| Autor: |
Cunha GS; Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.; Chemical Engineering Program-COPPE, Federal University of Rio de Janeiro, PO Box 68502, Rio de Janeiro, RJ, 21941-972, Brazil., Santos SGS; Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal., Souza-Chaves BM; Chemical Engineering Program-COPPE, Federal University of Rio de Janeiro, PO Box 68502, Rio de Janeiro, RJ, 21941-972, Brazil., Silva TFCV; Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. tania.silva@fe.up.pt., Bassin JP; Chemical Engineering Program-COPPE, Federal University of Rio de Janeiro, PO Box 68502, Rio de Janeiro, RJ, 21941-972, Brazil., Dezotti MWC; Chemical Engineering Program-COPPE, Federal University of Rio de Janeiro, PO Box 68502, Rio de Janeiro, RJ, 21941-972, Brazil., Boaventura RAR; Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal., Dias MM; Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal., Lopes JCB; Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal., Vilar VJP; Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. vilar@fe.up.pt. |
| Abstrakt: |
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. TiO 2 -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) BrO 3 - 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 BrO 3 - 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 BrO 3 - reduction efficiencies were reached in the presence of an SA using the FSI at pH 3.0; (iii) formic acid ([BrO 3 - ]:[CH 2 O 2 ] 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 BrO 3 - 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. TiO 2 -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 [BrO 3 - ]:[CH 2 O 2 ] molar ratio of 1:3. Notwithstanding, heterogeneous TiO 2 photocatalysis, using the NETmix mili-reactor can be used to promote the reduction of BrO 3 - into Br - , attaining concentrations below 10 μg L -1 (guideline value) after 2-h reaction. Graphical Abstract . |
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