No abstract

The production of benzoic acid from toluene in the liquid phase with pure oxygen was studied. Investigations have been carried out with a view to determining the most suitable reaction conditions with respect to operating variables including oxygen flow rate, reaction temperature, batch time and catalyst loading. In a series of batch experiments carried out at 4 atm, the optimum values of mole ratio of oxygen to toluene, temperature, reaction time, and catalyst loading were found to be 2, 157°C, 2 h and 0.57 g/L, respectively. In addition, a kinetic study was carried out by taking into consideration the optimum reaction conditions. The model dependent on the formation of benzyl radical was found to be feasible for describing the catalytic oxidation of toluene to benzoic acid in the liquid phase. The activation energy was determined as 40 kJ/mol.

In this paper, a model describing the cycle of nitrogen in a Step Sludge Recirculation (SSR) reactor, was developed. The SSR reactor is a multistage, continuous stirred tank reactor where the recycled biomass is distributed over all stages. The SSR system provides a uniform treatment of the wastewater and high purification efficiency for both carbon and nitrogen removal. The objective of this work was to develop a mathematical model of the SSR system, based on the analysis of various parameters that are present in the system. The simplified form of the IWA-ASM model was adapted to include the carbon removal, nitrification and denitrification processes. For model validation, a SSR pilot plant fed with synthetic wastewater was operated for approximately four months. The experimental results show that the SSR system seems to be appropriate to attain maximum TOC and nitrogen removal with minimum sludge production. The proposed model seems to be capable of expressing the behavior of carbon removal, nitrification, denitrification and various microorganism species in a SSR configuration of a nitrogen cycle. When the experimental results were compared with those estimated by the proposed model, the model predictions matched well with the experimental results.

Wastewater from the Afyon Alkaloids Factory (Afyon, Turkey) was subjected to low-pressure catalytic wet-air oxidation (CWAO) using Fenton's reagent, and the optimal reaction conditions were investigated. The CWAO using Fenton's reagent was applied to the factory effluent, diluted factory effluent, and aerobically pretreated wastewater. To find the optimum quantities of reagents, ferrous iron (Fe 12 )-to-substrate ratios of 1:10, 1:25, and 1:50 and hydrogen peroxide (H 2 O 2 )-to-Fe 12 ratios of 1, 5, and 10 were investigated, and the treatment was carried out at different temperatures. High chemical oxygen demand (COD) removals were obtained at 508C, with the Fe 12 -to-substrate ratio range between 1:10 and 1:25. The change in H 2 O 2 -to-Fe 12 ratios did not cause any considerable effect. Also, the percentages of COD removals were nearly the same, so the ratio H 2 O 2 :Fe 12 :1 is recommended. Aerobic pretreatment seems to be effective. On the other hand, no enhancement was observed in the case of the diluted wastewater. Water Environ. Res., 80, 540 (2008).