The boundary flux handbook. A comprehensive database of critical and threshold flux values for membrane practitioners

The Boundary Flux Handbook summarizes over 100 chemical compounds (single compounds, in mixed solution) and different feed streams from industry (complex streams exiting the agricultural, biological, pharmaceutical, food, dye, textile, and other industries) and the respective critical and threshold fluxes (or boundary flux), together with data on rejection and permeabilities. It gives the reader valuable data to quickly estimate membrane performances in respect to productivity, selectivity, and longevity, and aids in estimating capital and operating costs of membrane processes during the plant design operations. The book is valuable for scientific researchers and chemical engineers working with membrane technology as a reference for lab work, membrane process design, and control. For each specific feedstock, only the best performing membranes are listed. At least one commercial membrane module and a maximum of four different choices are reported, in order to assure easy integration of the proposed membranes into the systems by contacting the relevant commercial partner, and to define the best choice of the pretreatment steps, permitting quick membrane process optimization or revamping operations. Key Features This text summarizes over 100 chemical compounds, different feed streams from industry, and the respective critical and threshold fluxes. It gives the reader valuable data to quickly estimate membrane performances in respect to productivity, selectivity and longevity. For each studied feedstock, only the best performing membrane(s) are listed, including one commercial and a maximum of four different choices, to assure the possibility to easily integrate the proposed membranes into the systems by contacting the relevant commercial partner

On operating a nanofiltration membrane for olive mill wastewater purification at sub- and super-boundary conditions

In the last decades, membrane processes have gained a significant share of the market for wastewater purification. Although the product (i.e., purified water) is not of high added value, these processes are feasible both technically and from an economic point of view, provided the flux is relatively high and that membrane fouling is strongly inhibited. By controlling membrane fouling, the membrane may work for years without service, thus dramatically reducing operating costs and the need for membrane substitution. There is tension between operating at high permeate fluxes, which enhances fouling but reduces capital costs, and operating at lower fluxes which increases capital costs. Operating batch membrane processes leads to increased difficulties, since the feed fed to the membrane changes as a function of the recovery value. This paper is concerned with the operation of such a process. Membrane process designers should therefore avoid membrane fouling by operating membranes away from the permeate flux point where severe fouling is triggered. The design and operation of membrane purification plants is a difficult task, and the precision to properly describe the evolution of the fouling phenomenon as a function of the operating conditions is a key to success. Many reported works have reported on the control of fouling by operating below the boundary flux. On the other hand, only a few works have successfully sought to exploit super-boundary operating conditions; most super-boundary operations are reported to have led to process failures. In this work, both sub- and super-boundary operating conditions for a batch nanofiltration membrane process used for olive mill wastewater treatment were investigated. A model to identify a priori the point of transition from a sub-boundary to a super-boundary operation during a batch operation was developed, and this will provide membrane designers with a helpful tool to carefully avoid process failures

Spinning disk reactor technology in photocatalysis: nanostructured catalysts intensified production and applications

The use of photocatalysis in environmental remediation processes has become more important in the last decade, mainly due to the notable efforts made by researchers in this field. The photocatalytic process requires a semiconductor material (photocatalyst), usually a metal oxide, which can be activated through the energy transported by ultraviolet light or visible light waves. The activated photocatalyst generates active compounds, such as hydroxyl radicals and superoxide ion, able to degrade very recalcitrant and non-biodegradable compounds present on the catalyst surface or in the liquid medium. The efficiency of the pollutant removal process is affected by various factors related to the employed photocatalyst, such as mean dimension, size distribution, physical structure and energy required for the activation. The photocatalyst characteristics are strongly dependent on the production process, and several researchers have developed new intensified production nanostructured catalysts in a continuous Spinning Disk Reactor is discussed. The main features of Spinning Disk Reactor technology are reported and analysed, i.e. rotational velocity, disk diameter, disk surface material and roughness, focusing on the production of nanoparticles to be used in the photocatalytic application, in view of the process intensification of photocatalysis application in the field of environmental remediation. A general overview about process intensification and its application to chemical engineering is presented, and the advantages offered by Spinning Disk Reactor technology, in terms of an increase of process efficiency due to the misinformation of operative conditions in reactors, are illustrated. Basing on the Spinning Disk Reactor characteristics and operative conditions, nanoparticle production by Spinning Disk Reactor compared to conventional technologies and the current application of this technology to selected nanoparticles (titania, magnetite, MgO and hydroxyapatite), synthesis is discussed. Spinning Disk Reactor technology allows to produce active semiconductor particles, characterized by a mean size significantly below 100 nm and with a narrow unimodal distribution, improving the quality of these products in comparison with those produced through conventional processes and equipment. Finally, the application of vertical and horizontal Spinning Disk Reactor configuration to the degradation of refractory compounds by photocatalysis is reviewed, aiming at evaluating process efficiency and the produced nanoparticle characteristics, to assess the key parameters and the limiting factors of the technology