Gemma Gutiérrez

Treatment of a waste oil-in-water emulsion from a copper-rolling process by ultrafiltration and vacuum evaporation.

A process is proposed for the treatment of a waste oil-in-water (O/W) emulsion generated in an industrial copper-rolling operation. The use of demulsifier agents improves the subsequent treatment by techniques such as ultrafiltration (UF) or evaporation. The effluent COD is reduced up to 50% when the O/W emulsion is treated by UF using a flat 30 nm TiO(2) ceramic membrane (ΔP = 0.1 MPa) and up to 70% when it is treated by vacuum evaporation, after an emulsion destabilization pretreatment in both cases. Increases in the UF permeate flux and in the evaporation rate are observed when a chemical demulsifier is used in the pretreatment step. A combined process consisting of destabilization/settling, UF, and vacuum evaporation can yield a very high-quality aqueous effluent that could be used for process cooling or emulsion reformulation.

TREATMENT OF OILY WASTEWATER

Oily wastewaters are generated in many industrial processes, such as petroleum refining, petrochemical, food, leather and metal finishing. Fats, oils and greases (FOG’s) present in these wastewaters have to be removed before the water can be reused in a closed-loop process or discharged into the sewer system or to surface waters. These oily waters are mainly in the form of oil-in-water (O/W) emulsions that pose a great problem in facilities attempting to stay in compliance with discharge limits. Emulsion breaking and oil removal require a basic understanding of the physical properties and chemical composition of O/W emulsions. Several properties playing a key role in the stability of an O/W emulsion should be measured for the selection of the appropriate separation process. Only those of industrial relevance will be discussed here, specifically, surface and interfacial tension, contact angle (wetting), zeta potential and droplet size distribution. Treatment of oily wastewaters is performed by a variety of methods and the degree of oil removal depends mainly on the concentration and physical nature of the oil present and its droplet size. The purpose of this work is to study oil/water system characteristics and properties, and techniques for removing oil and grease from industrial wastewaters in analogy with sewage treatment processes. These techniques include gravity and centrifugal separations, chemical treatment, flotation, filtration, membrane processes, evaporation, activated carbon adsorption, biological treatment, and integrated or hybrid processes. Operating parameters, equipment design, treatment costs, range of operation, and the possibility of O/W emulsion reformulation before treatment will also be covered.

Influence of Coagulant Salt Addition on the Treatment of Oil‐in‐Water Emulsions by Centrifugation, Ultrafiltration, and Vacuum Evaporation

Abstract Droplet size is a key factor in the treatment of oil‐in‐water (O/W) emulsions, because of its influence on emulsion properties. The addition of a coagulant salt generally causes emulsion destabilization, increasing the droplet size, and enhancing coalescence between oil droplets, which helps its further treatment. The influence of CaCl2 addition on droplet size distribution of a commercial O/W emulsion used in machining processes was studied in order to facilitate oil removal and to improve its further treatment by centrifugation, ultrafiltration (UF) and vacuum evaporation. The critical coagulation concentration (CCC) was observed at a CaCl2 concentration of 0.05 M. The quality of the final aqueous effluent, expressed as its chemical oxygen demand (COD) value, was compared for all treatments. The highest COD values were obtained for centrifugation, while the COD of the UF permeate was approximately constant for all UF trials. The best effluent quality was obtained by vacuum evaporation. A combination of these techniques should be appropriate for most industrial treatments of O/W emulsions, depending on the subsequent use of the resulting aqueous effluent.

Formulation of resveratrol entrapped niosomes for topical use.

A new approach to the formulation of resveratrol (RSV) entrapped niosomes for topical use is proposed in this work. Niosomes were formulated with Gelot 64 (G64) as surfactant, and two skin-compatible unsaturated fatty acids (oleic and linoleic acids), commonly used in pharmaceutical formulations, as penetration enhancers. Niosomes were prepared by two different methods: a thin film hydration method with minor modifications followed by a sonication stage (TFH-S), and an ethanol injection modified method (EIM). Niosomes prepared with the EIM method were in the range of 299-402 nm, while the TFH-S method produced larger niosomes in the range of 293-496 nm. Moreover, niosomes with higher RSV entrapment efficiency (EE) and better stability were generated by the EIM method. Ex vivo transdermal experiments, carried out in Franz diffusion cells on newborn pig skin, indicated that niosomes prepared by the EIM method were more effective for RSV penetration in epidermis and dermis (EDD), with values up to 21% for both penetration enhancers tested. The EIM method, which yielded the best RSV-entrapped niosomes, seems to be the most suitable for scaling up.

Bifunctional viscous nanovesicles co-loaded with resveratrol and gallic acid for skin protection against microbial and oxidative injuries

&NA; Resveratrol and gallic acid were co‐loaded in phospholipid vesicles aiming at protecting the skin from external injuries, such as oxidative stress and microbial infections. Liposomes were prepared using biocompatible phospholipids dispersed in water. To improve vesicle stability and applicability, the phospholipids and the phenols were dispersed in water/propylene glycol or water/glycerol, thus obtaining PEVs and glycerosomes, respectively. The vesicles were characterized by size, morphology, physical stability, and their therapeutic efficacy was investigated in vitro. The vesicles were spherical, unilamellar and small in size: liposomes and glycerosomes were around 70 nm in diameter, while PEVs were larger (˜170 nm). The presence of propylene glycol or glycerol increased the viscosity of the vesicle systems, positively affecting their stability. The ability of the vesicles to promote the accumulation of the phenols (especially gallic acid) in the skin was demonstrated, as well as their low toxicity and great ability to protect keratinocytes and fibroblasts from oxidative damage. Additionally, an improvement of the antimicrobial activity of the phenols was shown against different skin pathogens. The co‐loading of resveratrol and gallic acid in modified phospholipid vesicles represents an innovative, bifunctional tool for preventing and treating skin affections. Graphical abstract Figure. No caption available.

Comparative Emulsifying Properties of Octenyl Succinic Anhydride (OSA)-Modified Starch: Granular Form vs Dissolved State

The emulsifying ability of OSA-modified and native starch in the granular form, in the dissolved state and a combination of both was compared. This study aims to understand mixed systems of particles and dissolved starch with respect to what species dominates at droplet interfaces and how stability is affected by addition of one of the species to already formed emulsions. It was possible to create emulsions with OSA-modified starch isolated from Quinoa as sole emulsifier. Similar droplet sizes were obtained with emulsions prepared at 7% (w/w) oil content using OSA-modified starch in the granular form or molecularly dissolved but large differences were observed regarding stability. Pickering emulsions kept their droplet size constant after one month while emulsions formulated with OSA-modified starch dissolved exhibited coalescence. All emulsions stabilized combining OSA-modified starch in granular form and in solution showed larger mean droplet sizes with no significant differences with respect to the order of addition. These emulsions were unstable due to coalescence regarding presence of free oil. Similar results were obtained when emulsions were prepared by combining OSA-modified granules with native starch in solution. The degree of surface coverage of starch granules was much lower in presence of starch in solution which indicates that OSA-starch is more surface active in the dissolved state than in granular form, although it led to unstable systems compared to starch granule stabilized Pickering emulsions, which demonstrated to be extremely stable.

Treatment of Oily Wastewater by Membrane Hybrid Processes

Oily wastewaters are usually treated by physical, chemical and biological methods. Most conventional methods (coagulation, sedimentation, centrifugation and filtration) are not efficient in treating stable oil-in-water (O/W) emulsions, especially when the oil droplets are finely dispersed and the concentration is very low. These techniques can reduce oil concentrations by no more than 1% by volume of the total wastewater and cannot efficiently remove oil droplets below 10 μm. Hence, further treatment is needed to meet effluent standards. Membrane processes have found an increasing number of applications in the treatment of complex oily wastewater. However, sometimes it is not desirable or even possible to use a membrane system to carry out the entire separation because of the effluent nature that may cause severe fouling of the membrane. In those situations a pretreatment of the effluent by conventional methods may be suitable for a better process performance. These membrane-based hybrid processes combine a conventional process (mechanical, chemical or thermal) with a membrane separation. In this review lecture the design parameters and performance of conventional processes for the treatment of oily wastewater are summarized and several membrane hybrid processes and chosen examples are presented.

Combined emulsifying capacity of polysaccharide particles of different size and shape

The aim of this study is to understand mixed systems of two types of particles with different size and shape, quinoa starch granules (NQ) and cellulose nanocrystals (CNC), to stabilize oil-in-water (O/W) emulsions. This study considers the extent of Pickering stabilization with respect to which particle type dominates at droplet interfaces and how stability is affected by the addition of one particle type to already formed emulsions, or combining both, simultaneously. Results demonstrate that the order of addition has an influence allowing to predominantly have NQ particles at the interface when both types are added simultaneously. However when CNC is added first, both types are responsible for emulsion stabilization leading to a system with an intermediate droplet size yet with a higher stability compared to single particle formulations. A dual stabilization mechanism is observed, large particles prevent coalescence and small particles regulate the curvature of the interface and govern the droplet size.

Therapeutic biomaterials based on extracellular vesicles: classification of bio-engineering and mimetic preparation routes

ABSTRACT Extracellular vesicles (EVs) are emerging as novel theranostic tools. Limitations related to clinical uses are leading to a new research area on design and manufacture of artificial EVs. Several strategies have been reported in order to produce artificial EVs, but there has not yet been a clear criterion by which to differentiate these novel biomaterials. In this paper, we suggest for the first time a systematic classification of the terms used to build up the artificial EV landscape, based on the preparation method. This could be useful to guide the derivation to clinical trial routes and to clarify the literature. According to our classification, we have reviewed the main strategies reported to date for their preparation, including key points such as: cargo loading, surface targeting strategies, purification steps, generation of membrane fragments for the construction of biomimetic materials, preparation of synthetic membranes inspired in EV composition and subsequent surface decoration.

Fully Artificial Exosomes: Towards New Theranostic Biomaterials

Bionanotechnology routes have been recently developed to produce fully artificial exosomes: biomimetic particles designed to overcome certain limitations in extracellular vesicle (EV) biology and applications. These particles could soon become true therapeutic biomaterials. Here, we outline their current preparation techniques, their explored and future possibilities, and their present limits.