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

In this work, low cost, locally available laterite-based iron nanoparticles were synthesized using Tectona Grandis 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 (R2 > 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.