Effects of operator parameters, anions and cations on the degradation of AY99 in an aqueous solution using Fenton’s reagent. Optimization and kinetics study

International Journal of Industrial Chemistry

دوره 3، شماره 1، اسفند 2012، صفحه 137-147

نوع مقاله: research article

شناسه دیجیتال (DOI): https://doi.org/10.1186/2228-5547-3-15

نویسندگان

Chafia Bouasla؛ Mohamed El-Hadi Samar^*

Department of Process Engineering, University of Annaba, Annaba, 23000, Algeria

چکیده

In the present work, the decolourization of azo dye Acid Yellow 99 (AY99) in an aqueous solution by Fenton oxidation process was investigated. The results indicated that the initial pH, the nature of the acid to adjust pH, the temperature and the initial concentrations of the Fenton’s reagent FeSO₄ of H₂O₂ and of the AY99 played an important role on the dye decolourization. It was found that under optimum conditions, which have been determined to be pH = 3, [H₂O₂]₀ = 1.8 mmol/L, [Fe²⁺]₀ = 0.09 mmol/L, [AY]₀ = 0.06 mmol/L and T = 30°C, efficiency of degradation obtained after 40 min of reaction was about 95%. The decolourization of AY99 by the Fenton process followed the second-order reaction kinetics. The empirical kinetic equation for AY99 decolourization under the conditions of 0.03 to 0.15 mmol/L of Fe²⁺, 0.9 to 1.8 mmol/L of H₂O₂, 0.03 to 0.15 mmol/L of Acid Yellow and pH = 3 was found to follow the relation:
K = 6.39 × 10⁷ [AY] ^−2.8[H₂O₂]^2.29[FeSO₄]^0.837 exp (−7021.3/T).
The decolourization efficiency Ef (in percent) was 88.36%, 87.93%, 85.98% and 39.61% in the presence of H₂SO₄, HNO₃, HCl and H₃PO₄ acids, respectively. We can deduce that H₂SO₄, HNO₃ and HCl acids lead almost to the same efficiency (Ef), but in the presence of H₃PO₄, it is too low:
Ef (H₂SO₄) ~ Ef (HNO₃) > Ef (HCl) > > Ef (H₃PO₄).
Effects of additives such as inorganic salts (sodium chloride, calcium chloride, sodium sulphate and calcium sulphate) and cations (sodium sulphate, calcium sulphate, copper sulphate, manganese sulphate and magnesium sulphate) on the efficiency (Ef) and on the rate constant (k₂) of AY99 degradation were also studied under optimum conditions.
Ef (Na₂SO₄) > Ef (CaSO₄) > Ef (NaCl) > Ef (CaCl₂)
k₂ (CaCl₂) < k₂ (NaCl) < k₂ (CaSO₄) < k₂ (Na₂SO₄)
Ef (ZnSO₄) > Ef (MgSO₄) > Ef (Na₂SO₄) > Ef (CaSO₄) > Ef (CuSO₄) > Ef (MnSO₄)
k₂ (Na₂SO₄) < k₂ (MnSO₄) < k₂ (CuSO₄) < k₂ (CaSO₄) < k₂ (ZnSO₄) < k₂ (MgSO₄).
The presence of anions and cations in the aqueous solution decreases the decolourization efficiency and the rate constant of the degradation of AY99. This inhibition may be due to a complexation and a radical scavenging.

کلیدواژه‌ها

Degradation؛ Decolourization؛ Acid Yellow 99؛ Fenton process؛ Kinetics