditional methods. And, in particular chiral activated membranes can be used for the enantioselective separation in continuous mode with a longer lifetime than corresponding liquid membrane systems. 2 In this work, chiral activated membranes have been tested for the enantioseparation of the racemic drug propranolol. Polysulfone (PS) based membranes have been prepared for this purpose, using N-hexadecyl-L-hydroxyproline (HHP) and L-din -dodecyltartrate (L-DDT) as chiral carriers, respectively. Kinetic experiments have been carried out using a membrane module with two rectangular channels separated by the membrane, which allows for a well-defined hydrodynamics of the feed and stripping phases. Propranolol transport across the membrane depends on its diffusion rate from the bulk solution to the membrane surface and also on the relative amount of carrier present in the membrane. Therefore, the influence of both the solute/carrier ratio and the flow rates of the feed and stripping phases on the rate of extraction and on the selectivity of the process was evaluated for both chemical systems. Modelling of kinetic experiments has been performed and mass transfer coefficients obtained for both systems were compared.

Research paper thumbnail of Removal of valeric acid from wastewaters by membrane contactors

Journal of Membrane Science, 1997

Membrane contactors, providing a non-dispersive extraction technique, were used for the removal o... more Membrane contactors, providing a non-dispersive extraction technique, were used for the removal of valeric 01-pentanoic) acid from synthetic aqueous solutions simulating an industrial wastewater from polymer manufacturing. Amberlite LA-2 (secondary amine) in toluene was chosen as the extraction system. Equilibrium conditions were determined and mechanistically modelled for different extractant concentrations allowing the further calculation of mass transfer coefficients. The influence of the hydrodynamics of both the aqueous and organic phases on the overall mass transfer coefficient, calculated through two proposed methods, was studied. The integration of extraction and backextraction was also carried out, allowing a further acid removal with lower extractant concentrations. ~(, 1997 Elsevier Science B.V.

Research paper thumbnail of Racemic resolution of propranolol in membrane contactors: Modelling and process optimisation

Journal of Membrane Science, 2007

This work reports the study of the chiral resolution of propranolol, an amino-alcohol with proven... more This work reports the study of the chiral resolution of propranolol, an amino-alcohol with proven efficacy in the treatment of hypertension, ischemic heart disease and arrhythmia. Among all β-blockers, propranolol was selected also due to the distinct properties of its enantiomers.Extraction and stripping kinetic studies were performed using a tubular module contactor, with ceramic ultrafiltration supporting membranes. Three different configurations were evaluated in terms of enantio-selectivity and enantiomeric excess of the desired enantiomer: (1) single extraction; (2) simultaneous extraction, where each enantiomer is preferentially recovered to a different extraction phase; (3) simultaneous selective extraction and stripping of a target enantiomer.The kinetic model developed, comprising an equilibrium modelling of the extraction process and differential mass balances in pseudo steady-state, fully describes the overall process. Moreover, the model allowed the optimisation of the operating conditions and enables to predict the optimum combination of module configurations in order to maximise the enantiomeric excess.

Research paper thumbnail of Hybrid modelling of the racemic resolution of propranolol in membrane contactors

Desalination, 2006

... in membrane contactors Rui MC Viegas*, João G. Crespo, Isabel M. Coelhoso CQFB/REQUIMTE – Dep... more ... in membrane contactors Rui MC Viegas*, João G. Crespo, Isabel M. Coelhoso CQFB/REQUIMTE – Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal email: rui.viegas@dq.fct.unl.pt ...

Research paper thumbnail of Removal of heavy metals from drinking water supplies through the ion exchange membrane bioreactor

Desalination, 2006

Arsenic (As) and mercury (Hg) are two highly toxic heavy metals that must be removed to very low ... more Arsenic (As) and mercury (Hg) are two highly toxic heavy metals that must be removed to very low levels in drinking water supplies. A novel treatment method for the removal of both compounds is the ion exchange membrane bioreactor (IEMB) process, which incorporates pollutant ...

Research paper thumbnail of Mass transfer correlations in membrane extraction: Analysis of Wilson-plot methodology

Journal of Membrane Science, 1998

Mass transfer correlations have been obtained for the past eight decades by the Wilson-plot metho... more Mass transfer correlations have been obtained for the past eight decades by the Wilson-plot method which has proved to be suitable for systems operating in steady-state conditions and where the only variable is the¯uid velocity. In this work, this methodology is evaluated by using a membrane extraction process with a hollow-®ber membrane contactor as a case study. Taking into consideration the currently available mathematical tools, alternative methods to obtain mass transfer correlations are proposed and discussed. The proposed one-step calculation methodology proved to be a most suitable approach, leading to a drastic reduction in the errors associated with the estimated parameters. Additionally, improvements were observed when accounting for the partition coef®cient variation.

Research paper thumbnail of Key Factors for Activated Carbon Adsorption of Pharmaceutical Compounds from Wastewaters: A Multivariate Modelling Approach

Water

Projection to Latent Structures (PLS) regression, a generalization of multiple linear regression,... more Projection to Latent Structures (PLS) regression, a generalization of multiple linear regression, is used to model two datasets (40 observed data points each) of adsorption removal of three pharmaceutical compounds (PhCs), of different therapeutic classes and physical–chemical properties (carbamazepine, diclofenac, and sulfamethoxazole), from six real secondary effluents collected from wastewater treatment plants onto different powdered activated carbons (PACs). For the PLS regression, 25 descriptors were considered: 7 descriptors related to the PhCs properties, 10 descriptors related to the wastewaters properties (8 related to the organic matrix and 2 to the inorganic matrix), and 8 descriptors related to the PACs properties. This modelling approach showed good descriptive capability, showing that hydrophobic PhC-PAC interactions play the major role in the adsorption process, with the solvation energy and log Kow being the most suitable descriptors. The results also stress the impo...

Research paper thumbnail of Hybrid Process of Adsorption/Coagulation/Ceramic MF for Removing Pesticides in Drinking Water Treatment—Inline vs. Contact Tank PAC Dosing

Membranes, 2021

Two pilot trials of powdered activated carbon (PAC)/(coagulation)/ceramic microfiltration were co... more Two pilot trials of powdered activated carbon (PAC)/(coagulation)/ceramic microfiltration were conducted to compare continuous 10–12 mg/L PAC inline dosing with 8–10 mg/L dosing to a 2 h-contact tank. Two low turbidity/low natural organic matter (NOM, total organic carbon <2 mg C/L) surface waters spiked with 7.2–10.3 µg/L total-pesticides were tested and the dosing options were compared towards operational performance, average removal of pesticides and NOM and costs. Removal differences between the two PAC dosing options depended on pesticides’ amenability to adsorption and NOM characteristics (254 nm absorbance, A254). Waters containing low A254-absorbing NOM and only pesticides amenable to adsorption showed very high removals (all pesticides ≥93%) and no significant differences between the two PAC dosing options. Waters containing higher A254-absorbing NOM and high loads of pesticides less amenable to adsorption (dimethoate, bentazone) required higher inline PAC dose. Those or...

Research paper thumbnail of Adsorption/Coagulation/Ceramic Microfiltration for Treating Challenging Waters for Drinking Water Production

Membranes

Pressurized powdered activated carbon/coagulation/ceramic microfiltration (PAC/Alum/MF) was inves... more Pressurized powdered activated carbon/coagulation/ceramic microfiltration (PAC/Alum/MF) was investigated at pilot scale for treating low turbidity and low natural organic matter (NOM) surface waters spiked with organic microcontaminants. A total of 11 trials with clarified or non-clarified waters spiked with pesticides, pharmaceutical compounds, or microcystins were conducted to assess the removal of microcontaminants, NOM (as 254 nm absorbance, A254, and dissolved organic carbon, DOC), trihalomethane formation potential (THMFP), aerobic endospores as protozoan (oo)cysts indicators, bacteriophages as viruses indicators, and regular drinking water quality parameters. PAC/(Alum)/MF achieved 75% to complete removal of total microcontaminants with 4–18 mg/L of a mesoporous PAC and 2 h contact time, with a reliable particle separation (turbidity < 0.03 NTU) and low aluminium residuals. Microcontaminants showed different amenabilities to PAC adsorption, depending on their charge, hydro...

Research paper thumbnail of Water reclamation with hybrid coagulation–ceramic microfiltration: first part of a long-term pilot study in Portugal

Journal of Water Reuse and Desalination, 2015

Sustainable water management must nowadays consider alternative water sources and the use of recl... more Sustainable water management must nowadays consider alternative water sources and the use of reclaimed water is a good candidate. Low-pressure ceramic membrane filtration is an emerging option for safe water reclamation given its high mechanical and chemical robustness with safety and operational advantages. One-year pilot studies of hybrid coagulation–ceramic filtration were developed in Portugal in two wastewater treatment plants in the Lisbon metropolitan area. The results obtained demonstrated the technology's effectiveness, reliability and efficiency towards water quality, with the hybrid process consistently producing water highly clarified (monthly median <0.1 NTU), bacteria-free and with reduced organic matter content, regardless of the strong and severe variations in its intake.

Research paper thumbnail of Modelling chlorine residual decay as influenced by temperature

Water and Environment Journal, 2015

ABSTRACT

Research paper thumbnail of How do the HSDM and Boyd’s model compare for estimating intraparticle diffusion coefficients in adsorption processes

Adsorption, 2014

Adsorption kinetics is a key-issue for a successful activated carbon selection and design of the ... more Adsorption kinetics is a key-issue for a successful activated carbon selection and design of the treatment system. Crucial predictive aspects are the determination of the diffusion coefficients and the establishment of the controlling adsorption step. Several kinetic models have been developed and two of the most frequently used, the homogeneous surface diffusion model (HSDM) and the Boyd’s model, were applied to microcystins, and particularly MC-LR adsorption. Different initial MC-LR concentrations and carbons (particle diameter, porosity), yielding diverse Biot numbers (Bi), were tested. The model outcomes were compared, namely the Boyd’s effective intraparticle diffusion coefficient (Di) with the HSDM surface diffusion coefficient (Ds), as well as the Bi and Boyd’s criteria to establish the controlling adsorption step, which constitute a novel approach. Very good HSDM fittings were achieved with a constant diffusion model (Ds independent of MC-LR surface concentration). Di was similar to Ds whenever Boyd plots intercepted the origin. The Biot limit above which it may be considered that intraparticle diffusion is the rate limiting step depended on the carbon. A lower limit was observed for smaller carbons.

Research paper thumbnail of Modelling and understanding the competitive adsorption of microcystins and tannic acid

Water Research, 2013

A predictive model integrating adsorption kinetics and competitive isotherm models (Homogeneous S... more A predictive model integrating adsorption kinetics and competitive isotherm models (Homogeneous Surface Diffusion Model, Freundlich-type and Fritz &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Schlünder isotherms) was developed to describe and understand the competing mechanism(s) and the ionic strength (IS) role on microcystins (MC) and tannic acid (TA) competitive adsorption. The developed model showed good agreement with the experimental data obtained from batch adsorption tests and isotherms conducted with MC extracts and TA model solutions (single-solute and multicomponent, IS presence and absence) using a mesoporous powdered activated carbon (PAC). Results confirm that similar size molecules such as MC and TA are strong competitors and tannin-rich waters may severely affect MC residuals in the treated water. Unlike usually considered, both direct site and pore blockage mechanisms seem relevant. Competition effects appear to be more dependent on the competitor/contaminant molar ratio than on the initial concentrations. The IS affects the extent and the mechanisms of MC-TA competitive adsorption, reducing PAC dose for safe control of MC residuals. The developed model, including a Ds analysis, is an important tool to understand the competitive adsorption of similar size adsorbates.

Research paper thumbnail of Aroma recovery by integration of sweeping gas pervaporation and liquid absorption in membrane contactors

Separation and Purification Technology, 2009

An integrated process for recovering of aroma compounds from dilute natural matrices is proposed,... more An integrated process for recovering of aroma compounds from dilute natural matrices is proposed, combining the advantages of organophilic and sweeping gas pervaporation with gas–liquid absorption in membrane contactors. This process avoids the use of vacuum conditions and condensation steps for aroma recovery. Additionally, it presents the advantage of stabilising the target aroma compounds after being captured in a liquid

Research paper thumbnail of Kinetics of phenylalanine extraction and reextraction by cationic reversed micelles using a diffusion cell

Chemical Engineering Science, 2000

ABSTRACT

Research paper thumbnail of Extraction and re-extraction of phenylalanine by cationic reversed micelles in hollow fibre contactors

Journal of membrane science, 1999

This work reports the extraction of phenylalanine with a reversed micellar system consisting of T... more This work reports the extraction of phenylalanine with a reversed micellar system consisting of TOMAC/hexanol/n-heptane using hydrophobic hollow ®bre modules. Extraction studies were performed under different hydrodynamic conditions and mass transfer correlations for the shell and tube sides were developed. The correlations were determined using a one-step calculation method and the results obtained are in agreement with the literature for the range of Reynolds numbers studied. Based on the obtained correlations and on the resistance in series model, a transport model was developed in which the phenylalanine concentration in the feed phase can be predicted during the experimental run. For the extraction process the model developed describes satisfactorily the evolution of phenylalanine concentration with time under different hydrodynamic conditions. The re-extraction process was found to be kinetically controlled due to the higher dynamic stability of reversed micelles when contacting a stripping phase with high ionic strength. The experimental results obtained were described using a kinetic model developed. Simultaneous extraction/stripping of phenylalanine was also accomplished using two hollow ®bre modules in series, using different volume phase ratios. The mass transfer process was modelled and compared with the experimental results.