Abdurrahman Akyol

Electrochemical treatment and operating cost analysis of textile wastewater using sacrificial iron electrodes

Electrocoagulation (EC) method with iron electrode was used to treat the textile wastewater in a batch reactor. Iron electrode material was used as a sacrificial electrode in monopolar parallel mode in this study. The removal efficiencies of the wastewater by EC were affected by initial pH of the solution, current density, conductivity and time of electrolysis. Under the optimal experimental conditions (initial pH 6.9, current density of 10 mA/cm(2), conductivity of 3,990 microS/cm, and electrolysis time of 10 min), the treatment of textile wastewater by the EC process led to a removal capacity of 78% of chemical oxygen demand (COD) and 92% of turbidity. The energy and electrode consumptions at the optimum conditions were calculated to be 0.7 kWh/kg COD (1.7 kWh/m(3)) and 0.2 kgFe/kg COD (0.5 kgFe/m(3)), respectively. Moreover, the operating cost was calculated as 0.2 euro/kg removed COD or 0.5 euro/m(3) treated wastewater. Zeta potential measurement was used to determine the charge of particle formed during the EC which revealed that Fe(OH)(3) might be responsible for the EC process.

Photocatalytic performance of ZnO coated tubular reactor.

The recovery of photocatalyst particles constitutes a serious drawback of slurry reactors. Therefore, depositing the catalyst mass on a suitable support without loss of photocatalytic activity is of practical importance. In this study, a chemical deposition method was applied to coat the inner surface of quartz tubes of various diameters with thin ZnO film. The method is economical, energy efficient and easy to apply. ZnO film is mechanically durable and resistant to chemical dissolution. Various physical tests were conducted to characterize the film. ZnO thin film exhibits the crystal wurtzite structure with band gap calculated as 3.24 eV. The film exhibits highly hydrophilic behavior. The average ZnO crystallite size is estimated as 72 nm. SEM analysis shows that the ZnO film has granular morphology with uniform particle size of about 300-400 nm. The film thickness is calculated as 1.41 microm after 20 coating cycles and the increase of the thickness of the thin film per cycle was approximately 70 nm. Photochemical activity tests were performed by measuring photo decolorization rate of a commercial azo dye (Rem Red F3B) solution in tubular reactor and as well as in slurry reactor for comparative purpose. First order rate constants were correlated to principal process parameters. The results showed that thin ZnO film has high photocatalytic activity comparable to that of ZnO powder.

Preparation and characterization of supported ZnO photocatalyst by zincate method

Supported ZnO film photocatalysts are prepared on glass and ceramic substrates by zincate method. Prepared ZnO films are seen rather strongly durable. They resist to chemical dissolution in a broad range of pH from 3 to 10. Various physical tests are conducted to measure the relevant characteristics of the films. Band gap of ZnO film is calculated as 3.24 eV. SEM analysis shows that the ZnO film has granular morphology with uniform particle size about 300-400 nm. The film thickness is calculated as 1.41 microm after twenty coating cycles and the thickness of the thin film per cycle was approximately 70 nm. Photochemical activity tests are performed by measuring photodecolorization rate of methyl orange solution. First order rate constants are correlated to principal process parameters. The results show that ceramic is the preferable supporting material with high activity. According to simulation study, the photocatalytic activity of film coated on ceramic ring of 8mm diameter is nearly equal to the activity of powder ZnO slurry of 120 mg/dm(3) density. It carried out about decolorization 65% in 3h. The calculations show that it is possible to prepare ZnO film on ceramic ring with similar activity as powder ZnO.

Electrochemical treatment of Baker's yeast wastewater containing melanoidin: optimization through response surface methodology

Effluents from Bakers yeast production plant contain a high percentage of color and a large amount of organic load. In the present study, Bakers yeast wastewater (BYW) is treated with the electrocoagulation (EC) process using Al electrodes. Operating parameters (pH, current density, color intensity and operating time) are optimized by response surface methodology (RSM). Quadratic models are developed for the responses which are removal efficiencies of color, chemical oxygen demand (COD) and total organic carbon (TOC) and operating cost (OC). Optimum operating parameters and responses are determined as initial pH 5.2, current density of 61.3 A/m(2) and operation time of 33 min, and 71% of color, 24% of COD, 24% of TOC removal efficiencies and OC of 0.869 €/m(3), respectively. The quadratic model fits for all responses very well with R(2) (>0.95). This paper clearly shows that RSM is able to optimize the operating parameters to maximize the color, COD and TOC removal efficiencies and minimize the OC.