intensification of advanced oxidation processes (POAs) for the elimination of persistent organic pollutants (POPs) in water.
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Date
2025-07-09
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University of 20 August 1955 Skikda
Abstract
This study investigates the application of two advanced oxidation processes: the activation
of inorganic oxidising species, specifically persulfate (PS) and Glidarc-type humid air plasma,
for the treatment of an aqueous solution containing the azo dye "Orange G." UV-visible analysis
was employed to monitor the degradation of the pollutant, while mineralisation was tracked by
measuring the chemical oxygen demand (COD).
Initially, an oxidation process based on the radical sulfate (SO4 •−), generated by the thermal
activation of PS and by the heat/Fe(II)/PS process, was evaluated. Several parameters were
studied, including reaction temperature (20–70°C), pH (2–12), potassium persulfate (PPS) and
ammonium persulfate (APS) dose (100–1000 mg/L), initial concentration of OG (10–70 mg/L),
and concentration of FeSO₄. 7H₂O (10–50 mg/L) and (NH₄)₂Fe(SO₄)₂ (8–100 mg/L), as well
as the impact of organic additives. These parameters were investigated to determine their
influence on the efficiency of the process.
The results show that the oxidation of OG follows a pseudo-first-order kinetic model, with
a high correlation coefficient (R² = 0.99). Complete decolourisation of 50 mg/L of OG was
achieved in 150 minutes at 70°C and in 240 minutes at 65°C, in the presence of 1 g/L of PPS.
The apparent activation energy was estimated to be 157.3 kJ/mol.
Furthermore, the results suggest a direct correlation between the oxidation of OG and high
persulfate concentrations, while an inverse relationship was observed with the initial substrate
concentrations. It was also found that higher reaction temperatures and a neutral initial pH
favoured the degradation of OG.
The results indicate that the sulfate radical (SO4 •−) is the primary agent responsible for the
oxidation of OG. Additionally, the presence of Cr (VI) ions in solution exhibited an inhibitory
effect on the degradation process. The coexistence of ferrous ions and persulfate at high
temperature demonstrated a synergistic effect, accelerating the oxidation of OG. In contrast, the
heat/persulfate/Fe (II) process achieved a relatively low mineralisation rate of 75.41% after 260
minutes of treatment.
Furthermore, the degradation of Orange G in aqueous solution using the Glidarc humid air
plasma process was investigated. Various concentrations of catalysts and oxidants were
introduced into the Glydarc reactor to optimise the conditions and improve the system's
performance. Under optimal treatment conditions, the degradation rates obtained were 66.46%,
100%, 72.79%, 71.19%, 90.48%, and 90.27%, respectively, using Glidarc alone, Glidarc/H2O2,
Glidarc/IO4-, Glidarc/Fe3+, Glidarc/Fenton, and Glidarc/PPS, after treatment times of 210 min,
80 min, 210 min, 210 min, 12 min, and 180 min. Furthermore, the energy efficiency of the
Description
Keywords
advanced oxidation, organic pollutants (POPs) in water.