The use of ECAS in plant protection: a green and efficient antimicrobial approach that primes selected defense genes.

The use of highly polluting chemicals for plant and crop protection is one of the components of the negative environmental impact of agricultural activities. In the present paper, an environmentally friendly alternative to pesticide application has been studied, based on the so-called electrochemically activated solutions (ECAS). Experiments have been carried out, by applying ECAS having different contents of active ingredients, on tobacco plants at a laboratory scale and on apple trees at fruit garden scale. The results, accumulated during a couple of years, have shown that properly selected dilute solutions of chlorides, once activated by an electrochemical treatment, exhibit a very effective protecting action of plants, irrespective of their nature. Extension of the research has shown that the observed effect is the result of two distinct factors: the expected anti-microbial action of the electrochemically synthesized oxidants, and an unexpected priming of immune plant defenses, which is clearly due to the treatment with ECAS. Interestingly, the repetition of ECAS application triggers an even stronger activation of defense genes. No oxidative damages, due to the use of the activated solutions, could be detected.

Electrochemical disinfection of groundwater for civil use - An example of an effective endogenous advanced oxidation process.

Lab-scale experiments using real groundwater were carried out using the CabECO® reactor system in order to evaluate its suitability for producing safe water, acceptable for civil purposes. Trials were carried out in discontinuous and in continuous mode, analyzing the influence of electrical and hydraulic process parameters on the quality of treated water. The use of highly boron-doped diamond electrodes in the reactor allowed the electrosynthesis of considerable amounts of ozone. Because of the relatively high amount of chloride in the groundwater samples, a mixture of HOCl/ClO- was also synthesized. Somewhat unexpectedly, the increase in the current density in the explored range 100-1000 A m-2 was accompanied by an increase in the faradaic yield of the electrosynthesis of oxidants, which was more pronounced for ozone than for free chlorine. As reported in literature, the main radical intermediate in the relevant reactions is OH, which can lead to different oxidation products, namely ozone and HOCl/ClO-. The electrolytic treatment also caused a decrease in the concentration of minor components, including NH4+ and Br-. Other byproducts were ClO3- and ClO4-, although their concentration levels were low. Moreover, due to alkali formation at the cathode surface, the precipitation of calcium and magnesium carbonates was also observed. In addition, the experimental investigation showed that even Pseudomonas aeruginosa and Legionella could be completely removed in the treated stream, due to the unique capacity of the reactor to synthesize biocidal agents like ozone, HOCl/ClO-, and chloramines. These effects were particularly evident during batch experiments.

Scale-up of electrochemical oxidation system for treatment of produced water generated by Brazilian petrochemical industry.

Scale-up of anodic oxidation system is critical to the practical application of electrochemical treatment in bio-refractory organic wastewater treatment. In this study, the scale-up of electrochemical flow system was investigated by treating petrochemical wastewater using platinized titanium (Ti/Pt) and boron-doped diamond (BDD) anodes. It was demonstrated that flow cell was successfully scaled-up because when it was compared with batch mode (Rocha et al. 2012b), higher performances on organic matter removal were achieved. Under the suitable operating conditions and better anode material, the chemical oxygen demand (COD) of petrochemical wastewater was reduced from 2,746 to 200 mg L(-1) within 5 h with an energy consumption of only 56.2 kWh m(-3) in the scaled-up BDD anode system. These results demonstrate that anode flow system is very promising in practical bio-refractory organic wastewater treatment.

Removal of the pesticide methamidophos from aqueous solutions by electrooxidation using Pb/PbO2, Ti/SnO2, and Si/BDD electrodes.

The anodic oxidation of methamidophos (MMD), a highly toxic pesticide used worldwide, was studied in a sodium sulfate aqueous solution on Pb/PbO2, Ti/SnO2, and Si/BDD (boron doped diamond) electrodes at 30 degrees C. Under galvanostatic conditions, it was observed thatthe performance of the electrode material is influenced by pH and current density as shown by HPLC and ATR-FTIR analysis of MMD and its oxidation products along the electrolysis. It was found that MMD degradation using Pb/PbO2 in acid media (pH 2.0 and 5.6) generates formaldehyde asthe main product of the reaction giving evidence of an indirect mineralization mechanism. Under the same conditions, Ti/SnO2 showed poor formaldehyde production compared to the Pb/PbO2 electrode. On Si/BDD electrodes formaldehyde production was not observed, instead the ATR-FTIR results showed the formation of phosphate as the reaction progressed suggesting a complete MMD mineralization on this electrode. In addition, HPLC results showed that the electrode efficiency is also dependent on the applied current density. This current density influence is remarkably clear on the Si/BDD electrodes where it was evident that the most efficient current density toward a complete MMD mineralization was reached with the application of 50 mA/cm2.

The 5-V window of polarizability of fluorinated diamond electrodes in aqueous solutions.

Heavily doped diamond films are quite actively studied for their promising applications in industrial as well as in fundamental electrochemistry (both for physicochemical studies and in the field of electroanalysis), because of their very high stability toward chemical and electrochemical oxidative attacks. Fluorinated diamond electrodes exhibit an exceptionally lower electrocatalytic activity toward reactions involving adsorbed intermediates, as a result of the F-termination of the surface dangling bonds. This feature allows the investigation of the widest range of potentials for an electrode material in aqueous solution, being limited only by the formation of free hydrogen [E degrees (H*/H2) = -2.3 V(SHE)] and hydroxyl [E degrees (*OH,H+/H2O) = 2.74 V(SHE)] radicals, at the two boundaries of the approximately 5-V polarization window.

Surface chemistry study of RuO2/IrO2/TiO2 mixed-oxide electrodes.

DSA metal oxide electrodes such as the RuO(2)/IrO(2)/TiO(2) mixed system are widely studied for their excellent electrocatalytic activity. In order to understand their catalytic properties, the comprehension of the surface chemistry involved during electrochemical treatments is crucial. With this aim, RuO(2)/IrO(2)/TiO(2) mixed-oxide electrodes having various noble metal contents were studied by means of secondary ion mass spectrometry (SIMS). In particular, cathodic and anodic polarization and O(2) evolution reactions were carried out to test the electrode behaviour and SIMS analyses were performed after all these treatments. In this way, surface changes induced by electrochemical treatments and depending on electrode composition were widely investigated by SIMS, revealing, for example, the presence of hydration or preferential dissolution phenomena induced by electrochemical processing.