Optimization of Fenton’s oxidation of herbicide dicamba in water using response surface methodology

Abstract In this study Fenton’s oxidation of dicamba in aqueous medium was investigated by using the response surface methodology. The influence of H2O2/COD (A), H2O2/Fe2+ (B), pH (C) and reaction time (D) as independent variables were studied on two responses (COD and dicamba removal efficiency). The dosage of H2O2 (5.35–17.4 mM) and Fe2+ (0.09–2.13 mM) were varied and optimum percentage removal of dicamba of 84.01% with H2O2 and Fe2+ dosage of 11.38 and 0.33 mM respectively. The whole oxidation process was monitored by high performance liquid chromatography (HPLC) along with liquid chromatography/mass spectrometry (LC/MS). It was found that 82% of dicamba was mineralized to oxalic acid, chloride ion, CO2 and H2O, which was confirmed with COD removal of 81.53%. The regression analysis was performed, in which standard deviation (2.74), coefficient of correlation (R 2 =  $$R_{\text{adj}}^{2}$$ R adj 2 ) and adequate precision (>12) were in good agreement with model values. Finally, the treatment process was validated by performing the additional experiments

Catalytic efficiency of laterite-based FeNPs for the mineralization of mixture of herbicides in water

<p>In this work, low cost, locally available laterite-based iron nanoparticles were synthesized using <i>Tectona Grandis</i> extract (Teak extract) with an average size of 75 nm. The synthesized FeNPs were applied as a heterogeneous Fenton catalyst for the oxidation of mixture herbicides, namely ametryn, dicamba and 2,4-D in water. The FeNPs were characterized for various analytical methods (field emission scanning electron microscopy-X-ray energy-dispersive spectrophotometer, XRD, FTIR and BET) and the effect of different variables (FeNPs dosage, H₂O₂, pH) was studied using the responses surface methodology. The initial herbicide concentration was considered as 25, 3.5 and 94 mg L⁻¹ for 2,4-D, ametryn and dicamba, respectively, with the COD value of 172 mg L⁻¹. The 100% degradation and mineralization was achieved in 135 min and >85% in 45 min (optimum dosage: FeNPs = 25.29 mg L⁻¹, H₂O₂= 430 mg L⁻¹ and pH = 5). The degradation kinetics were performed for both pseudo-first order and second order, it was observed that first-order kinetics (<i>R</i>²> 0.85) was well fitted in the treatment process. Recycling of FeNPs in five cycles was performed at optimum conditions and 10–40% of reduction in degradation efficiency was achieved. Finally, the whole treatment process was validated with a contour overlay plot and analysis of variance.</p