Innovative advanced processes for treatment of multiple emerging pesticides from water: Performance, statistical...

The objective of this study is the degradation of a mixture of three pesticides from three distinct families: Metalaxyl (fungicide), Metolachlor (herbicide), and Diazinon (organophosphate Insecticide). In this work, the enhanced advanced oxidation process known as "Photo-Fenton" was first optimized, and the mineralization step was determined. The experimental design and response surface "three-parameter Doehlert design" were employed as the experimental methodology to modeling and optimizing the experimental parameters. Hydrogen peroxide, ferrous iron, and pH were the factors examined in this investigation. The mathematical model obtained was also validated. In the optimal conditions C_Fe=5mg L^-1, [Formula: see text] = 395.2 mg L^-1 and pH=3.47, an 81 % mineralization rate was achieved. By combining the QuEChERS extraction method (Quick, Easy, Cheap, Effective, Rugged, and Safe), pre-concentration with the evaporation protocol, and GC-MS/MS analysis, a novel analytical methodology for determination of three analytes and the by-products of photo-degradation was developed. It was observed that this approach performed well for all analytes and the by-products detection at trace and ultra-trace levels. MTCh produced 12 by-products, DZN produced six, and MTX produced five intermediates after 15 min of degradation. Under the same ideal operating conditions, other alternative processes were tested to boost the mineralization yield: Fenton with an efficiency of 70 %, Photo-Fenton with two lamps 85 %. The yield for the adsorption procedure was 72 %. However, the cyclic approach, which started with Photo-Fenton and proceeded with adsorption, achieved a 90 % yield, and with the hybrid process (adsorption and Photo-Fenton process), the mineralization reached 99 % after just 60 min and was able to attain nearly complete mineralization by combining the processes of degradation and removal simultaneously.