Assessment of photo electro-Fenton and solar photo electro-Fenton processes for the efficient degradation of asulam herbicide.

The degradation of asulam herbicide by photo electro-Fenton (PEF) and solar photo electro-Fenton (SPEF) processes was studied using an undivided electrochemical BDD/carbon-felt cell to generate H2O2 continuously. A central composite design combined with response surface methodology was applied to determine the optimal operating conditions of current intensity = 0.30 A, [Fe2+] = 0.3 mM, and [Na2SO4] = 0.11 M at pH 3 to achieve the complete degradation of asulam by electro-Fenton. Subsequently, the SPEF process was more efficient treatment compared to PEF, achieving a complete degradation of asulam and 98% of mineralization in 180 min. Moreover, 4-aminobenzenesulfonamide, 4-aminophenol, and 4-benzoquinone were detected as aromatic intermediates, whereas acetic acid, oxalic acid, and NO3- ions were identified as final degradation by-products. Thus, the SPEF process is an efficient alternative for the complete degradation and mineralization of herbicide asulam in an aqueous solution under natural sunlight.

Ecological risk assessment associated with five endocrine-disrupting compounds in wastewater treatment plants of Northeast Mexico.

The ecological risk associated with five endocrine-disrupting compounds (EDCs) was studied in four wastewater treatment plants (WWTPs) in Monterrey, Mexico. The EDCs, 17ß-estradiol (E2), 17α-ethinylestradiol (EE2), bisphenol A (BPA), 4-nonylphenol (4NP), and 4-tert-octylphenol (4TOP) were determined by SPE/GC-MS method, where EE2 and 4TOP were the most abundant in effluents at levels from 1.6 - 26.8 ng/L (EE2) and < LOD - 5.0 ng/L (4TOP), which corroborate that the wastewater discharges represent critical sources of EDCs to the aquatic environments. In this study, the potential risk associated with selected EDCs was assessed through the risk quotients (RQs) and by estimating the estrogenic activity (expressed as EEQ). This study also constitutes the first approach for the ecological risk assessment in effluents of WWTPs in Northeast Mexico. The results demonstrated that the effluents of the WWTPs represent a high risk for the organisms living in the receiving water bodies because the residual estrogens effect E2 and EE2 with RQ values up to 49.1 and 1165.2. EEQ values between 6.3 and 24.6 ngEE2/L were considered the most hazardous compounds among the target EDCs, capable of causing some alterations in the endocrine system of aquatic and terrestrial organisms due to chronic exposition.

Development of an HPLC-DAD method for the simultaneous analysis of four xenoestrogens in water and its application for monitoring photocatalytic degradation.

A high-performance liquid chromatography with diode array detector (HPLC-DAD) method was developed and validated for the simultaneous quantification of 4 xenoestrogens in water for monitoring their photocatalytic degradation in synthetic water. The analytical parameters evaluated were linearity, limits of detection, and quantification (LODs and LOQs), selectivity, and accuracy, according to the US Food and Drug Administration (FDA) and Eurachem guidelines. The developed method shows good linearity (R2 > 0.995 for all compounds), and LODs ranged from 0.02 to 0.04 mg L-1, while LOQs ranged from 0.05 to 0.11 mg L-1. Moreover, accuracy expressed as recovery and precision were within the required limits. Therefore, the developed method was considered accurate, and reliable. In addition, it was successfully applied for monitoring a mixture of 4 xenoestrogens in water during the photocatalytic treatment.•An HPLC-DAD method was developed to quantify 4 xenoestrogens in water simultaneously.•The developed HPLC-DAD method shows excellent linearity, selectivity, and accuracy.•A mixture of 4 xenoestrogens was reliably monitored during their photocatalytic degradation.

Occurrence and seasonal distribution of five selected endocrine-disrupting compounds in wastewater treatment plants of the Metropolitan Area of Monterrey, Mexico: The role of water quality parameters.

Five endocrine-disrupting compounds (EDCs) were determined in four urban wastewater treatment plants (WWTPs) of the Metropolitan Area of Monterrey (MAM) in two seasonal periods (winter and summer). The MAM, one of the most urbanized areas in Mexico, is characterized by high industrial activity and population density, leading to extensive use of several EDCs. In the MAM, ∼90% of urban and industrial wastewater is treated in WWTPs, where EDCs can be partially eliminated. In this work, dissolved levels of 17ß-estradiol (E2), 17α-ethinyl estradiol (EE2), bisphenol A (BPA), 4-nonylphenol (4NP), and 4-tert-octylphenol (4TOP) in wastewater were determined. The EDCs' determination was carried out through solid-phase extraction (SPE) and gas chromatography coupled to mass spectrometry (GC-MS). High EDCs levels (0.4-450 ng/L) were found in the influents of WWTPs, while concentrations in the effluents ranged from 0.2 to 26.8 ng/L, with E2, EE2, and 4TOP being the most persistent. The Spearman correlation analysis revealed the association between E2 and EE2 (r = 0.4835, p < 0.05), and between BPA and 4NP (r = 0.5180, p < 0.05), suggesting that these EDCs have similar sources. Also, E2, BPA, and 4TOP were positively correlated with the chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) (r = 0.4080-0.5694, p < 0.05), indicating the association of the EDCs with the organic matter in the wastewater. The factor analysis confirmed the significant correlation of COD, BOD, TSS, temperature, and pH with the high occurrence of 4TOP during the summer. It was also confirmed that summer warmer temperatures favored the removal of BPA and 4NP in the studied WWTPs. Finally, the studied sites were classified by cluster analysis in three groups, revealing the impact that seasonality has on the behavior of the selected EDCs.

Performance of Bi2O3/TiO2 prepared by sol-gel on p-Cresol degradation under solar and visible light.

Photocatalytic degradation of p-Cresol was evaluated using the mixed oxide Bi2O3/TiO2 (containing 2 and 20% wt. Bi2O3 referred as TB2 and TB20) and was compared with bare TiO2 under simulated solar radiation. Materials were prepared by the classic sol-gel method. All solids exhibited the anatase phase by X-ray diffraction (XRD) and Raman spectroscopy. The synthesized materials presented lower crystallite size and Eg value, and also higher surface area as Bi2O3 amount was increased. Bi content was quantified showing near to 70% of theoretical values in TB2 and TB20. Bi2O3 incorporation also was demonstrated by X-ray photoelectron spectroscopy (XPS). Characterization of mixed oxides suggests a homogeneous distribution of Bi2O3 on TiO2 surface. Photocatalytic tests were carried out using a catalyst loading of 1 g L-1 under simulated solar light and visible light. The incorporation of Bi2O3 in TiO2 improved the photocatalytic properties of the synthesized materials obtaining better results with TB20 than the unmodified TiO2 under both radiation sources.

Optimization of solid-phase extraction of parabens and benzophenones in water samples using a combination of Plakett-Burman and Box-Behnken designs.

An automated method for the analysis of methylparaben, propylparaben, benzophenone-3, and benzophenone-4 in water effluents via on-line solid-phase extraction coupled with high-performance liquid chromatography/ultraviolet detection was proposed. The preconcentration parameters were studied using Plackett-Burman and Box-Behnken experimental designs using a C18 sorbent material. The results demonstrated that the eluent volume, composition, and sorbent amount were statistically significant. Optimal conditions for these variables were an eluent volume of 1.55 mL, eluent composition of acetonitrile 100% v/v, and sorbent amount of 100 mg. The eluted sample was analyzed on-line using high-performance liquid chromatography equipped with a reversed-phase C18 column and ultraviolet detection. Separation of the analytes was achieved in 15 min using gradient elution with acetonitrile/water. A simple, sensitive, and rapid analytical method was proposed for personal care compounds without sophisticated or expensive equipment. The limits of detection were 1.20, 1.73, 2.51, and 4.67 µg/L for propylparaben, methylparaben, benzophenone-3, and benzophenone-4, respectively. The analysis time was 48 min, consuming only 1.59 mL of eluent acetonitrile for the solid phase extraction step, with minimal sample handling. The method was applied to the analysis of spiked swimming pool and wastewater, with recoveries between 65-107%. These results indicate the reliability of the flow-based procedure.

Evaluating a 'biotic ligand model' applied to chloride-enhanced Cd uptake by Brassica juncea from nutrient solution at constant Cd2+ activity.

Evidence of chloride-enhanced cadmium uptake by plants in soil experiments has been reported. However, it is still unclear whether this finding is due to increased rates of Cd2+ diffusion to plant roots or the direct uptake of complexes such as CdC1+. A controlled hydroponic experiment was undertaken to distinguish and quantify the uptake rates of free and inorganic-complexed cadmium and to model the uptake of cadmium by Indian mustard plants with a 'biotic ligand model'. Plants were treated with NaCl (0 to 200 mM) including equivalent Na2SO4 treatments. Cadmium speciation in solution was calculated using the WHAM-VI model. Results of the current trials showed that higher Cl-concentrations in solution generally resulted in greater cadmium accumulation by plants than predicted by the Cd2+ activity. Activities of Cd-chloro complexes showed the best correlations with the cadmium concentrations in the plants compared with the activity of Cd2+. The biotic ligand model showed a reasonable good fit for the plants when assuming competition by Cd2+ and CdCl+ for sorption sites at root level. The relative values of the two reaction constants suggest that root affinity for Cd2+ is 3.4 times greater than for CdCl+. Nevertheless this clearly indicates a substantial role for chloro-complexed cadmium accumulation.