Low pH Solution Research Articles

Synergistically coupling membrane electrochemical reactor with Fenton process to enhance landfill leachate treatment

Landfill leachate is challenging to treat due to its complex composition. Advanced oxidation processes such as Fenton process can be effective to treat leachate. Herein, a previously developed membrane electrochemical reactor (MER) was coupled with Fenton oxidation through providing synergistic benefits with the low solution pH, reduced organics, and ammonia removal/recovery. This two-stage coupled system reduced the leachate COD by 88%, much higher than that from the standalone Fenton process treating raw leachate. In addition, the usage of chemical reagents has been greatly reduced. At a dimensionless oxidant dose of 1.0, the coupled MER-Fenton system reduced the consumption of both FeSO4⋅7H2O and H2O2 by 39%, H2SO4 by 100%, and NaOH by 55%. Consequently, the sludge production was reduced by 51% in weight and 12% in volume. Despite electricity consumption by the MER, the coupled system cost $4.76 per m3 leachate less than the standalone Fenton treatment. More notably, direct Fenton oxidation removed only 21% of ammonia; in comparison the MER-Fenton system removed ammonia by 98% with the possibility for recovery at a rate of 30.6–55.2 kg N m−3 reactor d−1. Those results demonstrate that coupling MER with Fenton process could mitigate some inherent drawbacks of Fenton oxidation such as ineffective ammonia removal, high acid and chemical reagents dose requirements, and a large amount of sludge generation. This system may be moved towards practical applications by addressing a few challenges such as using renewable energy to power MER.

PH-Responsive Copolymer Films Prepared by Surface-Initiated Polymerization and Simple Modification.

We report the preparation of pH-responsive, ester/carboxylic acid random copolymer films via simple modification of poly(norbornene diacyl chloride) (pNBDAC), prepared via surface-initiated ring-opening metathesis polymerization, with mixtures of water and ethanol to form carboxylic acid and ethyl ester side groups. The pNBDAC film serves as a compositionally versatile platform to controllably obtain copolymers with multiple functionalities. In modifying the pNBDAC to form the copolymer film, ethanol exhibits a significantly higher reactivity with acyl chloride groups within the film than does water. The magnitude and range of the pH-responsive performance are highly dependent on the carboxylic acid content in the copolymer films, which demonstrates the effect of film hydrophilicity on the pH-responsive switching of ionic barrier properties. The resistance of the film against ion transfer can be decreased by a factor of 104 through pH change, demonstrating pH-induced switching from hydrophobic and insulating to swollen and ion-permeable films. The interactions of the copolymer films with water at different pH values were also explored. When the copolymer contains 34% carboxylic acids, a 4× greater film thickness is obtained in high pH solution than in low pH solution due to ionically driven water swelling. The reversibility of the pH-responsive performance of these copolymer films is high based on measurements using quartz crystal microbalance with dissipation (QCM-D).

Ultrasound Accelerated Oxidation of Organic Dyes by a Micron‐Sized Copper/Peroxomonosulfate System

AbstractExperiments on the degradation of acid orange 7 (AO7) using micron‐sized zero‐valent copper (ZVC) are conducted in acidic aqueous solution under ultrasonic (US) irradiation. The US/ZVC/peroxymonosulfate (PMS) process for AO7 degradation is significantly better than that of an independent system. Based on the characterization of ZVC, it is observed that the corrosion speed of ZVC increases after ultrasound, owing to which a greater amount of Cu+ (0–3.03 mg L−1) and Cu2+ are produced. Exposure to US irradiation increases the available surface area of the catalysts to generate many new reactive sites for the degradation process. The AO7 degradation rate after the addition of a new copper reagent—neocuproine hemihydrate—from 6.33% to 100% proved that Cu+ is the main activator of PMS. Results indicated that free radicals (OH• and SO4−•) act as activators of PMS in the process. And higher ultrasound power, lower solution pH, and a larger ZVC dose are favorable for AO7 removal.

Comparative Effect of Calcium Mesoporous Silica Versus Calcium and/or Fluoride Products on the Reduction of Erosive Tooth Wear and Abrasive Enamel Lesion

Objective: To evaluate the effect of a calcium nanocompound on the reduction of erosive tooth wear and abrasion. Material and Methods: Bovine enamel specimens (BE), were randomly assigned to the following groups (n = 10): G1 = Calcium mesoporous silica nanoparticles (Ca 2+ MSNs); G2 = casein phosphopeptide-amorphous calcium phosphate (CPP-ACP, 2% CPP-ACP, GC ® ); G3 = casein phosphopeptide-amorphous calcium fluoride phosphate (CPP-ACFP, 2% CPP-ACP + 900 ppm F - , GC ® ); G4 = sodium fluoride NaF (900 ppm F-, positive control); and G5 = distilled and deionized water (negative control). Each product was applied to the exposed area for one minute, three times per day for three consecutive days, and followed by the immersion of the specimens in Sprite Zero™ - a low-pH solution (2.58) for five minutes (Coca-Cola™). After the first and last erosive challenges of the day, the specimens were submitted to abrasion in a toothbrush machine for 15 seconds (200 g/BE). The specimens were analysed using 3D non-contact optical profilometry, with tooth structure loss (TSL) measurements and scanning electron microscopy (SEM). TSL values were analysed by Kruskal-Wallis and Mann-Whitney tests (p<0.05) . Results: There were no significant differences between G1 (10.95 µm) and G3 (10.80 µm) treatments for TSL values; however both resulted in significantly reduced TSL values compared with the G5 (16.00 µm) (p<0.05). The G4 (12.26 µm) showed no statistically significant difference when compared to the G5 (16.00 µm). The groups G1 and G3 presented higher surface preservation than the G5 . Conclusion: Ca 2+ MSNs was effective for reducing tooth surface loss caused by erosive tooth wear and abrasion.

Seed germination response of a potential rangeland weed Psilocaulon granulicaule to selected environmental conditions

Studies show that just over 620 non-native naturalised plant species have been recorded within the Australian rangelands, some of which have a capacity to cause significant impacts on rangeland flora and grazing activity. Although Psilocaulon granulicaule (Haw.), Schwantes is listed as a highly invasive environmental weed species, there has been no previous research into its seed ecology. Therefore, this study was conducted to investigate the effects of temperature, light, pH, water stress, heat-shock, and salinity on the germination of P. granulicaule. In this study, four temperature regimes covering four different day and night temperature variations (17–7°C, 25–15°C, 30–25°C and 40–30°C) and two light regimes (12-h light–12-h dark, 24-h dark) were investigated. The effects of pH, water stress, heat-shock and salinity were investigated, using pH buffers, polyethylene glycol solutions, three heat shock events under four temperatures and a range of NaCl solutions. These tests were conducted under the identified optimum temperature range (25/15°C) and light regime for seed germination. The results showed that both temperature and photoperiod significantly influenced the germination rate, with 94.2% germination in the 25–15°C range under a 12-h light-12-h dark regime. Higher temperatures (30–40°C) reduced seed germination to &amp;lt;58% germination in both light regimes (57.5%, 12-h light-12-h dark; 54.17%, 24-h dark). The highest germination rates were observed in low pH solutions, high moisture levels, low heat-shocks and low salinity. The study showed that this species is sensitive to environmental factors such as temperature, light, pH, moisture, heat shock and salinity, suggesting that these factors can be used as critical indicators to guide effective management practices to address this weed problem. Given that seeds are sensitive to radiant heat, burning could be used as a tool to effectively manage this species.

Micro-CT Characterization of Wellbore Cement Degradation in SO42-–Bearing Brine under Geological CO2 Storage Environment

In order to explore the process of acid- and CO2-induced degradation of wellbore cement and the development of pre-existing leakage channels in wellbore cement under sulfate-rich geological CO2 storage conditions, wellbore cement samples were immersed in SO42--bearing brine solution for 7 days, and the samples after reacting with the low and circumneutral pH solutions were scanned by a micro-CT scanner. HCl+Na2SO4 solution was used to simulate the low-pH condition in deep formation waters and the possible existence of high sulfate ion content in deep formation waters. The acidification and carbonation results were compared, and the results given different pH values and different curing conditions were compared as well. The results show that the degradation of cement was related to the pH value of the reaction solution. There was a significant dissolution in the exterior of the cement sample after exposure to the low-pH solution, but the dissolution surrounding a penetrating borehole at the center of the sample (mimicking a leakage pathway within the wellbore cement in geological CO2 storage environment) was limited. Comparison between acidification and carbonation results in this study shows formation of a thick carbonate layer due to cement carbonation, and this layer was not observed in the acidification result. As for different curing conditions of cement samples, no significant difference in cement alteration depth was observed for the acidification case. For the carbonation case, precipitations in the borehole occurred in the cement sample cured at ambient pressure, while the cement sample cured at high pressure did not produce any precipitation in the borehole. This study provides valuable information on how low pH-induced corrosion and HCO3--induced cement carbonation contribute to structure evolution of wellbore cement in SO42--bearing brine under geological CO2 storage environment.

Periodate activation with manganese oxides for sulfanilamide degradation

This study presents a novel periodate oxidation system mediated by manganese oxides for the rapid removal of aqueous contaminants. The catalytic activation of periodate on manganese oxides was demonstrated as an efficient advanced oxidation system for degradation of sulfanilamide. The reactivity of manganese oxides with different Mn valence followed the order of MnO2>Mn3O4>Mn2O3, all of which showed extraordinary reusability during repeated activation of periodate. Sulfanilamide was rapidly degraded along with stoichiometric transformation of IO4− to IO3−, and both processes exhibited good linear correlations with the dosage of manganese oxides. While the degradation of sulfanilamide in the MnO2/IO4− system was accelerated at lower solution pH, it was only slightly affected by ionic strength, water anions and humic acid. In contrast to the homogeneous system of Mn2+/IO4−, sulfanilamide degradation was not influenced in oxic and anoxic environment. It was evidenced by quenching studies and EPR tests that both singlet oxygen (1O2) and iodate radicals (IO3•) were generated when the metastable Mn(IV)-O-IO3 interacted with sulfanilamide. The XPS spectra of Mn 2p and O 1s before and after reactions indicated that the catalytic activation of periodate on MnO2 was not in company with the redox cycling of Mn(IV) species.

Nano zerovalent zinc catalyzed peroxymonosulfate based advanced oxidation technologies for treatment of chlorpyrifos in aqueous solution: A semi-pilot scale study

Chlorpyrifos (CPY), an organophosphate pesticide is largely used throughout the world on different crops for the control of pests and causes severe health and environmental issues. In this study, highly efficient, crystalline, and nm-rang sized zerovalent zinc (nZVZn) catalyst was synthesized and used for removal of chlorpyrifos at semi-pilot scale. The nZVZn showed high activity and caused 55% removal of CPY at 90 min time under the conditions of [CPY] 0 = 10 mg/L, [nZVZn] 0 = 1.0 g/L, and flow rate of the reactor = 0.2 L/min. Using identical conditions of [CPY] 0 , [nZVZn] 0 and flow rate, the use of peroxymonosulfate (PMS) promoted the performance of nZVZn and caused 99.5% removal of CPY at [PMS] 0 = 40 mg/L. The electron spin resonance (ESR) spectroscopy studies revealed that nZVZn catalyzed PMS reactions yield hydroxyl and sulfate radicals that degraded CPY and removal of CPY was suppressed by applying radical scavengers. The nZVZn catalyzed PMS based removal of CPY was optimum at high [PMS] 0 , [nZVZn] 0 and low pH of solution. The flow rate of the pilot plant reactor also influenced the degradation efficiency of CPY. High pH of solution, high [CPY] 0 as well as use of alcohols, NOM, and some inorganic ions inhibited removal of CPY by nZVZn catalyzed PMS. The analysis of degradation products (DPs) of CPY were used to propose degradation pathways of CPY. The high TOC removal of CPY, low leaching of Zn 2+ from Zn 0 into aqueous solution, and toxicity reduction of CPY suggest the nZVZn catalyzed PMS process to be highly effective and environmental benign for treatment of CPY. • Nano zerovalent zinc was used for removal of chlorpyrifos at semi-pilot scale. • Removal of chlorpyrifos by zerovalent zinc was promoted by peroxymonosulfate. • Hydroxyl and sulfate radical rate constants with chlorpyrifos were calculated. • Proposed degradation pathways of chlorpyrifos were suggested. • Toxicities of treated chlorpyrifos solutions and zinc ion leaching were evaluated.

Experimental study on the pH for activating ground granulated blast-furnace slag activity at different temperatures

In order to explore the initial pH values of activator solution needed for early activation of slag at different temperatures, the effects of curing temperatures (5, 20 and 35°C) and pH (12.10, 12.55, 13.02 and 13.58) on the activation and hydration characteristics of ground granulated blast-furnace slag (GGBFS) were investigated. Sodium hydroxide (NaOH) was used as the alkaline activator. The compressive strength and non-evaporable water content of GGBFS paste cured for 1, 3, 7, 14 days were determined. The hydration characteristics of slag pastes at different temperatures and pH were analyzed by XRD and SEM. The results showed that the pH value required for slag activation decreased with increasing temperature. Based on the 3 days strength of slag paste, the pH values required for activation of slag activity at 5, 20 and 35°C were 13.58, 13.02 and 12.10, respectively. With the high temperature and high pH of solution, a dense calcium-rich product formed on the surface of slag particles, which suppressed the further slag reaction. With the low temperature and high pH of solution, a layer of network product was found on the surface of the slag particles, and the later strength developed rapidly as the further hydration was not prevented. This study provides a reference for the application of alkali-activated slag.

Influence of chloride and sulphate anions on the electronic and electrochemical properties of passive films formed on steel reinforcing bars

Reinforced concrete structures are suffering from the application of de-icing salts, particularly due to premature reinforcement corrosion. To understand and, thereby, identify solutions to this problem, a study has been conducted of the chloride- and sulphate-induced instability of the semiconductor passive films formed on carbon and 2304 stainless steel alloys in a simulated concrete pore solution environment. Steels’ vulnerability to corrosion when depassivation occurs, typically in the presence of chloride and/or low pH, makes it essential to understand the nature of their passive films in the effort to mitigate the effect of corrosion. The influence of major alloying elements in five different reinforcing bars and testing on different surface roughness was investigated in the first part of the study. In this second part, linear polarization resistance and potentiodynamic cyclic polarization techniques and Mott-Schottky (M-S) analysis were used to investigate the influence of varying ionic concentrations and, thus, pH of simulated concrete pore solutions on passive films formed on duplex 2304 stainless steel and carbon steel reinforcing bars. It was found that chloride ions increased the defect densities of passive films, most significantly in the lower pH solution, while sulphates decreased the densities. This is attributed to the formation of stable solid sulphides of Fe and Ni (as FeS, FeS2, NiS, Ni3S2) in the outer Fe-rich layer of the passive films as predicted by ThermoCalc© calculations.

A pH-dependent partial electrochemical exfoliation of highly oriented pyrolytic graphite for high areal capacitance electric double layer capacitor electrode

High electrolyte resistance severely limits the response time and energy efficiency of an electric double layer capacitor electrode. Vertically oriented graphene nanosheets (VOG) having open, straight channel morphology is a new, attractive morphology with low electrolyte resistance. While CVD remains the dominant synthesis method for VOG electrodes, electrochemical exfoliation of graphite, a facile, economical and scalable method for production of loose graphene flakes, can also provide a VOG electrode. Here we show, that the conditions of electrochemical exfoliation for producing VOG morphology is substantially different from using it to produce loose graphene flakes. In particular, a low pH solution leads to a better expansion of the graphite and substantially better VOG density while a high pH solution leads to the formation of loose graphene flakes. Sulfuric acid is better than other sulfate salt-based electrolyte solutions for the synthesis of a VOG electrode. The electrolyte concentration, exfoliation time, and current density also affect the electrode capacitance. The optimal process conditions provide a VOG electrode of areal capacitance 750 mF/cm2. A capacitor consisting of two identical VOG electrodes shows a volume capacitance density of 1.56 F cm−3 higher than most of the literature values for supercapacitors.

Layer-by-layer assembly of high negatively charged polycarbonate membranes with robust antifouling property for microalgae harvesting

To tailor low-biofouling membranes remains one of the most problematic issues in filtration for microalgae harvesting. The aim of this study is to develop a high negatively charged and hydrophilic membrane to reduce membrane fouling via bioinspired design and Layer-by-layer (LBL) self-assembly technique for the application in microalgae harvesting. Bioinspired adhesive based on the polydopamine and polyethylenimine (PDA/PEI) composite was first linked onto the neutrally charged PC membrane substrates, then the poly-(styrenesulfonate) (PSS)/poly-(diallyldimethylammonium chloride) (PDADMAC) layers were uniformly assembled by electrostatic attraction. The resultant highly negatively charged and hydrophilic PC membranes exhibit a zeta potential of -66.1 mV and a water contact angle of 26°. Moreover, the modified membranes present a high average flux (133.1 L m2 h-1·bar-1) in 1-h microalgae filtration, a high algae retention (~100%) as well as a high flux recovery rate (over 94%). Meanwhile, the resultant membranes exhibit excellent chemical stability in high salty solutions, the low pH solutions and tolerance to long-time running in DI water. The combination of bioinspired construction method and LBL self-assembly technique could be expected to be a universal way to endow neutrally charged materials with highly negative or positive surface charge for various applications.

On the thermodynamics and kinetics of scorodite dissolution

Scorodite (FeAsO4·2H2O)–water interaction is critical to As distribution and storage in surface environment but is inadequately understood due to ambiguities in the mineral’s stability and weathering rate at atmospheric conditions. In the present study we attempted to experimentally determine the thermodynamic and kinetic parameters needed to compute solubility and dissolution rate of scorodite at 25 °C. Experiments were carried out in low pH (1.15) solutions using specially synthesized large scorodite crystals (with Mean Diameter of 27.9 μm). Such experimental conditions ensured the results were not subject to the influence of secondary Fe-bearing phase precipitation and grain size effect. Measured equilibrium concentrations of Fe and As, along with newly published Fe-As complexes association constants, were first used to determine the solubility products Ksp and dissolution rates rn at 50–90 °C. The obtained Ksp ∼ T and rn ∼ T dependence was then used to derive the Gibbs free energy, enthalpy, entropy, heat capacity, and activation energy for the dissolution reaction. Finally, we extrapolated the measurements to 25 °C and obtained room temperature solubility and dissolution rate, scrutinized the pH effect on dissolution, and analyzed the ΔG ∼ rn relation of the dissolution reaction. Our results show that literature data are likely overestimated scorodite solubility at pH > 4 ∼ 4.5 due to neglecting the effect of ferric iron hydrolysis. Estimated ambient condition dissolution rate is an order magnitude lower than the earlier report, implicating the importance of size effect, but is one to two orders of magnitude higher than that of common rock-forming minerals, cautioning the proposed use of scorodite for As fixation and storage. The determined rn ∼ ΔG relation cannot be fully fitted by the transition state model, particularly at near equilibrium, suggesting dissolution in this study may be controlled by defect-assisted surface reactions.

Alginate-chitosan hydrogel as controlled release of NPK macronutrient

Alginate-chitosan hydrogel as controlled release of Nitrogen, Phosphorus, and Potassium (NPK) macronutrient has been studied. Variations of alginate and chitosan mass, N; P and K concentration, pH solution, swelling ratio and mass ratio of alginate and chitosan were optimized. Hydrogel was prepared by mixing alginate, chitosan and CaCl2 as a cross linker in the water media. Hydrogel product was characterized by Fourier Transform Infrared (FTIR). N; P; and K release were measured by UV-Vis spectrophotometer and Atomic Absorption Spectrophotometer (AAS). The result showed that addition of chitosan in the hydrogel caused a decrease of swelling ratio hydrogel and a decrease of N; P and K release. The release of N; P and K was affected by N; P and K concentration and pH solution. The higher N; P and K concentrations and lower pH solution caused an increase of release rate of N; P and K. The mechanism of N; P and K release from the alginate-chitosan hydrogel followed the Korsmeyer-Peppas model. The ratio of alginate and chitosan in the hydrogel also affected to the the release rate of N; P and K.

US REG sells life sciences assets

It has been appraised that the world energy spending will more than double by 2050. The global energy depends mostly on fossil fuels at present, while the estimated amount of fossil-fuel deposits goes on decreasing. The greater part of fossil fuels may be exhausted within next hundred years. In view of this situation, the electrochemical and selective conversion process of CO2 to ethylene that can be driven by the electricity derived from renewable energy is attractive, since CO2 can be utilized as an energy carrier regardless of fossil fuel. The developed CO2 conversion process takes place under rather specific conditions involving three-phase (gas/solution/solid) interface, concentrated solution of potassium halide, low pH, and copper or Cu(I) halide-confined metal electrode. Herein, the bases for leading to the augmentation of the efficiency and selectivity in the electrochemical reduction of CO2 to ethylene are discussed in association with the reduction pathway.

Influence of Sulphate on the Electronic and Electrochemical Properties of Passive Films Formed on Steel Reinforcing Bars

Reinforced concrete structures are suffering from the application of de-icing salts, particularly due to premature reinforcement corrosion. To understand and, thereby, identify solutions to this problem, a study has been conducted of the chloride- and sulphate-induced instability of the semiconductor passive films formed on carbon and 2304 stainless steel alloys in a simulated concrete pore solution environment. Steels' vulnerability to corrosion when depassivation occurs, typically in the presence of chloride and/or low pH, makes it essential to understand the nature of their passive films in the effort to mitigate the effect of corrosion. The influence of major alloying elements in five different reinforcing bars and testing on different surface roughness was investigated in the first part of the study. In this second part, linear polarization resistance and potentiodynamic cyclic polarization techniques and Mott-Schottky (M-S) analysis were used to investigate the influence of varying ionic concentrations and, thus, pH of simulated concrete pore solutions on passive films formed on duplex 2304 stainless steel and carbon steel reinforcing bars. It was found that chloride ions increased the defect densities of passive films, most significantly in the lower pH solution, while sulphates decreased the densities. This is attributed to the formation of stable solid sulphides of Fe and Ni (as FeS, FeS2, NiS, Ni3S2) in the outer Fe-rich layer of the passive films as predicted by ThermoCalc© calculations.

Geochemical modelling of experimental O2–SO2–CO2 reactions of reservoir, cap-rock, and overlying cores

Carbon dioxide streams stored geologically from industrial sources e.g. coal oxy-fuel firing sources, steel or cement processing, may contain gas impurities including O2, NOx and SOX which may have higher reactivity to rock than pure CO2. Supercritical CO2 with O2 and SO2 impurities (0.16 and 2% respectively) was reacted with core from the Precipice Sandstone, Evergreen Formation, and Hutton Sandstone of the Surat Basin, Australia. The Precipice Sandstone is a low salinity target reservoir for CO2 storage, where the Evergreen Formation would be the overlying cap-rock, and the Hutton Sandstone is an overlying aquifer. High and low water regimes were investigated with core sections either submerged in bulk gas saturated water, or suspended in the water saturated supercritical gas head at reservoir in situ conditions of 60 °C and 12 MPa. During O2–SO2–CO2 water rock reactions in bulk solution, a low solution pH (~1–2) was measured owing to the relatively high gas impurity concentrations used. Dissolution of reactive minerals from the core including Fe-chlorite, ankerite, siderite, and plagioclase was directly observed. The Evergreen Formation cap-rock and Hutton Sandstone cores reacted here contained ~ 5–10 times higher total concentrations of elements such as Fe, Al, Ti, Ba than the Precipice Sandstone core. Several cations were mobilised to solution including Mn, Co, Zn, Sr, Si, and Mg. Increasing dissolved concentrations of Mn, and Co were strongly correlated with Fe (R2 = 0.99) during reaction of the Precipice Sandstone core. Dissolved Co and Sr were strongly correlated with Fe during reaction of the Evergreen Formation core. Dissolved Mn was somewhat correlated with Fe (R2 = 0.99) from reaction of the Hutton Sandstone core, from both carbonate and chlorite dissolution. During gas-water reaction with the Hutton Sandstone core, dissolved element concentrations subsequently decreased, by incorporation into newly formed Fe oxide precipitates observed with Cr and Ni signatures. Geochemical models were built and validated with good agreement attained with experiments, predicting Fe-chlorite and minor carbonate minerals were the main minerals dissolving. Reactive surface areas initially estimated by a modified geometric method needed substantial increases for example in the case of chlorite (up to 2000x), and decreases for carbonates (2–10x) to match experimental data. A 30 year simulation of reservoir rock reactivity showed that the lowered pH was buffered by mineral dissolution. Compared to previously published pure CO2-water-rock reactions, the concentrations of ions such as Si generally were initially higher through reaction of more silicate minerals at the lower generated pH, and the oxidation of sulphides. Compared to SO2–CO2-water reactions, the concentrations of cations were similar, but with O2 present dissolved Fe subsequently decreased as Fe-oxide, sulphate and clay minerals precipitated. Cap-rock showed reactivity to wet supercritical O2–SO2–CO2 fluid in the supercritical gas headspace. Corrosion of minerals including ankerite and Fe-chlorite were observed, along with precipitation of oxide, sulphate and silicate minerals on rock surfaces. These results have implications for impacts in CO2 storage sites where gas impurities may be co-injected with CO2 and accumulate in the near wellbore region.

Infrequent Occurrence of Peach Skin Streaking and the Role of Rainwater Attributes on Symptom Development.

Streaks lacking pigmentation have impacted red blush cultivars of peaches in many East Coast production areas, but the underlying cause is still unclear. Some evidence suggests that streaking may be caused by reactive agents in rainwater. Peach skin streaking was monitored over two consecutive years at a commercial farm with a history of streaking problems located near Ridge Spring, SC. Six cultivars (two early season, two midseason, and two late season) were evaluated, each in two locations (LocA and LocB). Among those 12 experimental block cultivars, streaking occurred only in 2017 in cv. Scarletprince of LocA with an incidence of 6%. That same year two nearby nonexperimental blocks with 'Scarletprince' revealed 11 and 25% streaking. Streaking was also monitored at the Musser Fruit Research Center (MFRC) in Seneca, SC. At that location, a high incidence of streaking was observed, with 50 and 64% in 'Julyprince' (2017) and 'Carored' (2018), respectively. Rainwater pH taken from each of the 12 experimental blocks ranged from 3.03 to 7.4, ozone (O3) levels ranged from <0.02 to 0.37 mg/liter, and chlorine (Cl2) and chlorine dioxide (ClO2) levels were either just above or under the detection limit of 0.01 mg/liter and 0.02 mg/liter, respectively. Although the electrical conductivity (EC) was below 100 µS/cm on average, we did measure EC values as high as 1,500 µS/cm. For all samples, the oxidation-reduction potential (ORP) ranged from 90 to 302 mV, indicating oxidizing conditions. Fruit harvested 1 or 2 weeks prior to commercial maturity and treated with solutions of high (10) or low (3) pH, ozone >0.37 mg/liter, and EC values of up to 3,000 µS/cm did not produce symptoms. However, streaking was reproduced with collected rainwater, but the remaining sample volume did not allow further analyses. Using 0.05% ClO2 to induce streaking, we show that fruit of different cultivars varied in susceptibility when treated 1 week prior to commercial maturity, with 'Juneflame' being the most susceptible and 'August Lady' being the least susceptible. Our study shows that multiple factors determine the occurrence of streaking in peach orchards, including cultivar susceptibility, ripening stage, and the presence of rainwater with sufficient amounts of a yet unknown reactive agent or agent combination.

A novel protocol for cryopreservation of paediatric red blood cell units allows increased availability of rare blood types.

There is a growing concern for shortage in future blood supply, caused by a predicted decrease in eligible blood donors and simultaneous increase in recipients. Cryopreservation of split red blood cell units could increase stock supply by reducing waste of rare blood. This would be particularly useful in paediatric care where very small volumes often are transfused. The aim of this study was to develop a cryopreservation protocol for split units using the closed-system automated cell processor ACP215, as such protocols are currently missing. Using a pool-and-split design, red blood cell units (N=8) were glycerolized and frozen, either as standard volume reference units, or further divided into three smaller split units each. After thawing/deglycerolization, the supernatant of the smaller splits was reduced by additional centrifugation, and new SAGM was added to 60% haematocrit. The units were analysed for storage lesion effects up to ten days post-thawing. Haemolysis and extracellular potassium ion levels were lower in the split units than in the whole units from day three onwards. The metabolic parameters pH, ATP, glucose and lactate were also lower, though likely caused by lower additive solution pH rather than storage. Split units of red blood cells can be successfully cryopreserved using the ACP215. In addition to favourably low haemolysis and potassium, they also have higher haematocrit than corresponding whole units and enable involvement of fewer donors at repeated transfusions. These characteristics are all desirable features in paediatric care.

The stabilization of food grade copper-chlorophyllin in low pH solutions through association with anionic polysaccharides

This work investigates the potential for anionic polysaccharides, such as alginate and xanthan gum, to impart solution and color stability to dilute solutions of copper chlorophyllin (Cu-ChP) buffered at acidic pH. Under cold storage, both polysaccharides tested were shown with sufficient loading to mitigate Cu-ChP aggregation at pH 3.0 and 5.0; xanthan gum use required lower loadings than the sodium alginate tested. Analysis of polysaccharide stabilized Cu-ChP solutions by dynamic light scattering suggests complex formation does occur; this is likely driven by electrostatic interactions between copper cations coordinated at the pigment core and the heavily anionic surfaces of the polyccharide matrices created by the large number of uronic acid substituents on the hydrocolloids.. During accelerated stability testing at elevated temperature (40 °C), pure Cu-ChP controls readily aggregated and lost the solution color distribution, while both polysaccharides maintained both solution and color stability through the initial 5-day test; xanthan gum showed the best promise in this regard, maintaining solution stability and most of the original color through 14 days at both pH tested. CIE a* and b* color data further show more than half of the original green tones and nearly all of the original yellow tones are preserved during heating with either polysaccharide present. Despite this, the slight transition in overall color towards more olive-green tones suggest a level of pheophytinization (metal ion loss) occurs. Finally, quartz crystal microbalance with dissipation monitoring (QCM-D) provides initial insight into the stabilization of Cu-ChP solutions by these polysaccharides and suggests that the weaker, yet stable, association of the pigment source with xanthan gum compared to the sodium alginate tested may be key to its superiority as a stabilizer.