No abstract

Highlights  Investigation of process conditions for the degradation of sulfamethoxazole  Identification of degradation products for elucidation of the degradation mechanism  Elucidation of pH influence on formation of degradation products

No abstract

In this study, the degradation of ciprofloxacin (CIP) in wastewater was investigated using UVbased sulfate radical advanced oxidation processes (SR-AOP) and UV-based advanced reduction processes (ARP). More specifically, a comparison of the UV-based persulfate advanced oxidation process (the UV/PS process) and the UV-based sulfite advanced reduction process (the UV/sulfite process) was made. As for the UV-based SR-AOPs, the UV/PS process was much more efficient than the UV-based peroxymonosulfate advanced oxidation process (the UV/PMS process), with pseudo first order reaction rate constants (kobs) of 0.752 and 0.145 min -1 , respectively. For the UV-based ARPs, the UV/sulfite process was the most efficient, compared to the UV/sulfide and the UV/dithionite process (kobs of 0.269, 0.0157 and 0.0329 min -1 , respectively). The optimal process parameters for both the UV/PS and the UV/sulfite process were determined and the contribution of the produced reactive species were identified.For the UV/PS process, maximal CIP degradation was found at pH 8, and both •OH and •SO4were responsible for CIP degradation. For the UV/sulfite process, •H and •eaqwere responsible for CIP degradation, with •eaqbeing the predominant radical at pH 8.5. Although CIP degradation was much faster for the UV/PS process, the UV/sulfite process was determined to be much more efficient in the defluorination of CIP.

No abstract

Abstract:In this study, the degradation of 4-chlorophenol (4-CP) is investigated by using a combination of microwave (MW) irradiation and hydrogen peroxide as oxidant (the MW-H 2 O 2 -process). The influence of the critical parameters on the efficiency of the process is examined by applying Partial Least Square Regression (PLS) on a Design of Experiments (DOE). Also, a kinetic evaluation of the process is carried out. Results showed that the MW-H 2 O 2 -process is effective in the degradation of 4-CP. The most influential parameter of the MW-H 2 O 2 -process is the reaction temperature. Besides this parameter, the reaction time, initial 4-CP concentration, and initial hydrogen peroxide concentration have a (minor) influence on the 4-CP degradation. A maximum degradation efficiency within the levels of the DOE (remaining percentage of 4-CP of 34%) was achieved with an initial 4-CP concentration of 1000 mg/L, an initial H 2 O 2 concentration of 11 g/L, reaction temperature of 180 • C, and reaction time of 20 min. The process follows pseudo first order reaction kinetics.

No abstract

The aim of this study was to predict the residual adsorbable organic halides (AOX) concentration in an industrial wastewater using conventional, easy-to-measure wastewater parameters. In a pilot test unit, the wastewater was subjected to ozonation at various intensities, resulting in an AOX-removal and hence varying AOX concentrations. In first instance, the parameters used for modeling were selected using Pearson and Spearman correlations. Secondly, multiple linear regression (MLR) was used as a modeling tool to predict both the soluble and total AOX concentration in wastewater samples. To prevent overfitting, a 10-fold cross-validation was carried out. It was found that both the soluble and the total AOX concentration can be predicted using typical wastewater parameters. The measured parameters were pH, chloride concentration, Water-Soluble Organic Carbon concentration (WSOC), UV-VIS spectrum, turbidity, and Solids Removable by Filtration (SRF). Out of these parameters, the following parameters were found to be significant for prediction of the total AOX concentration: turbidity; SRF; UV-VIS absorbance at 200; 227, and 250 nm; and pH. UV-VIS absorbance at 200 and 227 nm and turbidity of the wastewater were found to contribute significantly to the final model. For the soluble AOX concentration, the significant parameters were turbidity; SRF; absorbance at 200, 227, and 250 nm; pH, and chloride concentration. Here, UV-VIS absorbance at 200 and 227 nm were found to contribute significantly to the final model. The obtained final models had an adjusted R2 of 0.921 and 0.916 for the total and soluble AOX, respectively. As a result of the obtained models, both AOX concentrations can be predicted using parameters that are easier to determine. This allows for a significant reduction in wastewater sampling and analysis time and offers the opportunity to optimize the ozone dosing in the wastewater treatment process in the future.