Optimisation of decolourisation and degradation of Reactive Black 5 dye under electro-Fenton process using Fe alginate gel beads

Abstract

The aim of this work was to improve the ability of the electro-Fenton process using Fe alginate gel beads for the remediation of wastewater contaminated with synthetic dyes and using a model diazo dye such as Reactive Black 5 (RB5). Batch experiments were conducted to study the effects of main parameters, such as voltage, pH and iron concentration. Dye decolourisation, reduction of chemical oxygen demand (COD) and energy consumption were studied. Central composite face-centred experimental design matrix and response surface methodology were applied to design the experiments and to evaluate the interactive effects of the three studied parameters. A total of 20 experimental runs were set, and the kinetic data were analysed using first-order and second-order models. In all cases, the experimental data were fitted to the empirical second-order model with a suitable degree for the maximum decolourisation of RB5, COD reduction and energy consumption by electro-Fenton-Fe alginate gel beads treatment. Working with the obtained empirical model, the optimisation of the process was carried out. The second-order polynomial regression model suggests that the optimum conditions for attaining maximum decolourisation, COD reduction and energy consumption are voltage, 5.69 V; pH 2.24 and iron concentration, 2.68 mM. Moreover, the fixation of iron on alginate beads suggests that the degradation process can be developed under this electro-Fenton process in repeated batches and in a continuous mode.

Electrochemical degradation of RB-5 dye by anodic oxidation, electro-Fenton and by combining anodic oxidation–electro-Fenton in a filter-press flow cell

“…These results are better than other reported data in the literature for example an electro-Fenton process applied to RB-5 using graphite electrode of 84.16 cm 2 geometrical area reported only 52% in colour removal, applying a cell potential of 3 V [28]; other reports using glassy carbon achieved 95% in colour removal at the best condition [29] and also using graphite (geometric area of 15 cm 2 ) and Fe alginate gel beads a maximum of 90% colour removal was observed [30]. 97.2% in colour removal was achieved when iron-loaded sepiolite and graphite electrodes (geometric area of 15 cm 2 ) were used [31].…”

“…EF processes have been used to degrade RB-5 using anode and cathode graphite electrodes of 84.16 cm 2 area [28]. Glassy carbon electrodes also have been used [29] as well as graphite (area 15 cm 2 ) and Fe alginate gel beads and iron-loaded sepiolite [30,31]. Bocos et al used two graphite sheets electrodes of 15 cm 2 area and an iron supported in polyacrylamide hydrogel [32].…”

Electrochemical removal of Reactive Black 5 azo dye using non-commercial boron-doped diamond film anodes

“…RB5 has been chosen as a model organic pollutant by a number of researchers, and details are available concerning degradation of the dye by electro-assisted Fenton and Fentonlike oxidation [4,[22][23][24][25], photo-electrochemical [26,27] and electro-coagulation [28] processes, electrochemical reduction [29][30][31][32], and electrochemical oxidation with Ti/SnO2-SbPt [3], Pt [33], graphite [34] and Pt/Ti [35] electrodes. However, very few studies have focused on the application of BDD as electrodic material for the removal of RB5.…”

“…Although RB5 is used widely in textile dying [2], the vinyl sulfone moieties of the molecule are hydrolyzed during processing to 2-hydroxyethylsulfone groups that do not fix onto cellulose fibers. The hydrolyzed form is, therefore, easily discarded to wastewater [3], a situation that can cause environmental problems since RB5 is considered a recalcitrant compound [4]. It is noteworthy that the EC50 value of the non-hydrolyzed form of RB5 against the bioluminescent bacterium Vibrio fischeri is 27.59 ± 4.01 mg L -1 while that of the hydrolyzed form is 11.49 ± 3.68 mg L -1 [5].…”

Electrochemical Oxidation of Reactive Black 5 and Blue 19 Dyes Using a Non Commercial Boron-Doped Diamond Electrode

“…10 No entanto, o RP5, além de ser considerado um composto recalcitrante, 11 também foi classificado como moderadamente tóxico por Ramsay e Nguyen 12 contra as bactérias bioluminescentes Vibrio fischeri com uma 25% < EC20 < 50%. A concentração EC20 é a concentração do composto necessária para inibir a bioluminescência das bactérias em 20%.…”