We compared two H 2 O 2 oxidation methods for the treatment of industrial wastewater: oxidation using Fenton's reagent [H 2 O 2 /Fe(II)] and microwave irradiation. Both methods were applied to the treatment of synthetic phenol solutions (100 mg L −1 ) and of an industrial effluent containing a mixture of ionic and non-ionic surfactants at high load (20 g L −1 of COD). The effects of initial pH, initial H 2 O 2 concentration, Fenton catalyst amount and irradiation time were assessed. According to the oxidation of phenol, it has been found that the oxidation by Fenton's reagent is dependent on the pH, contrary to the microwave system, which is not influenced by this parameter. For both systems, a limiting amount of oxidant has been found; above this point the oxidation of phenol is not improved by a further addition of peroxide. The oxidation of the industrial surfactant effluent has only been successful with the Fenton's reagent. In this case, large amounts of ferrous ions are necessary for the precipitation of the ionic surfactants of the effluent, followed by the oxidation of the non-ionic constituents of the solution.

This study investigates the environmental quality of water treatments by evaluating the effectiveness of advanced oxidation technologies, such as H2O2/Fe(II) and H2O2/UV, in treating phenol-contaminated effluents. Toxicity measurements complement the chemical analyses used to evaluate the environmental quality of a treated effluent and are an additional method for interpreting the effects of chemicals not directly measured. This study proposes an estimation model for toxicity based on the Microtox test that is adaptable to the contaminant concentration of each case. The model allows for analysis of the contribution of the different components of the treated effluent: hydrogen peroxide, phenolics, colored compounds, and others. In the second part of this work, a study was conducted of the toxicity of samples treated with the aforementioned oxidative systems. In the Fenton system, the sample after oxidation was analyzed, and it was observed that the toxicity was due to intermediate oxidation compounds, such as carboxylic acids, which rejects the influence of compounds of color and other phenolics. The H2O2/UV system tracks the progress of toxicity. This parameter quickly reaches minimum values (within about 15 min) from the start of the reaction and is a representation of the final values of primary degradation. Therefore, it is not recommended to extend the oxidation beyond this point to minimize the toxicity.

BACKGROUND Advanced oxidation includes a number of technologies, all of them appropriate to achieve environmental remediation. One of them is the organic compounds degradation by ozonation. The ozonation of rhodamine 6G (R6G) was investigated to study the effect of pH and subsequent predominance of the control stage, whether mass transfer from gas to liquid phase or chemical reaction, during oxidation. Several pH conditions are studied to achieve greater efficiency of the process. RESULTS A mathematical model enables analysis of the controlling stage. It was satisfactorily verified, showing that, initially, the process is controlled by the G‐L mass transfer stage but, as the R6G ozonation progresses the process becomes controlled by the kinetic reaction. While 99% of the rhodamine dye is removed during the mass transfer control stage regardless of the pH value, the percentage of TOC removal is increased only during the kinetic reaction control stage. CONCLUSION The most favourable pH, given the mass transfer characteristics of this case, was found to be an intermediate value around 6.0 where a minimum value for coefficient for R6G mineralization zav of about 23 mol O3 mol−1 R6G mineralized, and near its theoretical value, was obtained. © 2016 Society of Chemical Industry

No abstract

No abstract