Paraquat is resistant to degradation by conventional treatments, being necessary to use treatments with greater effectiveness, such as advanced oxidative processes. In this work, different advanced oxidative processes were applied (Fenton, electro-Fenton, photoelectro-oxidation and photoelectro-Fenton) employing oxide electrodes to degrade Gramoxone, a commercial herbicide that contains paraquat in its composition. The degradation and formation of by-products were accompanied by high performance liquid chromatography, total organic carbon (TOC) and chemical oxygen demand (COD). The results showed that the photoelectro-Fenton process was the most efficient due to the synergistic effect, reaching 79% degradation of the initial compound and 82% and 71% removal of TOC and COD, respectively. After the application of the electro-Fenton and photoelectro-Fenton oxidation processes, short-chain carboxylic acids such as succinic acid, oxalic acid, acetic acid and formic acid were identified as by-products of the oxidation of Gramoxone. The results were satisfactory and deserve to be highlighted, as a commercial formulation was used, making the scenario more realistic.

Climate change is causing an increase in dry spells, altering rainfall patterns and soil moisture, and affecting water and nutrient plant uptake, which inevitably affects vegetable production. To mitigate this issue, some technologies that allow the maintenance of the ideal soil moisture for the uptake process are being investigated. Considering this, we hypothesize that the use of water treated with a magnetic field can increase water use efficiency in lettuce crop production. Thus, the present study aimed to evaluate the effect of the irrigation rate of magnetically treated water on biomass accumulation and nutrient uptake by lettuce plants. An experiment was conducted in a randomized block design with a 2 × 5 factorial arrangement of two water sources (conventional water and magnetically treated water) and five irrigation application rates to replace crop evaporation: 25, 50, 75, 100, and 125%, with five replicates. The use of magnetically treated water increased the concentrations of nitrogen and phosphorus in leaves, meaning that it induced higher nitrogen assimilation, leading to increases in agronomical characteristics (leaf number, fresh and dry shoot weight, fresh and dry root weight). The conclusions of this study showcase that magnetically treated water has beneficial effects on lettuce plants, improving their nutritional status and yield. Moreover, the results presented can lead to an increase in water use efficiency, thus optimizing irrigation management.

This article provides an overview of the use of electrochemical advanced oxidation processes (EAOPs) applied to the treatment of water contaminated by pesticides. Given the global increase in the use of pesticides and the ineffectiveness of conventional treatment methods, EAOPs emerge as promising alternatives. They stand out for their efficiency in the degradation of organic compounds, minimal reliance on additional chemical reagents, and minimal generation of waste. The main methods addressed include anodic oxidation, photoelectro-oxidation, electro-Fenton and photoelectro-Fenton, which use hydroxyl radicals, a potent non-selective oxidant, to mineralize pollutants. A total of 165 studies were reviewed, with emphasis on the contributions of countries such as China, Spain, Brazil, and India. Factors such as electrode type, presence of catalysts, pH, and current density influence the effectiveness of treatments. Combined processes, especially those integrating UV light and renewable sources, have proven to be more efficient. Despite challenges related to electrode cost and durability, recent advances highlight the sustainability and scalability of EAOPs for the treatment of agricultural and industrial effluents contaminated with pesticides.