Decontamination of real urban sewage-comparison between Fenton and electrochemical oxidation.

Advanced oxidation processes have been used for wastewater treatment due to their capacity to reduce the organic loading and for their fast reactions. In this paper, we explore the viability of isolated and sequential use of electrochemical oxidation and Fenton processes into treatment of real raw urban sewage. The electrochemical process was carried out using DSA®-Cl2 electrodes and factorial planning in order to investigate the influence of pH, current density, and electrolyte. Fenton reaction was also used and H2O2 and Fe2+ concentration effects were investigated. The efficiency was estimated by chemical oxygen demand (COD) removal and in the optimized conditions the effluent was characterized by turbidity, suspended/dissolved/total solids, ammonia, chloride ions, free chlorine, nitrite, and potassium analysis and bioassays with Artemia ssp. and Lactuca sativa. The study demonstrated that the use of electrochemical technique followed by Fenton allowed an improvement in the degradation of organic matter and reduction of turbidity and solid content, reaching reductions of 86.8, 96.4, 99.4, 56.1, and 66.7% for COD, turbidity, SS, DS, and TS, respectively. The associated treatment also contributed to the reduction of energy consumption by 74.9%, from the 23.9 kWh m-3 observed during the electrochemical treatment isolated to the 6 kWh m-3 during the associated process. All the treatments presented toxicity reduction, with the electrochemical process achieving the best results.

Characterization and kinetic study of the brain and muscle acetylcholinesterase from Danio rerio.

Acetylcholinesterase (AChE) plays an important role in the therapy of Alzheimer's disease and in the detection of pesticides such as organophosphates which are also widely used in chemical warfare. The aim of this study is the physicochemical and kinetic characterization of brain and muscle ChE from Danio rerio (Zebrafish). Optimal activity was found for brain ChE at alkaline pH 9.0 at 30 °C, and for muscle ChE at alkaline pH 8.5 at temperatures between 20 °C and 35 °C. The apparent kinetic constants, Kmapp and Vmaxapp, for brain ChE were determined as 0.191 ±â€¯0.024 mM and 0.566 ±â€¯0.028 U/mg protein, and for muscle ChE as 0.230 ±â€¯0.030 mM and 0.677 ±â€¯0.039 U/mg protein. Both brain and muscle ChE showed inhibition at high substrate concentrations. Brain and muscle ChE showed IC50 values for physostigmine of 0.61 µM and 0.37 µM, respectively. The ChE activity in brain was significantly inhibited by BW254c51 in all concentrations tested, but not by Iso-OMPA, while muscle ChE presented a moderate decrease (13 to 29%) in the activity values, indicating that BuChE is present.

Electrochemical removal of synthetic textile dyes from aqueous solutions using Ti/Pt anode: role of dye structure.

In this work, the efficiency of electrochemical oxidation (EO) was investigated for removing a dye mixture containing Novacron Yellow (NY) and Remazol Red (RR) in aqueous solutions using platinum supported on titanium (Ti/Pt) as anode. Different current densities (20, 40 and 60 mA cm(-2)) and temperatures (25, 40 and 60 °C) were studied during electrochemical treatment. After that, the EO of each of these dyes was separately investigated. The EO of each of these dyes was performed, varying only the current density and keeping the same temperature (25 °C). The elimination of colour was monitored by UV-visible spectroscopy, and the degradation of organic compounds was analysed by means of chemical oxygen demand (COD). Data obtained from the analysis of the dye mixture showed that the EO process was effective in colour removal, in which more than 90% was removed. In the case of COD removal, the application of a current density greater than 40 mA cm(-2) favoured the oxygen evolution reaction, and no complete oxidation was achieved. Regarding the analysis of individual anodic oxidation dyes, it was appreciated that the data for the NY were very close to the results obtained for the oxidation of the dye mixture while the RR dye achieved higher colour removal but lower COD elimination. These results suggest that the oxidation efficiency is dependent on the nature of the organic molecule, and it was confirmed by the intermediates identified.

The application of electrochemical technology to the remediation of oily wastewater.

The successful application of electrochemical technology, employing a dimensionally stable anode (DSA((R))), for the remediation of wastewater from the oil extraction industry has been demonstrated. Samples from the oil-water separation box of an effluent treatment plant were submitted to voltammetry, chronoamperometry and electrolysis studies using a DSA anode of nominal composition Ti/Ru(0.34)Ti(0.66)O(2). Electrolysis of the oily wastewater lead to a time-dependent reduction in chemical oxygen demand (COD) in the sample that could be attributed to: (i) the direct oxidation of oil components at the electrode, by the metal oxide itself or by OH() radicals available at the electrode surface, (ii) the indirect oxidation of oil components by intermediate oxidising agents formed in parallel reactions (ex. ClO(-)), and (iii) the aggregation of suspended oil droplets by electroflotation. The largest reduction (57%) in COD was obtained following electrolysis of an oily sample for 70 h at 50 degrees C with a current density of 100 mA cm(-2). The stability of DSA electrodes for use in oily wastewater remediation has been assessed.