Patricia Luis Alconero

Forward osmosis: Understanding the hype

The scientific interest in forward osmosis has increased dramatically over the last decade. The hype has resulted in a high scientific production, but research activities seem to go in all directions, and the real benefits of the process are not always well understood. This paper aims to give some directions based on the current state of the art. Without going into details about the process itself, the current research lines and their background are described. While some of these are important, others – notably the search for alternative draw solutions – have become the Holy Grail of forward osmosis. The further analysis of the process is based on suggested applications and uses the observations made on contemporary research topics in the field. At first, direct application of forward osmosis for potable water production is considered. This leads back to the research challenges of the reverse draw solute flux, concentration polarization, and the regeneration of the draw solution. Special attention is given to desalination, as forward osmosis is often incorrectly denoted as a desalination technology. It can be used in the context of desalination; however, the question remains in which applications this is of interest. Combining desalination and wastewater treatment is one such interesting application, which is further described in this paper for some types of wastewater found in the literature. In the last part, the paper emphasizes the need to develop processes in which the challenge of the draw solution is intrinsically solved. The foremost example of such application is the one for which forward osmosis was developed four decades ago: the use of impaired water sources diluted through a forward osmosis membrane by using a concentrated fertilizer solution to provide osmotic pressure. This application was suggested four decades ago but was never applied on any scale. Process economics and an insufficiently developed technology may have been the basis of this failure. However, a renewed focus on such applications would allow forward osmosis to come to its real potential and contribute to solving the global water challenge.

A biologically inspired hydrophobic membrane for application in pervaporation

An artificial polydimethylsiloxane/polyphenylsulfone (PDMS/PPSU) membrane, which emulates the hydrophobic behavior of natural membranes, was synthesized. Hydrophobicity was achieved by coating the membrane surface sublayer using conventional silicon material, which imitates the character of epicuticular wax (EW) of Prunus laurocerasus L. leaves. It was then applied as a separation medium in pervaporation (PV) of diluted mixtures of ethyl acetate and aroma compounds. The membranes biomimetic characteristics were evaluated using surface morphology analyses, that is, Fourier transform infrared (FTIR), water contact angle measurements, and SEM imaging. A comparison of properties of the membranes synthesized in this work against selected hydrophobic plant leaves indicated a good agreement. PV using these biologically inspired artificial membranes demonstrated preference for the permeation of ethyl acetate. Besides intrinsic characteristics, it was also observed that the chemical potential is highly influential in activating sorption, diffusion, and desorption of a specific compound.

Hybrid Molecular QSAR Model for Toxicity Estimation: Application to Ionic Liquids

Abstract Ionic Liquids have been suggested as one of the main possibilities to avoid solvent losses in chemical processes, but toxicity needs to be evaluated before technical applications. A quantitative structure-activity relationship (QSAR) based on a hybrid molecular QSAR model has been applied to the modeling of the aquatic ecotoxicity ( Vibrio fischeri EC 50 ) of ionic liquids. In this work, the ionic liquids database has a number of 96 data, which has been improved using data from the literature and experimental data following the UNE EN ISO 11348-3 procedure; these data involve nine different cations and seventeen anions, thus, 9×17=153 different combinations can be considered. The range of ecotoxicity covered by the novel QSAR corresponds to: Log EC 50 values from −0.23 to 5.00. The modeling has been performed using mechanistic and stochastic considerations, hybrid model. The influence of the anion, cation and substitutions in the ecotoxicity has been estimated to design ionic liquids with lower toxicity, giving the pTS and N(CF 3 ) 2 anions and the imidazolium cation the lowest aquatic toxicity (statistically shown).

Pervaporation membrane reactors: Biomass conversion into alcohols

The use and production of bioalcohols, butanol and ethanol, are described in this chapter. In the first part, the state of art of their production is explained, as well as the reaction pathways, the different reaction geometries, and the importance of the sources as raw material. The possibility of using pervaporation (PV) coupled with a conversion reactor is shown. The use of two membranes in series (hydrophobic–hydrophilic) allows a high-quality product to be produced. A brief revision of the current performance of the membrane used is described, which allows us to understand the direction in which research has to go to improve this technology. A comparison of PV with current technologies used to purify these alcohols is reported as well. The current state of production for these two alcohols is illustrated, along with future perspectives.

Intensification of sulfur dioxide absorption: Environmental and economic optimization

Abstract Process intensification offers significant improvements in chemical manufacturing and processing, leading to cheaper, safer and sustainable technologies. Recovery of sulfur dioxide from gas emissions using an intensified process instead of the absorption by means of scrubbers is in the spotlight of many investigations. The substitution of the equipment by a membrane device intensifies the process from an environmental point of view, increasing process efficiency and reducing solvent losses, but the economic impact needs to be studied. This work considers a ceramic hollow fibre membrane contactor as membrane device and the modeling of mass transfer in the membrane contactor is performed in order to establish the influence of the operation conditions on the process efficiency and to carry out an environmental and cost evaluation-optimization study.