Simultaneous decolorization and detoxification of black reactive 5 using TiO2 deposited over borosilicate glass

Johana Puentes-Cárdenas,Alex Florido-Cuellar,Aura Pedroza-Rodríguez,Viviana Gutiérrez-Romero,Paola Bohorquez-Echeverry,Claudia Campos-Pinilla,Jairo Cardona-Bedoya

doi:10.11144/javeriana.sc17-1.sdad

Johana Puentes-Cárdenas, Alex Florido-Cuellar + Show 5 more

Open Access

https://doi.org/10.11144/javeriana.sc17-1.sdad

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Abstract

Objective. Removal and detoxification of azo dye by photocatalysis with TiO2. Materials and methods. TiO2 films were prepared by sedimentation at pH 1.3, using as support a borosilicate glass, annealed for 1 hour at 450 °C. Physical characterization was performed by Scanning Electron Microscopy, X-ray diffraction and UV/VIS spectrometry. Dye Black Reactive 5 removal was carried-out in a quartz photo-reactor. Results. Optical characterization revealed the films displayed evident TiO2 spherical particles of various irregular sizes, porous, and without fractures. The average crystal size was 77.5 nm and 77.7 nm for 50 °C (dried temperature) and 450 ºC (annealed temperature) respectively. The energy of the band gap (GAP) was 3.02 and 2.68 eV respectively. Maximum concentration of dye that negatively affected color removal was 80 mg/L (17%). At lower dye’s concentrations (10, 50 and 70mg/L) decolorization was greater than 80%. TiO2 films were reused for five consecutive cycles of 6 hours at 10 mg/L (&gt;80%), and three cycles of 10 hours at 70 mg/L (&gt; 80%). Toxicity results demonstrate that Daphnia magna was more sensitive than Lactuca sativa. Conclusions. TiO2 films obtained by sedimentation demonstrated a high reactive black 5 decolorization and COD removal (86% and 100%), as well as toxicity reduction.Key words: photocatalysis with TiO2, sedimentation techniques, reactive black 5, Lactuca sativa and Daphnia magna.

Highlights

Reactive black 5 ((tetrasodium-4-amino-5-hydroxy-3, 6 (bis(4-(2-(sulfonatooxi) ethylsulfonyl) phenyl) azo)naphthalene-2, 7-disulfonate)) is a common dye used in the textile industry
These intermediates are not detected by spectrometry visible, because they absorb in the ultraviolet range between 200 and 400 nm) [1]
The solution prepared probably determined a settling area or hindered settling, due to high solid concentration. This probably caused collision between aggregates producing a massive deposit over the substrate, most likely due to the solution’s acidity

Summary

Introduction

Reactive black 5 ((tetrasodium-4-amino-5-hydroxy-3, 6 (bis(4-(2-(sulfonatooxi) ethylsulfonyl) phenyl) azo)naphthalene-2, 7-disulfonate)) is a common dye used in the textile industry. Biological degradation implementing traditional treatment systems (activated sludge reactor, upflow anaerobic reactors and bio optional) is slow and may form an intermediate compound, which is more persistent than the original These intermediates are not detected by spectrometry visible, because they absorb in the ultraviolet range between 200 and 400 nm) [1]. Photocatalytic oxidation near to the azo bond is the attacked site and the aromatic intermediates are released [6] These phenolic compounds can be transformed into organic acid by naphthalene ring opening to form aliphatic intermediates. Daphnia magna is often used for evaluation of acute, as well as chronic toxicity, in industrial waste-water and dyes Different countries employ this organism because of its fastgrowing properties, ease of maintenance, high sensitivity towards chemical pollutants, and very reproducible results [7]. We verified the numbers of cycles that TiO2 films can be re-used at a laboratory scale

Materials and methods

Results and discussion

Conclusions