Special Issue "Photocatalytic Membrane Reactors"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Photocatalysis".

Deadline for manuscript submissions: closed (31 January 2020).

Special Issue Editors

Prof. Dr. Raffaele Molinari

Guest Editor
Department of Environmental and Chemical Engineering, Università della Calabria, 87036 Rende (CS), Italy
Interests: membrane processes; catalytic and photocatalytic membrane reactors; complexation reactions coupled with membranes (supported liquid membranes; ultrafiltration assisted by polymers); saving, recovery and recycle of matter and energy by membrane processes
Prof. Dr. Sylwia Mozia

Guest Editor
West Pomeranian University of Technology in Szczecin, Faculty of Chemical Technology and Engineering, Department of Inorganic Chemical Technology and Environment Engineering, ul. Pułaskiego 10, 70-322, Szczecin, Poland
Interests: inorganic chemical technology; water/wastewater treatment; membrane processes, especially pressure driven membrane techniques and membrane distillation; hybrid membrane processes; advanced oxidation processes; photocatalysis; photocatalytic membrane reactors

Special Issue Information

Dear Colleagues,

Since Honda and Fujishima described their research on photocatalytic splitting of water on TiO2 electrodes (Nature, 1972), the interest of scientific world in various applications of photocatalysis has been systematically increased. It is commonly accepted that photocatalysis fits to the Green Chemistry principles allowing both removal of toxic compounds or synthesis of useful substances. The most commonly investigated applications of this process are air and water/wastewater purification in terms of degradation of organic contaminants to innocuous products, such as water, carbon dioxide or inorganic salts, as well as removal of toxic metals. The most recent attempt is utilization of photocatalysis in organic synthesis.

The advantages of photocatalysis can be significantly enhanced by coupling this process with membrane technology. Photocatalytic membrane reactors (PMRs) are hybrid systems of various configurations which combine photocatalysis with membrane separation taking advantages of both processes. PMRs have been found a promising tool for water/wastewater treatment and organic synthesis. Application of a membrane gives a possibility to realize a continuous operation with a simultaneous recovery of a photocatalyst (immobilized or in suspension), coupled with the photoreaction and separation of the substrates or (by)products from the reaction environment. Improvement of process efficiency compared to conventional photoreactors, modularity and easy scale up are some other potential advantages of PMRs. All of these resulted in a significant growth of interest in this area observed in the recent years. Nonetheless, the full-scale applications of PMRs still need detailed investigations to improve the processes performance. This Special Issue aims to cover all aspects of hybrid photocatalysis–membrane systems, including both photocatalytic membranes and reactors with suspended photocatalyst. Experimental and theoretical contributions being within the scope of this Special Issue, including original research papers, short communications and review articles are invited for submission.

Prof. Dr. Raffaele Molinari
Prof. Dr. Sylwia Mozia
Guest Editors

Manuscript Submission Information

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Keywords

  • Photocatalysis
  • Membrane separation
  • Photocatalytic membrane reactor
  • Photocatalytic membrane
  • Immobilized photocatalyst
  • Water treatment
  • Wastewater treatment
  • Organic photosynthesis
  • Photodegradation
  • Photodecomposition

Published Papers (6 papers)

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Research

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Open AccessArticle
Comparison of Photocatalytic Membrane Reactor Types for the Degradation of an Organic Molecule by TiO2-Coated PES Membrane
Catalysts 2020, 10(7), 725; https://doi.org/10.3390/catal10070725 - 29 Jun 2020
Abstract
Photocatalytic membrane reactors with different configurations (design, flow modes and light sources) have been widely applied for pollutant removal. A thorough understanding of the contribution of reactor design to performance is required to be able to compare photocatalytic materials. Reactors with different flow [...] Read more.
Photocatalytic membrane reactors with different configurations (design, flow modes and light sources) have been widely applied for pollutant removal. A thorough understanding of the contribution of reactor design to performance is required to be able to compare photocatalytic materials. Reactors with different flow designs are implemented for process efficiency comparisons. Several figures-of-merit, namely adapted space-time yield (STY) and photocatalytic space-time yield (PSTY), specific energy consumption (SEC) and degradation rate constants, were used to assess the performance of batch, flow-along and flow-through reactors. A fair comparison of reactor performance, considering throughput together with energy efficiency and photocatalytic activity, was only possible with the modified PSTY. When comparing the three reactors at the example of methylene blue (MB) degradation under LED irradiation, flow-through proved to be the most efficient design. PSTY1/PSTY2 values were approximately 10 times higher than both the batch and flow-along processes. The highest activity of such a reactor is attributed to its unique flow design which allowed the reaction to take place not only on the outer surface of the membrane but also within its pores. The enhancement of the mass transfer when flowing in a narrow space (220 nm in flow-through) contributes to an additional MB removal. Full article
(This article belongs to the Special Issue Photocatalytic Membrane Reactors)
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Open AccessFeature PaperArticle
A Dialysis Photocatalytic Reactor for the Green Production of Vanillin
Catalysts 2020, 10(3), 326; https://doi.org/10.3390/catal10030326 - 14 Mar 2020
Abstract
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 [...] Read more.
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 membrane reactor obtained by the effective coupling of dialysis with the photocatalytic reaction improved the production yield. For instance, with the utilized experimental set up, the total amount of vanillin produced after 5 h in the membrane reactor was more than one-third higher than in the photocatalytic reactor without dialysis. The results obtained with a mathematical model agree with the experimentally observed behavior. The model allowed estimating vanillin diffusivity in the membrane and showed that concentration polarization might limit the process. Full article
(This article belongs to the Special Issue Photocatalytic Membrane Reactors)
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Open AccessArticle
Novel Submerged Photocatalytic Membrane Reactor for Treatment of Olive Mill Wastewaters
Catalysts 2019, 9(9), 769; https://doi.org/10.3390/catal9090769 - 13 Sep 2019
Cited by 1
Abstract
A new hybrid photocatalytic membrane reactor that can easily be scaled-up was designed, assembled and used to test photocatalytic membranes developed using the sol–gel technique. Extremely high removals of total suspended solids, chemical oxygen demand, total organic carbon, phenolic and volatile compounds were [...] Read more.
A new hybrid photocatalytic membrane reactor that can easily be scaled-up was designed, assembled and used to test photocatalytic membranes developed using the sol–gel technique. Extremely high removals of total suspended solids, chemical oxygen demand, total organic carbon, phenolic and volatile compounds were obtained when the hybrid photocatalytic membrane reactor was used to treat olive mill wastewaters. The submerged photocatalytic membrane reactor proposed and the modified membranes represent a step forward towards the development of new advanced treatment technology able to cope with several water and wastewater contaminants. Full article
(This article belongs to the Special Issue Photocatalytic Membrane Reactors)
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Open AccessArticle
Synthesis of High Crystalline TiO2 Nanoparticles on a Polymer Membrane to Degrade Pollutants from Water
Catalysts 2018, 8(9), 376; https://doi.org/10.3390/catal8090376 - 05 Sep 2018
Cited by 14
Abstract
Titanium dioxide (TiO2) is described as an established material to remove pollutants from water. However, TiO2 is still not applied on a large scale due to issues concerning, for example, the form of use or low photocatalytic activity. We present [...] Read more.
Titanium dioxide (TiO2) is described as an established material to remove pollutants from water. However, TiO2 is still not applied on a large scale due to issues concerning, for example, the form of use or low photocatalytic activity. We present an easily upscalable method to synthesize high active TiO2 nanoparticles on a polyethersulfone microfiltration membrane to remove pollutants in a continuous way. For this purpose, titanium(IV) isopropoxide was mixed with water and hydrochloric acid and treated up to 210 °C. After cooling, the membrane was simply dip-coated into the TiO2 nanoparticle dispersion. Standard characterization was undertaken (i.e., X-ray powder diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, water permeance, contact angle). Degradation of carbamazepine and methylene blue was executed. By increasing synthesis temperature crystallinity and photocatalytic activity elevates. Both ultrasound modification of nanoparticles and membrane pre-modification with carboxyl groups led to fine distribution of nanoparticles. The ultrasound-treated nanoparticles gave the highest photocatalytic activity in degrading carbamazepine and showed no decrease in degradation after nine times of repetition. The TiO2 nanoparticles were strongly bound to the membrane. Photocatalytic TiO2 nanoparticles with high activity were synthesized. The innovative method enables a fast and easy nanoparticle production, which could enable the use in large-scale water cleaning. Full article
(This article belongs to the Special Issue Photocatalytic Membrane Reactors)
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Open AccessArticle
Photocatalytic Membrane Reactor (PMR) for Virus Removal in Drinking Water: Effect of Humic Acid
Catalysts 2018, 8(7), 284; https://doi.org/10.3390/catal8070284 - 16 Jul 2018
Cited by 1
Abstract
In the actual water environment, the health risk of waterborne viruses is evaluated to be 101–104 times higher at a similar level of exposure compared with bacteria and has aroused strong concern in many countries in the world. Photocatalytic membrane [...] Read more.
In the actual water environment, the health risk of waterborne viruses is evaluated to be 101–104 times higher at a similar level of exposure compared with bacteria and has aroused strong concern in many countries in the world. Photocatalytic membrane reactor (PMR), a new process for virus inactivation in water, has gradually become one of the main tools to inactivate pathogenic organisms in water. However, there is relatively little attention to the effect of natural organic matters (NOMs) on the PMR system, which actually exists in the water environment. In this paper, the TiO2-P25, a common type in sales and marketing, was selected as the photocatalyst, and humic acid was regarded as the representative substance of NOMs for investigating thoroughly the influence of humic acid on virus removal by the PMR system. It was found that competitive adsorption between the virus and humic acid occurred, which markedly reduced the amount of virus adsorbed on the surface of the photocatalyst. Moreover, with humic acid, the direct contact behavior between the virus and the photocatalyst was blocked to some extent, and the disinfection of phage f2 by the active free radicals produced by photocatalysis was furthermore badly affected. Meanwhile, the special structure of humic acid, which made humic acid be able to absorb light of 270–500 nm, led to the reduction of photocatalytic efficiency. Further experiments showed that when there was a certain concentration of humic acid in water, intermittent operation mode or higher membrane flux (>40 L/(m2·h)) was selected to partly alleviate the adverse effects of humic acid. Full article
(This article belongs to the Special Issue Photocatalytic Membrane Reactors)
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Review

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Open AccessReview
Overview of Photocatalytic Membrane Reactors in Organic Synthesis, Energy Storage and Environmental Applications
Catalysts 2019, 9(3), 239; https://doi.org/10.3390/catal9030239 - 04 Mar 2019
Cited by 8
Abstract
This paper presents an overview of recent reports on photocatalytic membrane reactors (PMRs) in organic synthesis as well as water and wastewater treatment. A brief introduction to slurry PMRs and the systems equipped with photocatalytic membranes (PMs) is given. The methods of PM [...] Read more.
This paper presents an overview of recent reports on photocatalytic membrane reactors (PMRs) in organic synthesis as well as water and wastewater treatment. A brief introduction to slurry PMRs and the systems equipped with photocatalytic membranes (PMs) is given. The methods of PM production are also presented. Moreover, the process parameters affecting the performance of PMRs are characterized. The applications of PMRs in organic synthesis are discussed, including photocatalytic conversion of CO2, synthesis of KA oil by photocatalytic oxidation, conversion of acetophenone to phenylethanol, synthesis of vanillin and phenol, as well as hydrogen production. Furthermore, the configurations and applications of PMRs for removal of organic contaminants from model solutions, natural water and municipal or industrial wastewater are described. It was concluded that PMRs represent a promising green technology; however, before the application in industry, additional studies are still required. These should be aimed at improvement of process efficiency, mainly by development and application of visible light active photocatalysts and novel membranes resistant to the harsh conditions prevailing in these systems. Full article
(This article belongs to the Special Issue Photocatalytic Membrane Reactors)
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