Cationic Dye Degradation and Real Textile Wastewater Treatment by Heterogeneous Photo-Fenton, Using a Novel Natural Catalyst

Abstract

A photo-Fenton process using a local iron oxide as a natural catalyst was compared to Fenton and UV/H2O2 advanced oxidation processes for degrading crystal violet (CV) dye in aqueous solutions. The catalyst was characterized by transmission electron microscopy (TEM), energy dispersive X-ray microanalysis (EDX), Fourier transform infrared spectroscopy (FT-IR), Raman spectrum, X-ray diffraction (XRD), UV-vis spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The optical properties proved that the catalyst represents a good candidate for photocatalytic activity. The impact of different parameters (catalyst dose, initial CV concentration, initial H2O2 concentration, pH) on the photo-Fenton efficiency was evaluated. A photo-Fenton process operated under UVC light irradiation, at spontaneous pH, with 1.0 g/L of catalyst and 30 mg/L of H2O2 was the most effective process, resulting in 98% CV dye removal within 3 h. LC-MS and ion-chromatography techniques were used to identify demethylated organic intermediates during the process. Furthermore, a regeneration study of the catalyst showed its stability and reusability (after three treatment cycles, CV dye degradation decreased from 94% to 83%). Finally, the photo-Fenton process was tested in the treatment of real textile wastewater, and the effluent was found to be in compliance with standards for industrial wastewater disposal into sewerage.

Sustainable-by-Design Approach of Active Catalysts to Produce Reactive Oxygen Species in Water Matrices

“…First, heterogeneous systems proposed in the literature include catalytic systems based on bulk catalysts containing metallic iron or iron oxides, as hematite, goethite or magnetite [14][15][16]. Interestingly, a naturally occurring iron-containing mineral was applied as a heterogeneous catalyst for the degradation of a recalcitrant cationic dye, the crystal violet [17]. Moreover, the same catalyst was also tested in the treatment of real textile wastewater.…”

Fenton: A Systematic Review of Its Application in Wastewater Treatment

“…Among these studies, the majority focused on the removal of dyes (227; 18%), organic compounds (216; 17%), and pharmaceuticals (114; 9%); fewer were focused on removing phenol (62; 5%), inorganic compounds/metals (40; 3%), pesticides (22; 1.7%), hygiene and cleaning products (11; 0.87%), and vinasse (5; 0.39%). However, a large proportion of the studies (418; 33.1%) examined the use of the Fenton technique to remove a diverse range of other compounds, including solvents, polymers, organic molecules, wastewater from kitchens, dairies, slaughterhouses, tanneries, petroleum industry, mining, biodiesel, edible oil refineries, tertiary pulp treatment, wood industries and municipal effluents, bacteria, oilseed, and olive-oil industries [29,30]. We noted an increase in the number of articles over time for all compounds evaluated (Table 1); however, this increase occurred to a greater extent for dyes (r = 0.85; p < 0.001), organic compounds (0.87, p < 0.001), pharmaceuticals (r = 0.81; p < 0.001), phenol (r = 0.81; p < 0.001), inorganic compounds/metals (r = 0.82, p < 0.001), pesticides (r =0.59; p < 0.001), hygiene and cleaning products (r = 0.42; p = 0.02), vinasse (r = 0.32; p = 0.09), and other types of specific composite products (r = 0.69; p < 0.001).…”

Addressing main challenges in the tertiary treatment of urban wastewater: are homogeneous photodriven AOPs the answer?

“…Therefore, the target aqueous matrix should be first acidified and subsequently neutralized before effluent (re)use or disposal, with sludge formation and increased treatment costs. Different approaches have been investigated to overcome this limitation, including: (i) process operation at mild conditions (low reagents concentrations, in particular of metal to minimize its precipitation at pH>3); 15 (ii) using chelating agents (e.g., Ethylenediamine-N,N′-disuccinic acid (EDDS), nitrilotriacetic acid (NTA)) to form complexes with metal and avoid its precipitation at neutral pH; 16,17 (iii) heterogeneous photo-Fenton process; 18,19 non-iron Fenton catalysts 20,21 . Fe(III) forms complexes with some organic compounds, typically characterized by higher molar absorption coefficients in the near-UV and visible regions than aqueous complexes.…”