Search results for "membrane reactor"

Sensitivity analysis and uncertainty assessment of a SMBR model

2008

Over the last decade new technologies are emerging even more for wastewater treatment. Among the new technologies, a recent possible solution regards membrane bioreactors (MBRs) that represent a promising alternative to conventional processes. Nowadays, the recurrence to mathematical models as reliable tools in planning as well as management issues is of growing interest in Wastewater Treatment Plants field. Regarding MBR modelling, due to the intrinsic complexity and uncertainty in some processes, basic models that can provide a holistic understanding of the technology at a fundamental level are of great necessity. Many mathematical models have been developed for modelling the MBR which ba…

A Dialysis Photocatalytic Reactor for the Green Production of Vanillin

2020

In the present work, dialysis was used to recover vanillin while being produced by partial photocatalytic oxidation of ferulic acid in an aqueous solution at ambient temperature. The relatively high value of the permeate flux through a dense polyether-block amide membrane allowed continuously extracting vanillin from the reacting solution, thus avoiding its successive oxidation. The rate of vanillin formation was improved, compared to other reactor configurations, because intermediate compounds permeated from the reacting solution and did not hinder the reaction, while ferulic acid permeated in the opposite direction to partially replenish the reactor with the substrate. The photocatalytic …

Heterogeneous Photocatalysis and Photoelectrocatalysis: From Unselective Abatement of Noxious Species to Selective Production of High-Value Chemicals

2015

Heterogeneous photocatalysis and photoelectrocatalysis have been considered as oxidation technologies to abate unselectively noxious species. This article focuses instead on the utilization of these methods for selective syntheses of organic molecules. Some promising reactions have been reported in the presence of various TiO2 samples and the important role played by the amorphous phase has been discussed. The low solubility of most of the organic compounds in water limits the utilization of photocatalysis. Dimethyl carbonate has been proposed as an alternative green organic solvent. The recovery of the products by coupling photocatalysis with pervaporation membrane technology seems to be a…

Photocatalytic Membrane Reactors in Water Purification

2004

Potable water, industrial water, and wastewater are often polluted by toxic organic species. New methods, such as those involving heterogeneous photocatalytic reactions, allow in many cases a complete degradation of organic pollutants to small and non-noxious species, without using chemicals, avoiding sludge production and its disposal. When combined with membrane separation processes, photocatalytic membrane reactors (PMRs) are obtained. These have some advantages compared to conventional photoreactors. Indeed, confining of the photocatalyst in the reaction environment as a result of the presence of the membrane (separation at molecular level) enables operation with high amounts of catalys…

Photocatalytic Membrane Reactors in the Conversion or Degradation of Organic Compounds

2009

Photocatalytic membrane reactors for water treatment

2015

Abstract Heterogeneous photocatalysis is an advanced oxidation process largely studied in the field of environment recovery by the total degradation of organic and inorganic pollutants and for synthesis. In this chapter, the basic principles of photocatalysis are discussed with the advantages related to its coupling with a membrane separation in photocatalytic membrane reactors (PMRs). The types of membranes most widely used and their criteria of selection are briefly discussed. PMRs’ classification based on their configuration and on the type of membrane operation is also discussed, evidencing as their appropriate choice is a key step in view of large-scale implementation. Finally, some ca…

The combination of heterogeneous photocatalysis with chemical and physical operations: a tool for improving the photoprocess performance

2006

Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste treatment. In order to improve the overall performance of the photoprocess, heterogeneous photocatalysis is being combined with physical or chemical operations, which affect the chemical kinetics and/or the overall efficiency. This review addresses the various possibilities to couple heterogeneous photocatalysis with other technologies to photodegrade organic and inorganic pollutants dissolved in actual or synthetic aqueous effluents. These combinations increase the photoprocess efficiency by decreasing the reaction time in respect to the separated operations or they decrease the cost in respect o…

Photocatalytic processes in membrane reactors

2017

Photocatalytic membrane reactors (PMRs) represent an interesting alternative technology useful both in the field of water and air purification and in organic syntheses. The necessity to develop chemical products and industrial processes that reduce or eliminate the use and the generation of toxic substances along with the risk for human health and for environment constitutes the aim of the research efforts based on the principles of green chemistry. Heterogeneous photocatalysis is a technology extensively studied for about three decades, since Fujishima and Honda1 discovered the photocatalytic splitting of water on TiO2 electrodes in 1972, which includes a large range of reactions. When a s…

PMRs Utilizing Non–Pressure-Driven Membrane Techniques

2018

In the present chapter it is shown how photocatalytic membrane reactors utilizing membrane processes, which are not pressure driven, can exploit various mechanisms to obtain a substantial improvement of the process. The fundamentals of this particular type of membrane reactors are reviewed including the effects of the most important parameters and the methods and rules of coupling photocatalysis and membrane separation. The survey of the studies on photocatalytic membrane reactors (PMRs) utilizing pervaporation, dialysis, membrane contactors and membrane distillation offers the opportunity of discussing the advantages with respect to PMRs adopting pressure driven membrane processes. Indeed,…

Photocatalytic Membrane Reactors: Case Studies and Perspectives

2009

Photocatalysis by polycrystalline semiconductor oxides is being successfully applied to the abatement of organic and inorganic pollutants both in gas and in liquid phase. In order to increase the efficiency of this method, the coupling of this technology with the membrane separation process has been the object of sound investigation. In this combination, the membrane may act in different ways: to confine the photocatalytic powder in the reacting suspension, to selectively separate the photoreaction products, or to be the support of photocatalyst. This article reports recent studies in which different types of membranes (such as distillation, dialysis, nanofiltration, pervaporation and osmos…