Electrochemical degradation of sinapinic acid on a BDD anode

The electrochemical oxidation of sinapinic acid (4-hydroxy-3,5-dimethoxy-cinnamic acid), one of the most representative polyphenolic type compounds present in olive oil mill wastewater, was studied by galvanostatic electrolysis using boron-doped diamond (BDD) as anode. The influence of several operating parameters, such as applied current density, initial sinapinic acid concentration, temperature, flow rate and initial pH value was investigated. UV spectroscopy and Chemical Oxygen Demand measurements were conducted to study the reaction kinetics of sinapinic acid mineralization. The experimental results showed that the electrochemical process was suitable for almost completely removing COD, due to the production of hydroxyl radicals on the diamond surface. In particular, the COD removal follows a pseudo first-order kinetics and the apparent rate constant increased with flow rate and temperature, while it is almost unaffected by applied current and pH. Under optimal experimental conditions of flow-rates (i.e. 300 L h-1), temperature (T=50 \ub0C) and current density (i.e. 10 mA cm-2), 97% of COD was removed in 3 h electrolysis, with 17 kWh m-3 energy consumption

Electrochemical and sonoelectrochemical degradation of Allura Red and Erythrosine B dyes with Ti-PbO2 anode

The degradation of food dyes such as Allura Red AC and Erythrosine B is studied using electrochemical (ECh) and sonoelectrochemical (SECh) oxidation. The electrochemical cell has a Ti/PbO2 anode and stainless steel cathode. SECh process used an ultrasound transducer with a frequency of 40 kHz. The influence of process parameters on removal performance is examined, such as the effect of US, current intensity, stirring rate, nature and concentration of supporting electrolytes (Na2SO4, NaCl, Na2CO3) and energy consumptions are discussed as a function of chemical oxygen demand removal. The results show that ultrasonic irradiation promotes the removal of organic matter due to the activation of oxidant species. The synergistic index gives useful information about the effect of ultrasounds, which have a higher relevance working in mild conditions (low current intensity, stirring rate and supporting electrolyte concentrations). The most relevant impact has been detected in the presence of chloride, which promotes the removal of pollutants and chemical oxygen demand (COD), with a substantial reduction of the required time. On the other hand, bicarbonate ions in solution had a detrimental effect on both processes. Nevertheless, in all cases tested in this paper, this index has a value greater than one, pointing out a positive influence of ultrasound application. Then, the integration of such technology with electrochemical advanced oxidation processes can improve the removal of Allura Red and Erythrosine B with a PbO2-based anode