Advances in Photoassisted and Photocatalytic Processes for Water Remediation

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

Deadline for manuscript submissions: closed (10 December 2022) | Viewed by 29358

Special Issue Editors


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Guest Editor
Universidad Autónoma de Madrid, Chemical Engineering Department, Madrid, Spain
Interests: photocatalysis; catalytic wet peroxide oxidation; advanced oxidation processes for wastewater treatment; catalyst synthesis and characterization

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Guest Editor
Department of Industrial Chemical and Environmental Engineering, Escuela Técnica Superior de Ingenieros Industrial (ETSII), Universidad Politécnica de Madrid (UPM), 28006 Madrid, Spain
Interests: photocatalysis; photoassisted processes; development of new catalysts; new technologies based on AOPs combination for water remediation

Special Issue Information

Dear Colleagues,

Over the last few years, a remarkable amount of research has been devoted to the application of advanced oxidation processes (AOPs) as viable and effective technologies for the treatment of pollutants that are hardly removed by other conventional wastewater treatments.

In this context, the development of new trends covering new photoassisted AOPs-based processes and the design of active and stable photocatalysts keeping economic feasibility and technical applicability aspects seem relevant key issues of the whole process.

For this purpose, this Special Issue is aimed at covering the latest trends in water remediation, either for purification (including oxidation and reduction processes) or for disinfection, as well as novel achievements related to the syntheses of feasible catalysts for different photoassisted AOPs. Thus, we welcome both original and review articles, covering not only but mainly the following topics:

  • Solar wastewater treatment;
  • Water treatment/disinfection;
  • Photoassisted AOPs combined with other technologies;
  • Emerging pollutants removal;
  • Real wastewater applications;
  • Design of new photocalysts;
  • Scale-up, engineering aspects of light-assisted AOPs.

Dr. Jaime Carbajo
Prof. Dr. Patricia García-Muñoz
Guest Editors

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Keywords

  • Advanced oxidation processes (AOPs)
  • Photoassisted processes
  • Solar-based AOPs
  • Photocatalysis
  • Visible-driven photocatalysts
  • Wastewater disinfection
  • Emerging pollutants
  • Wastewater regeneration

Published Papers (13 papers)

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Research

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21 pages, 8264 KiB  
Article
Pristine TiO2 and Sr-Doped TiO2 Nanostructures for Enhanced Photocatalytic and Electrocatalytic Water Splitting Applications
by Mohd Fazil and Tokeer Ahmad
Catalysts 2023, 13(1), 93; https://doi.org/10.3390/catal13010093 - 02 Jan 2023
Cited by 15 | Viewed by 2346
Abstract
Pristine TiO2 and Sr-doped TiO2 (1%, 2.5% and 5%) nanoparticles were synthesized at low temperatures via an eco-friendly hydrothermal route for water-splitting applications. XRD, EDAX and Raman analysis were performed to analyze the crystallinity, purity and structure of the as-synthesized materials. [...] Read more.
Pristine TiO2 and Sr-doped TiO2 (1%, 2.5% and 5%) nanoparticles were synthesized at low temperatures via an eco-friendly hydrothermal route for water-splitting applications. XRD, EDAX and Raman analysis were performed to analyze the crystallinity, purity and structure of the as-synthesized materials. TEM, SEM, BET and UV-DRS studies were carried out to elucidate the size, morphology, surface area and optoelectronic properties of the nanoparticles. High surface areas of 169, 182, 178 and 141.16 m2 g−1 for pristine TiO2 (12 ± 0.6 nm) and 1% (11.1 ± 0.6 nm), 2.5% (12.1 ± 0.6 nm) and 5% (13 ± 0.7 nm) Sr-doped TiO2 nanoparticles were obtained, respectively. One-percent Sr-doped TiO2 nanoparticles were found to be active photocatalysts, as they showed higher hydrogen production (26.30 mmolgcat1). Furthermore, electrocatalysis was investigated for HER and OER in 0.5 N H2SO4 and 0.1 N KOH electrolytic solutions using calomel as a reference electrode, revealing that 1% and 5% Sr-doped TiO2 showed maximum current density for both HER (≈10 mA/cm2) and OER (≈2.49 mA/cm2), with an onset potential of 0.96 V for HER and 1.55 V for OER, and Tafel slopes of 84.09 and 91.60 mV/dec, respectively. Full article
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8 pages, 1830 KiB  
Communication
Study on Optimum Preparation Conditions of ZnIn2S4 to Effectively Reduce Cr(VI) under Visible Light Radiation
by Yali Song, Huan Zhang, Ziyan Li, Long Huang, Junhao Xie, Long Han, Ruoying Zheng, Yuqing Zhang and Hongzhong Zhang
Catalysts 2022, 12(11), 1429; https://doi.org/10.3390/catal12111429 - 14 Nov 2022
Viewed by 1080
Abstract
Previous studies have displayed various conclusions about the effect of preparation factors on the photoreduction property of ZnIn2S4. Therefore, it is not easy to figure out the optimal preparation conditions of ZnIn2S4 for Cr(VI) photoreduction. To [...] Read more.
Previous studies have displayed various conclusions about the effect of preparation factors on the photoreduction property of ZnIn2S4. Therefore, it is not easy to figure out the optimal preparation conditions of ZnIn2S4 for Cr(VI) photoreduction. To ensure Cr(VI) reduction efficiency, various ZnIn2S4 photocatalysts were prepared in different solvents (i.e., water and ethylene glycol) and temperatures (i.e., 120 °C, 150 °C and 180°C). Different characterization methods were used to explain the difference in optical performance and photocatalytic property among the obtained samples. The results show that all the samples exhibit a similar band gap. The reaction solvent and temperature have a great influence on the surface morphology and optical property, leading to the different photocatalytic properties. ZnIn2S4 synthesized at 120 °C in the solvothermal condition shows the optimal efficiency on Cr(VI) photoreduction due to the effective utilization of photo-induced carriers. The reasonable analysis and effective conclusion presented may provide the optimal synthesis method of ZnIn2S4 to effectively remove Cr(VI) from water environment. Full article
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15 pages, 2049 KiB  
Article
An Evaluation of the Kinetic Properties Controlling the Combined Chemical and Biological Treatment of Toxic Recalcitrant Organic Compounds from Aqueous Solution
by Seshibe Makgato and Evans Nkhalambayausi-Chirwa
Catalysts 2022, 12(9), 965; https://doi.org/10.3390/catal12090965 - 29 Aug 2022
Viewed by 1529
Abstract
Due to their high toxicity, propensity for cancer, teratogenicity, mutagenicity, and genotoxicity, hazardous water-soluble phenolic compounds must be controlled immediately. In this study, a model was created to simulate the degradation of harmful recalcitrant organic compounds in a combined chemical and biological treatment [...] Read more.
Due to their high toxicity, propensity for cancer, teratogenicity, mutagenicity, and genotoxicity, hazardous water-soluble phenolic compounds must be controlled immediately. In this study, a model was created to simulate the degradation of harmful recalcitrant organic compounds in a combined chemical and biological treatment system. The parameter estimations with inhibition coefficient (Haldane model) and without inhibition coefficient (Michaelis-Menten model) were assessed over a wide range of initial concentrations using the Monod-like model. The kinetic parameters were optimized using AQUASIM 2.0 software. At a 50 mg·L−1 feed concentration of 4-chlorophenol, removal efficiencies of more than 98% were attained under these circumstances. The primary kinetic parameters were identified and their values models were validated using the fitted parameter values that reached a good degree of agreement (R2 = 0.998). We may better comprehend and make use of the complex phenolic compounds’ biodegradation processes, such as progress optimization and scale-up, by understanding the mechanisms of substrate interaction and the new kinetic models that have been provided in this work. Full article
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13 pages, 2220 KiB  
Article
Abatement of Naphthalene by Persulfate Activated by Goethite and Visible LED Light at Neutral pH: Effect of Common Ions and Organic Matter
by Andrés Sánchez-Yepes, David Lorenzo, Patricia Sáez, Arturo Romero and Aurora Santos
Catalysts 2022, 12(7), 732; https://doi.org/10.3390/catal12070732 - 01 Jul 2022
Viewed by 1319
Abstract
Naphthalene (NAP) has received particular attention due to its impact on the environment and human health, mandating its removal from water systems. In this work, the abatement of NAP in the aqueous phase was achieved using persulfate (PS) activated by Fe (III) and [...] Read more.
Naphthalene (NAP) has received particular attention due to its impact on the environment and human health, mandating its removal from water systems. In this work, the abatement of NAP in the aqueous phase was achieved using persulfate (PS) activated by Fe (III) and monochromatic LED light at a natural pH. The reaction was carried out in a slurry batch reactor using goethite as the Fe (III) source. The influence of the PS concentration, goethite concentration, irradiance, temperature and presence of organic matter, chloride, and bicarbonate on the abatement of NAP was studied. These variables were shown to have a different effect on NAP removal. The irradiance showed a maximum at 0.18 W·cm2 where the photonic efficiency was the highest. As for the concentration of goethite and PS, the influence of the first one was negligible, whereas for PS, the best results were reached at 1.2 mM due to a self-inhibitory effect at higher concentrations. The temperature effect was also negative in the PS consumption. Regarding the effect of ions, chloride had no influence on NAP conversion but carbonates and humic acids were affected. Lastly, this treatment to remove NAP has proved to be an effective technique since minimum conversions of 0.92 at 180 min of reaction time were reached. Additionally, the toxicity of the final samples was decreased. Full article
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12 pages, 3693 KiB  
Article
Facile Synthesis of Various ZrO2 Phases and ZrO2-MO2 (M = Ti, Hf) by Thermal Decomposition of a Single UiO-66 Precursor for Photodegradation of Methyl Orange
by Ira Nur Arba’atul Jannah, Hanu Fiorena Sekarsari, Sri Mulijani, Karna Wijaya, Arief Cahyo Wibowo and Aep Patah
Catalysts 2022, 12(6), 609; https://doi.org/10.3390/catal12060609 - 02 Jun 2022
Cited by 3 | Viewed by 1783
Abstract
A zirconia-based catalyst with controlled crystalline phases is synthesized through a simple thermal decomposition of a parent UiO-66 single precursor. The introduction of Ti(IV) and Hf(IV) cation into the Zr(IV) framework has been successfully obtained to tune the photocatalytic activity over methyl orange [...] Read more.
A zirconia-based catalyst with controlled crystalline phases is synthesized through a simple thermal decomposition of a parent UiO-66 single precursor. The introduction of Ti(IV) and Hf(IV) cation into the Zr(IV) framework has been successfully obtained to tune the photocatalytic activity over methyl orange (MO) solution. Their resulting crystalline phases, morphologies, elemental analysis, band gap values, surface area, and photocatalytic degradation study over MO dye are presented and discussed. The tetragonal zirconia (t-ZrO2) catalyst exhibits the highest photocatalytic activity with 89% decoloration efficiency under UV irradiation (λ = 254 nm) for 300 min compared to m-ZrO2 (67%), the mixed phases (t-ZrO2 and m-ZrO2), as well as the synthesized mixed oxides ZrO2-MO2 (M = Ti or Hf), where the photocatalytic activities are 74% and 63%, respectively. This result is on par with commercially available anatase TiO2 and other reported t-ZrO2 catalysts. Full article
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14 pages, 3534 KiB  
Article
A Facile Synthesis of Bi2O3/CoFe2O4 Nanocomposite with Improved Synergistic Photocatalytic Potential for Dye Degradation
by Abdul Basit Naveed, Fakhira Riaz, Azhar Mahmood, Ammara Shahid and Saman Aqeel
Catalysts 2021, 11(10), 1180; https://doi.org/10.3390/catal11101180 - 28 Sep 2021
Cited by 11 | Viewed by 2557
Abstract
Semiconductor-based photocatalysis is a probable approach to overcoming many pollution problems and eradicating toxic organic materials from wastewater. This research endeavor aimed to explore the synergistic potential of different semiconductor nanocomposites for photocatalytic degradation of organic pollutants in contaminated water. A facile hydrothermal [...] Read more.
Semiconductor-based photocatalysis is a probable approach to overcoming many pollution problems and eradicating toxic organic materials from wastewater. This research endeavor aimed to explore the synergistic potential of different semiconductor nanocomposites for photocatalytic degradation of organic pollutants in contaminated water. A facile hydrothermal approach was employed to synthesize bismuth oxide and cobalt ferrite nanoparticles from their precursors—bismuth nitrate pentahydrate, ferric chloride hexahydrate and cobalt chloride hexahydrate—with various concentrations and conditions to optimize the product. Subsequently, nanocomposites of bismuth oxide and cobalt ferrite were prepared by solid-state mixing in varying concentrations followed by calcination. UV/visible diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and elemental dispersive X-ray spectroscopic techniques have corroborated the successful synthesis of nanocomposites. The energy gaps of bismuth oxide and cobalt ferrite nanocomposites were computed in the range of 1.58–1.62 eV by Tauc plots. These nanocomposite materials were ascertained for photocatalytic potential to degrade methyl orange organic dye in water. A nanocomposite with equiquantic proportions has shown the best photocatalytic degradation activity, which may be attributed to the type-II band configuration and a synergistic effect, because Bi2O3 acts as an electron sink. This synergism has reduced the cogent band gap, hindered electron hole recombination and increased electron hole availabilities for photodegradation reactions, thus ensuing an efficient photodegradation co-work of Bi2O3/CoFe2O4 nanocomposites. Full article
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12 pages, 2186 KiB  
Article
Photocatalytic Removal of Pharmaceuticals from Greywater
by Bukola Ojobe, Radek Zouzelka, Barbora Satkova, Magdalena Vagnerova, Alzbeta Nemeskalova, Martin Kuchar, Jan Bartacek and Jiri Rathousky
Catalysts 2021, 11(9), 1125; https://doi.org/10.3390/catal11091125 - 18 Sep 2021
Cited by 5 | Viewed by 2470
Abstract
High concentrations of pharmaceuticals have been detected in greywater effluents treated using up-to-date technologies. Finding a suitable additional treatment before this effluent is reused is urgently needed to ensure the reused water meets quality standards. This paper reports the use of heterogeneous photocatalysis [...] Read more.
High concentrations of pharmaceuticals have been detected in greywater effluents treated using up-to-date technologies. Finding a suitable additional treatment before this effluent is reused is urgently needed to ensure the reused water meets quality standards. This paper reports the use of heterogeneous photocatalysis on anatase and rutile nanopowders to remove naproxen, metformin and sulfamethoxazole, at practically relevant concentrations found in membrane bioreactor (MBR)-treated greywater. A low anatase concentration of 400 mg L−1 was sufficient to efficiently degrade the pharmaceuticals listed above, with complete degradation observed in 5 h. The effect of background species presented in greywater was, to some extent, comparable to that of the OH-radical scavenger. These results prove that photocatalysis using anatase TiO2 is a feasible additional treatment for greywater recycling. Full article
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13 pages, 5073 KiB  
Article
Low-Temperature Mineralisation of Titania-Siloxane Composite Layers
by Tomáš Svoboda, Michal Veselý, Radim Bartoš, Tomáš Homola and Petr Dzik
Catalysts 2021, 11(1), 50; https://doi.org/10.3390/catal11010050 - 01 Jan 2021
Cited by 3 | Viewed by 2273
Abstract
This paper deals with low-temperature mineralisation of coatings made with titania-siloxane compositions (TSC). Methyltriethoxysilane has been adopted as the precursor for the siloxane, and during its synthesis, an oligomeric siloxane condensate with methyl moieties acting as TiO2 binder has been produced. These [...] Read more.
This paper deals with low-temperature mineralisation of coatings made with titania-siloxane compositions (TSC). Methyltriethoxysilane has been adopted as the precursor for the siloxane, and during its synthesis, an oligomeric siloxane condensate with methyl moieties acting as TiO2 binder has been produced. These methyl moieties, contained in TSC, provide solubility and prevent gelling, but reduce the hydrophilicity of the system, reduce the transfer of electrons and holes generated in the TiO2. In order to avoid these unfavourable effects, TSC mineralisation can be achieved by nonthermal treatment, for example, by using UV-radiation or plasma treatment. Characterisation of the siloxane was performed by gel permeation chromatography (GPC), which showed the size of the siloxane chain. Thermogravimetric analysis revealed a temperature at which the siloxane mineralises to SiO2. Printed layers of two types of TSC with different siloxane contents were studied by a scanning electron microscope (SEM), where a difference in the porosity of the samples was observed. TSC on fluorine-doped tin oxide (FTO) coated glass and microscopic glass were treated with non-thermal UV and plasma methods. TSC on FTO glass were tested by voltammetric measurements, which showed that the non-thermally treated layers have better properties and the amount of siloxane in the TSC has a great influence on their efficiency. Samples on microscopic glass were subjected to a photocatalytic decomposition test of the model pollutant Acid orange 7 (AO7). Non-thermally treated samples show higher photocatalytic activity than the raw sample. Full article
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12 pages, 4813 KiB  
Article
Modeling and Experimental Studies on Adsorption and Photocatalytic Performance of Nitrogen-Doped TiO2 Prepared via the Sol–Gel Method
by Zhuoying Jiang, Sameera Wickramasinghe, Yu Hsin Tsai, Anna Cristina S. Samia, David Gurarie and Xiong Yu
Catalysts 2020, 10(12), 1449; https://doi.org/10.3390/catal10121449 - 11 Dec 2020
Cited by 2 | Viewed by 1837
Abstract
Nitrogen-doped TiO2 has a great potential as a photocatalyst under visible light irradiation with applications in the removal of air and water pollutants, and the treatment of bacterial contaminations. In this study, nitrogen-doped TiO2 nanoparticles were synthesized via the sol–gel method [...] Read more.
Nitrogen-doped TiO2 has a great potential as a photocatalyst under visible light irradiation with applications in the removal of air and water pollutants, and the treatment of bacterial contaminations. In this study, nitrogen-doped TiO2 nanoparticles were synthesized via the sol–gel method and a post-annealing heat treatment approach. The effects of annealing treatment on the photocatalyst crystalline size and degree of crystallinity were analyzed. Methylene blue dye was used as the model water contaminant for the evaluation of the photoactivity of the synthesized nitrogen-doped TiO2 nanoparticles. The degradation of methylene blue was attributed to three mechanisms, i.e., adsorption, photocatalysis, and direct light photolysis. A kinetic model was developed to distinguish the impact of these three different mechanisms on the removal of contaminants. Adsorption and photocatalysis are heterogeneous processes for removing water organic contaminants. The characterization analysis demonstrates that they are relevant to the microstructures and surface chemical compositions of nitrogen-doped TiO2 photocatalysts. The processing–structure–performance relationship helped to determine the optimal processing parameters for nitrogen-doped TiO2 photocatalyst to achieve the best performance. While we used methylene blue as the model contaminant, the generalized quantitative model framework developed in this study can be extended to other types of contaminants after proper calibration. Full article
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Review

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36 pages, 3496 KiB  
Review
Intensification of Photo-Assisted Advanced Oxidation Processes for Water Treatment: A Critical Review
by Jorge Rodríguez-Chueca, Jaime Carbajo and Patricia García-Muñoz
Catalysts 2023, 13(2), 401; https://doi.org/10.3390/catal13020401 - 13 Feb 2023
Cited by 14 | Viewed by 1942
Abstract
In recent decades, ultraviolet-assisted advanced oxidation processes (UV-AOPs) have been successfully applied to remove a wide range of contaminants from polluted water. Despite this, their extended use on an industrial scale is still far from being a reality, largely limited by the operational [...] Read more.
In recent decades, ultraviolet-assisted advanced oxidation processes (UV-AOPs) have been successfully applied to remove a wide range of contaminants from polluted water. Despite this, their extended use on an industrial scale is still far from being a reality, largely limited by the operational costs that these processes still entail. In recent years, many researchers have been working to increase UV-AOP efficiency and reduce capital and operating costs. This work aims to review different strategies devoted to the intensification of UV-AOPs. Firstly, the optimization of operational parameters, such as catalyst loading, pH, temperature, or oxidant concentration, has been reviewed as a strategy to augment the efficiency of the photocatalytic processes and reduce reagent consumption and/or treatment time. The review also discusses the development of photocatalytic materials to intensify the UV-AOPs process, and finally, the combination or integration of different UV-AOPs for the treatment of pollutants is also examined. Full article
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14 pages, 2361 KiB  
Review
Photochemical Water Splitting via Transition Metal Oxides
by Fateh Mikaeili, Tessa Gilmore and Pelagia-Iren Gouma
Catalysts 2022, 12(11), 1303; https://doi.org/10.3390/catal12111303 - 24 Oct 2022
Cited by 15 | Viewed by 2645
Abstract
Rapid population growth and ever-increasing energy consumption have resulted in increased environmental pollution and energy demands in recent years. Accordingly, studies and research on innovative and efficient ways of wastewater clean-up and exploiting eco-friendly and renewable energy sources such as sunlight have become [...] Read more.
Rapid population growth and ever-increasing energy consumption have resulted in increased environmental pollution and energy demands in recent years. Accordingly, studies and research on innovative and efficient ways of wastewater clean-up and exploiting eco-friendly and renewable energy sources such as sunlight have become a necessity. This review focuses on recent progress with photocatalysis for water splitting capabilities. It introduces photocatalysis and hydrogen as a fuel source, before moving on to explain water splitting. Then, the criteria for ideal photocatalytic materials are discussed along with current material systems and their limitations. Finally, it concludes on the TiO2 systems and their potential in future photocatalysis research. Full article
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42 pages, 3604 KiB  
Review
Semiconductors Application Forms and Doping Benefits to Wastewater Treatment: A Comparison of TiO2, WO3, and g-C3N4
by Eryk Fernandes, João Gomes and Rui C. Martins
Catalysts 2022, 12(10), 1218; https://doi.org/10.3390/catal12101218 - 12 Oct 2022
Cited by 16 | Viewed by 2754
Abstract
Photocatalysis has been vastly applied for the removal of contaminants of emerging concern (CECs) and other micropollutants, with the aim of future water reclamation. As a process based upon photon irradiation, materials that may be activated through natural light sources are highly pursued, [...] Read more.
Photocatalysis has been vastly applied for the removal of contaminants of emerging concern (CECs) and other micropollutants, with the aim of future water reclamation. As a process based upon photon irradiation, materials that may be activated through natural light sources are highly pursued, to facilitate their application and reduce costs. TiO2 is a reference material, and it has been greatly optimized. However, in its typical configuration, it is known to be mainly active under ultraviolet radiation. Thus, multiple alternative visible light driven (VLD) materials have been intensively studied recently. WO3 and g-C3N4 are currently attractive VLD catalysts, with WO3 possessing similarities with TiO2 as a metal oxide, allowing correlations between the knowledge regarding the reference catalyst, and g-C3N4 having an interesting and distinct non-metallic polymeric structure with the benefit of easy production. In this review, recent developments towards CECs degradation in TiO2 based photocatalysis are discussed, as reference catalyst, alongside the selected alternative materials, WO3 and g-C3N4. The aim here is to evaluate the different techniques more commonly explored to enhance catalyst photo-activity, specifically doping with multiple elements and the formation of composite materials. Moreover, the possible combination of photocatalysis and ozonation is also explored, as a promising route to potentialize their individual efficiencies and overcome typical drawbacks. Full article
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22 pages, 1572 KiB  
Review
Photocatalytic Degradation of Recalcitrant Pollutants of Greywater
by Mohammad Aslam, Dawood Bin Fazal, Faizan Ahmad, Abdullah Bin Fazal, Ahmad Zuhairi Abdullah, Mukhtar Ahmed, Mohammad Qamar and Mohd Rafatullah
Catalysts 2022, 12(5), 557; https://doi.org/10.3390/catal12050557 - 18 May 2022
Cited by 7 | Viewed by 3491
Abstract
These days, many countries have a water shortage and have limited access to clean water. To overcome this, a new treatment is emerging, namely, the photocatalytic processing of greywater. Photocatalytic processes to remove the organic matter from different greywater sources are critically reviewed. [...] Read more.
These days, many countries have a water shortage and have limited access to clean water. To overcome this, a new treatment is emerging, namely, the photocatalytic processing of greywater. Photocatalytic processes to remove the organic matter from different greywater sources are critically reviewed. Their efficiency in degrading the organic matter in greywater is scrutinized along with factors that can affect the activity of photocatalysts. Modified TiO2, ZnO and TiO2 catalysts show great potential in degrading organic materials that are present in greywater. There are several methods that can be used to modify TiO2 by using sol-gel, microwave and ultrasonication. Overall, the photocatalytic approach alone is not efficient in mineralizing the organic compounds, but it works well when the photocatalysis is combined with oxidants and Fe3+. However, factors such as pH, concentration and catalyst-loading of organic compounds can significantly affect photocatalytic efficiency. Full article
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