Nito Angelo Debacher

The development of functional textiles offers wide-ranging applications, with nanoencapsulation of essential oils emerging as a promising strategy for antimicrobial purposes. This study focused on biodegradable nanoparticles loaded with citronella essential oil (CEO), deposited on cotton textiles using three methods, with or without non-thermal plasma (NTP) treatment. The immersion method achieved the highest CEO content per textile area (5.9 µL cm -2). XPS and FT-IR analyses revealed that NTP treatment enhanced the hydrophilic functional groups through oxidation, as confirmed by contact angle assays and textile mass loss. Despite these changes, NTP treatment did not significantly alter the in vitro release profile of the CEO. Non-treated NTP samples were tested against S. aureus and P. aeruginosa, showing a stronger antibacterial effect against gram-positive S. aureus. These findings highlight the potential of these materials for use as functional antibacterial textiles with promising applications in health and hygiene products.

The desulfurization of carbons modified with SO₂ was studied as a dispersion in boiling cyclohexane (81°C) using activated carbon (mAC) and graphene oxide (mGO), modified by SO₂. The steady‐state species in the carbon matrix after the catalytic reduction of SO₂ was considered a trisulfane. For mAC, there was a burst of a sulfur species identified as S₂ by UV spectrum with a maximum at 217 nm (ε_M at 217 nm = 2.56 × 10³) that showed a second‐order decay of absorbance with = 47.29 M^‐1·sec^‐1 ( = 18.1 kcal·mol^‐1). The product was postulated to be S₄. No other consecutive reaction was observed because of the possible adsorption of S₄ in the carbon matrix. The desulfurization of mGO was shown by XPS and the kinetics were a second‐order decay up to 16 min ( 18.41 M^‐1·sec^‐1; = 18.8 kcal·mol^‐1) followed by a second‐order increase of absorbance with = 3.84 M^‐1·sec^‐1 ( = 19.9), where the product showed a double maximum at 260‐285 nm typical of S₈. These results are consistent with a mechanism of consecutive thermodynamically favorable dimerizations of S₂ and S₄ and with the desulfurization mechanism that has been previously postulated.

Petroleum reserves available worldwide are geologically based mainly on sedimentary and carbonate rocks, and the reservoir performance depends on the intrinsic properties of each rock and their response to changes in wettability. Recently, the change in wettability with low-salinity brine has been used to improve the oil recovery, which is an environmentally friendly and low investment, but there is no unanimity about the mechanisms of oil recovery process. Therefore, the aim of this study is to investigate the process involved in the wettability associated with interactions between the surface of powdered reservoir rock samples and the surrounding fluids. The reservoir rock surface (sandstone, calcite and dolomite) was evaluated under three different conditions. The total amount of adsorbed oil on aged samples was twice as high in carbonate rocks as in sandstone. The thermal gravimetric analysis (TGA) for the desorption steps of the organic fraction on dolomite and calcite indicates that the treatment under high brine concentration favored the oil desorption and the opposite result was observed for sandstone. This behavior suggests that carbonate rocks adsorb more strongly the organic phase compared to sandstone.

Tetracyclines comprise a large group of broad-spectrum antibiotics used in human and veterinary medicine. Its mechanism of action, via oral ingestion, is to inhibit bacterial protein synthesis, but a large amount (70%) is eliminated without being metabolized, which presents a risk for the arising of antibiotic-resistant species. In this study, the degradation of Tetracycline TC by non-thermal plasma NTP and the antimicrobial sensitivity of the treated solution are investigated. The degradation was followed by chromatographic analysis while the efficiency of NTP in inhibiting the action of TC on bacteria was evaluated by antimicrobial sensitivity test by disk diffusion method. The results showed a high rate of TC degradation, over 90%, in 10 min of NTP treatment for a 60 mL (107 mg L-1) sample and very slow increase up to 94% in 30 min. The antimicrobial sensitivity test of TC after degradation by NTP showed no antibiotic activity. Therefore, our findings are encouraging, since the removal efficiency is below the minimum threshold require, to prevent with high probability, outgrowth of antibiotic-resistant bacteria. In addition, the results confirm that the NTP treated solution is safe to the environment.

The kinetics of the ozonation of graphite with different particle sizes (106 μm, G106; 6.20 μm, G6.2) was studied at several temperatures under a flow of O3 diluted in O2. The reaction was first-order with respect to graphite and to the consumption of ozone. XPS spectrum showed that the reactions occurring in the solid under steady-state conditions maintain the original stoichiometry, as predicted by the postulated mechanism for SO2. The deoxygenation reaction occurred along with the ozonation reaction at 100 oC. The rate of oxygen elimination in the flow system has the same rate determining kinetic barrier as ozone insertion. Ozonation and deoxygenation reactions are sequentially related. The ozonation occurs with the insertion of O3 forming a 1,2,3-trioxolane followed by an oxygen transfer that produces a peroxide valence tautomer in equilibrium with a 1,3-dicarbonyl, [peroxide↔dicarbonyl], and an oxirene that eliminates atomic oxygen. The decarboxylation reaction was studied at 600 oC from the ozonated G106 (ΔG≠ = 83.60±0.08 kcal·mol-1). Total decarboxylation at 600 oC, matched the number of moles of CO2 removed and the oxygen content after ozonation, showing that the reduction of ozone on graphite was essentially a clean reduction with no secondary oxidations. When ozonized graphite was heated to 600 oC, only [peroxide↔dicarbonyl] species remained in the matrix. The peroxide tautomer isomerized to dioxirane and eliminated CO2 as a dioxicarbene. Total deoxygenation of decarboxylated graphite G106 was obtained by pyrolysis. There was a residual oxygen that arise from the atomic oxygen eliminated from the oxirene, intercalated in graphite layers and forming basal epoxy groups. Also incoming O atoms reacted with the intercalated O atoms to produce O2 molecules. Thermal annealing de-intercalated molecular oxygen (600-900 oC).