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Alicyclobacillus spp. is a potential spoiling agent of acidic products and citrus drinks, leading to sensory alterations in contaminated products and consequent economic losses. Treatments such as pasteurization eliminate vegetative cells, but also create a favorable atmosphere for spore germination. To guarantee quality and safety, the application of natural substances as bioconservatives is a considerable and promising alternative for the food industry. This study evaluated the effect of hexane extract of Matricaria chamomilla L. (HE), Nisin (N) and their combination (HE + N). These compounds are present in some studies describing their antibacterial action, but no studies were found on the association of these compounds against the species Alicyclobacillus spp. This study aimed to analyze the antioxidant activity (AA) for the DPPH• (0,23 µmol Trolox/mg) and ABTS (27.93 µmol Trolox/mg), the Checkboard test revealed synergism between HE and N with a fractional inhibitory index (FIC) of 0.068., and to study the antibacterial and sporicidal effect. The antibacterial and sporicidal activity was satisfactory against Alicyclobacillus acidoterrestris with MIC and MBC of 1.95 µg/mL and MSC of 7.81 µg/mL in analyzes using HE + N. The application in orange juice proved to be effective, with an MBC of 0.007 µg/mL. The MIC results served as a parameter for other tests carried out in this study, such as flow cytometry and Scanning Electron Microscopy (SEM), and for the evaluation of sensory characteristics with Electronic Nose (E-nose).

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This paper explores the feasibility of functionalizing mango stones with iron oxide magnetic nanoparticles (MS-Fe3O4) by coprecipitation in batch adsorption processes. The synthesized material was characterized and applied in chloroquine (CQN) and sertraline hydrochloride (SER) removal from contaminated waters. The biosorbent was subjected to a regenerative study and treatment using a synthetic mixture of contaminants to evaluate its applicability in real effluents. The biosorbent was analyzed by transmission electron microscopy images, scanning electron microscopy, dispersive X-ray spectroscopy, Fourier transform infrared spectra, and zeta potential to characterize its chemical and morphology properties. The techniques applied showed the effectiveness of the proposed modification. In the adsorption experiments, the optimal adsorbent dosage was 0.01 g for both contaminants. The pH strongly influenced the adsorption of the drugs on MS-Fe3O4, and the best results were obtained in the pH range of 5-6. Kinetic data showed a better fit to the pseudo-second-order model, and the equilibrium time was achieved in 16 h for CQN and 4 h for SER. Isotherm studies revealed maximum adsorptive capacities of 49.42 and 64.79 mg g-1, respectively, for CQN and SER, at 318 K, demonstrating that the increase in temperature is a favorable factor, and the Sips model better describes the process. The thermodynamic parameters indicate an endothermic (ΔH° >0), spontaneous (ΔG° <0), and reversible (ΔS° >0) nature of the adsorption. This process is essentially governed by physical forces, such as hydrogen and π-π bonds. However, it is also valid to consider the presence of electrostatic forces due to the ionizing nature of CQN and SER. The MS-Fe3O4 biosorbent showed good performance when evaluated in a synthetic mixture of four contaminants, with an overall removal efficiency of approximately 86% and the regenerative capacity of three reusing cycles.

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The presence of micropollutants, such as caffeine (CAF), has been detected throughout the world, since conventional treatment plants are not able to properly degrade them. CAF is a widely consumed stimulant, and has been demanding the development of efficient methodologies for its removal. Aiming at the agriculture waste valorization, a new hydrochar was developed based on chemical and thermal modification of peach stones (mod-PS) for CAF removal from water and from a synthetic mixture. The morphology, functional groups and surface electrical charge of the adsorbent were characterized by SEM, FTIR and zeta potential, respectively. Regarding CAF adsorption performance, the equilibrium time was reached at 480 min and the pseudo-second-order model presented the best fit for the experimental data. The maximum adsorption capacity was 68.39 mg g-1 (298 K) and the Langmuir model exhibited a better fit for the isothermal data. The thermodynamic properties confirmed that the process was exothermic, spontaneous and reversible. The main adsorption mechanisms were hydrogen bonds and π-interactions. The global removal efficiency was satisfactory in the synthetic mixture simulating real wastewater (67%). Therefore, the proposed new hydrochar has potential application as a low-cost adsorbent for CAF removal.

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ABSTRACTThe combined approach of specific surface area (SSA), porosity, microprobe analysis (EMPA), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with EDX and infrared spectroscopy (FTIR) provided the mica mineral physico-chemical and morphological characterisation. The electrostatic surface properties were assessed through the determination of the Point of Zero Charge (pHPZC) by the drift method and the electrokinetic mica mineral features represented by the Isoelectric Point (pHIEP) which was carried out through zeta potential measurements. Adsorption tests were performed to correlate the surface charge behaviour of the mica mineral and its influence on the adsorption efficiency of two different dyes, namely: Safranin Orange (SO), as a cationic dye and Reactive Black 5 (RB5), as an anionic dye. The higher adsorption capacity SO dye was observed at pH 9 and achieved almost 83% of removal, while RB5 dye adsorption on mica surface had the highest result, about 45% of removal efficiency, on pH of 3. In both cases, the main mechanism identified that drove this results is the electrostatic force of attraction between the adsorbent edge surface charge (pH-dependent) and the ionic nature (anionic or cationic) of the pollutant dyes particles. The preliminary adsorption experiments demonstrated that the raw grounded mica mineral has a greater potential associated with its application on cationic dye removal in wastewater. The present study aimed to detail the main characteristics of the mica mineral in order to evaluate the potential use of such mineral residues in the removal efficiency of contaminated wastewater.

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