{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,6]],"date-time":"2026-05-06T03:09:52Z","timestamp":1778036992583,"version":"3.51.4"},"reference-count":47,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2011,12,14]],"date-time":"2011-12-14T00:00:00Z","timestamp":1323820800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO2 P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a 125 W mercury vapor lamp. The effects of the amount of TiO2 used, UV-light irradiation time, pH of the solution under treatment, initial concentration of the azo dye and addition of different concentrations of hydrogen peroxide were investigated. The effect of the simultaneous photodegradation of the two azo dyes was also investigated and we observed that the degradation rates achieved in mono and bi-component systems were identical. The repeatability of photocatalytic activity of the photocatalyst was also tested. After five cycles of TiO2 reuse the rate of colour lost was still 77% of the initial rate. The degradation was followed monitoring the change of azo dye concentration by UV-Vis spectroscopy. Results show that the use of an efficient photocatalyst and the adequate selection of optimal operational parameters may easily lead to a complete decolorization of the aqueous solutions of both azo dyes.<\/jats:p>","DOI":"10.3390\/molecules161210370","type":"journal-article","created":{"date-parts":[[2011,12,14]],"date-time":"2011-12-14T11:39:05Z","timestamp":1323862745000},"page":"10370-10386","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":172,"title":["Use of Titanium Dioxide Photocatalysis on the Remediation of Model Textile Wastewaters Containing Azo Dyes"],"prefix":"10.3390","volume":"16","author":[{"given":"Enrico Mendes","family":"Saggioro","sequence":"first","affiliation":[{"name":"Centro de Estudos da Sa\u00fade do Trabalhador e Ecologia Humana Escola Nacional de Sa\u00fade P\u00fablica - Funda\u00e7\u00e3o Oswaldo Cruz, Av. Leopoldo Bulh\u00f5es, 1480, Rio de Janeiro, 21041-210 RJ, Brazil"}]},{"given":"Anabela Sousa","family":"Oliveira","sequence":"additional","affiliation":[{"name":"CQFM - Centro de Qu\u00edmica-F\u00edsica Molecular and IN \u2013 Instituto de Nanociencias e Nanotecnologia, Complexo Interdisciplinar, Instituto Superior T\u00e9cnico, Universidade T\u00e9cnica de Lisboa, Av. Rovisco Pais 1049-001, Lisboa, Portugal"},{"name":"C3i - Centro Interdisciplinar de Investiga\u00e7\u00e3o e Inova\u00e7\u00e3o, Escola Superior de Tecnologia e Gest\u00e3o, Instituto Polit\u00e9cnico de Portalegre, Lugar da Abadessa Apartado 148 - 7301901 Portalegre, Portugal"}]},{"given":"Thelma","family":"Pavesi","sequence":"additional","affiliation":[{"name":"Centro de Estudos da Sa\u00fade do Trabalhador e Ecologia Humana Escola Nacional de Sa\u00fade P\u00fablica - Funda\u00e7\u00e3o Oswaldo Cruz, Av. Leopoldo Bulh\u00f5es, 1480, Rio de Janeiro, 21041-210 RJ, Brazil"}]},{"given":"C\u00e1tia Gil","family":"Maia","sequence":"additional","affiliation":[{"name":"C3i - Centro Interdisciplinar de Investiga\u00e7\u00e3o e Inova\u00e7\u00e3o, Escola Superior de Tecnologia e Gest\u00e3o, Instituto Polit\u00e9cnico de Portalegre, Lugar da Abadessa Apartado 148 - 7301901 Portalegre, Portugal"}]},{"given":"Luis Filipe Vieira","family":"Ferreira","sequence":"additional","affiliation":[{"name":"CQFM - Centro de Qu\u00edmica-F\u00edsica Molecular and IN \u2013 Instituto de Nanociencias e Nanotecnologia, Complexo Interdisciplinar, Instituto Superior T\u00e9cnico, Universidade T\u00e9cnica de Lisboa, Av. Rovisco Pais 1049-001, Lisboa, Portugal"}]},{"given":"Josino Costa","family":"Moreira","sequence":"additional","affiliation":[{"name":"Centro de Estudos da Sa\u00fade do Trabalhador e Ecologia Humana Escola Nacional de Sa\u00fade P\u00fablica - Funda\u00e7\u00e3o Oswaldo Cruz, Av. Leopoldo Bulh\u00f5es, 1480, Rio de Janeiro, 21041-210 RJ, Brazil"}]}],"member":"1968","published-online":{"date-parts":[[2011,12,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"204","DOI":"10.1016\/j.dyepig.2007.05.003","article-title":"Photocatalytic degradation of C.I. Acid Orange 52 in the presence of Zn-doped TiO2 prepared by a stearic acid gel method","volume":"77","author":"Chen","year":"2008","journal-title":"Dyes Pigm."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"46","DOI":"10.1006\/jcat.2001.3232","article-title":"Photocatalytic Degradation of Dyes in Water: Case Study of Indigo and of Indigo Carmine","volume":"201","author":"Vautier","year":"2001","journal-title":"J. Catal."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"817","DOI":"10.1016\/j.dyepig.2007.02.004","article-title":"Photocatalytic degradation of C.I. Basic Violet 10 using TiO2 catalysts supported by Y zeolite: An investigation of the effects of operational parameters","volume":"76","author":"Wang","year":"2008","journal-title":"Dyes Pigm."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/j.jhazmat.2005.05.013","article-title":"Removal of dyes using immobilized titanium dioxide illuminated by fluorescent lamps","volume":"125","author":"Zainal","year":"2005","journal-title":"J. Hazard. Mater."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1016\/j.cej.2006.09.013","article-title":"Photocatalytic degradation of an azo dye in a tubular continuous-flow photoreactor with immobilized TiO2 on glass plates","volume":"127","author":"Behnajady","year":"2007","journal-title":"Chem. Eng. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1016\/S0960-8524(00)00080-8","article-title":"Remediation of dyes in textile effluent: A critical review on current treatment technologies with a proposed alternative","volume":"77","author":"Robinson","year":"2001","journal-title":"Bioresour. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/j.jphotochem.2004.11.009","article-title":"The effect of operational parameters on the photocatalytic degradation of three textile azo dyes in aqueous TiO2 suspensions","volume":"172","author":"Habibi","year":"2005","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.jhazmat.2005.11.017","article-title":"Photocatalytic decolorization and degradation of dye solutions and wastewaters in the presence of titanium dioxide","volume":"136","author":"Bizani","year":"2006","journal-title":"J. Hazard. Mater."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"120","DOI":"10.1016\/j.jphotochem.2005.11.013","article-title":"Photocatalytic degradation of ethyl violet in aqueous solution mediated by TiO2 suspensions","volume":"181","author":"Chen","year":"2006","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_10","first-page":"462","article-title":"Surface Photocatalysis: A Study of the Thickness of TiO2 Layers on the Photocatalytic Decomposition of Soluble Indigo Blue Dye","volume":"62","author":"Oliveira","year":"2011","journal-title":"Rev. Chim. (Bucharest, Rom.)"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"2994","DOI":"10.3390\/molecules15052994","article-title":"Photocatalytic Degradation of Mecoprop and Clopyralid in Aqueous Suspensions of Nanostructured N-doped TiO2","volume":"15","author":"Todorova","year":"2010","journal-title":"Molecules"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"5769","DOI":"10.3390\/molecules16075769","article-title":"Use of Novel Cardanol-Porphyrin Hybrids and Their TiO2-Based Composites for the Photodegradation of 4-Nitrophenol in Water","volume":"16","author":"Vasapollo","year":"2011","journal-title":"Molecules"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"433","DOI":"10.1016\/S0045-6535(99)00313-6","article-title":"Semiconductor-assisted Photocatalytic Degradation of Reactive Dyes in Aqueous Solution","volume":"40","author":"Wypych","year":"2000","journal-title":"Chemosphere"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"781","DOI":"10.1016\/S0045-6535(99)00013-2","article-title":"Photochemical treatment of solutions of azo dyes containing TiO2","volume":"39","author":"Campos","year":"1999","journal-title":"Chemosphere"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"358","DOI":"10.1016\/j.dyepig.2006.08.045","article-title":"Heterogeneous photocatalytic degradation of an anthraquinone and a triphenylmethane dye derivative in aqueous suspensions of semiconductor","volume":"76","author":"Tariq","year":"2008","journal-title":"Dyes Pigm."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"506","DOI":"10.1016\/j.jhazmat.2006.10.065","article-title":"Degradation and mineralization of Direct Blue 71 in a circulating upflow reactor by UV\/TiO2 process and employing a new method in kinetic study","volume":"144","author":"Saien","year":"2007","journal-title":"J. Hazard. Mater."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"725","DOI":"10.1016\/j.jhazmat.2007.04.038","article-title":"Photocatalytic degradation of Azure and Sudan dyes using nano TiO2","volume":"149","author":"Aarthi","year":"2007","journal-title":"J. Hazard. Mater."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"300","DOI":"10.1016\/j.jenvman.2007.03.012","article-title":"Photocatalytic degradation of disperse blue 1 using UV\/TiO2\/H2O2 process","volume":"88","author":"Saquib","year":"2008","journal-title":"J. Environ. Manage."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1016\/j.dyepig.2007.01.026","article-title":"Photocatalytic discolorization of methyl orange solution by Pt modified TiO2 loaded on natural zeolite","volume":"77","author":"Huang","year":"2008","journal-title":"Dyes Pigm."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"6294","DOI":"10.1016\/j.tsf.2006.11.150","article-title":"TiO2 thin films for dyes photodegradation","volume":"515","author":"Andronic","year":"2007","journal-title":"Thin Solid Films"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1016\/j.cej.2005.07.012","article-title":"Optimal decolorization efficiency of Reactive Red 239 by UV\/TiO2 photocatalytic process coupled with response surface methodology","volume":"112","author":"Liu","year":"2005","journal-title":"Chem. Eng. J."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1016\/j.cej.2008.10.019","article-title":"Heterogeneous photocatalytic degradation of reactive dyes in aqueous TiO2 suspensions: Decolorization kinetics","volume":"149","author":"Bergamini","year":"2009","journal-title":"Chem. Eng. J."},{"key":"ref_23","first-page":"L1","article-title":"Photocatalytic degradation od Reactive Black 5 A comparison between TiO2-Tytanpol A11 and TiO2-Degussa P25 photocatalysts","volume":"35","author":"Zielinska","year":"2001","journal-title":"Appl. Catal.B"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1016\/S1010-6030(01)00440-3","article-title":"Photochemical and Heterogeneous photocatalytic degradation of waste vinylsulphone dyes: A case study with hydrolysed Reactive Black 5","volume":"141","author":"Alaton","year":"2001","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1371","DOI":"10.1016\/j.jhazmat.2006.03.030","article-title":"Solar assited photocatalytic and photochemical degradation of Reactive Black 5","volume":"137","author":"Muruganandham","year":"2006","journal-title":"J. Hazard. Mater."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2775","DOI":"10.1016\/j.watres.2004.03.020","article-title":"The photocatalytic degradation of reactive black 5 using TiO2\/UV in an annular photoreactor","volume":"38","author":"Tang","year":"2004","journal-title":"Water Res."},{"key":"ref_27","first-page":"2581","article-title":"Photocatalytic degradation of two selected textile dye derivates, Eosine Yellowish and \u03c1-Rosaniline, aqueous suspensions of titanium dioxide","volume":"38","author":"Saquib","year":"2003","journal-title":"J. Environ. Sci. Health Part A Toxic\/Hazard. Subst. Environ. Eng."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1021\/cr00017a016","article-title":"Heterogeneous Photocatalysis","volume":"93","author":"Fox","year":"1993","journal-title":"Chem. Rev."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.apcatb.2003.11.010","article-title":"TiO2-assisted photocatalytic degradation of azo dyes in aqueous solution: kinetic and mechanistic investigations: A review","volume":"49","author":"Konstantinou","year":"2004","journal-title":"Appl. Catal. B"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1233","DOI":"10.1016\/S0045-6535(99)00538-X","article-title":"Degradation mechanism of azo dye C.I. reactive red 2 by iron powder reduction and photooxidation in aqueous solutions","volume":"41","author":"Feng","year":"2000","journal-title":"Chemosphere"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1016\/j.apcatb.2004.02.009","article-title":"Photocatalytic degradation of the alimentary azo dye amaranth. Mineralization of the azo group to nitrogen","volume":"51","author":"Karkmaz","year":"2004","journal-title":"Appl. Catal. B"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"60","DOI":"10.1016\/j.dyepig.2006.05.012","article-title":"Photodegradation of azo dye Acid Red 18 in a quartz labyrinth flow reactor with immobilized TiO2 bed","volume":"75","author":"Mozia","year":"2007","journal-title":"Dyes Pigm."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"5726","DOI":"10.1021\/j100331a036","article-title":"Photocatalytic degradation of chlorinated phenols in aerated aqueous-solutions over TiO2 supported on a glass matrix","volume":"92","author":"Serpone","year":"1988","journal-title":"J. Phys. Chem."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1016\/j.jphotochem.2008.03.021","article-title":"Highly photocatalytic activity of metallic hydroxide\/titanium dioxide nanoparticules prepared via a modified wet precipitation process","volume":"198","author":"Wang","year":"2008","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_35","first-page":"70","article-title":"Influence of process parameters on the photodegradation of synthesized azo pyridine dye in TiO2 water suspension under simulated sunlight","volume":"46","author":"Dostanic","year":"2011","journal-title":"J. Environ. Sci. Health Part A Toxic\/Hazard. Subst. Environ. Eng."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"6375","DOI":"10.1007\/s10853-005-1825-y","article-title":"Transparent TiO2 sol nanocrystallites mediated homogeneous-like photocatalytic reaction and hydrosol recycling process","volume":"40","author":"Xie","year":"2005","journal-title":"J. Mater. Sci."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.apcata.2009.02.043","article-title":"Tailored titanium dioxide photocatalysts for the degradation of organic dyes in wastewater treatment: A review","volume":"359","author":"Han","year":"2009","journal-title":"Appl. Catal. A"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/j.dyepig.2005.01.004","article-title":"Photocatalytic decolourisation and degradation of Reactive Orange 4 by TiO2-UV process","volume":"68","author":"Muruganandham","year":"2006","journal-title":"Dyes Pigm."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1016\/S1010-6030(03)00015-7","article-title":"Photocatalytic degradation of azo dye acid red 14 in water: investigation of the effect of operational parameters","volume":"157","author":"Daneshvar","year":"2003","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1016\/S0926-3373(01)00275-2","article-title":"Photocatalytic decomposition of azo-dye acid black 1 in water over modified titanium dioxide","volume":"36","author":"Grzechulska","year":"2002","journal-title":"Appl. Catal. B"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"659","DOI":"10.1021\/es9905750","article-title":"UV\/H2O2 Treatment of methyl tert-butyl ether in contaminated waters","volume":"34","author":"Carter","year":"2000","journal-title":"Environ. Sci. Technol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"347","DOI":"10.1016\/S0926-3373(98)00019-8","article-title":"Enhancement of the rate of solar photocatalytic mineralization of organic pollutants by inorganic oxidizing species","volume":"17","author":"Malato","year":"1998","journal-title":"Appl. Catal. B"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1016\/j.colsurfa.2006.05.012","article-title":"Decolorization and mineralization of textile dyes at solution bulk by heterogeneous nanophotocatalysis using immobilized nanoparticles of titanium dioxide","volume":"290","author":"Mahmoodi","year":"2006","journal-title":"Colloids Surf. A"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1016\/j.apcatb.2008.01.024","article-title":"Nb2O5 as efficient and recyclable photocatalyst for indigo carmine degradation","volume":"82","author":"Prado","year":"2008","journal-title":"Appl. Catal. A"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/j.apcatb.2004.10.009","article-title":"Photocatalytic degradation of azo-dyes reactive black 5 and reactive yellow 145 in water over a newly deposited titanium dioxide","volume":"57","author":"Aguedacha","year":"2005","journal-title":"Appl. Catal. B"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1016\/S0045-6535(99)00487-7","article-title":"Photocatalytic degradation of AZO dyes by supported TiO2\/UV in aqueous solution","volume":"41","author":"Zhu","year":"2000","journal-title":"Chemosphere"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1016\/S0143-7208(01)00014-6","article-title":"Decolourization of textile industry wastewater by the photocatalytic degradation process","volume":"49","author":"Hachem","year":"2001","journal-title":"Dyes Pigm."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/16\/12\/10370\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:58:20Z","timestamp":1760219900000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/16\/12\/10370"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2011,12,14]]},"references-count":47,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2011,12]]}},"alternative-id":["molecules161210370"],"URL":"https:\/\/doi.org\/10.3390\/molecules161210370","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2011,12,14]]}}}