Patricia Palo

Advanced photochemical oxidation of emergent micropollutants: Carbamazepine

The combination of UV radiation with hydrogen peroxide has been widely used for the photodegradation of pollutants in aqueous solutions. Statistical design of experiments is a powerful tool to optimize this kind of process. Initial hydrogen peroxide concentration, pH and temperature were considered as the variables for the process optimization. The interactions existing between these three variables were analyzed. Initial concentration of hydrogen peroxide proved to be the most important variable conditioning the removal efficiency, followed by temperature, and pH shows a non-significant positive influence along the whole operation interval. The ANOVA test reported significance for five of the nine involved variables. The Response Surface Methodology technique was used to optimize carbamazepine degradation. Under optimal conditions (hydrogen peroxide concentration = 0.38·10−3 mol L−1, pH = 1 and temperature = 35.6°C) total carbamazepine degradation was achieved.

Feasibility of electrochemical degradation of pharmaceutical pollutants in different aqueous matrices: Optimization through design of experiments

Electrochemical degradation of different effluents polluted with carbamazepine, a well-known refractory pharmaceutical contaminant, was addressed in this article. Ultrapure water (Milli-QTM technology), surface water from a lake and urban wastewater were the matrices used to evaluate the feasibility of performing the electro-oxidation of carbamazepine. Specific designs of experiments were planned for each of the aqueous media. The initial carbamazepine concentration and the electric current density were considered as the operational variables. Although the optimal values of both variables follow the same trend in the three cases, significant differences are observed regarding the comparative influence of each variable on the degradation of carbamazepine.

Parabens abatement from surface waters by electrochemical advanced oxidation with boron doped diamond anodes

The removal efficiency of four commonly-used parabens by electrochemical advanced oxidation with boron-doped diamond anodes in two different aqueous matrices, namely ultrapure water and surface water from the Guadiana River, has been analyzed. Response surface methodology and a factorial, composite, central, orthogonal, and rotatable (FCCOR) statistical design of experiments have been used to optimize the process. The experimental results clearly show that the initial concentration of pollutants is the factor that influences the removal efficiency in a more remarkable manner in both aqueous matrices. As a rule, as the initial concentration of parabens increases, the removal efficiency decreases. The current density also affects the removal efficiency in a statistically significant manner in both aqueous matrices. In the water river aqueous matrix, a noticeable synergistic effect on the removal efficiency has been observed, probably due to the presence of chloride ions that increase the conductivity of the solution and contribute to the generation of strong secondary oxidant species such as chlorine or HClO/ClO −. The use of a statistical design of experiments made it possible to determine the optimal conditions necessary to achieve total removal of the four parabens in ultrapure and river water aqueous matrices.