Removal of bromate from drinking water using a heterogeneous photocatalytic mili-reactor: impact of the reactor material and water matrix

  • Gustavo S. Cunha
  • Sara G. S. Santos
  • Bianca M. Souza-Chaves
  • Tânia F.C.V. SilvaEmail author
  • João Paulo Bassin
  • Márcia W.C. Dezotti
  • Rui A.R. Boaventura
  • Madalena M. Dias
  • José Carlos B. Lopes
  • Vítor J.P. VilarEmail author
Research Article


The main goal of this study was to evaluate the removal of bromate from drinking water using a heterogeneous photocatalytic mili-photoreactor, based on NETmix technology. The NETmix mili-reactor consists of a network of channels and chambers imprinted in a back slab made of acrylic (AS) or stainless steel (SSS) sealed, through mechanical compression and o-rings, with an UVA-transparent front borosilicate glass slab (BGS). A plate of UVA-LEDs was placed above the BGS window. TiO2-P25 thin films were immobilized on the BGS (back-side illumination, BSI) or SSS (front-side illumination, FSI) by using a spray deposition method. The photoreduction rate of a 200 μg L−1 (1.56 μM) BrO3 solution was assessed taking into account the following: (i) catalyst film thickness, (ii) catalyst coated surface and illumination mechanism (BSI or FSI), (iii) solution pH, (iv) type and dose of sacrificial agent (SA), (v) reactor material, and (vi) water matrix. In acidic conditions (pH 3.0) and in the absence of light/catalyst/SA, 28% and 36% of BrO3 was reduced into Br only by contacting with AS and SSS during 2-h, respectively. This effect prevailed during BSI experiments, but not for FSI ones since back SSS was coated with the photocatalyst. The results obtained have demonstrated that (i) the molar rate of disappearance of bromates was similar to the molar rate of formation of bromides; (ii) higher BrO3 reduction efficiencies were reached in the presence of an SA using the FSI at pH 3.0; (iii) formic acid ([BrO3]:[CH2O2] molar ratio of 1:3) presented higher performance than humic acids (HA = 1 mg C L−1) as SA; (iv) high amounts of HA impaired the BrO3 photoreduction reaction; (v) SSS coated catalyst surface revealed to be stable for at least 4 consecutive cycles, keeping its photonic efficiency. Under the best operating conditions (FSI, 18 mL of 2% wt. TiO2-P25 suspension, pH 3.0), the use of freshwater matrices led to (i) equal or higher reaction rates, when compared with a synthetic water in the absence of SA, and (ii) lower reaction rates, when compared with a synthetic water containing formic acid with a [BrO3]:[CH2O2] molar ratio of 1:3. Notwithstanding, heterogeneous TiO2 photocatalysis, using the NETmix mili-reactor can be used to promote the reduction of BrO3 into Br, attaining concentrations below 10 μg L−1 (guideline value) after 2-h reaction.

Graphical Abstract



Bromate photocatalytic reduction NETmix mili-photoreactor |Illumination mechanism Reactor material Sacrificial agent Water matrix 


List of acronyms


Average carbon oxidation state


Acrylic slab


Borosilicate glass slab


Backside Illumination


Dissolved organic carbon


Frontside illumination


Freshwater sample


Freshwater sample after the ozonation process


Freshwater sample after sequential ozonation-coagulation/flocculation-filtration process


Freshwater sample before the ozonation process


Humic acid


Limit of detection


Limit of quantification


Maximum contaminant level


Methyl methacrylate


Natural organic matter


pH value at the point of zero charge


Poly (methyl methacrylate)


Photocatalytic space-time yield


Radiant power


Sacrificial agent


Stainless steel slab


Synthetic water


Total organic carbon


Ultrapure water




World Health Organization


Water treatment plants

Latin letters


Pseudo-first order kinetic constant


Flow rate


Initial reaction rate


Coefficient of determination


Residual variance







Greek letters


Photonic efficiency


Photon flux



This work is a result of Project “AIProcMat@N2020-Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020,” with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); and Associate Laboratory LSRE-LCM-UID/EQU/50020/2019, funded by national funds through FCT/MCTES (PIDDAC). Gustavo S. Cunha acknowledges his doctoral scholarship (process no. 153965/2016-9) supported by CNPq (Brazil). Bianca M. Souza-Chaves gratefully acknowledges her postdoctoral scholarship (process no. 201989/2014-0) supported by CNPq (Brazil) through the Science without Borders Program (Ciência sem Fronteiras). T. Silva and V. Vilar acknowledge the FCT Individual Call to Scientific Employment Stimulus 2017 (CEECIND/01386/2017 and CEECIND/01317/2017, respectively).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Gustavo S. Cunha
    • 1
    • 2
  • Sara G. S. Santos
    • 1
  • Bianca M. Souza-Chaves
    • 2
  • Tânia F.C.V. Silva
    • 1
    Email author
  • João Paulo Bassin
    • 2
  • Márcia W.C. Dezotti
    • 2
  • Rui A.R. Boaventura
    • 1
  • Madalena M. Dias
    • 1
  • José Carlos B. Lopes
    • 1
  • Vítor J.P. Vilar
    • 1
    Email author
  1. 1.Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de EngenhariaUniversidade do PortoPortoPortugal
  2. 2.Chemical Engineering Program–COPPEFederal University of Rio de JaneiroRio de JaneiroBrazil

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