Showing papers by "João G. Crespo published in 2017"

Morphological, chemical surface and filtration characterization of a new silicon carbide membrane

Abstract: A new silicon carbide ceramic membrane consisting of a unique top layer on a SiC support for application in oily wastewaters filtration was produced and characterized in terms of morphology and chemical surface composition by scanning electron microscopy and X-ray photoelectron spectroscopy measurements. The manufacturing process of this new membrane allows time and economic savings when compared with a two layers membrane previously obtained. The new membrane has a smooth top layer with controlled porosity and a higher permeability compared to already developed commercial membranes. Moreover, it is extremely efficient to remove total suspended solids as well as oil and grease and, consequently, it can be applied to effective treatment of industrial oily wastewaters.

Assessment of a New Silicon Carbide Tubular Honeycomb Membrane for Treatment of Olive Mill Wastewaters.

Abstract: Extremely high removals of total suspended solids and oil and grease were obtained when olive mill wastewaters were filtered using new silicon carbide tubular membranes. These new membranes were used at constant permeate flux to treat real olive mill wastewaters at pilot scale. The filtration conditions were evaluated and optimized in terms of the selection of the permeate flux and flux maintenance strategies employed—backpulsing and backwashing—in order to reduce fouling formation. The results obtained reveal that the combination of backpulses and backwashes helps to maintain the permeate flux, avoids transmembrane pressure increase and decreases the cake resistance. Moreover, membrane cleaning procedures were compared and the main agents responsible for fouling formation identified. Results also show that, under total recirculation, despite an increased concentration of pollutants in the feed stream, the quality of the permeate is maintained. Membrane filtration using silicon carbide membranes is an effective alternative to dissolved air flotation and can be applied efficiently to remove total suspended solids and oil and grease from olive mill wastewaters.

Pilot scale nanofiltration treatment of olive mill wastewater: a technical and economical evaluation

Abstract: The treatment of large volumes of olive mill wastewater is presently a challenge. This study reports the technical and economical feasibility of a sequential treatment of olive mill wastewater comprising a dissolved air flotation pre-treatment and nanofiltration. Different pilot nanofiltration assays were conducted in a concentration mode up to different volume reduction factors (29, 45, 58, and 81). Data attained demonstrated that nanofiltration can be operated at considerably high volume reduction factors and still be effective towards the removal of several components. A flux decline of approximately 50% was observed at the highest volume reduction factor, mainly due to increase of the osmotic pressure. Considerably high rejections were obtained across all experiments for total suspended solids (83 to >99%), total organic carbon (64 to 99%), chemical oxygen demand (53 to 77%), and oil and grease (67 to >82%). Treated water was in compliance with European legal limits for discharge regarding total suspended solids and oil and grease. The potential recovery of phenolic compounds was evaluated and found not relevant. It was demonstrated that nanofiltration is economically feasible, involving operation costs of approximately 2.56–3.08 €/m3, depending on the working plan schedule and volume reduction factor, and requiring a footprint of approximately 52 m2 to treat 1000 m3 of olive mill wastewater.

2D Fluorescence spectroscopy for monitoring Dunaliella salina concentration and integrity during membrane harvesting

Abstract: Dunaliella salina is able to produce simultaneously several valuable compounds (such as lipids, carotenes and functional proteins) within the biorefinery concept. However due to the lack of rigid cell wall, this microalgae can easily disrupt during harvesting, losing valuable compounds to the saline water, affecting the downstream processing. Therefore, the development of non-invasive tools able to monitor cell concentration and integrity in real-time, can assist the development of harvesting methodologies. In the present work, a monitoring approach was developed based on two-dimensional (2D) fluorescence spectroscopy. Mathematical analysis of the monitoring data involved the use of Principal Component Analysis (PCA) and Projection to Latent Structures (PLS) modelling. For green D. salina, the models developed for prediction of cell number and percentage of viability captured 90.6% and 86.3% of variance, respectively. Both models have R2 of 0.8 and 0.9, respectively for validation and training. Similar values were found for the prediction of cell number when using data from growth kinetics and harvesting combined. Orange D. salina rupture was also successfully modelled with 95% of variance captured and R2 of 0.9 for both training and validation. The combined approach using 2D fluorescence spectroscopy and the mathematical analysis proved to have the potential to monitor D. salina during cell growth and harvesting within a biorefinery concept.

Development of photocatalytic titanium dioxide membranes for degradation of recalcitrant compounds

Abstract: BACKGROUND Immobilization of TiO2 photoactive nanoparticles on a nanofiltration membrane without loss of permselectivity properties is currently a challenge. In this study, immobilization of TiO2 nanoparticles on a ceramic commercial membrane surface by direct current reactive magnetron sputtering was addressed. The best membrane was compared with an unmodified membrane and a membrane modified by a generic chemical–physical method in terms of membrane permselectivity and photocatalytic properties. RESULTS Magnetron sputtering was able to achieve similar photocatalytic activity to the chemical–physical method, where Evonik P25 TiO2 nanoparticles were used, while maintaining membrane rejection and permeability. The layer formed by magnetron sputtering exhibits uniformly distributed nanostructured columns, aligned perpendicularly to the membrane surface. Furthermore, the membrane hydrophilicity increase achieved is promising for fouling control. A shorter sputtering time and distance between the titanium target and the membrane were preferable to effectively degrade the pesticides diuron and chlorfenvinphos. Under optimum sputtering conditions, 95% and 78% increases were attained for the degradation of diuron and chlorfenvinphos, respectively, compared with the unmodified membrane. CONCLUSION The photocatalytic membranes developed are potential candidates for the simultaneous retention and photocatalytic degradation of recalcitrant micropollutants. However, if the purpose is to retain low molecular weight molecules, retentive properties should be improved. © 2016 Society of Chemical Industry

Ion-Exchange Membranes for Stable Derivatization of Protein Crystals

Abstract: Ion-exchange membranes were applied in this work to diffuse ions and heavy atoms inside protein crystals in order to gently perform their derivatization. The ion-exchange process rate for three different ions, bromide (Br–), platinum (Pt+ through PtCl42–), and mercury (Hg2+), was evaluated, allowing to determine the concentration of these ions in the crystal solution over time and to evaluate their effect on the crystals. Nafion and Neosepta AXE01, cation and anion exchange-membranes, respectively, were used for transport of cations and anions to hen egg white lysozyme (HEWL) crystals, selected as model protein. X-ray diffraction analysis of the crystals confirmed the attainment of the derivatives and allowed the ab initio building of the bromide derivative model. Derivatization experiments were also conducted by the conventional method, directly soaking the crystals in the heavy atom solution. It was possible to conclude that the controlled diffusion, regulated by the membrane, increases the crystal’s st...