Ebru Cokay Catalkaya

A statistical experiment design approach for advanced oxidation of Direct Red azo-dye by photo-Fenton treatment.

Advanced oxidation of an azo-dye, Direct Red 28 (DR 28) by photo-Fenton treatment was investigated in batch experiments using Box-Behnken statistical experiment design and the response surface analysis. Dyestuff (DR 28), H(2)O(2) and Fe(II) concentrations were selected as independent variables in Box-Behnken design while color and total organic carbon (TOC) removal (mineralization) were considered as the response functions. Color removal increased with increasing H(2)O(2) and Fe(II) concentrations up to a certain level. High concentrations of H(2)O(2) and Fe(II) adversely affected the color and TOC removals due to hydroxyl radical scavenging effects of high oxidant and catalyst concentrations. Both H(2)O(2) and Fe(II) concentration had profound effects on decolorization. Percent color removal was higher than TOC removal indicating formation of colorless organic intermediates. Complete color removal was achieved within 5min while complete mineralization took nearly 15min. The optimal reagent doses varied depending on the initial dyestuff dose. For the highest dyestuff concentration tested, the optimal H(2)O(2)/Fe(II)/dyestuff ratio resulting in the maximum color removal (100%) was predicted to be 715/71/250 (mgL(-1)), while this ratio was 1550/96.5/250 for maximum mineralization (97.5%).

Photochemical Degradation and Mineralization of Phenol: A Comparative Study

Abstract In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV, UV/H2O2, and UV/H2O2/Fe2+ (Photo-Fenton process) were investigated in lab-scale experiments for the degradation and mineralization of phenol. The major parameters investigated were the initial phenol concentration, pH, hydrogen peroxide, and iron doses, and the effect of the presence of radical scavengers ( , and Cl− ions). It was observed that the phenol degradation efficiency decreased with increasing phenol concentration and pH in UV process. Maximum phenol oxidation efficiency for an initial concentration of 100 mg L−1 and at pH 3 was around 30% in direct photolysis. The efficiency increased to 97% with UV/H2O2 process, however, there was still negligible mineralization (9%) and the required irradiation time was still long (300 min). The results showed that the Photo-Fenton process was the most effective treatment process under acidic conditions. Complete disappearance of 100 mg L−1 phenol was achieved in 2.5 min and almost complete mineralization (97%) was also possible after 300 min of irradiation. The efficiency was negatively affected from H2O2 in UV/H2O2 process and Fe2+ in Photo-Fenton process over a certain concentration. The highest negative effect was observed with solution containing ions. Required reaction time for complete disappearance of 100 mg L−1 phenol increased from 2.5 min for an ion-free solution to 60 min for that containing . The photodegradation of phenol was found to follow the first-order law.

Advanced oxidation and mineralization of simazine using Fenton's reagent

Removal of simazine from aqueous solution by Fentons reagent oxidation was investigated. Box-Behnken statistical experiment design and the response surface methods were used to investigate the effects of simazine, H(2)O(2) and Fe (II) concentrations on simazine degradation and mineralization. Total organic carbon (TOC) and simazine removals were investigated at different reagent doses to determine the experimental conditions yielding the highest removal of simazine and TOC. Fe (II) concentration had more profound effect than H(2)O(2) for simazine removal while all parameters affected mineralization (TOC removal). Complete disappearance of simazine was achieved within 6 min reaction period. However, only 32% of simazine was mineralized after 15 min indicating formation of some intermediate products. The optimal H(2)O(2)/Fe (II)/simazine ratio resulting in the maximum pesticide (100%) and TOC removal (32%) was found to be 55/15/3 (mg L(-1)). The initial rate of simazine degradation was found to be first-order with respect to the initial simazine concentration.

Degradation and Mineralization of Simazine in Aqueous Solution by Ozone/Hydrogen Peroxide Advanced Oxidation

Advanced oxidation of simazine in aqueous solution by the peroxone (hydrogen peroxide/ozone) treatment was investigated using Box-Behnken statistical experiment design and response surface methodology. Effects of pH, simazine and H2 O2 concentrations on percent simazine and total organic carbon (TOC) removals were investigated. Ozone concentration was kept constant at 45 mg  L−1 . The optimum conditions yielding the highest simazine and TOC removals were also determined. Both simazine and peroxide doses affected simazine removal while pH and pesticide dose had more pronounced effect on mineralization (TOC removal) of simazine. Nearly 95% removal of simazine was achieved within 5 min for simazine and peroxide concentrations of 2.0 and 75 mg  L−1 , respectively at pH=7 . However, mineralization of simazine was not completed even after 60 min at simazine doses above 2 mg  L−1 indicating formation of some intermediate compounds. The optimum H2 O2 /pH/Simazine ratio resulting in maximum pesticide (94%) and TOC...

Improvement in Anaerobic Degradation of Olive Mill Effluent (OME) by Pre-Treatment Using H2O2, UV-H2O2 and Fenton's Process

The pre-treatment using single H2O2, UV-H2O2 and Fentons process as a pre-treatment option for olive mill effluent (OME), which is known to contain a significant amount of inhibitory compounds (e.g., phenolics and tannins) was carried out in order to enhance anaerobic degradation of OME. Biochemical Methane Potential (BMP) assay was employed in order to monitor and comparatively evaluate any increase in biogas production as an indicator of improvement in anaerobic biological degradation before and after pre-treatment. The results suggested that pre-treatment using Fentons process resulted in an almost 3.5-fold enhancement in the biodegradability of OME, which was much lower if it was digested alone (without pre-treatment). Pre-treatment in the form of UV-H2O2 also significantly increased the biogas production (1.75-fold higher gas production than raw OME sample); on the other hand, the use of H2O2 alone negatively affected the biogas production. It was demonstrated that the anaerobic biodegradability of OME could be significantly enhanced by pre-treatment using Fentons process and therefore anaerobic degradation after a suitable pre-treatment could be proposed for the safe disposal of OME.

Dehalogenation, degradation and mineralization of diuron by peroxone (peroxide/ozone) treatment

Removal of diuron from aqueous solution by peroxone (hydrogen peroxide/ozone) oxidation was investigated using Box-Behnken statistical experiment design and the response surface methodology (RSM). Effects of diuron, H2O2 concentrations and initial pH on the extent of diuron, total organic carbon (TOC) and adsorbable organic halogen (AOX) removals were investigated. Ozone dose was kept constant at 45 mg min−1. Optimum reagent doses yielding the highest diuron, TOC and AOX removals were also determined. Hydrogen peroxide dose and pH were the most effective parameters for pesticide removal while hydrogen peroxide dose had the most significant effect on AOX removal (dehalogenation). All parameters affected mineralization (TOC removal) of diuron. Nearly complete removal of diuron was achieved within 5 minutes, while complete mineralization and dehalogenation were not achieved even within 60 minutes at high diuron doses indicating formation of some intermediate products. The optimal H2O2/pH/diuron ratio resulting in the maximum pesticide (100%), TOC (82%) and AOX (95%) removal was found to be 340/8/10.