Routes for the electrochemical degradation of the artificial food azo-colour Ponceau 4R by advanced oxidation processes

Abstract

a b s t r a c tThe performance of three electrochemical advanced oxidation processes, namely electro-oxidation with electrogenerated H 2 O 2 (EO-H 2 O 2 ), electro-Fenton (EF) and photoelectro-Fenton (PEF) for the treatment of aqueous solutions of the food azo dye Ponceau 4R in an undivided cell with a BDD anode and an airdiffusion cathode was compared in terms of colour, dye concentration and total organic carbon (TOC) removals. PEF treatments in ultrapure water with Na 2 SO 4 were performed to assess the effect of current density, as well as supporting electrolyte and dye concentrations. At 100 mA cm −2 , solutions of 130 mL of 254 mg L −1 of the dye in 0.05 M Na 2 SO 4 became colourless and totally mineralized after 50 and 240 min, respectively, which can be explained by the synergistic action of BDD( • OH) at the anode surface and homogeneous • OH formed in the bulk from Fenton's reaction promoted in the presence of Fe 2+ catalyst. Furthermore, UVA photons induced the continuous Fe 2+ regeneration and photolytic decomposition of refractory intermediate complexes. In that aqueous matrix, the cleavage of the dye molecules proceeded through several reaction routes to yield N-containing and non-N-containing derivatives with one or two aromatic rings, short-chain aliphatic carboxylic acids and inorganic ions. Oxalic and oxamic acids and sulfate ions were accumulated at different rates in EO-H 2 O 2 , EF and PEF. The three methods allowed the progressive decontamination of Ponceau 4R solutions in a real water matrix even without the addition of electrolyte, although complete TOC abatement after 360 min at 33.3 mA cm −2 was only ensured by the iron-catalyzed PEF process.

Facile fabrication of Bi2S3/SnS2 heterojunction photocatalysts with efficient photocatalytic activity under visible light

“…Such dye molecules are difficult to be decomposed by natural means. Various methods, such as adsorption [6], advanced oxidation processes [7], biological treatment [8], electrocatalysis [9] and photocatalysis [10], have been developed to remove organic dyes. Among them, photocatalytic degradation of organic pollutants receives increasing interest owing to the absence of secondary pollution and the low cost by using solar light.…”

New Insight into the Synthesis of Aromatic Azo Compounds Assisted by Surface Plasmon Resonance

“…Aromatic azo compounds have been widely used not only as dyes [1], pigments [2], food additives [3,4], indicators [5], free radical initiators [6], and therapeutic drugs [7], but also show good prospects for drug delivery [8] and electronics [9]. With the -N = N-bond and the unique structure of a large π electronic system, aromatic azo compounds can be freely and reversibly inter-converted between cis and trans configurations [10].…”

Electrocoagulation treatment of the food dye waste industry: Theoretical and experimental study

“…[NaCl] in g/l), electrolysis time (X 3 : t in mn) and pH of the solution (X 4 : initial pH), on the color removal efficiency was studied using a rotatable, uniform and central composite designs 2 4 with seven repetitions of the central point (N 0 ), which will allow to estimate the repeatability of the method and therefore to test the significance of the model coefficients. The graphical representation of the distribution of these experimental points was given in figure 3.…”

“…The number of central points as well as the distance from the axial points to the center are determined according to the rotational isovariance criterion (the error on the prediction model must only be a function of the distance at the center of the design) using the JMP Software [30]. For four factors, realization of a complete factorial design had five levels requiring 5 4 =625 experiments, this number was very large, in order to achieve a reasonable number of experiments, we realized a rotatable central composite design with uniform precision with only 31 experiments [23].…”

“…Thus, serious ecological and environmental problems are created [3]. Various elimination techniquesof monoazo dyes have been used, like advanced oxidation process "electro Fenton" [2,4], Fenton [5] , photocatalysis [6,7] and adsorption [8,9]. Oxidation by ozone, super-iron (VI) and hypochlorite were the most efficient treatment methods, but they are less preferable due to the operating cost and the generation of a second pollution resulting from the presence of residual chlorine [10,11].…”