UV-Catalyzed Persulfate Oxidation of an Anthraquinone Based Dye

Abstract

Wastewater from the textile industry has a substantial impact on water quality. Synthetic dyes used in the textile production process are often discharged into water bodies as residues. Highly colored wastewater causes various of problems for the aquatic environment such as: reducing light penetration, inhibiting photosynthesis and being toxic to certain organisms. Since most dyes are resistant to biodegradation and are not completely removed by conventional methods (adsorption, coagulation-flocculation, activated sludge, membrane filtration) they persist in the environment. Advanced oxidation processes (AOPs) based on hydrogen peroxide (H2O2) have been proven to decolorize only some of the dyes from wastewater by photocatalysis. In this article, we compared two very different photocatalytic systems (UV/peroxydisulfate and UV/H2O2). Photocatalyzed activation of peroxydisulfate (PDS) generated sulfate radicals (SO4•−), which reacted with the selected anthraquinone dye of concern, Acid Blue 129 (AB129). Various conditions, such as pH and concentration of PDS were applied, in order to obtain an effective decolorization effect, which was significantly better than in the case of hydroxyl radicals. The kinetics of the reaction followed a pseudo-first order model. The main reaction pathway was also proposed based on quantum chemical analysis. Moreover, the toxicity of the solution after treatment was evaluated using Daphnia magna and Lemna minor, and was found to be significantly lower compared to the toxicity of the initial dye.

Do We Still Need a Laboratory to Study Advanced Oxidation Processes? A Review of the Modelling of Radical Reactions used for Water Treatment

“…This utility allows the creation of theoretical UV-Vis / infrared (etc.) spectra, facilitating the determination of reaction products without more sophisticated instruments such as mass spectrometry [28]. For example, the theoretical spectra of AB129 (studied here) was determined to be 594 nm, which matches the experimentally-obtained value (595 nm) almost exactly [28].…”

“…). Our group has already experimentally determined that this is precisely what happens, i.e., the sulphate radical reacts selectively with the -NH-group [28]. The reason why the AB129 -NH 2 group is not the most reactive with the radicals, as indicated by ALIE analysis, could be trivially explained by the protonation of this group, which is possible in acidic and neutral pH values [33].…”

“…An extended investigation of our previous work [28] on the Acid Blue 129 (AB129) compound was presented herein. In this specific case, the HOMO and HOMO-1 of AB129 seem to be largely delocalized, making it more challenging to determine the reactive site available for free radicals (Fig.…”

“…Although when based only on HOMO distributions it is difficult to determine the reactive sites, it can be assumed that an electrophilic attack will probably occur somewhere within the vertical axis (Fig. 3) of the AB129 [28].…”

Tandem Structures Semiconductors Based on TiO2_SnO2 and ZnO_SnO2 for Photocatalytic Organic Pollutant Removal

“…Advanced oxidation processes (AOPs) are considered as future alternative to traditional methods of removing organic pollutants: pharmaceutical active compounds [ 28 , 29 ], pesticides [ 30 , 31 ], dyes [ 32 , 33 ], volatile organic compounds [ 34 , 35 ], etc. The sustainability represents an important advantage of AOPs due to the use of light radiation as the main energy source to provide oxidative species responsible for pollutant mineralization [ 36 , 37 , 38 ].…”