First Minutes Of Contact Research Articles

Anise essential oil immobilized in chitosan microparticles: a novel bactericidal material for food protection.

Foodborne infections in humans are one of the major concerns of the food industries, especially for minimally processed foods (MPF). Thereby, the packaging industry applies free chlorine in the sanitization process, ensuring the elimination of any fecal coliforms or pathogenic microorganisms. However, free chlorine's propensity to react with organic matter, forming toxic compounds such as trihalomethanes and haloacetic acid. Therefore, the present work aimed to synthesize a novel organic biomaterial as an alternative to free chlorine. Chitosan microparticles were produced, with Pimpinella anisum (anise) essential oil immobilized in the biopolymer matrix (MPsQTO). The characterization of this biomaterial was done through GC-MS/MS, FT-IR, and SEM. Antimicrobial assays proved that the MPsQTO presented antibacterial activity for Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, and Bacillus subtilis at 300 µL mL-1 of concentration. The fluorescence microscope also showed the MPsQTO targets the cytoplasmatic membrane, which is responsible for cell death in the first minutes of contact. Studies with the mutant B. subtilis (amy::pspac-ftsZ-gfpmut1) and the Saccharomyces cerevisiae D7 also proved that the biomaterial did not affect the genetic material and did not have any mutagenic/carcinogenic effect on the cells. The sanitization assays with pumpkin MPF proved that the MPsQTO is more effective than free chlorine, increasing the shelf-life of the MPF. Consequently, the novel biomaterial proposed in this work is a promising alternative to traditional chemical sanitizers.

Bifunctional peptides as alternatives to copper-based formulations to control citrus canker

Citrus canker is an infectious bacterial disease and one of the major threats to the orange juice industry, a multibillion-dollar market that generates hundreds of thousands of jobs worldwide. This disease is caused by the Gram-negative bacterium Xanthomonas citri subsp. citri. In Brazil, the largest producer and exporter of concentrate orange juice, the control of citrus canker is exerted by integrated management practices, in which cupric solutions are intensively used in the orchards to refrain bacterial spreading. Copper ions accumulate and are as heavy metals toxic to the environment. Therefore, the aim of the present work was to evaluate bifunctional fusion proteins (BiFuProts) as novel and bio-/peptide-based alternatives to copper formulations to control citrus canker. BiFuProts are composed of an anchor peptide able to bind to citrus leaves, and an antimicrobial “killer” peptide to protect against bacterial infections of plants. The selected BiFuProt (Mel-CgDEF) was bactericidal against X. citri at 125 μg mL−1, targeting the bacterial cytoplasmic membrane within the first minutes of contact. The results in the greenhouse assays proved that Mel-CgDEF at 250 μg mL−1 provided protection against X. citri infection on the leaves, significantly reducing the number of lesions by area when compared with the controls. Overall, the present work showed that the BiFuProt Mel-CgDEF is a biobased and biodegradable possible alternative for substitute cupric formulations.Key points• The bifunctional fusion protein Mel-CgDEF was effective against Xanthomonas citri.• Mel-CgDEF action mechanism was the disruption of the cytoplasmic membrane.• Mel-CgDEF protected citrus leaves against citrus canker disease.

Environmentally safe sorbent from ash-and-slag waste of heat power engineering

Objectives. To determine the physical and chemical properties (bulk density, ash content, total pore volume, abrasion, humidity, sorption capacity) of sorbent based on ash-and-slag waste from heat power engineering, calcined and modified with a Tiprom K organosilicon water repellent.Methods. The physicochemical properties of the modified sorbent were determined using an experimental method according to the methods of regulatory documents on equipment verified and certified in the prescribed manner.Results. Ash and slag taken from the ash dump of the Novocherkasskaya GRES power station were dried, then calcined at a temperature of 600 °C for 30 min and modified with a Silor hydrophobizing silicon-containing liquid (HSL). The modifier/ash ratios (by weight) were 1:20, 1:10, 1:5, 1:3, and 1:2. The optimal ratio was 1:5 at a sorption capacity with respect to hexane of 0.86 g/g. The modification temperature was optimized in the temperature range of 110–200 °C. The optimal approach it to dry samples at 160 °C to constant weight. At a temperature of 200 °C, sintering of the material was observed. The analysis of HSL modifiers was carried out in terms of the price/sorption properties ratio. The following were considered as HSL: Silor, HSL-11BSP, HSL 136-157M, PROFILUX, Tiprom K, Tiprom U. The optimal modifier Tiprom K was selected. The physicochemical properties of the modified sorbent obtained at a ratio of 1:5 (by weight) and dried at 160 °C were experimentally determined. The sorption properties were studied on the water surface with respect to various oil products: fuel oil, kerosene, AI-92 gasoline, nefras, oil sludge, and n-hexane. The smallest sorption capacity was obtained with respect to n-hexane, amounting to 0.86 g/g. During the experiment, it was found that half of the sorption capacity was filled with oil in the first minutes of contact. Complete sorption time was 30–40 min for relatively light hydrocarbons (n-hexane, AI-92 gasoline, kerosene, nefras), 40–60 min for oil sludge, and more than 60 min for fuel oil. Experiments established that the sorption process does not depend on the matrix (salinity) of water. A visual assessment of the color intensity of the residual spot of oil sludge allowed a conclusion to be made about a significant content of oil products in the case of sorption of oil sludge by quartz sand based on the residual yellow layer of oil sludge. In the case of sorption of oil sludge by calcined and modified sorbents, the residual oil products were insignificant. A comparative analysis of data on the effectiveness of the developed sorbent and currently available analogues based on sludge and slag is presented.Conclusions. The next physicochemical properties of the sorbent modified with HSL Tiprom K were determined: bulk density was 0.621 g/mL, ash content was 97.1%, total pore volume by water was less than 0.05 mL/g, attrition was 8.8%, humidity was less than 0.5%; sorption capacity, in g/g: for n-hexane, 0.86; for AI-92 gasoline, 0.89; for nefras, 0.93; for kerosene, 0.99; for oil sludge, 1.18; for fuel oil, 1.46. The efficiency of cleaning a solid surface from oil sludge with a calcined sorbent was 97%, and with a modified sorbent 95%. The modified sorbent has high buoyancy when saturated with oil products and the ability to retain them for a long time.

Antibacterial activity of CuO-Ag Janus like nanoparticles against recombinant strain Escherichia coli.

The toxic action of CuO-Ag Janus particles and a bicomponent mixture of CuO and Ag particles have been studied against a recombinant strain Escherichia coli K12 TG1 with cloned luxCDABE genes of marine bacteria Photobacterium leiognathi 54D10. An original method was used for the preparation CuO-AgJanus like nanoparticles by simultaneous electrical explosion of twisted Cu and Ag wires in a mixture of argon and oxygen gases. The bioluminescence inhibition on recombinant strain E. coli shows that CuO-Ag Janus NPs were effective. The concentration by 50% (EC50) for CuO-Ag Janus NPs was 0.03 ± 0.001mg/ml (p < 0.05). The bioactivity of the bicomponent mixture of CuO and Ag NPs (EC50) was 0.25 ± 0.002mg/ml (p < 0.05). The effective concentration of CuO-Ag Janus NPs against E. coli was comparatively lower than those of bicomponent mixture CuO and Ag against which explains the higher activity of CuO-Ag Janus NPs. The toxicity values of CuO and Ag as monocomponent nanoparticles were 2-32 times lower compared with the bicomponent nanoparticles. A dose-dependent inhibition of bacterial luminescence developed over time was noted. The result of contact E. coli with CuO-Ag Janus particles was 100% suppression of bacterial luminescence from the first minutes of contact occured starting with a content of 2.0mg/ml and within the next 180min. The effect of bioactivity prolonged in the final concentration of nanopowder (EC100 = 0.0625 ± 0.002mg/ml) (p < 0.05). CuO-Ag Janus particles exhibited more pronounced antibacterial activity compared to CuO, Ag nanoparticles and their mechanical mixture.

The effect of using illustrated materials for communication on the anxiety and comfort of cardiac surgery patients receiving mechanical ventilator support: A randomized controlled trial

BackgroundUsing illustrated communication materials with patients receiving mechanical ventilation support increases patient satisfaction and reduces communication difficulties. However, there are no randomized controlled clinical studies showing the effect of the use of these materials on patient care outcomes. ObjectiveTo determine the effect of using illustrated communication materials on the anxiety and comfort levels of patients receiving mechanical ventilation support. MethodsIn this controlled clinical trial, patients were randomly assigned to either the intervention group that used illustrated communication materials or the control group that used routine communication methods. In the first minute of contact with patients in the intensive care unit, then at 30 min and 60 min, patients’ numerical pain-rating scale scores, hemodynamic values, and face-anxiety scale scores were recorded. Satisfaction with communication and perianesthesia comfort scale scores were obtained the day after operation. ResultsAfter 30 min of communication, the percentage of face-anxiety points difference decreased in the intervention group (-14.16) compared to the control group (-6.11), and the difference was statistically significant (p < 0.05). In terms of perceived comfort during postoperative mechanical ventilation, the mean score of the patients in the intervention group (106.10) was higher than the control group (88.53), and the difference was statistically significant (p < 0.05). Furthermore, 90% of the patients in the intervention group and 30% of the patients in the control group were satisfied with the communication method used, and the difference between the groups was statistically significant. ConclusionUsing illustrated communication materials reduces anxiety and increases patient satisfaction and comfort levels. In communicating with intubated patients, the use of illustrated communication materials is recommended.

EFFICIENCY OF PLANTING CALCIUM IONS FROM DILUTE AQUEOUS SOLUTIONS IN THE FORM OF PHOSPHATES

The specifics of calcium phosphate formation process during diluted aqueous solutions softening for home or office were researched. Studies have shown that, unlike calcium carbonate, effective precipitation of calcium ions with phosphate is possible even at doses less than stoichiometric. The ratio between concentrations of phosphate ions and calcium ions K = [PO43-, mg-eq] / [Ca2+, mg-eq] is a determining factor. Already at K = 0.5 there is a decrease in the content of calcium ions by more than half. In stoichiometry (K = 1), the residual concentrations of calcium ions in the treated water fall below 1 mg-eq/dm3. At K &gt; 1.5, the content of calcium ions in the treated water stabilizes at the level of 0.2 – 0.1 mg-eq/dm3. Water temperature does not significantly affect the deposition of calcium ions with phosphates. A noticeable decrease in efficiency is recorded only at a temperature of 5 ° C. But even in this case, this decrease is 0.1 – 1.5 mg-eq/dm3, which is quite acceptable for living conditions, since it provides soft and very soft water. The reaction between calcium ions and phosphates is quite complete in the first minutes of contact. The settling of mixed solutions for an hour showed that the reaction of the formation of a solid phase takes place at the time of draining the solutions and over time the residual hardness of the water practically does not change. From the point of view of softening efficiency, phosphate is quite suitable as a reagent for removing calcium ions from hard natural waters. An important aspect of the softening technology is the separation of the precipitate formed from the treated water. To do this, it is necessary to determine the conditions for the formation of a crystalline, most compact and formed precipitate. The clarification of the hard water sample treated with sodium phosphate showed that there was no significant difference in deposition at different initial pH values.

SORPTION OF CADMIUM, LEAD, AND CHROMIUM (VI) BY CELLULOSIC COMPLEXES OF ARCTIC BROWN ALGAE

The purpose of this work is to establish the mechanism of sorption of heavy metal ions (Cd, Pb, and Cr (VI)) by cellulose complexes (CC) of the arctic brown algae Laminaria digitata and Saccharina latissima. These complexes are fibrous mesoporous materials with active sorption centers -COOH, -OH, and -NH2 and a developed surface, which makes them potentially effective preparations for the enterosorption removal of heavy metal ions. The kinetics and thermodynamics of sorption have been studied as well as the influence of the acidity on the sorption capacity. It has been established that the sorption rate is highest during the first minutes of contact between the two phases; the sorption equilibrium is reached by 60 min. According to the sorption enthalpy values, temperature has a positive effect on sorption (endothermic process), with a maximum sorption capacity at 37 °C. Optimal pH of the medium: 5-6 for cadmium and lead, and 2 for chromium (VI), which indicates the possibility of using this material in a wide range of medium acidity, corresponding to the conditions of the human gastrointestinal tract. The results obtained indicate a high prospect of using CC as an effective enterosorbent for health preservation.

Evaluation of calcium hydroxide, calcium hypochlorite, peracetic acid, and potassium bicarbonate as citrus fruit sanitizers.

Xanthomonas citri (X. citri) is a quarentenary plant pathogen and the causal agent of the citrus canker. X. citri forms biofilms and remains fixed on the surface of plant tissues, especially on leaves and fruits. Considering this, all the citrus fruits have to be sanitized before they can be commercialized. NaOCl is the main sanitizer used to decontaminate fruits in the world. Due to its toxicity, treatment with NaOCl is no longer accepted by some Europe Union countries. Therefore, the aim of this work was to evaluate potassium bicarbonate (KHCO3), calcium hydroxide (Ca(OH)2), calcium hypochlorite (Ca(OCl)2) and peracetic acid (CH3CO3H) as alternatives to NaOCl for the sanitization of citrus fruit. By monitoring cell respiration and bacterial growth, we determined that peracetic acid and calcium hypochlorite exhibit bactericidal action against X. citri. Time-response growth curves and membrane integrity analyses showed that peracetic acid and calcium hypochlorite target the bacterial cytoplasmatic membrane, which is probably responsible for cell death in the first minutes of contact. The simulation of the sanitization process of citrus fruit in packinghouses showed that only peracetic acid exhibited a performance comparable to NaOCl. Among the tested compounds, peracetic acid constitutes an efficient and safer alternative to NaOCl.

Early-Stage Dissolution Kinetics of Silicate-Based Bioactive Glass under Dynamic Conditions: Critical Evaluation.

This manuscript presents a systematic and detailed study of ion release from 45S5 bioactive glass to develop a methodology to directly monitor dissolved ions in a simulated fluid via inductively coupled plasma optical emission spectrometry (ICP OES). For the kinetic study, two dynamic tests, an inline ICP test and a flow-through test, are performed with the same flow rate, temperature, pH, ionic strength of the solution, and sample surface to leaching solution volume ratio. The flow-through test allows for the measurement of an initial dissolution rate, as well the maximum amount of any species released from the surface of the glass. In addition, the data from the inline ICP test are obtained by immediate and direct monitoring of ions from the first minutes of contact of the glass with aqueous fluids with pH values of 4 and 7.4. The overall dissolution rates of the tested commercial bioactive glass in simulated body fluid (SBF) (pH 7.4) were significantly lower compared to the initial rate acquired. The methodology developed in this study can be applied to monitor the controlled release of ions with additional therapeutic functionalities, where the amount of ions released in the first minutes can be critical for the resulting biological performance.

Mechanistic insights into fast adsorption of perfluoroalkyl substances on carbonate-layered double hydroxides

Layered double hydroxide (LDH) with the metal composition of Cu(II)Mg(II)Fe(III) was prepared as an adsorbent for fast adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA). 84% of PFOS and 48% of PFOA in relation to the equilibrium state were adsorbed in the first minutes of contact with 0.1 g/L of suspended µm-sized LDH particles. The adsorption mechanisms of PFOS and PFOA on the CuMgFe-LDH were interpreted. Hydrophobic interactions were primarily responsible for the adsorption of these compounds in accordance with the different adsorption affinities of long-chain (C8, Kd = 105 L/kg) and short-chain (C4, Kd = 102 L/kg) perfluorinated carboxylic acids. PFOA adsorption on CuMgFe-LDH was strongly suppressed under alkaline conditions while PFOS uptake was only slightly affected in the pH range from 4.3 to 10.7, indicating a significant role of electrostatic interactions for PFOA adsorption. The adsorption of PFOS and PFOA was rather insensitive to competition by monovalent anions. The previously reported ‘memory effect’ of calcined CuMgFe-LDH for sorption of organic anions was not confirmed in the present study. Spent CuMgFe-LDH could be easily regenerated by extraction with 50 vol% methanol in water within 1 h and maintained a high PFOS removal in subsequent usage cycles.

Transformation Kinetics of Burnt Lime in Freshwater and Sea Water.

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it “slaked” as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8.

Energetic properties of peat saturated with petroleum products

This paper presents a method of sorption using peat for elimination of emergency spills of crude oil and petroleum products and the possibility of energy use of oil-saturated peat. The results of assessment of the sorbent capacity of peat are presented, with waste motor oil and diesel fuel chosen as petroleum products. Natural peat has been found to possess sorption properties in relation to petroleum products. The sorbent capacity of peat can be observed from the first minutes of contact with motor oil and diesel fuel, and significantly depends on their viscosity. For the evaluation of thermal properties of peat saturated with petroleum products, experimental studies have been conducted on determination of moisture and ash content of as-fired fuel. It is shown that adsorbed oil increases the moisture and ash content of peat in comparison with the initial sample. Therefore, when intended for energy use, peat saturated with petroleum products is to be subjected to additional drying. Simulation of net calorific value has been performed based on the calorific values of peat and petroleum products with different ratios of petroleum product content in peat and for a saturated peat sample. The obtained results are compared with those of experiments conducted in a calorimetric bomb and recalculated for net calorific value. A satisfactory discrepancy is obtained, which amounts to about 12%. Options have been considered providing for combustion of saturated peat as fuel (burnt per se and combined with a solid fuel) and processing it to produce liquid, gaseous and solid fuels. Peat can be used to solve environmental problems of elimination of emergency spills of crude oil and petroleum products and as an additional resource in solving the problem of finding affordable energy.

Rapid and sensitive extraction of aflatoxins by Fe3O4/zeolite nanocomposite adsorbent in rice samples

In this study, a magnetic nanocomposite was synthesized using a simple and efficient method, and its performance was evaluated through magnetic dispersive solid-phase extraction (MDSPE) of aflatoxins (AFs) in rice samples. The aqueous extract of Centaurea cyanus was used as a stabilizer and reducing agent in the synthesis of Fe3O4/zeolite nanocomposite. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FT-IR), zeta potential, Brunauer–Emmett–Teller (BET), and vibrating sample magnetometer (VSM) were used to characterize the morphology of the adsorbent. The effects of nanocomposite dosage, vortex time, ionic strength, sample volume, and desorption conditions on the extraction efficiency of AFs were studied. The proposed nanocomposite showed excellent binding properties to AFs in the range of 2–10 ng g−1, and 82–96% of AFs were extracted within the first minute of contact. The limits of detection (LODs) were 0.1 and 0.02 ng g−1 for AFB1-AFG1 and AFB2-AFG2, respectively. Moreover, the limits of quantification (LOQs), were 0.4 and 0.08 ng g−1 for AFB1-AFG1 and AFB2-AFG2, respectively. Compared to other methods for the extraction and determination of AFs, the suggested MDSPE-LC/FD method possessed advantages such as rapidity, simplicity, excellent figures of merit, and eco-friendly nature.

GENDER DIFFERENCES OF CLINICAL FLOW AND PREDICTION OF COMPLICATIONS IN PRACTICE OF FIRST CONTACT DOCTOR IN PATIENTS WITH MIOCARDIAL INFARCTION OF LEFT VENTRICLE

The article provides an assessment of gender differences in patients with myocardial infarction. Early diagnosis and prognosis of the development of acute heart failure in case of myocardial rupture, cardiogenic shock and death from the first minutes of contact with the patient is a crucial point in the physician’s decision of the further management of the patient with MU. It has been shown that women have a higher risk of complications of myocardial infarction than men, despite the similar treatment.

In situ immobilization on the silica gel surface and adsorption capacity of poly[4-methacroyloxy-(4′-carboxy-2′-nitro)-azobenzene] on toxic metals ions

A new organo-mineral composite material has been synthesized by in situ immobilization of poly[(4-methacroyloxy-(4′-carboxy-2′-nitro)azobenzene on the silicagel surface. As a result of thermogravimetric analysis and DSC-MS analysis it has been found that the composition of synthesized composite includes 10,1 wt. % of polymer. It has been found that the synthesized composite exhibits the sorption ability in terms of microquantities of Cu (II), Cd (II), Pb (II) and Fe (III) ions in a neutral aqueous medium. The maximum degree of sorption of ions Cu (II), Pb (II) and Fe (III) is achieved during the first minutes of contact, and for Cd (II) ions the equilibrium is established within a day. The sorption capacity of silica gel as a result of modification by this polymer increases with respect to Cu (II) ions more than 14 times, with respect to Pb (II) ions - 5 times.

REMOCIÓN DE CADMIO MEDIANTE ADSORBENTES CERÁMICOS EMPACADOS EN COLUMNAS DE LECHO FIJO

Se evaluó la remoción de iones de cadmio (Cd2+) a partir de una disolución acuosa sobre cantera Blanco Cancún y Tezontle rojo, utilizando una fracción &gt;2000 ?m, a 23 °C bajo condiciones dinámicas en un lecho empacado. Se investigó el porcentaje de extracción de cadmio mediante cinéticas de adsorción, y con ello se calculó la capacidad de adsorción total y el tiempo de vida útil de la columna de sorción. Se utilizó un flujo volumétrico de 0.3 ml s-1 y una concentración inicial de 861.75 mg L-1, a un pH de 7.5. La cantera Blanco Cancún reporta un porcentaje máximo de extracción (%E) de 99.59 al primer minuto de contacto, en comparación con el tezontle que reporta %E=83.78 al mismo tiempo. Sin embargo, la capacidad de adsorción total fue de 3.60 mg y 6.62 mg respectivamente. El tiempo de vida útil de la columna sugiereusar al tezontle como adsorbente.

Experimental assessment of the bioconcentration of 15N-tamoxifen in Pseudokirchneriella subcapitata

Nowadays, pharmaceutical compounds (PC) are ubiquitous in aquatic ecosystems. In addition to direct ecotoxicity, the bioconcentration of PC in organisms is a phenomenon which could have an impact on the whole ecosystem. In order to study this phenomenon, we exposed unicellular algae (Pseudokirchneriella subcapitata) to 15N-tamoxifen, an anticancer drug labelled with a stable nitrogen isotope used as a tracer. By measuring 15N enrichment over time, we were able to measure the increase of tamoxifen content in algae. This enrichment was measured by an elemental analyser coupled with an isotopic ratio mass spectrometer (EA–IRMS). Algal cells were exposed for 7d to 3 concentrations of tamoxifen: 1, 10 and 100μgL−1. Our result shows a high bioconcentration in algae from the first minutes of contact. The highest bioconcentration factor measured is around 26500. We also observe that bioconcentration is not linked to the exposure concentration. This study is the first to use stable isotopes in order to monitor PCs in aquatic organisms such as algae. The use of stable isotopes in ecotoxicology offers interesting perspectives in the field of contaminant transfer in organisms and along the trophic web.

Sorption Media for Stormwater Treatment—A Laboratory Evaluation of Five Low‐Cost Media for Their Ability to Remove Metals and Phosphorus from Artificial Stormwater

Five sorption materials were studied with a focus on polishing pretreated stormwater: crushed limestone, shell-sand, zeolite, and two granulates of olivine. These materials are commercially available at comparatively low cost and have been subjected to a minimum of modification from their natural states. The sorbents were tested for phosphorus, arsenic, cadmium, chromium, copper, nickel, lead, and zinc at concentration and conditions relevant for typical stormwater. The materials were tested for sorption capacity and kinetics. Desorption was tested under neutral and alkaline conditions and in the presence of chloride. For most sorbent/sorbate combinations, significant sorption occurred within the first minutes of contact between sorbent and sorbate. Treatment to the low microgram per liter range could be achieved by contact times of less than 1 hour. The study indicated that sorption filters can be designed for long life expectancy at comparatively low cost by applying the materials tested.

Perchlorate removal by quaternary amine modified reed

We report a kinetic and equilibrium study of perchlorate adsorption onto giant reed modified by quaternary amine (QA) functional groups in batch reactors. The effect of pH, contact time, and initial perchlorate concentration on removal was investigated. The adsorption capacity for perchlorate was 169 mg/g on the modified reed (MR) particles ranging in size from 100 to 250 μm. The isotherm results were best described by the combined Langmuir–Freundlich equation. Optimum removal occurred in the pH range 3.5–7.0 and was reduced at pH > 8.5. The maximum adsorption rate occurred within the first minute of contact and equilibrium was achieved within 7 min. A three-stage adsorption occurred. In stage 1, adsorption was rapid and was controlled by boundary layer diffusion. In stage 2, adsorption was gradual and was controlled by both boundary layer and intraparticle diffusion. In stage 3, adsorption reached a plateau. The kinetic results fit well with a pseudo second-order equation. The adsorption mechanism was explored using Zeta potential analysis and Raman spectroscopy. Zeta potential measurements showed that reed modification enhanced perchlorate removal by increasing the surface potential. Electrostatic attraction between perchlorate anion and positively charged quaternary amine groups on the MR was the primary mechanism responsible for perchlorate removal.

Experimental 70% hydrofluoric acid burns: histological observations in an established human skin explants ex vivo model

Background: Hydrofluoric acid (HF) is particularly dangerous due to the potential for systemic effects and induction of severe skin necrosis through two mechanisms: corrosiveness and local tissue toxicity. In addition, because it is only partially dissociated (pKa 3.2), it is capable of penetrating deeply into tissues. There is a lack of experimental studies that objectively characterize the behavior of HF diffusion into human skin, specifically the kinetics of tissue penetration resulting in severe cellular lesions.Methodology/principal findings: We describe the cutaneous effects of HF using an established ex vivo human skin model. The diffusion of 70% HF starts within the first minute of contact at the epidermal surface and after 2 min reaches the basal layer. In the subsequent minute, the epidermis is destroyed and lesions appear in the papillary dermis after 4 min. Soon after, damage appears in the upper reticular dermis. Thus, 70% HF needs only 5 min of contact to completely penetrate human skin explants. This experiment is reproducible and corroborates previous studies and clinical effects reported in accidental HF exposures.Conclusion/significance: This study shows that the management of HF chemical skin exposure is a question of minutes, especially for initial decontamination. These experimental observations could be useful for objectively comparing skin decontamination methods. Further studies should help to confirm these preliminary results.