Edwin Chica

Petrochemical Wastewater Treatment by Photo-Fenton Process

In recent decades, the rise in the generation of extremely toxic and refractory wastewaters, as petroleum refinery plant effluents, is demanding increasingly efficient treatment technologies, among which photo-Fenton advanced oxidation processes are highlighted due to their rapid and effective petroleum-derived pollutant degradation. However, these systems are costly for their application at industrial scale, especially due to the associated electric energy and reagent costs. Several strategies have been adapted for overcoming these limitations, including the use of ferricarboxylate complexes or heterogeneous iron catalysts, the automated dosing of the oxidant, and even the combination of different AOPs, such as photo-electro-Fenton or sono-photo-Fenton hybrid methods. Nonetheless, the reduction of energy costs is not successfully accomplished. In this sense, further studies are required for minimizing operational costs by taking profit of solar light and coupling photo-Fenton-derived processes to biological treatments so industries can afford to implement these degradation systems and thus meet environmental legislation.

Rapid Determination of Anthracene and Benzo(a)pyrene by High-Performance Liquid Chromatography with Fluorescence Detection

ABSTRACT A rapid and simple method was optimized and validated for the separation and quantification of anthracene and benzo(a)pyrene, two of the most toxic polycyclic aromatic hydrocarbons, at ultratrace levels in aqueous samples by direct injection. The determination of anthracene and benzo(a)pyrene was performed by reverse-phase high-performance liquid chromatography (HPLC) with fluorescence detection. A fractional factorial matrix and a Box–Behnken design were chosen for screening and optimization purposes, respectively. The optimized parameters that significantly influenced the system were the flow rate (1 mL min−1), mobile-phase strength (90% acetonitrile:10% deionized water), column temperature (35°C), and excitation wavelength (254 and 267 nm for anthracene and benzo(a)pyrene, respectively). The injection volume and emission wavelength were fixed at 100 µL and 416 nm, respectively. The quantification limits were 75 ng L−1 for anthracene and 30 ng L−1 for benzo(a)pyrene. The relative standard deviations for the recovery and intra and interday precision values were lower than 20%. The method allows the analysis of aqueous samples with a good resolution for anthracene and benzo(a)pyrene below values permitted by the recently developed European Directive 2013/39/EU for inland surface waters. In addition, this work provides guidelines for the simultaneous optimization of several parameters by experimental design.

Kinetic Modeling of the UV/H2O2 Process: Determining the Effective Hydroxyl Radical Concentration

A kinetic model for pollutant degradation by the UV/H2O2 system was developed. The model includes the background matrix effect, the reaction intermediate action, and the pH change during time. It was validated for water containing phenol and three different ways of calculating HO° level time-evolution were assumed (non-pseudo-steady, pseudo-steady and simplified pseudo-steady state; denoted as kinetic models A, B and C, respectively). It was found that the kind of assumption considered was not significant for phenol degradation. On the other hand, taking into account the high levels of HO2° formed in the reaction solution compared to HO° concentration (~10–7 M >>>> ~10–14 M), HO2° action in transforming phenol was considered. For this purpose, phenol-HO2° reaction rate constant was calculated and estimated to be 1.6x103 M-1 s-1, resulting in the range of data reported from literature. It was observed that, although including HO2° action allowed slightly improving the kinetic model degree of fit, HO° developed the major role in phenol conversion, due to their high oxidation potential. In this sense, an effective level of HO° can be determined in order to be maintained throughout the UV/ H2O2 system reaction time for achieving an efficient pollutant degradation.