Sonoelectrochemical Oxidation for Decolorization of Basic Blue 41 based on Central Composite Design

As an auxiliary to electrochemical processing, ultrasonic cavitation at/near a solid surface has potential advantages: (i) ultrasonic degassing at an electrode surface prevents gas bubbleaccumulation, which interferes with the passage of current; (ii) agitation via cavitation at the electrode surface assists in ion transport through the diffusion layer; and (iii) cavitation at the electrode surface results in continuous cleaning and activation of the electrode [1, 2]. Powerultrasound can be applied as a hydrodynamic tool to increase the signal-to-background ratio for diffusion controlled redox systems and to remove the effects of electrode surface fouling. Acombination of sonication and electrochemical oxidation is a hybrid technology developed for thetreatment of organic pollutant [3, 4]. In this study, a four-factor five-level Central Composite Design (CCD) was applied to develop mathematical model and optimize process parameters for Basic Blue 41 dye (BB41) decolorization from aqueous solutions using sonoelectrochemical process. Methods Generally, at optimum condition, 5.0 mL of BB41 (1.0 g L-1), 5.0 mL buffer solution with pH =6.0 were added to 50 mL volumetric flask and diluted to the volume with double-distilled water.The solution was moved to the electro analyzer cell, which placed in ultrasound bath and potential of 0.65 V was applied the working electrode for 118 min. The initial and final adsorption of the dye solution were determined at the maximum wave length λmax= 617 nm usinga UV-VIS spectrophotometer. The percentage removal of dye was calculated as follows:% dye removal = 1 − / × 100 Where A0 and A is the initial and final absorbance of solution, respectively and the removal was taken as a response (Y) of the experimental design. Results and Discussion The discoloration rate constantly increases with the increase in the time. By increasing of time,the free radicals such as OH and HOO would be increased, which promotes the discoloration rate. More dye molecules was also moved to electrode and was oxidized on electrode. Moreover,the dye removal percentage increased with increased the applied potential. The OH productionrate was increased with increasing potential, and thus, more OH can diffuse from the surface of the electrode into the solutionConclusionBased on ANOVA results, the order of factors from high to low contribution on decolorization efficiency was found as initial dye concentration, time, pH and applied potential with respect tosum of squares. Optimization results showed that the optimal settings for significant experimental factors were initial dye concentration= 108 mg L-1, pH= 6.0, applied potential= 0.67 V and contact time= 118 min. At this condition, predicted maximum removal efficiency was over 99%.

Keywords:

Sonochemistry , Electrochemical , Basic Dye , decolorization