Asli Yuksel

Electrolysis of glycerol in subcritical water

Recently, there has been a rising interest for the disposal of biorelated components that cannot be treated easily by biological processes. Because of the development of biodiesel production, the production of by-products such as crude glycerol has increased dramatically. Presently, in many biodiesel plants with low capacity, the aqueous phase containing produced/left glycerol, which is an important molecule in the context of renewable biomass resources to provide hydrogen energy and chemical intermediates, methanol and salts as by-products, is discharged as wastewater. In this manner, both environmental pollution and economical losses are created. Therefore, we developed a new hydrothermal electrolysis system, by which these organics can be converted into value added chemicals, under high-temperature and high-pressure aqueous conditions. In this study, hydrothermal electrolysis reactions of glycerol with an alkali were investigated systematically to determine the intermediate products and current efficie...

Complete degradation of Orange G by electrolysis in sub-critical water.

Complete degradation of azo dye Orange G was studied using a 500 mL continuous flow reactor made of SUS 316 stainless steel. In this system, a titanium reactor wall acted as a cathode and a titanium plate-type electrode was used as an anode in a subcritical reaction medium. This hydrothermal electrolysis process provides an environmentally friendly route that does not use any organic solvents or catalysts to remove organic pollutants from wastewater. Reactions were carried out from 30 to 90 min residence times at a pressure of 7 MPa, and at different temperatures of 180-250°C by applying various direct currents ranging from 0.5 to 1A. Removal of dye from the product solution and conversion of TOC increased with increasing current value. Moreover, the effect of salt addition on degradation of Orange G and TOC conversion was investigated, because in real textile wastewater, many salts are also included together with dye. Addition of Na(2)CO(3) resulted in a massive degradation of the dye itself and complete mineralization of TOC, while NaCl and Na(2)SO(4) obstructed the removal of Orange G. Greater than 99% of Orange G was successfully removed from the product solution with a 98% TOC conversion.

Hydrothermal Degradation of Congo Red in Hot Compressed Water and its Kinetics

A di-azo dye, Congo Red (CR) was used as a model compound to investigate the degradation mechanism in hot compressed water (HCW). The unique properties of HCW facilitated the degradation efficiency without addition of any organic solvent. The influences of reaction time, temperature, initial dye concentration and amount of hydrogen peroxide (H2O2) on the degradation of CR and the removal of total organic carbon (TOC) from the product solution were investigated. The presence of H2O2 was found to enhance the degradation of CR. The results showed that the degradation yield could reach 99.0% with a solution of 100 ppm CR and 50 mM H2O2 at 150°C at the end of 60 min. Maximum conversion of the total organic carbon was recorded as 62.2%. Moreover, the effect of the presence of several co-existing negative ions such as SO4 2-, Cl-, CO32- were investigated. It was found that the presence of SO42- accelerated evidently the degradation of CR. The other chosen anions (CO32- and Cl-) had an inhibitory effect on the decolorization of CR. Finally, kinetic study was carried out and the order of the reaction was calculated as 0.37.