Effects of LED lights and cytokinin on the phytotreatment of simulated swine wastewater by Azolla spp.: Pollutant removal and biomass valorization.

Phytoremediation is an eco-friendly and affordable option for tackling wastewater pollutants. The study focused on how light-emitting diodes (LED) light exposure, measured by intensity and duration (photoperiod), along with cytokinin, impacts Azolla microphylla's simulated swine wastewater treatment performance and biomass production. Under optimal treatment conditions, high removals of COD (89.2 % to 90.8 %), N-NH4+ (72.6 % to 91.2 %), N-NO3- (84.4 % to 88.6 %), Cu (75.4 % to 86.4 %), sulfamethoxazole (77.0 % to 79.0 %), P-PO43- (54.1 % to 59.9 %) and DOC (67.4 % to 71.3 %) while Zn presented a more moderate reduction (2.0 % to 9.7 %). Biomass productivity reached up to 34.8 t ha-1 yr-1. Protein production accounted for 23 % to 27 % of dry weight, while lipids ranged from 20 % to 34 % of dry biomass. Carbohydrate content varied from 8 % to 28 % of fresh weight. Higher light intensities, with both high or low values of photoperiods, and low concentrations of cytokinin were identified as optimal conditions for removal of almost all pollutants. However, pollutant removal was impacted differently by LED light and cytokinin concentration. In treatment conditions with the shortest photoperiods (8 h), the lowest residual Cu and Zn concentrations, whereas with longer photoperiods (24 h), the lowest residual concentrations of N-NH4+ and P-PO43- concentrations were recorded. On the other hand, SMX was the only parameter in which cytokinin had a clear influence on its removal, with the lowest residual concentration observed under 8-hour photoperiods combined with the lowest tested cytokinin concentrations (0.3 mg L-1). For residual COD and N-NO3-, no discernible pattern was evident for any of the analyzed factors. Therefore, the study demonstrates the potential for treating simulated swine wastewater using Azolla microphylla, aligned with its ability to produce biomass rich in high-value compounds.

Photo-Fenton process applied for the treatment of industrial wastewaters containing diclofenac: optimization with low iron ions concentrations and without pH control.

Diclofenac (DCF) can cause several adverse effects in the environment and it should be removed from industrial pharmaceutical wastewaters. Advanced oxidation processes (AOPs) are promising methods for the DCF degradation. But, in many cases, AOPs require acidic pH. However, at this condition, DCF precipitates, which may hinder its oxidation. Thus, in this work, some AOP were studied for the DCF degradation, especially the photo-Fenton process, applying the experimental design technique (Doehlert matrix), operating without and with pH control (between 6.5 and 7.0). As independent variables, the initial ferrous ion concentration ([Fe2+]) and the molar addition rate of H2O2 (FH2O2) were evaluated. Empirical models were proposed and optimized conditions were determined without ([Fe2+] = 0.27 mmol L-1 and FH2O2 = 1.64 mmol min-1) and with pH control ([Fe2+] = 1.0 mmol L-1 and FH2O2 = 1.64 mmol L-1), with the following predicted mineralization percentages: 93% and 68%, respectively. So, photo-Fenton process without pH control presented the best performances. Furthermore, at this condition, iron concentration respects the limit value established by the Brazilian environmental legislation. That is, in this condition, additional processes, in order to remove iron ions, would not be necessary, that is very interesting for applications on an industrial scale.

Multivariate optimization of dispersive liquid-liquid microextraction using ionic liquid for the analysis of ultraviolet filters in natural waters.

In this work, a vortex-assisted dispersive liquid-liquid microextraction method, using an ionic liquid as the extracting solvent was developed, for the simultaneous analysis of three UV filters in different water samples. The extracting and dispersive solvents were selected in a univariate way. Then, the parameters such as the volume of the extracting and dispersive solvents, pH and ionic strength were evaluated using a full experimental design 24, followed by Doehlert matrix. The optimized method consisted of 50 µL of extracting solvent (1-octyl-3-methylimidazolium hexafluorophosphate), 700 µL of dispersive solvent (acetonitrile) and pH of 4.5. When combined with high-performance liquid chromatography, the method limit of detection ranged from 0.3 to 0.6 µg L-1, enrichment factors between 81 and 101%, and the relative standard deviation between 5.8 and 10.0%. The developed method demonstrated effectiveness in concentrating UV filters in both river and seawater samples, being a simple and efficient option for this type of analysis.

Assessment and optimization of the use of a novel natural coagulant (Guazuma ulmifolia) for dairy wastewater treatment.

A feasible, novel, and natural coagulant extracted from G. ulmifolia stem bark was characterized and used in experiments of coagulation/dissolved air flotation (C/DAF) to treat synthetic dairy wastewater (SDW). The performance of G. ulmifolia to remove turbidity, chemical oxygen demand (COD), and UV254 was evaluated by using response surface methodology (Doehlert matrix). G. ulmifolia dosage and pH were evaluated and optimized in the C/DAF process and its characterization was performed by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and also zeta potential. Results showed that G. ulmifolia stem bark is composed of large quantities of condensed tannins represented by the groups C=C-C and CO of pyran (flavonoid C-rings), which serve as bridges during coagulation. Moreover, the presence of porous cavities in surface of G. ulmifolia, shown by SEM, indicated capacity for adsorption. G. ulmifolia dosage and pH were significant (p ≤ 0.05) for pollutant removal from the SDW. Jar test results revealed that 95.8% of turbidity, 76.0% of COD, 81.2% of BOD, and 85.6% of UV254 were removed from SDW by using G. ulmifolia stem bark at a dose of 775.8 mg L-1 and pH 5.00. Finally, our results showed promising use of G. ulmifolia as a coagulating agent due to its novelty, efficiency, low-cost, and eco-friendly properties as an alternative for the treatment of dairy wastewaters.

Speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry.

In this work, a methodology for chemical speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry is proposed. Doehlert design and desirability function were used to find the optimum conditions for hydride generation (1.0 mol L-1 HCl and 0.9% m v-1 NaBH4). The accuracy of the analytical method was evaluated by analysis of reference material fly ash (BCR 176R), addition and recovery tests for inorganic As species, and comparison of independent methods for Sb determination in urban dust samples. The determination of the total concentrations of As and Sb and their inorganic species presented good accuracy, between 80 ± 1 and 101 ± 6%. Precision was expressed as the relative standard deviation and was better than 4.7% (n = 3). The limit-of-quantification values were 0.23 and 1.03 mg kg-1 for As and Sb, respectively. The methodology was applied to eight samples of dust collected in an urban area of Salvador and Jaguaquara cities, Bahia, Northeast, Brazil, with an aerodynamic size lower than 38 µm. Concentrations of pentavalent inorganic species (iAs5+ and iSb5+) in relation to trivalent species (iAs3+ and iSb3+) were found in urban dust collected in the city of Salvador, which are regarded as more toxic for both elements. The enrichment factor and geoaccumulation index (Igeo) values showed that for some samples, the concentrations of iAs and iSb presented strong enrichment and, and regarding environment, strong to moderately polluted by iAs and iSb, with an indication of anthropogenic contributions. The occurrence of these inorganic constituents in the urban area of Salvador can be related with intense industrial activities and vehicular traffic.

Optimization of UV/H2O2 and ozone wastewater treatment by the experimental design methodology.

The objective of this study was to optimize UV/H2O2 and ozonation systems by means of an experimental design using as a response the efficiency of the operational conditions to remove the methylene blue (MB) dye. Two classes of experimental planning were used: the Doehlert matrix (DM) and the central composite design (CCD). The most important variables for each process were hydrogen peroxide concentration, the ratio of illuminated volume/total volume of the reactor and recirculation flow rate for UV/H2O2, and ozone flow rate, consumed ozone and MB concentration for the ozonation. The DM was more efficient in optimizing the systems, since it used a smaller number of experiments and achieved similar results when compared to the CCD. After optimization, the disinfection efficiency of the systems was tested with secondary effluent evaluating the inactivation of microbiological indicators, Escherichia coli and total coliforms, using the optimized and the worst condition previously obtained with MB removal as response. The inactivation efficiencies in the optimum conditions were about 99%, allowing an efficient disinfection as well as the production of an effluent with quality to be reused according to specific legislations, while at the worse conditions, the inactivation did not reach standards for reuse.

A new spectrophotometric method for determination of EDTA in water using its complex with Mn(III).

EDTA is an important ligand used in many industrial products as well as in agriculture, where it is employed to assist in phytoextraction procedures and the absorption of nutrients by plants. Due to its intensive use and recalcitrance, it is now considered an emerging pollutant in water, so there is great interest in techniques suitable for its monitoring. This work proposes a method based on formation of the Mn(III)-EDTA complex after oxidation of the Mn(II)-EDTA complex by PbO2 immobilized on cyanoacrylate spheres. A design of experiments (DOE) based on the Doehlert matrix was used to determine the optimum conditions of the method, and the influence of the variables was evaluated using a multiple linear regression (MLR) model. The optimized method presented a linear response in the range from 0.77 to 100.0µmolL(-1), with analytical sensitivity of 7.7×10(3)Lmol(-1), a coefficient of determination of 0.999, and a limit of detection of 0.23µmolL(-1). The method was applied using samples fortified at different concentration levels, and the recoveries achieved were between 97.0 and 104.9%.

Doehlert design-desirability function multi-criteria optimal separation of 17 phenolic compounds from extra-virgin olive oil by capillary zone electrophoresis.

In Brazil, the consumption of extra-virgin olive oil (EVOO) is increasing annually, but there are no experimental studies concerning the phenolic compound contents of commercial EVOO. The aim of this work was to optimise the separation of 17 phenolic compounds already detected in EVOO. A Doehlert matrix experimental design was used, evaluating the effects of pH and electrolyte concentration. Resolution, runtime and migration time relative standard deviation values were evaluated. Derringer's desirability function was used to simultaneously optimise all 37 responses. The 17 peaks were separated in 19min using a fused-silica capillary (50µm internal diameter, 72cm of effective length) with an extended light path and 101.3mmolL(-1) of boric acid electrolyte (pH 9.15, 30kV). The method was validated and applied to 15 EVOO samples found in Brazilian supermarkets.