Release Of Cations Research Articles

КОНВЕРСИЯ ПОЛИМЕРОВ ЗЕРНА ПШЕНИЦЫ И КУКУРУЗЫ ПОД ВЛИЯНИЕМ ФИТОЛИТИЧЕСКИХ И ПРОТЕОЛИТИЧЕСКИХ ФЕРМЕНТОВ

Grain, in addition to starch, hemicelluloses and protein, is known to be phytic acid and its salts. It has been shown that the use of phytolytic enzymes promotes the release of phosphorus, improves the digestibility of feed nutrients and increases the meat productivity of livestock and poultry. However, the catalytic effect of phytases and their combinations with proteases on degradation of polysaccharides and protein polymers in grain raw materials, on the release of cations and anions, especially in grain wort for the production of alcohol, has been little studied. This work shows for the first time that phytolytic enzymes improve qualitative estimates, rheological properties and change the ionic composition of grain wort by not only releasing phosphates and metal cations, but also by increasing the concentration of organic salt anions. The combined action of phytolytic and proteolytic enzymes on polymers of grain raw materials provides their catalytic degradation to soluble carbohydrates, nitrogenous substances, cations and anions to produce the enriched grain wort. This work aimed to assess the degree of phytolytic and proteolytic conversion of high-molecular-weight polymers in grain wort. For grain wort, 50 g portions of wheat (Triticum sp.) or corn (Zea mays) grain flour put into Erlenmeyer flasks were added with 150 cm3 of water and incubated in a water bath. At grain batching for starch dextrinization, a thermo-stable a-amylase was added (0.6 units/g starch). For starch conversion to sugars and hydrolysis of non-starch polysaccharides in the control, we used glucoamylase (9.0 units/g starch) and xylanase (0.15 units/g raw material). Phytase (from 1.0 to 2.5 units/g raw material) and a proteolytic enzyme preparation (0.1 units/g raw material) were also added. The control was added neither with phytase, nor the proteolytic enzyme. The profiles of the main polymers of grain raw materials, the grain wort concentration, the content of reducing carbohydrates (RС) were determined according to the techno-chemical instructions for the control of alcohol production, the amine nitrogen (NH2+) concentration was measured by a method based on the ability of amino acids to form soluble copper compounds with a suspension of copper phosphate. The dynamic viscosity of the grain wort was evaluated by vibrational viscometry. The study of the ionic composition of the grain mix and wort was carried out using a PrinCE-560 series capillary electrophoresis system (PrinCE Technologies B.V., Netherlands) equipped with a conductometric detector. The optimal dosage of phytase was 1.5 units/g raw material which ensures the maximum release of ions identified by capillary electrophoresis and the effective conversion of polysaccharides, protein and phytin substances of the grain. It was found that the phytolytic enzymes contributed to a decrease in the viscosity of wheat and corn wort of more than 20 %, a 9.5-11.3 % increase in the concentration of reducing carbohydrates, and a 2.1-2.4-fold increase in the concentrations of released ions. The concentration of amino nitrogen in the wort did not change significantly. It was shown that as a result of the phytolytic action, the concentration of not only metal phosphates and cations, but also anions of organic salts, such as oxalates, malates, citrates, and succinates (in wheat wort) and oxalates, malates, citrates, and lactates (in corn wort) increased. A more significant effect of phytase for corn wort was revealed: the concentration of phosphates in the nutrient medium increased 3.9 times vs. 1.6 times for wheat wort, the levels of potassium and magnesium ions were 12 % and 22 % higher, respectively, as compared to the control in which the phytase was not used. The optimal composition of the enzyme complex is proposed which ensures the effective hydrolysis of polysaccharides, phytin and protein substances of processed raw materials. The synergistic effect of phytolytic and proteolytic enzymes enhances the catalytic hydrolysis of high molecular weight polymers of plant origin and enriches the grain wort with carbohydrates, nitrogenous substances, phosphates, and minerals in bioavailable form. Biocatalytic treatment of grain with the developed enzyme complex which, along with amylases and xylanase, contains phytase and proteases, provides a 16.8 % and 18.8 % increase in the concentration of reducing carbohydrates in wheat and corn wort, a 1.7- and 1.9-fold increase in amine nitrogen and a decrease in wort viscosity by 41.7 % and 44.7 %, respectively.

Ultrasonication-assisted chelating ligand-free extraction of Pb(II) from aqueous solution by using room temperature ionic liquids

This work aims to study the extraction of Pb(II) from contaminated aqueous solutions using imidazolium-based room temperature ionic liquids as sole extracting agent, i.e., without using any chelating agent and mixing agent. Secondly, ultrasonication technique is employed first time, to facilitate the swift contact of potentially toxic metal ions present in aqueous solution with ionic liquid. Furthermore, various salting-out agents were investigated to reduce the leaching of ionic liquid (IL) cations into aqueous phase upon extraction of toxic metal ion. > 90% of Pb(II) was removed from artificially contaminated aqueous solution using 100 mg of IL in 6 min sonication time. Moreover, the used ionic liquid was proved to be selective for Pb(II) in real water conditions. MgSO4 salt at 1.0 M concentration found to be superior salting-out agent without having any adverse effect on the extraction efficiency. Determination of total dissolved organic carbon in treated aqueous solution was used as potential tool to propose the mechanism of metal ions transfer to ionic liquid phase from aqueous solution. This study show that ultrasonication-assisted extraction of potentially toxic lead metal ion from aqueous system using imidazolium-based ionic liquids as sole extracting agent followed by the application of salting-out agents to reduce the release of IL cations in aqueous phase offers great potential for practical application.

Degradation of an imidazolium-based ionic liquid in water using monopersulfate catalyzed by Dahlia flower-like cobalt oxide

As the imidazolium-based ionic liquid (IL), 1-Butyl-3-methylimidazolium chloride (BMIMCl), is increasingly employed in various applications, release of BMIM cation into the environment has posed serious threats on aquatic ecology. Thus, it is imperative to eliminate BMIM from water, and, among various techniques for eliminating BMIM, chemical oxidation is the most effective technique. Nevertheless, studies of using SO4−-based chemical oxidation methods for degrading BMIM are still very limited; thus this study aims to develop an effective SO4−-based chemical oxidation process for degrading BMIM. As monopersulfate (MPS) is employed as a source of SO4−, a special cobalt (Co)-based catalyst is proposed and developed here by fabricating Co3O4 into a unique Dahlia flower-like morphology. Such a Dahlia flower-like Co3O4 (DFCoO) not only can exhibit the flower configuration, but also its floral petal components can consist of many filament-like Co3O4 nanostructures, making this DFCoO possess several advantageous properties over the conventional Co3O4 nanoparticle (NP), including higher redox activity, more reactive surface, higher surface area and larger pore volume. Thus, DFCoO shows a much higher catalytic activity than Co3O4 NP to activate MPS for degrading BMIM. A higher MPS dosage and reaction temperature also enhance BMIM degradation by DFCoO + MPS. DFCoO is reusable for activating MPS to degrade BMIM over multiple cycles. BMIM degradation mechanism and pathway by this DFCoO + MPS is also elucidated by identifying radical species and degradation intermediates. The findings of this study offer an useful approach for developing an advantageous catalyst for sulfate-based degradation of BMIMCl.

Carbonation of calcium-magnesium pyroxenes: Physical-chemical controls and effects of reaction-driven fracturing

The weathering of primary silicates, and their carbonation in particular, is key for the geochemical cycling of elements, strongly affecting the C cycle and the long-term regulation of the Earth's climate. The knowledge on the controlling factors and mechanisms of aqueous carbonation of primary silicates is however still far from complete. This precludes a better understanding of their chemical weathering in nature and is a strong handicap to implement effective Carbon Capture and Storage (CCS) strategies. Here, dissolution-carbonation reactions of two abundant Ca-Mg pyroxenes, augite and diopside, have been investigated in experiments conducted at hydrothermal conditions, in the presence/absence of different carbonate sources (NaHCO3 and Na2CO3). We show that the main reaction products are low-magnesium calcite and amorphous silica. A higher conversion of augite (∼38 wt%) than diopside (∼15 wt%) was achieved. The presence of abundant Fe and Al (and minor Na) in the former pyroxene strongly enhances the release of cations to the solution, and contributes to the formation of abundant secondary crystalline and amorphous silicates as well as carbonates (Na-phillipsite and magnesium silicate hydrate, MSH, as well as calcite). In particular, Na-phillipsite nucleates in etch pits exerting a crystallization pressure ∼100 MPa exceeding the tensile strength of augite (i.e, failure under tension due to breaking of inter-atomic bonds as well as opening and propagation of subcritical fractures or flaws) and causing extensive fracturing. This takes place via an interface-coupled dissolution-precipitation mechanism, despite the bulk system being undersaturated with respect to this phase. Limited reaction-induced fracturing was also observed following MSH precipitation within diopside crystals. Reaction-induced fracturing increases exposed reactive surface area and creates channels for solution flow, thereby contributing to the progress of the reaction via a positive feedback loop. Ultimately, our results help to understand differences in the kinetics and mechanisms of chemical weathering of these two abundant rock forming inosilicates relevant for CCS strategies, showing that secondary phase formation (other than carbonates) are fostered by moderately alkaline pH and the presence of alkali metals, resulting in reaction-driven fracturing that enables the progress of silicate carbonation for an effective, safe, and permanent CO2 mineral storage. We also show that under our experimental conditions the precipitation of amorphous silica and calcite cannot generate sufficient pressure as to create fracturing, an effect that limits carbonation of Mg-Ca-Fe pyroxenes.

Resonance energy transfer between cyanine dyes in hybrid films of layered silicate prepared by layer-by-layer method

Layer-by-layer (LbL) assemblies exhibiting efficient resonance energy transfer (RET) were prepared by alternating deposition on a quartz slide substrate. Each of the prepared films contained alternating layers of polyelectrolyte: poly(diallyldimethylammonium chloride) (PDDA) and saponite nanolayers (SapNL), which were prepared from layered synthetic saponite (Sap), which adsorbs cyanine dye cations, 3,3′-diethyl-oxocyanine iodide (OxCy) or 3,3′-diethyl-2,2′-thiacyanine iodide (ThCy). These dyes had been also selected due to their high photoactivity in Sap systems, and because they form a suitable pair for RET. Films with both the dyes were prepared to obtain alternating layers containing these dyes. Simpler films containing one type of dye were prepared for comparison. Absorption spectroscopy was used to monitor any changes occurring during the deposition of the films. The dyes did not alter their spectral properties, and the formation of dye aggregates was negligible. The deposition of each new PDDA layer led to the release of the dye cations from the outer surface of the film. This phenomenon was interpreted as competitive adsorption between the dye and PDDA cations. Fluorescence spectroscopy was applied to characterize the luminescence of the films and the efficiency of energy transfer. Typical values of RET efficiency were in the range of 0.8–0.9, and slightly increased with the number of deposited layers. This could be interpreted as a consequence of increasing film thickness as the number of layers that were actively involved in this photophysical process gradually increased. LbL assemblies are very interesting materials that can be prepared in a simple way but exhibit very interesting properties.

Release of lanthanum cations loaded into piperazine-modified SBA-15 to inhibit the mild steel corrosion

Abstract The lanthanum cations loaded into piperazine-modified SBA-15 was synthesized in three steps, and it was utilized as nanocontainers for inorganic corrosion inhibitor. The N2 adsorption-desorption analysis revealed that the lanthanum ions were loaded into the nanochannels due to the reduction of pore diameter, pore volume, and specific surface area. EDS evaluations proved that lanthanum ions were successfully encapsulated into the nanotubes up to 13 wt %. The ICP results confirmed the release of lanthanum ions up to 7 ppm during 24 h. The Polarization and EIS analysis revealed the considerable inhibition effect of lanthanum cations doped into SBA-15. La3+-loaded nanoreservoirs were incorporated in an epoxy-silicone coating. The |Z|0.01 Hz of specimens with scratched coating, including the La-loaded SBA-15, was about 2 and 5 times superior to that of neat coated samples after 1 and 24 h, respectively. The EIS assessments demonstrated the active protection of the coating incorporating La-loaded SBA-15. The EDS investigation indicated the release of lanthanum cations in the defect zone.

Long Term Effects of Forest Liming on the Acid-Base Budget

In Rhineland-Palatinate (Germany), a high percentage of the forest area is located on poor soils with low buffering capacity. Extensive liming applications were performed to compensate for the negative consequences of acid deposition. In 1988, three experimental sites with untreated control plots and different liming treatments were established in coniferous stands to investigate the effectiveness of liming on acidification and its effect on forest ecosystems. Measuring deposition and seepage waters for 24 years allowed for calculating long-term acid-base budgets. The original approach was expanded by data from a detailed sampling of the forest stand and mineral weathering rates. Without liming, the acid load exceeded the buffer capacity by base cation release from silicate weathering during the whole observation period. As a result, there was a high release of aluminum. After liming seepage water output of organic anions, nitrate and sulfate increased in some cases, leading to a higher acid load. However, the carbonates of dolomitic limestone compensated for a higher acid load, resulting in less aluminum released compared to the control plots. Until sulfate output by seepage water declines and nitrogen emissions are reduced, liming and restricted biomass harvesting are required for forest stands on base poor soils to prevent further acidification, decline of nutrient stocks, and the destruction of clay minerals.

Evaluation and Comparison of Antimicrobial Properties of Natural and Synthetic Zeolites Exchanged with Silver, Zinc, Copper and Nickel Ions

Zeolites are high-porous active crystalline biomaterials. Recently many studies have been done on their antibacterial properties especially on zeolites exchanged with metallic cations. In this paper, we investigate the effective factors on the antimicrobial activity of natural and synthetic zeolites exchanged with silver, zinc, copper nickel, and bromide cations. This study reviews the published articles on the antibacterial properties of the natural and synthetic pure zeolites as well as the ion exchange ones. The results of our investigation show that ion exchange zeolites exhibit a very good antibacterial effects even in comparison with other conventional antibacterial materials. The strongest antibacterial activity was reported in silver exchanged zeolites against Bacillus cereus and Escherichia coli with MIC of 16 μg/ml. According to the results reported derived from different articles, it can be concluded that zeolites with biocompatibility and high ion exchange capacity can be used as efficient antibacterial materials. Pure zeolites have antibacterial activity at high concentrations, whereas all synthetic and natural zeolites exchanged with metal cations investigated in this paper exhibit good antibacterial activity at very low concentrations generally due to sustained and prolong release of metal cations.

Ion release from hydroxyapatite and substituted hydroxyapatites in different immersion liquids: in vitro experiments and theoretical modelling study.

Multi-substituted hydroxyapatites (ms-HAPs) are currently gaining more consideration owing to their multifunctional properties and biomimetic structure, owning thus an enhanced biological potential in orthopaedic and dental applications. In this study, nano-hydroxyapatite (HAP) substituted with multiple cations (Sr2+, Mg2+ and Zn2+) for Ca2+ and anion () for and OH−, specifically HAPc-5%Sr and HAPc-10%Sr (where HAPc is HAP-1.5%Mg–0.2%Zn–0.2%Si), both lyophilized non-calcined and lyophilized calcined, were evaluated for their in vitro ions release. These nanomaterials were characterized by scanning electron microscopy, field emission-scanning electron microscopy and energy-dispersive X-ray, as well as by atomic force microscope images and by surface specific areas and porosity. Further, the release of cations and of phosphate anions were assessed from nano-HAP and ms-HAPs, both in water and in simulated body fluid, in static and simulated dynamic conditions, using inductively coupled plasma optical emission spectrometry. The release profiles were analysed and the influence of experimental conditions was determined for each of the six nanomaterials and for various periods of time. The pH of the samples soaked in the immersion liquids was also measured. The ion release mechanism was theoretically investigated using the Korsmeyer–Peppas model. The results indicated a mechanism principally based on diffusion and dissolution, with possible contribution of ion exchange. The surface of ms-HAP nanoparticles is more susceptible to dissolution into immersion liquids owing to the lattice strain provoked by simultaneous multi-substitution in HAP structure. According to the findings, it is rational to suggest that both materials HAPc-5%Sr and HAPc-10%Sr are bioactive and can be potential candidates in bone tissue regeneration.

Mineral dissolution and precipitation reactions and their net balance controlled by mineral surface area: An experimental study on the interactions between continental flood basalts and CO2-saturated water at 80 bars and 60 °C

Continental flood basalts are currently considered as unconventional CO2 storage reservoirs given several knowledge gaps remain. This study addresses the question whether subvertical fractures and joints in the storage complex and its overburden may lead to long-term CO2 leakage or whether commencement of self-sealing can be expected at an early stage of geochemical reactions. The latter occurs when mineral precipitation outcompetes mineral dissolution. The nature of secondary mineral precipitation and the change of ion concentrations over time were studied in a batch reactor experiment where basalt wafers with a low surface area were exposed to CO2-saturated formation water at a pressure of 80 bars and 60 °C. Primarily stilbite (a zeolite) and montmorillionite (a smectite) were observed in suspension and kaolinite, Fe-oxide and Na-nontronite were additionally identified as authigenic minerals on the surface of the basalt wafers at the end of the incubation. These observations are in agreement with the state of mineral saturation based on the water composition throughout the incubation. Carbonate minerals were undersaturated throughout the incubation suggesting limited carbon mineral trapping capacity under the given conditions. A mineral nucleation phase (day 1 to 6) dominated by cation release due to dissolution and a mineral growth phase (day 8 to 44) dominated by cation uptake due to precipitation were identified. The latter resulted in the formation of considerable mineral mass, which was deposited almost completely on the wafer surface.

Encapsulation of two fermentation agents, Lactobacillus sakei and calcium ions in microspheres

Alginate microspheres loaded with two fermentation active agents, calcium cations and strain LS0296 identified as Lactobacillus sakei, have been prepared and characterized. The role of calcium cation is twofold, it acts as gelling cation and as fermentation active agent. Encapsulation and the presence of calcium ions in the same compartment do not inhibit the activity of LS0296. Molecular interactions in microspheres are complex, including mainly hydrogen bonds and electrostatic interactions.In vitro calcium cations and strain LS0296 release profiles were fitted to the Korsmeyer–Peppas empirical model. The calcium cation release process is driven at first by Fickian diffusion through microspheres and then by anomalous transport kinetics. The in vitro LS0296 release process is driven by Fickian diffusion through microspheres showing a much slower releasing rate than calcium cations. The release of LS0296 strain is followed by a decrease in the pH value.Results obtained give us a new insight into complex interactions between bacterial cultures and microsphere constituents. Prepared formulations of calcium alginate microspheres loaded with LS0296 could be used as a new promising tool and a model for different starter cultures encapsulation and use in the production of fermented foods.

SPECTROSCOPIC METHODS TO DETERMINATION OF GEOTHITE IN KAOLINITE

One of the main contaminants of kaolinite, the iron, directly impacts quality in its commercial value. The spectroscopic monitoring, measured the depth of absorption of kaolinite, is compared with the literature in order to identify possible contaminants. The occurrence of kaolinite is due to the formation of primary minerals after the partial release of cations and silicon. This clay-mineral has a simple shape, with variable crystallographic imperfections, especially in the presence of iron, which replaces aluminum in the mineral chain, causing various structural disorganizations. The extraction of industrial minerals combined with geological studies, allows the development of new sources of energy, such as clay minerals, in particular kaolinite. Depending on the origin of the kaolinites, the presence of iron oxides in its structure, Fe2O3 and FeO(OH), are common. By comparing the results of spectroscopy (X-ray fluorescence, X-ray diffraction, RAMAN) and imaging using SEM-EDS, it was possible to identify kaolinite, with a higher determination coefficient, when the proportion of kaolinite reaches 60% or more in the mix. Kaolinite can be identified and quantified with a high correlation in the mixture from the sample absorption. Thus, the method has great potential to assist in quantifying and, consequently, in discriminating the quality of kaolinite.

Novel fluoride rechargeable dental composites containing MgAl and CaAl layered double hydroxide (LDH)

ObjectiveThis study aims to incorporate 2:1 MgAl and 2:1 CaAl layered double hydroxides (LDHs) in experimental dental-composites to render them fluoride rechargeable. The effect of LDH on fluoride absorption and release, and their physico-mechanical properties are investigated. Methods2:1 CaAl and 2:1 MgAl LDH-composite discs prepared with 0, 10 and 30wt% LDH were charged with fluoride (48h) and transferred to deionized water (DW)/artificial saliva (AS). Fluoride release/re-release was measured every 24h (ion-selective electrodes) with DW/AS replaced daily, and samples re-charged (5min) with fluoride every 2 days. Five absorption-release cycles were conducted over 10 days. CaAl and MgAl LDH rod-shaped specimens (dry and hydrated; 0, 10 and 30wt%) were studied for flexural strength and modulus. CaAl and MgAl LDH-composite discs (0, 10, 30 and 45wt% LDH) were prepared to study water uptake (over 7 weeks), water desorption (3 weeks), diffusion coefficients, solubility and cation release (ICP-OES). ResultsCaAl LDH and MgAl LDH-composites significantly increased the amount of fluoride released in both media (P<0.05). In AS, the mean release after every recharge was greater for MgAl LDH-composites compared to CaAl LDH-composites (P<0.05). After every recharge, the fluoride release was greater than the previous release cycle (P<0.05) for all LDH-composites. Physico-mechanical properties of the LDH-composites demonstrated similar values to those reported in literature. The solubility and cation release showed a linear increase with LDH loading. SignificanceLDH-composites repeatedly absorbed/released fluoride and maintained desired physico-mechanical properties. A sustained low-level fluoride release with LDH-composites could lead to a potential breakthrough in preventing early stage carious-lesions.

Catchment export of base cations: improved mineral dissolution kinetics influence the role of water transit time

Abstract. Soil mineral weathering is one of the major sources of base cations (BC), which play a dual role in forest ecosystems: they function as plant nutrients and buffer against the acidification of catchment runoff. On a long-term basis, soil weathering rates determine the highest sustainable forest productivity that does not cause acidification. It is believed that the hydrologic residence time plays a key role in determining the weathering rates at the landscape scale. The PROFILE weathering model has been used for almost 30 years to calculate weathering rates in the rooting zone of forest soils. However, the mineral dissolution equations in PROFILE are not adapted for the saturated zone, and employing these equations at the catchment scale results in a significant overprediction of base cation release rates to surface waters. In this study, we use a revised set of PROFILE equations which, among other features, include retardation due to silica concentrations. Relationships between the water transit time (WTT) and soil water concentrations were derived for each base cation, by simulating the soil water chemistry along a one-dimensional flow path, using the mineralogy from a glacial till soil. We show how the revised PROFILE equations are able to reproduce patterns in BC and silica concentrations as well as BC ratios (Ca2+/BC, Mg2+/BC and Na+/BC) that are observed in the soil water profiles and catchment runoff. In contrast to the original set of PROFILE equations, the revised set of equations could reproduce the fact that increasing WTT led to a decreasing Na+/BC ratio and increasing Ca2+/BC and Mg2+/BC ratios. Furthermore, the total release of base cations from a hillslope was calculated using a mixing model, where water with different WTTs was mixed according to an externally modeled WTT distribution. The revised set of equations gave a 50 % lower base cation release (0.23 eq m−2 yr−1) than the original PROFILE equations and are in better agreement with mass balance calculations of weathering rates. Thus, the results from this study demonstrate that the revised mineral dissolution equations for PROFILE are a major step forward in modeling weathering rates at the catchment scale.

An innovative multi-component fluoropolymer-based coating on outdoor patinated bronze for Cultural Heritage: Durability and reversibility

Abstract The application of protective coatings for the conservation of outdoor metallic artworks is currently considered the best approach actively employed. This paper focuses on the evaluation of the protectiveness of an optimised fluorosilane (FA-MS) coating with low occupational hazard impact and high inhibition efficiency. FA-MS coating was applied on a typical historical as-cast bronze (Cu-Sn-Zn-Pb), artificially patinated by synthetic acid rain dropping, to simulate natural unsheltered patinas. Subsequently, the patinated bronze was coated by brushing and then artificially aged by synthetic rain dropping. In order to investigate the coating-patina system, a multi-analytical approach was applied including scanning electron microscopy coupled with elemental analysis (FEG-SEM with EDS), microstructural analysis of cross-sections produced by Focused Ion Beam milling (FIB) and X-ray Photoelectron Spectroscopy (XPS). The coating homogenously covered the whole patinated surface producing a transparent layer few μms thick. The weathering solutions were also analysed for the assessment of metallic cations release. FA-MS showed excellent protective performances for the patinated bronze exposed to simulated outdoor conditions. Very high values of inhibiting efficiency in terms of metal release in the weathering solutions (up to 99%) were measured. In order to investigate all the necessary requirements for application in conservation field, the durability of FA-MS was also tested on a real bronze artistic casting, in terms of limiting the alloy composition changes (measured by in situ XRF) over time. A good durability of the coating was observed during the ongoing field exposure test. Lastly, reversibility of FA-MS was investigated by applying different mechanical cleaning methods, such as brushing and blasting. The reversibility was assessed by the evaluation of the morphology (colour change, surface roughness and optical microscopy) and the composition (SEM-EDS and Py-GC-MS chromatography) of the cleaned surfaces. Cleaning by brushing proved to be an efficient method for removing this coating without significantly altering the bronze patina.

Antimicrobial release from cleaning poultices for the conservation and disinfection of stone surfaces

Poultices, predominantly based on clays or silica powders, are commonly used by restorers for cleaning operations and disinfection of stone surfaces. However, operators often use poultices without paying particular attention to kinetics of release of the used antimicrobial agent from different types of supporting material. Cleaning procedures with poultices generally require fast and nearly complete release of the active agent. In this paper, releases of a commonly used antimicrobial ammonium salt (i.e. N-alkyl-N-benzyl-N,N-dimethylammonium chloride, shortly known as benzalkonium chloride, BAC) from poultices based on a sepiolite clay (Sep) or on a silica fume (SiO2), are studied by different techniques (WAXD, TGA, FT-IR, UV–Vis). Cation release from these poultices in aqueous media has been compared with those observed from intercalated compounds with a smectite clay (montmorillonite, Mt). Our results show that, for cleaning and disinfecting operations that require fast ammonium salt release, silica-based poultices would be preferred.

Desorption of hexavalent chromium from active aerobic granular sludge: Effects of operation parameters on granular bioactivity and stability

This study explored hexavalent chromium (Cr (VI)) adsorption onto active aerobic granular sludge (AGS) under neutral condition and then focused on Cr (VI) desorption from the Cr-loaded AGS. The changes of AGS bioactivity and stability were also analyzed with respect to cations release and extracellular polymeric substances (EPS). Among the 6 test desorbents, sodium carbonate (Na2CO3) showed the best performance for Cr (VI) desorption from Cr-loaded AGS, reflecting a better fit to the pseudo-second-order kinetic model (R2 = 0.985–0.995). Granular specific oxygen uptake rate (SOUR) was detected to decrease from the initial 22.38 to 5.55 mg-O2/g-VSS·h after 60 min desorption by 1 M Na2CO3, with integrity coefficient increased from 5.52% to 25.63%. Release of Ca2+, Mg2+ and K+ was mainly from EPS, especially the tightly bound EPS during the desorption process. Moreover, proteins rather than polysaccharides were found to be more sensitive to the increasing Na2CO3 concentration during the desorption process.

Probing silicate weathering reactions in soils with B isotopes

The determination of the mechanisms and extent of soil mineral weathering can be challenging, and the caveats reside in 1) difficulty identifying minerals that are actually involved in weathering reactions, 2) non-stoichiometric release of cations during weathering processes due to coupled dissolution, precipitation and transformation reactions and, 3) impact of vegetation activity on elemental cycles in upper soil horizons.To better characterize mechanisms controlling mineral weathering in soils and trace the evolution of B concentration and isotope ratios during chemical weathering, quantitative mineralogical analyses were coupled to B isotopes in a group of minerals (biotite, muscovite, K-feldspar and albite). Samples were selected along an Alocrisol (Alumic Cambisol, WRB FAO) soil profile from the bedrock (at 130 cm depth) up to 20 cm depth, developed on granitic bedrock in the Breuil-Chenue forest (France). The samples consist of residual primary minerals associated with weathering secondary phases (vermiculite, kaolinite…) in varying proportions.The B isotopic compositions of the most pristine minerals span a very narrow range of values (around −31‰), whereas all secondary phases point to a much heavier value (around −16‰), regardless of mineralogy. Our results also show a mineral-dependent evolution of B concentration or isotopic composition as weathering progresses: no variation is observed during dissolution of K-feldspars; B behaves like a very mobile element in micas (biotite and muscovite), whereas it concentrates in weathered products derived from albite. However, rates of B concentrations and changes in isotopic compositions appear to be much faster than those inferred from mineralogy or major element concentrations determined by XRD and bulk chemical analyses, respectively. These results indicate that B is involved in very early weathering reactions and raises the question of its actual location in the structure of the various soil minerals as well as its pathway to solution.

Antimicrobial and antibiofilm activity of the EeCentrocin 1 derived peptide EC1-17KV via membrane disruption

BackgroundThe antibiotic resistance and biofilm formation of pathogenic microbes exacerbate the difficulties of anti-infection therapy in the clinic. The structural modification of antimicrobial peptides (AMP) is an effective strategy to develop novel anti-infective agents.MethodSeventeen amino acids (AA) in the longer chain of EeCentrocin 1 (from the edible sea-urchin Echinus esculentus) were truncated and underwent further modification. To produce lead peptides with low toxicity and high efficacy, the antimicrobial activity or cytotoxicity of peptides was evaluated against various multidrug-resistant bacteria/fungi or mammalian cells in vivo/ in vitro. In addition, the stability and modes of action of the lead peptide were investigated.FindingsEC1-17KV displayed potent activity and an expanded antimicrobial spectrum, especially against drug-resistant gram-negative bacteria and fungi, attributable to its enhanced amphiphilicity and net charge. In addition, it exhibits bactericidal/fungicidal activity and effectively increased the animal survival rate and mitigated the histopathological damage induced by multidrug-resistant P. aeruginosa or C. albicans in infected mice or G. mellonella. Moreover, EC1-17KV had a poor ability to induce resistance in bacteria and fungi and exhibited desirable high-salt/high-temperature tolerance properties. In bacteria, EC1-17KV promoted divalent cation release to damage bacterial membrane integrity. In fungi, it changed C. albicans membrane fluidity to increase membrane permeabilization or reduced hyphal formation to suppress biofilm formation.InterpretationEC1-17KV is a promising lead peptide for the development of antimicrobial agents against antibiotic resistant bacteria and fungi.FundingThis work was funded by the National Natural Science Foundation of China (No. 81673483, 81803591); National Science and Technology Major Project Foundation of China (2019ZX09721001-004-005); National Key Research and Development Program of China (2018YFA0902000); "Double First-Class" University project (CPU2018GF/GY16); Natural Science Foundation of Jiangsu Province of China (No. BK20180563); and A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Shale weathering: A lysimeter and modelling study for flow, transport, gas diffusion and reactivity assessment in the critical zone

Shale weathering was characterized and quantified in a lysimeter and modelling study that jointly considered the flow, transport, gas diffusion and reactivity processes induced by exposure to the atmosphere of a recently excavated shale. In this mechanically disaggregated shale presenting preferential pathways for water and a hydraulic conductivity at saturation of 100 cm/day, the water content and the seasonal saturation and desaturation cycles were identified as the main driving mechanisms of shale alteration. The water content determined the diffusion of gaseous oxygen in the shale’s unsaturated porosity, which gave rise to a zonation of the oxidation of pyrite, contained at 1 wt% in the shale. The acidification associated with this oxidation of pyrite was efficiently buffered by calcite but a release of sulphates, cations, iron and trace metals (Pb, Ni, Zn, Co, Cu and As, mainly) was observed. Besides pyrite and calcite dissolution, iron (oxy-)hydroxide formed and proved to be a good phase for sorbing trace metals, whose content remained at low concentrations in the drainage water. Seasonal precipitation of gypsum was also identified, in connection with the summer desaturation of the shale’s shallow layers. The hydraulic, chemical and mineralogical observations made in the lysimeters were reproduced using HP1, a reactive transport code, under unsaturated conditions. It was possible to account for the gas diffusion where O2 availability controlled the reactivity with the shale, depending on the meteorological conditions and the drainage at the base of the lysimeter.