Background and purpose: Paraquat (PQ) is a bipyridinium herbicide that is very soluble in water. This non-selective contact herbicide is widely used in agriculture for weed control. In addition to the environmental impact, paraquat affects the entire body, especially the respiratory system, central nervous system and lymph nodes. In this study degradation of paraquat was investigated using Fenton and Fenton like processes.

Materials and methods: This research was an experimental study in laboratory scale batch reactor (1L). During these processes, the effects of pH, Fenton and Fenton like agent concentrations (Fe^{2 +}, Fe³⁺and H₂O₂) and initial concentration of paraquat in the removal efficiency were studied. The residual PQ concentration and the amount of organic carbon removal were measured by HPLC (259nm) and TOC measurement device, respectively.

Results: Fenton like and Fenton processes could remove 86.44% and 84.53% of paraquat under optimal condition (pH=3, H₂O₂=29.4 mM, Fe=0.9 mM, PQ=0.194 mM) in 120 minutes, respectively. The TOC removal in Fenton like and Fenton processes was 52.15% and 45%, respectively. The PQ removal by Fenton and Fenton like process followed a pseudo-first order reaction kinetic model.

Conclusion: Fenton process showed better performance in removal of PQ than Fenton process. So, it can be used as an appropriate and a supplementary treatment process in removing PQ from aqueous solution or final purification in a longer reaction time.