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Photocatalysis in the Wastewater Treatment

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

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 35029

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Prof. Dr. Gassan Hodaifa

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Molecular Biology and Biochemical Engineering Department, Chemical Engineering Area, Universidad Pablo de Olavide, ES-14013 Seville, Spain
Interests: advanced oxidation processes; kinetic growth; biomass growth, industrial and urban wastewater, contaminant removal; wastewater treatment; clean technologies; sustainability and regeneration of wastewater; circular economy
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Dr. Rafael Borja

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Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, Carretera de Utrera km 1, Building 46, ES-41013 Seville, Spain
Interests: anaerobic digestion; aerobic treatment; agricultural and food solid wastes; integral treatments (pre-treatments + anaerobic digestion); agro-industrial wastewaters
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The modernization of our society and the great technological advances whether in the agro-food, chemical, pharmaceutical or biotechnological sectors have allowed the establishment of large industries in the last fifty years. Most of these industries are characterized by the high consumption of drinking water that is transformed into wastewater as it leaves these industrial processes. Unfortunately, a large part of this wastewater is difficult to treat due to the presence of a high organic load, persistent compounds, toxic and inhibitory compounds, etc. This fact has generated a challenge to conventional urban wastewater treatment plants (CUWTPs) that are increasingly unable to meet the standards set by local, national or international legislation. Being the accomplishment of pre-treatments or treatments of adaptation before their discharge to the CUWTPs of obligatory compliment by the industries. On the other hand, in the last decade climate change has been evident due to the high values of the carbon footprint and the hydraulic footprint registered by the industries. Not to mention, the availability of drinking water is scarce in many countries.

The use of photocatalysis for wastewater treatment is an important area of research, which is not yet fully exploited at an industrial level and has significant potential in the disposal of many industrial effluents. In particular, the effluents that are difficult to treat by conventional treatment processes. This special Issue tries to know the latest advances in the field of wastewater treatment by photocatalysis. In this sense, it is worth mentioning the treatments based on photolysis, TiO₂/solar light, ozone/ultraviolet irradiation, oxidants/ultraviolet irradiation, oxidants/catalyst/ultraviolet irradiation, high-energy electron beam irradiation (E-beam), sonication/photocatalysis, etc. The Special Issue also includes combined processes that integrate photocatalysis techniques as pre-treatment or post-treatment stages.

Prof. Dr. Gassan Hodaifa
Dr. Rafael Borja
Guest Editors

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Keywords

Photocatalysis with solar energy
Photo-Fenton
O₃/UV
TiO₂/Catalyzed/UV oxidation
H₂O₂/UV
High energy electron beam
Sonication/Photo-Fenton
Photoreactor configuration
Pesticide removal
Wastewater treatment

Published Papers (13 papers)

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Research

20 pages, 8664 KiB

Open AccessArticle

Ti₂O₃/TiO₂-Assisted Solar Photocatalytic Degradation of 4-tert-Butylphenol in Water

by Saule Mergenbayeva, Timur Sh. Atabaev and Stavros G. Poulopoulos

Catalysts 2021, 11(11), 1379; https://doi.org/10.3390/catal11111379 - 16 Nov 2021

Cited by 14 | Viewed by 2611

Abstract

Colored Ti₂O₃ and Ti₂O₃/TiO₂ (mTiO) catalysts were prepared by the thermal treatment method. The effects of treatment temperature on the structure, surface area, morphology and optical properties of the as-prepared samples were investigated by XRD, BET, SEM, TEM, Raman and UV–VIS spectroscopies. Phase transformation from Ti₂O₃ to TiO₂ rutile and TiO₂ anatase to TiO₂ rutile increased with increasing treatment temperatures. The photocatalytic activities of thermally treated Ti₂O₃ and mTiO were evaluated in the photodegradation of 4-tert-butylphenol (4-t-BP) under solar light irradiation. mTiO heated at 650 °C exhibited the highest photocatalytic activity for the degradation and mineralization of 4-t-BP, being approximately 89.8% and 52.4%, respectively, after 150 min of irradiation. The effects of various water constituents, including anions (

{CO}_{3}^{2 -}

{NO}_{3}

Cl

and

{HCO}_{3}^{-}

) and humic acid (HA), on the photocatalytic activity of mTiO-650 were evaluated. The results showed that the presence of carbonate and nitrate ions inhibited 4-t-BP photodegradation, while chloride and bicarbonate ions enhanced the photodegradation of 4-t-BP. As for HA, its effect on the degradation of 4-t-BP was dependent on the concentration. A low concentration of HA (1 mg/L) promoted the degradation of 4-t-BP from 89.8% to 92.4% by mTiO-650, but higher concentrations of HA (5 mg/L and 10 mg/L) had a negative effect. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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13 pages, 3259 KiB

Open AccessArticle

Quarry Residue: Treatment of Industrial Effluent Containing Dye

by Lariana Negrão Beraldo de Almeida, Tatiana Gulminie Josué, Othavio Henrique Lupepsa Nogueira, Daniele Toniolo Dias, Angelo Marcelo Tusset, Onélia Aparecida Andreo dos Santos and Giane Gonçalves Lenzi

Catalysts 2021, 11(7), 852; https://doi.org/10.3390/catal11070852 - 16 Jul 2021

Cited by 1 | Viewed by 2035

Abstract

This work is devoted to the investigation of the discoloration of the synthetic and industrial effluent, using a quarry residue (MbP), which is a material naturally composed of mixed oxides, compared to zinc oxide (ZnO), acting as photocatalysts and adsorbents. The optimization of the pH and catalyst concentration parameters was carried out, and the industrial effluent was then treated by photocatalytic reactions, adsorption, and photolysis. Industrial effluent was supplied by a packaging company and was collected for a period of seven consecutive days, showing the oscillation of the parameters in the process. The material characterizations were obtained by scanning electron microscopy (SEM-EDS), X-Ray diffraction (XRD), and photoacoustic spectroscopy (PAS). The results indicated that the composition of the quarry waste is mainly silica and has E_gap 2.16 eV. The quarry residue as photocatalyst was active for the artificial effluent (synthetic dye solution), with a maximum of 98% discoloration, and as an adsorbent for industrial effluent, with a maximum of 57% of discoloration. Although the quarry residue has shown results lower than ZnO, it is considered a promising material in adsorption processes and photocatalytic reactions for discoloration of aqueous solutions. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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15 pages, 2195 KiB

Open AccessArticle

Synthesis and Photocatalytic Activity of Hierarchical Zn-ZSM-5 Structures

by Hongji Li, Yu Zhang, Jiaqi Diao, Mengmeng Qiang and Zhe Chen

Catalysts 2021, 11(7), 797; https://doi.org/10.3390/catal11070797 - 29 Jun 2021

Cited by 6 | Viewed by 2064

Abstract

Hierarchical Zn-ZSM-5 photocatalyst structures were synthesized via a hydrothermal one-pot synthesis route using a double template. Activated attapulgite (Si-ATP) and zinc nitrate (Zn(NO₃)₂) precursors were used as silicon and zinc sources, respectively. The structural properties, morphology, photocatalytic activity and the texture properties of the synthesized Zn-ZSM-5 photocatalysts were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), diffracted ultraviolet–visible (UV–Vis) spectrometry (DRUV–Vis) and N₂ adsorption/desorption, respectively. It was found that the composites exhibit a typical MFI framework structure, a hexahedral twin structure and typical UV absorption peaks at 292 nm and 246 nm, when the Zn/Si mole ratio reaches its optimum value of 1:100. The hierarchical nanocrystals exhibit a similar Brunauer–Emmett–Teller surface area (309 m² g⁻¹) and a high mesopore ratio (37.47%) as compared to commercial zeolites. Sub-nano-sized zinc oxide (ZnO) particles with small size moieties were implanted and isolated in the silica matrices of micro-mesoporous zeolite, which had a significant photocatalytic activity and reusability of degrading methylene blue (MB) dyeing wastewater. Using a 500 W mercury lamp with the wavelength range from 185–500 nm operating during an illumination time of 30 min, the concentration of MB decreases significantly in the presence of Zn-ZSM-5 photocatalyst leading to a 95.56% of degradation, where the ratio still remained at 94.32% after six times of reuse. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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13 pages, 2406 KiB

Open AccessArticle

Experimental and Physico-Chemical Comparison of ZnO Nanoparticles’ Activity for Photocatalytic Applications in Wastewater Treatment

by Stefano Alberti, Irene Basciu, Marco Vocciante and Maurizio Ferretti

Catalysts 2021, 11(6), 678; https://doi.org/10.3390/catal11060678 - 26 May 2021

Cited by 20 | Viewed by 2629

Abstract

In this contribution, the photoactivity upon activation by simulated sunlight of zinc oxide (ZnO) obtained from two different synthetic pathways (Acetate and Nitrate) is investigated for water purification. Different reagents and processes were exploited to obtain ZnO nanoparticles. Products have been characterized by means of X-Ray Diffraction, Scanning Electron Microscopy along with Energy Dispersive Spectrometer, Dynamic Light Scattering, and Diffuse Reflectance Measurements, to highlight the different outcomes ascribable to each synthesis. A comparison of characteristics and performances was also carried out with respect to commercial ZnO. Nanoparticles of this semiconductor can be obtained as aggregates with different degrees of purity, porosity, and shape, and their physical-chemical properties have been addressed to the specific use in wastewater treatment, testing their effectiveness on the photocatalytic degradation of methylene blue (MB) as a model pollutant. Excluding the commercial sample, experimental results evidenced a better photocatalytic behavior for the ZnO Nitrate sample annealed at 500 °C, which was found to be pure and stable in water, suggesting that ZnO could be effectively exploited as a heterogeneous photocatalyst for the degradation of emerging pollutants in water, provided that thermal treatment is included in the synthetic process. Full article

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14 pages, 28487 KiB

Open AccessArticle

UV Stimulated Manganese Dioxide for the Persulfate Catalytic Degradation of Bisphenol A

by Guihua Dong, Bing Chen, Bo Liu, Stanislav R. Stoyanov, Yiqi Cao, Min Yang and Baiyu Zhang

Catalysts 2021, 11(4), 502; https://doi.org/10.3390/catal11040502 - 16 Apr 2021

Cited by 18 | Viewed by 3263

Abstract

One of the most commonly produced industrial chemicals worldwide, bisphenol A (BPA), is used as a precursor in plastics, resins, paints, and many other materials. It has been proved that BPA can cause long-term adverse effects on ecosystems and human health due to its toxicity as an endocrine disruptor. In this study, we developed an integrated MnO₂/UV/persulfate (PS) process for use in BPA photocatalytic degradation from water and examined the reaction mechanisms, degradation pathways, and toxicity reduction. Comparative tests using MnO₂, PS, UV, UV/MnO₂, MnO₂/PS, and UV/PS processes were conducted under the same conditions to investigate the mechanism of BPA catalytic degradation by the proposed MnO₂/UV/PS process. The best performance was observed in the MnO₂/UV/PS process in which BPA was completely removed in 30 min with a reduction rate of over 90% for total organic carbon after 2 h. This process also showed a stable removal efficiency with a large variation of pH levels (3.6 to 10.0). Kinetic analysis suggested that ¹O₂ and SO₄^•⁻ played more critical roles than •OH for BPA degradation. Infrared spectra showed that UV irradiation could stimulate the generation of –OH groups on the MnO₂ photocatalyst surface, facilitating the PS catalytic degradation of BPA in this process. The degradation pathways were further proposed in five steps, and thirteen intermediates were identified by gas chromatography-mass spectrometry. The acute toxicity was analyzed during the treatment, showing a slight increase (by 3.3%) in the first 30 min and then a decrease by four-fold over 2 h. These findings help elucidate the mechanism and pathways of BPA degradation and provide an effective PS catalytic strategy. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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15 pages, 3957 KiB

Open AccessArticle

Photocatalytic Nanocomposite Polymer-TiO₂ Membranes for Pollutant Removal from Wastewater

by Khelil Bouziane Errahmani, Ouassila Benhabiles, Sohbi Bellebia, Zohra Bengharez, Mattheus Goosen and Hacene Mahmoudi

Catalysts 2021, 11(3), 402; https://doi.org/10.3390/catal11030402 - 23 Mar 2021

Cited by 18 | Viewed by 2877

Abstract

Photocatalytic TiO₂-PVDF/PMMA nano-composites flat sheet membranes were fabricated by phase inversion and then employed in a crossflow filtration pilot to remove model pollutants of various sizes and charge from aqueous solution. The dope solution contained a mixture of PVDF and PMMA as polymers, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) as additives, triethyl phosphate (TEP) as green solvent and TiO₂ as immobilized photo catalyst. After undergoing characterization tests such as SEM morphology thickness, porosity, contact angle and water permeability, the membranes were used to eliminate the model pollutants from synthetic aqueous solution. The impact of the operating conditions (i.e., pH, pressure and initial pollutant concentration) and composition of the doping solution on the performance and photocatalytic and antifouling activity of the membranes was investigated. The results showed that Congo Red and Tartrazine despite their small size were rejected at 99% and 81%, respectively, because of their negative charge, while Ciprofloxacin, which is larger than Tartrazine but of neutral charge, crossed the membrane. The permeability did not decrease with a decline in pollutant concentration but diminished when the pressure increased and was reduced by more than half for wastewater. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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13 pages, 4538 KiB

Open AccessArticle

Colour Changes during the Carbamazepine Oxidation by Photo-Fenton

by Natalia Villota, Cristian Ferreiro, Hussein Ahmad Qulatein, Jose María Lomas, Luis Miguel Camarero and José Ignacio Lombraña

Catalysts 2021, 11(3), 386; https://doi.org/10.3390/catal11030386 - 18 Mar 2021

Cited by 3 | Viewed by 2238

Abstract

The oxidation of aqueous solutions of carbamazepine is conducted using the Fenton reagent, combined with the photolytic action of a 150 W medium pressure UV lamp, operating at T = 40 °C. The effect of acidity is analysed at an interval pH = 2.0–5.0, verifying that operating at pH = 5.0 promotes colour formation (Colour = 0.15 AU). The effect of iron is studied, finding that the colour of the water increases in a linear way, Colour = 0.05 + 0.0075 [Fe]₀. The oxidising action of hydrogen peroxide is tested, confirming that when operating with [H₂O₂]₀ = 2.0 mM, the maximum colour is generated (Colour_max = 0.381 AU). The tint would be generated by the degradation of by-products of carbamazepine, which have chromophoric groups in their internal structure, such as oxo and dioxocarbazepines, which would produce tint along the first minutes of oxidation, while the formation of acridones would slowly induce colour in the water. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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8 pages, 2649 KiB

Open AccessArticle

Enhanced Photocatalytic Activity of ZnO-Graphene Oxide Nanocomposite by Electron Scavenging

by Syed Nabeel Ahmed and Waseem Haider

Catalysts 2021, 11(2), 187; https://doi.org/10.3390/catal11020187 - 31 Jan 2021

Cited by 8 | Viewed by 2335

Abstract

Advances in nanotechnology have opened new doors to overcome the problems related to contaminated water by introducing photocatalytic nanomaterials. These materials can effectively degrade toxic contaminants, such as dyes and other organic pollutants, into harmless by-products such as carbon dioxide and water. Consequently, these photocatalytic nanomaterials have the potential to provide low-cost and environment-friendly alternatives to conventional water and wastewater treatment techniques. In this study, a nanocomposite of zinc oxide and graphene oxide was developed and evaluated for photocatalysis. This nanocomposite was characterized by XRD, FTIR, FESEM, Diffuse Reflectance Spectroscopy (DRS), TEM and UV-Vis spectrophotometer. The photocatalytic behavior of the nanocomposite was studied through the degradation of methyl orange under ultraviolet light. It is reported that the weight ratios of zinc oxide and graphene oxide do not considerably affect the photocatalytic performance, which gives this process more compositional flexibility. Moreover, hydrogen peroxide was used as an electron scavenger to increase the time-efficiency of the process. The photodegradation rate can be significantly improved (up to 24 times) with the addition of hydrogen peroxide, which increases the number of trapped electrons and generates more oxidizing species, consequently increasing the reaction rate. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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12 pages, 3700 KiB

Open AccessArticle

Hole Doping to Enhance the Photocatalytic Activity of Bi₄NbO₈Cl

by Jingbang Sun, Ni Han, Yan Gu, Xiaowang Lu, Liang Si and Qinfang Zhang

Catalysts 2020, 10(12), 1425; https://doi.org/10.3390/catal10121425 - 05 Dec 2020

Cited by 6 | Viewed by 2169

Abstract

An increase of carrier concentration is one of the most important routes for enhancing the catalytic performance of semiconductor photocatalysts. In this study, the Sillén–Aurivillius oxychloride Bi₄NbO₈Cl with hole doping was successfully prepared by a solid-state reaction method. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible diffuse reflectance spectra (UV–vis DRS), X-ray photoelectron spectrometry (XPS) and photoluminescence spectra (PL) were used to characterize and analyze the prepared samples. The experimental results and density functional theory calculations demonstrate that hole doping can be formed in Bi₄NbO₈Cl by inserting zinc into the niobium site, and the photocatalytic activity can be improved by introducing additional holes into Bi₄NbO₈Cl. The photogenerated hole (h⁺) is considered to be the main active species to degrade trypan blue (TB) through trapping experiments. The optimal photocatalyst of Bi₄Nb_0.8Zn_0.2O₈Cl exhibits excellent photocatalytic activity in degradation of trypan blue under visible light irritation. Moreover, a possible photocatalytic degradation mechanism is discussed according the experimental and analytical results. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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16 pages, 4264 KiB

Open AccessArticle

Visible Light Driven Spherical CuBi₂O₄ with Surface Oxygen Vacancy Enhanced Photocatalytic Activity: Catalyst Fabrication, Performance, and Reaction Mechanism

by Xin Zhong, Yihong Cai, Heping Bai, Wei Huang and Binxue Zhou

Catalysts 2020, 10(8), 945; https://doi.org/10.3390/catal10080945 - 17 Aug 2020

Cited by 16 | Viewed by 2822

Abstract

Here, a spherical CuBi₂O₄ catalyst with surface oxygen vacancy was fabricated through a facile hydrothermal method, which exhibited remarkable enhanced photocatalytic activity of refractory chemicals in the heterogeneous sulfate radical-based Fenton-like reaction under visible light emitting diode (LED) light irradiation. The property of the catalysts was systematically characterized by scanning electron microscopy (SEM)/high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV/vis methods. The effects of parameters of solution pH, potassium peroxymonosulfate (PMS) concentration, catalyst dosage, and catalyst reusability on Rhodamine B (RhB) degradation were investigated. In the interface reaction, the improved photodegradation efficiency could be attributed to the decomposition of PMS, which produced sulfate radicals and hydroxyl radicals owing to the transmission of photo-generated electron/hole pairs. Herein, the introduction of surface oxygen vacancy as well as the cycling of copper valence states (Cu(II)/Cu(I) pairs) can facilitate the production of free reactive radicals, leading to the high degradation efficiency. The catalyst showed high removal efficiency and presented good cycle stability in the reaction. Additionally, the free radical quencher experiment and electron spin resonance (EPR) experiments were conducted, and a proposed photocatalytic mechanism was also illustrated. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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17 pages, 6482 KiB

Open AccessArticle

Enhanced Visible-Light Driven Photocatalytic Activity of Ag@TiO₂ Photocatalyst Prepared in Chitosan Matrix

by Ivana Grčić, Andreja Gajović, Milivoj Plodinec, Kristina Šimunković, Hrvoje Ivanković and Marc-Georg Willinger

Catalysts 2020, 10(7), 763; https://doi.org/10.3390/catal10070763 - 08 Jul 2020

Cited by 5 | Viewed by 2935

Abstract

Ag doped TiO₂ photocatalysts (Ag@TiO₂) were prepared with an aim to extend the absorption range of TiO₂ into the visible region, for tentative application under solar irradiation. Photocatalyst synthesized by the novel method using chitosan for reduction of Ag⁺ to Ag⁰ nanoparticles was compared to similar catalysts previously reported. The photocatalytic activity of Ag@TiO₂ obtained by a simple novel method was evaluated based on degradation of salicylic acid as a model compound. The higher activity under visible irradiation can be attributed to the surface plasmon resonance and suppression of the electron-hole recombination when deposition of Ag nanoparticles on TiO₂ was achieved using chitosan. The photocatalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), high resolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDXS), selected area diffraction (SAED), and diffuse reflectance spectroscopy (DRS). The photochromism of Ag was observed and explained. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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17 pages, 1652 KiB

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Study of Catalysts’ Influence on Photocatalysis/Photodegradation of Olive Oil Mill Wastewater. Determination of the Optimum Working Conditions

by Gassan Hodaifa, Cristina Agabo García and Rafael Borja

Catalysts 2020, 10(5), 554; https://doi.org/10.3390/catal10050554 - 17 May 2020

Cited by 4 | Viewed by 2059

Abstract

The high production of raw olive oil mill wastewater (OMW) is a current environmental problem due to its high organic load and phenol compounds. In this work, photo-Fenton reaction as an advanced oxidation process has been chosen for OMW treatment. In this sense, different iron salts (FeCl₃, Fe₂(SO₄)₃, FeSO₄·7H₂O, and Fe(ClO₄)₃) as catalysts were used in order to compare their effects on treatment. For each catalyst, different H₂O₂ concentrations (2.5, 5.0, 7.5, 10.0, 15.0, 20.0, and 30.0%, w/v) as oxidizing agents were tested. The common experimental conditions were temperature 20 °C, the catalyst/H₂O₂ ratio = 0.03, pH = 3, and ultraviolet light. The Lagergren kinetic model, in cases of total organic carbon removal, for the best H₂O₂ concentration per catalyst was used. During the experiments, the water quality was determined by measuring the removal percentages on chemical oxygen demand, total carbon, total organic carbon, total nitrogen, total phenolic compounds, total iron, turbidity and electric conductivity. The best catalyst was FeCl₃ and the optimum H₂O₂ concentration was 7.5% (w/v). At these optimal conditions, the removal percentages for chemical oxygen demand, total phenolic compounds, total carbon, total organic carbon and total nitrogen were 60.3%, 88.4%, 70.1%, 63.2% and 51.5%, respectively. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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14 pages, 2835 KiB

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Preparation of CdS Nanoparticles-TiO₂ Nanorod Hererojunction and Their High-Performance Photocatalytic Activity

by Jianhua Song, Dedong Zeng, Yu Xie, Fayun Zhang, Shenli Rao, Fahui Wang, Jinsheng Zhao, Jinbing Zhang and Lei Wang

Catalysts 2020, 10(4), 441; https://doi.org/10.3390/catal10040441 - 19 Apr 2020

Cited by 7 | Viewed by 2864

Abstract

As a new and emerging technology, photocatalytic oxidation is widely used in the fields of sewage treatment and organic pollution control. In this study, CdS nanoparticles were prepared at room temperature by an innovative preparation method, then TiO₂ nanorod–CdS nanoparticle heterojunction photocatalysts were prepared using the solvothermal method, with TiCl₃ used as the precursor for TiO₂ nanorods. This study mainly took advantage of the small size of the CdS nanoparticles in combination with TiO₂ nanorods, and the resultant heterojunctions had large specific surface areas, thereby increasing the contact area between the catalysts and the contaminants. In addition, due to the lower band gap energy (2.4 eV) of CdS, the photo response range of the heterojunction photocatalysts was also increased. In an experimental study, through photocatalytic performance tests of the catalysts with different weight ratios, it was found that the TiO₂(40%)@CdS composite had the best photocatalytic performance and the highest catalytic rate. BET, SEM, and other tests showed that the specific surface area of the TiO₂(40%)@CdS composite was the largest. TiO₂ nanorods and CdS particles were uniformly distributed in the composite, and the optical response range was extended to the visible light region. Full article

(This article belongs to the Special Issue Photocatalysis in the Wastewater Treatment)

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