Diamond-sensing microdevices for environmental control and analytical applications

Maleic acid (MA) is one of the main intermediates formed during mineralization, by electrooxidation, of aromatic compounds contained in aqueous wastes. This work investigates oxidation of maleic acid with or without the presence of oxalic acid (OA) and formic acid (FA) in aqueous solution by using boron-doped diamond (BDD) electrodes. OA and FA are the main products formed in MA electrooxidation. Voltammetric studies conducted with a BDD electrode of small surface (0.196 cm 2 ) show that MA oxidation takes place at a potential very close to that of the discharge of water. But, under potentiostatic conditions and at concentrations higher than 0.001 M, adsorption of MA blocks its own oxidation. Oxalic and formic acids are oxidized before the discharge of water. Again, the presence of maleic acid blocks the oxidation of formic and oxalic acids. Galvanostatic electrolyses of aqueous solutions of MA, OA, FA and mixtures of theses acids were conducted on a BDD electrode. Electrolyses were controlled by measurements of Total Organic Carbon, Chemical Oxygen Demand and by Liquid Chromatography. Results showed that MA was totally mineralized; FA and OA were very low concentration intermediaries. Electrolyses of solutions containing MA, initially in the presence of OA or FA, showed that the OA was oxidized at the same rate as the MA, whereas the FA oxidation began only when the MA had completely disappeared. These results suggest that OA oxidizes by a mass transport limited process coupled with a direct electron transfer with the anode. Under galvanostatic conditions, maleic acid and formic acid are probably oxidized via OH • radicals generated by water discharge.

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“…The diamond films were about 1lm thick. This HF CVD process produces columnar, randomly textured, polycrystalline films [11].…”

Section: Electrolysis and Electrode Materialsmentioning

confidence: 99%

A kinetic study of the electrochemical oxidation of maleic acid on boron doped diamond

et al. 2006

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“…By means of electrochemical oxidation, pollutants can be completely mineralised using high oxygen overvoltage anodes such as PbO 2 [4][5][6][7] and boron-doped diamond (BDD) [8][9][10][11][12][13]. In fact, using these anodes, organics are incinerated to CO 2 by electrogenerated hydroxyl radicals [14]:…”

Section: Introductionmentioning

confidence: 99%

Electrochemical degradation of anionic surfactants

2005

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This study was performed to investigate the electrochemical oxidation of anionic surfactants. In particular, a synthetic solution of sodium dodecyl benzene sulfonate and a real car wash wastewater were treated by galvanostatic electrolysis using a Ti-Ru-Sn ternary oxide and a boron-doped diamond (BDD) anode. Measurements of the Chemical Oxygen Demand (COD) and the concentration of the anionic surfactants were used to follow the oxidation. Using the Ti-Ru-Sn ternary oxide anode, the complete removal of COD and sodium dodecyl benzene sulfonate was obtained only in the presence of chloride ions that act as inorganic mediators. The oxidation rate was almost independent of current density and electrolyte flow rate. In the case of BDD the mineralisation of the sodium dodecyl benzene sulfonate was achieved in all experimental conditions due to reaction with hydroxyl radicals electrogenerated on the diamond surface during electrolysis. The COD removal rate increased with increase in electrolyte flow rate, indicating that the oxidation was mass-transfer controlled. Comparison of the results of the two electrodes showed that chlorine mediated oxidation at the Ti-Ru-Sn ternary oxide anode allowed a faster COD removal of both the synthetic solution and real car wash wastewater.

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“…Values for the Young's modulus ͑or effective modulus͒ reported in the literature vary over a wide range, e.g., from 242-1050 GPa. 24,26 Measured values considerably lower than the theoretical value of ϳ1143 GPa are not unusual, 24,27,28 particularly for measurement techniques which sample relatively large volumes of the diamond wafer, as is the case for the Lamb waves studied here. Recently, using a laser surface acoustic wave method, Schneider et al 29 measured Young's modulus values ranging from 400 to 1100 GPa for low sp 2 content diamond films deposited on tungsten carbide; they have also suggested that a high defect density and micropores could account for the lower E values observed in their films.…”

Section: B Temperature and Dispersion Measurementsmentioning

confidence: 69%

Characterization of acoustic Lamb wave propagation in polycrystalline diamond films by laser ultrasonics

Whitfield

Audic

Flannery

et al. 2000

Journal of Applied Physics

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Diamond-sensing microdevices for environmental control and analytical applications

Cited by 47 publications

References 10 publications

A kinetic study of the electrochemical oxidation of maleic acid on boron doped diamond

A kinetic study of the electrochemical oxidation of maleic acid on boron doped diamond

Electrochemical degradation of anionic surfactants

Characterization of acoustic Lamb wave propagation in polycrystalline diamond films by laser ultrasonics

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