Enhanced degradation of Direct Red 80 dye via Fenton-like process mediated by cobalt ferrite: generated superoxide radicals and singlet oxygen.

Azo dyes, widely used in the textile industry, contribute to effluents with significant organic content. Therefore, the aim of this work was to synthesize cobalt ferrite (CoFe2O4) using the combustion method and assess its efficacy in degrading the azo dye Direct Red 80 (DR80). TEM showed a spherical structure with an average size of 33 ± 12 nm. Selected area electron diffraction and XRD confirmed the presence of characteristic crystalline planes specific to CoFe2O4. The amount of Co and Fe metals were determined by ICP-OES, indicating an n(Fe)/n(Co) ratio of 2.02. FTIR exhibited distinct bands corresponding to Co-O (455 cm-1) and Fe-O (523 cm-1) bonds. Raman spectroscopy detected peaks associated with octahedral and tetrahedral sites. For the first time, the material was applied to degrade DR80 in an aqueous system, with the addition of persulfate. Consistently, within 60 min, these trials achieved nearly 100% removal of DR80, even after the material had undergone five cycles of reuse. The pseudo-second-order model was found to be the most fitting model for the experimental data (k2 = 0.07007 L mg-1 min-1). The results strongly suggest that degradation primarily occurred via superoxide radicals and singlet oxygen. Furthermore, the presence of UV light considerably accelerated the degradation process (k2 = 1.54093 L mg-1 min-1). The material was applied in a synthetic effluent containing various ions, and its performance consistently approached 100% in the photo-Fenton system. Finally, two degradation byproducts were identified through HPLC-MS/MS analysis.

Electrochemically reduced graphene oxide films from Zn-C battery waste for the electrochemical determination of paracetamol and hydroquinone.

Contributing to the development of sustainable electroanalytical chemistry, electrochemically reduced graphene oxide (ERGO) films obtained from residual graphite of discharged Zn-C batteries are proposed in this work. Graphite from the cathode of discarded Zn-C batteries was recovered and used in the synthesis of graphene oxide (GO) by the modified Hummer's method. The quality of the synthesized GO was verified using different characterization methods (FT-IR, XRD, SEM, and TEM). GO films were deposited on a glassy carbon electrode (GCE) by the drop coating method and then electrochemically reduced by cathodic potential scanning using cyclic voltammetry. The electrochemical features of the ERGO films were investigated using the ferricyanide redox probe, as well as paracetamol (PAR) and hydroquinone (HQ) molecules as model analytes. From the cyclic voltammetry assays, enhanced heterogeneous electron transfer rate constants (k0) were observed for all redox systems studied. In analytical terms, the ERGO-based electrode showed higher analytical sensitivity than the bare and GO-modified GCE. Using differential pulse voltammetry, wide linear response ranges and limits of detection of 0.14 µmol L-1 and 0.65 µmol L-1 were achieved for PAR and HQ, respectively. Furthermore, the proposed sensor was successfully applied to the determination of PAR and HQ in synthetic urine and tap water samples (recoveries close to 100%). The outstanding electrochemical and analytical properties of the proposed ERGO films are added to the very low cost of the raw material, being presented as a green-based alternative for the development of electrochemical (bio)sensors with unsophisticated resources.

Development of inclusion complexes of 2-hydroxypropyl-ß-cyclodextrin with Psidium guajava L. essential oil by freeze-drying and kneading methods for application as Aedes aegypti L. larvicide.

Inclusion complexes (ICs) of 2-hydroxypropyl-ß-cyclodextrin with the essential oil (EO) from Seculo XXI cultivar of Psidium guajava were prepared using kneading (KN) and freeze-drying (FD) methods. The resulting ICs clusters have a nanometric size, with a diameter of approximately 80 and 40 nm for KN and FD, respectively. Complexation efficiency was 80.3% and 50.8% for KN and FD methods, respectively. The larvicidal activity of the EO in DMSO on A. aegypti had LC50 and LC90 values of 51.49 and 64.51 µg mL-1, respectively. For the KN method, the toxicity corresponded to 77.54 and 107.29 µg mL-1 for LC50 and LC90, respectively. FD method demonstrated toxicity at concentrations above 600 µg mL-1. Thus, ICs enable the use of EO in breeding sites for A. aegypti, thus being potential products to be commercially exploited.

Physiological quality of bean seeds after application of desiccant herbicides / Qualidade fisiológica de sementes de feijão após aplicação de herbicidas dessecantes

ABSTRACT: The application of desiccant herbicides in the bean crop is fundamental in the production of quality seeds, since it anticipates the harvesting season, which makes it possible to obtain seeds in the period of physiological maturation, when they are reported with maximum accumulation of dry matter, high vigor levels and germination percentage. However, there is little information about the ideal application time of these products to obtain beans of high physiological quality. Therefore, the objective of this study was to evaluate the physiological quality of bean seeds after application of desiccant herbicides at different times in preharvest. The experimental design was a randomized complete block design in a 2x3+1 factorial scheme, with four replications. Desiccant herbicides paraquat (400g ha-1) and paraquat + diuron (200 + 400g ha-1) were applied in three phenological stages (R8, R8/R9 and R9), plus one control (without herbicide application). Yield (Kg ha-1), mass of one thousand seeds (g), germination (%) and seed vigor were evaluated through tests of accelerated aging, electrical conductivity and primary root length. Application of paraquat molecule at the R8 stage and the paraquat + diuron mixture at the R8/R9 stage reduced the viability and vigor of the bean seeds, and compromised yield. Applications of the paraquat herbicide at the R8/R9 and R9 stages or of the mixture (paraquat + diuron) at the R9 stage preserved the physiological quality of the seeds without;however, affecting yield.

RESUMO: A aplicação de herbicidas dessecantes na cultura do feijoeiro é fundamental na produção de sementes de qualidade porque antecipa a época de colheita, o que possibilita a obtenção de sementes no período de maturação fisiológica, quando se encontram com máximo acúmulo de matéria seca, elevados níveis de vigor e alta porcentagem de germinação. Todavia, são escassas as informações acerca da época ideal de aplicação desses produtos na obtenção de sementes de feijão de alta qualidade fisiológica. Por essa razão, objetivou-se avaliar a qualidade fisiológica de sementes de feijão após aplicações de herbicidas dessecantes em diferentes épocas na pré-colheita. O delineamento experimental utilizado foi o de blocos casualizados dispostos em esquema fatorial 2x3+1, com quatro repetições. A aplicação dos herbicidas dessecantes paraquat (400g ha-1) e paraquat + diuron (200+400g ha-1) foi realizada em três estádios fenológicos (R8, R8/R9 e R9), mais uma testemunha (sem aplicação do herbicida). Avaliou-se a produtividade (Kg ha-1), a massa de mil sementes (g), a germinação (%) e o vigor das sementes por meio dos testes de envelhecimento acelerado, condutividade elétrica e comprimento da raiz primária. A aplicação da molécula de paraquat no estádio R8 e da mistura paraquat + diuron no estágio R8/R9 reduziu a viabilidade e o vigor das sementes de feijão, além disso comprometeu a produtividade. Aplicações dos herbicidas paraquat nos estádios R8/R9 e R9 ou da mistura (paraquat + diuron) no estádio R9 preservaram a qualidade fisiológica das sementes, sem, entretanto, afetar a produtividade.

A digital image method of spot tests for determination of copper in sugar cane spirits.

In this work the development and validation of analytical methodology for determination of copper in sugarcane spirit samples is carried out. The digital image based (DIB) method was applied along with spot test from the colorimetric reaction employing the RGB color model. For the determination of copper concentration, it was used the cuprizone - a bidentate organic reagent - which forms with copper a blue chelate in an alkaline medium. A linear calibration curve over the concentration range from 0.75 to 5.00mgL-1 (r2=0.9988) was obtained and limits of detection and quantification of 0.078mgL-1 and 0.26mgL-1 were acquired, respectively. For the accuracy studies, recovery percentages ranged from 98 to 104% were obtained. The comparison of cooper concentration results in sugar cane spirits using the DIB method and Flame Atomic Absorption Spectrometry as reference method showed no significant differences between both methods, which were performed using the paired t-test in 95% of confidence level. Thus, the spot test method associated with DIB allows the use of devices as digital cameras and smartphones to evaluate colorimetric reaction with low waste generation, practicality, quickness, accuracy, precision, high portability and low-cost.