The corrosion behavior of Titanium in a simulated saliva solution was improved by Nanotubular Oxide via electrochemical anodizing treatment using three electrodes cell potentiostat at 37°C. The anodization treatment was achieved in a non-aqueous electrolyte with the following composition: 200mL ethylene glycol containing 0.6g NH4F and 10 ml of deionized water and using different applied directed voltage at 10°C and constant time of anodizing (15 min.). The anodized titanium layer was examined using SEM, and AFM technique.
The results showed that increasing applied voltage resulted in formation titanium oxide nanotubes with higher corrosion resistance (more positive value of the corrosion potential). The results revealed that good adhered well-ordered vertically aligned titania nanotubes with inner tube diameter of 82nm an mean length of 3microns could be obtained at 30VDC. Low corrosion current density (579 nA.cm-2) and corrosion potential equal to (-209 mV) were observed for untreated titanium metal while a dramatic fall down of the corrosion current was observed for nanotubes TiO2 (76 nA.cm-2) and more positive value of corrosion potential (-138 mV) was observed revealing good corrosion resistance of the improved titanium in saliva solutions.
The present paper deals with the treatment of wastewaters generated from Al-Dewaniya petroleum refinery plant by Electro-Fenton process in a batch electrochemical reactor using porous graphite as anode and cathode materials. Effects of operating factors such as current density (5-25mA/cm 2 ), FeSO4 concentration (0.1-0.7mM), NaCl addition (0-2g/l), and time (15-45min) on the efficiency of the chemical oxygen demand (COD) removal were studied. The results revealed that FeSO4 concentration has the main effect on the efficiency of COD removal confirming that the Electro-Fenton process was governed by reaction conditions in the bulk of solution between ferrous ions and H2O2 not upon the electrochemical reactions on the surface of electrodes. Parametric optimization was carried out using response surface methodology (RSM) combined with Box-Behnken Design (BBD) to maximize the removal of COD. Under optimized operating conditions: FeSO4 concentration (0.7mM), current density (25 A/cm 2 ), and time (45 min) with no addition of NaCl, the removal efficiency of COD was found to be 95.9% with an energy consumption of 8.921kWh/kg COD.
A detailed experimental study was devoted to the anodic oxidation of oxalic acid using manganese dioxide rotating cylinder anode with the objective to evaluate in a systematic way the effect on the oxalic acid oxidation process of several relevant parameters, including the presence of sodium chloride, the current density (J), the rotation speed, the temperature, and the initial concentration of oxalic acid. Thin manganese dioxide film on graphite substrate has been prepared by electrochemical oxidation from MnSO4-H2SO4 electrolyte. The morphology of this electrode was investigated by XRD, SEM, EDS and AFM techniques. The results show that a firm γ-structure of MnO2 film on graphite rod can be obtained successfully. The results indicate that the presence of NaCl has a vital role on the performance of the oxalic acid incineration process. Also current density has the major effect on the removal and current efficiencies. Positive effect of temperature on the removal and current efficiencies and negative effect of rotation speed were observed. The best adopted operative conditions were T = 50°C, J = 40 mA/cm2 and 200 rpm in the presence of 1g/l NaCl where a conversion of about 97% and a current efficiency close to 55% with energy consumption less than 28 kWh(kg of COD)−1 were obtained after four hours of electrolysis time. The findings of the present research validate that incineration of oxalic acid can be carried out successfully on MnO2 anode.
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