Sodium Chloride Salt Solutions Research Articles

Microfluidically Produced Microcapsules with Amphiphilic Polymer Conetwork Shells

AbstractMicrocapsules with an aqueous core can be conveniently prepared by water‐in‐oil‐in‐water double emulsion microfluidics. However, conventional shell materials are based on hydrophobic polymers or colloidal particles. Thus, these microcapsules feature a hydrophobic shell impermeable to water‐soluble compounds. Capsules with semipermeable hydrogel shells have been demonstrated but may exhibit poor mechanical properties. Here, amphiphilic polymer conetworks (APCNs) based on poly(2‐hydroxyethyl acrylate)‐linked by‐polydimethylsiloxane (PHEA‐l‐PDMS) are introduced as a new class of wall materials in double emulsion microcapsules. These APCNs are mechanically robust silicone hydrogels that are swellable and permeable to water and are soft and elastic when dry or swollen. Therefore, the microcapsules can be dried and rehydrated multiple times or shrunken in sodium chloride salt solutions without getting damaged. Moreover, the APCNs are permeable for hydrophilic organic compounds and impermeable for macromolecules. Thus, they can be loaded with macromolecules or nanoparticles during microfluidic formation and with organic molecules after capsule synthesis. The microcapsules serve as microreactors for catalytically active platinum nanoparticles that decompose hydrogen peroxide. Finally, the surface of the APCN microcapsules can be selectively functionalized with a cholesterol‐based linker. Concluding, APCN microcapsules could find applications for the controlled delivery of drugs, as microreactors for synthesis, or as scaffolds for synthetic cells.

Experimental Investigation on the Effect of Salt Solution on the Soil Freezing Characteristic Curve for Expansive Soils

With the development of the Belt and Road Initiative in China, high-speed railways are booming and inevitably pass through seasonal frost regions. In Nanyang basin, due to seasonal changes, railway subgrades will undergo frost heaving and thawing subsidence. The freezing characteristics of the soil are characterized by the freezing characteristic curve, and the important factors affecting the freezing characteristic curve are the content of expansive clay minerals in the soil and the salt solution. Therefore, three soil samples with different montmorillonite contents were saturated with salt solutions of different concentrations, and the freezing temperature of the soil samples was controlled by a cold bath. After the temperature equilibrium, the frozen stable soil samples were put into a nuclear magnetic resonance instrument to test the unfrozen water content, and the relationship between the freezing temperature and the unfrozen water content of expansive soil under different salt solution concentrations was obtained. Additionally, a unified model was used to simulate the test results. The results show that SFCC shifts to the left, that is, the sodium chloride salt solution reduces the freezing point of the soil sample so that it has more unfrozen water at the same temperature. At the same time, the soil’s freezing characteristic curves are closely related to content of expansive clay minerals in the soil. The more expansive clay mineral content, the greater the corresponding unfrozen water content. These results provide some basic insights for improving the frost heave and thaw subsidence problems of railway subgrades in seasonal permafrost regions, which will have a positive impact on promoting the management and rational application of land resources and the promotion of sustainable development.

Mechanical and durability performance of 100% recycled aggregate concrete pavers made by compression casting

Sustainable infrastructure developments require optimal use of natural resources and the recycling of the materials generated at the end of the service life of concrete structures. Construction and Demolition (C&D) waste in the form of Recycled Concrete Aggregates (RCA) has been used to manufacture structural and non-structural concrete which is known as Recycled Aggregate Concrete (RAC). However, not all the C&D waste could be incorporated into the structural concrete and the development of innovative construction products for the efficient and economic utilization of RCA is still under investigation. This study aimed to produce concrete pavers with 100% recycled aggregates and a minimum amount of cement through Compression Casting Technique (CCT). A comprehensive experimental investigation was carried out to find out the optimum values of fine to coarse aggregate ratio, cement contents, and casting pressure for the concrete pavers so that a minimum target compressive strength of 35 MPa at 7-days is achieved. The concrete mixes with fine and coarse aggregate contents of 60% and 40%, respectively, cement contents of 15% and 20%, and casting pressure of 20 MPa were found to be the most economical and feasible to produce concrete pavers exhibiting the target compressive strength. The mechanical (i.e., compressive and flexural strength) as well as durability (i.e., drying shrinkage, water absorption, cyclic ponding in sulfuric acid and sodium chloride salt solution) properties were investigated in detail for the pavers made from the selected optimum concrete mixes. The compressive and flexural strength of RAC pavers satisfied the minimum required strength values specified in international standards [GB – 28 635–2012, IS 15658:2021, A231.2–14, ASTM C936, ASTM C 1272, ASTM C902] and local [NHA & AJK] specification. The durability tests showed that the RAC pavers are resilient against salt and acid attack. The porous nature of RAC positively affected the pavers’ compressive strength, especially under a saline environment. The maximum water absorption of the RAC pavers was 6.34% which was found to be in the acceptable range, however, their drying shrinkage was higher than Natural Aggregate Concrete (NAC) pavers. As for the impact of casting technique, the properties of the RAC pavers were improved by employing CCT. To predict compressive strength based on the parameters of this study, an equation is proposed by regression analysis of the obtained compressive strength results which showed reasonable accuracy in predicting the strength of pavers. Finally, this study concluded that it is feasible and reliable to manufacture concrete pavers of 35 MPa compressive strength at 7-days (or 55 MPa at 28-days) by replacing 100% natural aggregates with recycled aggregates (both fine and coarse), using 20% cement content, and employing compression casting.

Hybrid structure of u bent optical fiber local surface plasmon resonance sensor based on graphene

<p>In this paper, a fiber optic sensor was designed and implemented to detect the change in refractive index of sodium chloride salt solution based on the local surface plasmon resonance (LSPR) phenomenon. This sensor was manufactured using a plastic optical fiber (POF), this optical fiber was bent in a U-shape with 0.5cm bending diameter, and then the cladding and part from core of the fiber were removed by polishing at the sensor head to become as a D-shape in cross section. The sensor was coated with 30 nm thickness of gold nano particles (GNPs) by DC plasms coating technology and it was tested with sodium chloride solution, the detection sensitivity was 466.66 nm/RIU. To enhancement the sensitivity, the latest sensor was coated with 20nm thickness of graphene nano material and retested with same samples of sodium chloride solutions. It was found that graphene improved the sensitivity by an excellent amount, where shift in wavelength was 20nm and highest sensitivity obtained was 666.666 nm/RIU.</p>

Comparison of Salt Exclusion in Muscadine and Interspecific Hybrid Grapes Using a Greenhouse Screening Procedure

Bunch grapes (Euvitis) are classified as moderately salt-tolerant. However, little is known about the salt tolerance of muscadine grapes (Vitis rotundifolia). The objective of this research was to evaluate the salt exclusion capacity of muscadine grapes relative to common bunch grape rootstocks and hybrid winegrapes using a greenhouse screening assay. In two separate experiments, 31 muscadine, six bunch grape rootstocks, and five hybrid winegrape cultivars were irrigated daily with a 25-mm sodium chloride salt solution for a period of 14 d, followed by a destructive harvest to determine sodium (Na) and chloride (Cl) concentrations in root and shoot tissues. Generally, the muscadines studied exhibited a greater range of salt concentration relative to bunch grape rootstocks. Total tissue (shoot and root) salt varied by 250% and 430% across muscadines and by 180% and 190% across bunch grape rootstocks for Na and Cl, respectively. Despite the wider range, muscadine grapes expressed significantly less leaf necrosis than the bunch grape rootstocks. The most effective salt-excluding muscadines, ‘Janebell’, ‘Scuppernong’, ‘Late Fry’, and ‘Eudora’, were not distinguishable from the bunch grape rootstocks [‘Paulsen 1103’ (1103P), ‘Ruggeri 140’ (140Ru), ‘Schwarzmann’, ‘Millardet et de Grasset 101-14’ (101-14 Mgt.), ‘Millardet et de Grasset 420A’ (420A), and ‘Matador’]. Overall, there was no discernable difference between the salt exclusion capacity of muscadine and bunch grapes. The hybrid winegrape ‘Blanc Du Bois’ displayed poor Na and Cl exclusion properties but showed only moderate leaf necrosis symptoms. In both experiments, ‘Blanc Du Bois’ accumulated more than two-fold higher root and shoot concentrations of Na and Cl compared with the best-performing rootstocks (1103P, 140Ru, 101-14 Mgt.), suggesting that ‘Blanc Du Bois’ could benefit from grafting if salinity is a limiting factor.

Nanosecond and sub-nanosecond laser-assisted microscribing of Cu thin films in a salt solution

Pulsed laser-based material removal is a preferred technique for microscribing of copper (Cu) film coated on polymers, as the pulse width limits the heat diffusion. However, experimental studies have shown that microscribing of Cu in air results in recast/redeposit formation and oxidation. Although the water medium can reduce these effects to a certain extent, the material removal rate is lesser for Cu. This article reports the influence of laser pulse duration on a hybrid method to enhance the pulsed laser-assisted microscribing of a copper thin film in the presence of an environmentally friendly sodium chloride salt solution (NaCl). The focused laser beam irradiation of Cu film results in ablation with a temperature of the zone well above the boiling point of Cu, which in turn, can assist in accelerating the chemical reaction. In this hybrid scribing technique, along with laser-based material removal, laser-activated chemical etching also helps in removing the material selectively. A sub-nanosecond laser with a pulse width of 500 ps (picosecond [ps] laser) and a nanosecond laser with a pulse width of 6 ns (nanosecond [ns] laser), with a wavelength of 532 nm, are used to understand the influence of laser pulse duration on this hybrid material removal mechanism. Hybrid microscribing with the ps- and ns lasers in salt solution resulted in an increase in the channel depth by ≈5 µm and ≈9 µm, respectively, compared to the channel depth obtained in deionized water. The theoretical model shows that during the ns laser ablation, the cooling rate is slower, resulting in a high temperature in the ablation zone for a longer duration and improved material removal.

Study of Anti-A Antibody Conjugated Gold Nanoparticles as a Biomolecular Detection Probe for a Substance in Saliva

In this research studied on the conjugation of antibodies on gold nanoparticles (GNPs) and the optimization in term of antibody concentration and albumin blocking concentration. Gold nanoparticleswith diameter size of ~20 nm were synthesized via chemical reduction of HAuCl4 with trisodium citrate as reducing and stabilizing agent. Gold nanoparticles and anti-A antibody at various concentrations were mixed and nonspecific binding sites were blocked by using bovine serum albumin (BSA) at various concentrations. The antibody conjugated gold nanoparticles were tested by coagulation with 1% sodium chloride salt solution to obtain the optimal antibody concentration. BSA 50, 100 and 200 μg/mL were added in solution after antibody covered on gold nanoparticles. The solutions were characterized by measuring absorbance spectra. From the results found that the optimal concentration of antibodies and BSA blocking were 45 μg/mL and 50 μg/mL, respectively. The anti-A conjugated gold nanoparticles were tested with saliva of blood group A sample to monitor the specific interaction between antibody on gold surface and antigen in saliva via the change of absorbance spectra.

Graphene Oxide (GO) Based Coated Geopolymeric Membrane for Concentrating Orange Juice through Forward Osmosis

ABSTRACT Dewatering of fruit juice through forward osmosis (FO) has attracted great attention in recent years; however, its application for fruit juice concentration through FO is limited due to high fouling rate, low flux, and expensive nature of membranes. Inorganic membranes are expensive due to heat-intensive steps and expensive raw materials that are involved in its synthesis, while geopolymerization technique for inorganic membrane synthesis reduced the cost due to its sintering-free steps and using fly ashes as a source material. In this research work, we report sintering-free economical and eco-friendly geopolymeric membrane in FO pilot-scale plant for orange juice concentration. However, the low flux of geopolymeric membrane was enhanced through coating of graphene oxide (GO) layer for high hydrophilicity. In this work, water flux through GO-based coated and uncoated geopolymeric membrane for concentrating sugar solution through FO was investigated. Prepared GO was coated on geopolymeric substrate through spin technique. The pore size of both geopolymeric substrate and GO was 1.8 and 5 µm, while porosity was 51.09% through the gravimetric method for both active and supportive layer. The orange juice solution was concentrated to 26.1 ± 0.5° and 21.87° Brix from 15.2 ± 0.5° Brix reaching flux of 0.405 and 0.360 kg.m−2.h−1 at a temperature of 30°C using sodium chloride salt solution (10 M) by coated and uncoated geopolymeric membranes, respectively. This study indicates that GO-based coated geopolymeric substrate is an eco-friendly and cost-effective feasible approach for fruit juice concentration through FO application.

PH-Sensitive Hydrogel from Polyethylene Oxide and Acrylic acid by Gamma Radiation

Hydrogel as a good water absorbent has attracted great research interest. A series of hydrogel based on polyethylene oxide (PEO) and acrylic acid (AAc) was prepared by applying gamma radiation with variation in the concentration of acrylic acid. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize the PEO/ AAc hydrogel. The properties of the prepared hydrogels such as gel content, swelling behavior, tensile strength, and pH sensitivity were evaluated. The formation of the hydrogels was confirmed from FTIR spectra. SEM images showed the inner porous structure of the hydrogels. The dose of gamma radiation was optimized to get a hydrogel with good swelling property and mechanical strength. The swelling ratio and gel content of the hydrogels were increased with increasing acrylic acid content. The pH of the solutions affected the swelling which indicated the pH-responsive property of the prepared hydrogels. Swelling of the prepared hydrogels in sodium chloride salt solutions decreased with increasing the ionic strength.

Proposed mechanism for the formation of oxychloride crystals during sodium chloride application as a deicer salt in carbonated concrete

Even though freeze and thaw performance for uncarbonated concrete may be considered good, its resistance may be considerably affected by carbonation and the presence of deicing salts.Besides the general belief that the major single mechanism that contributes to frost-scaling damage is purely mechanical and due to stresses caused by the differences in thermal expansion coefficients between ice and the underlying concrete, there is also experimental evidence of scaling deterioration on concrete that has been exposed to chloride deicers at temperatures just above freezing without the influence of ice formation. This fact is suggestive of another deterioration mechanism occurring at low temperatures.Blast furnace slag (BFS) and ordinary Portland cement (OPC) concretes with different slag/binder ratio and a high sulfate resistant cement concrete (HSR) were wet cured during a short period, followed by additional exposure to accelerated and natural CO2 environments. It was found that carbonation predisposition depends on amount of BFS replacement and cement type. Vaterite and Calcite were the two types of carbonated minerals identified by XRD analysis. The carbonated face of concrete was exposed to freeze and thaw cycles under deicing sodium chloride salt solution. It was noticed that the deicing scaling resistance of carbonated concrete decreases, as the ratio between carbonates coming from CSH decomposition over the ones coming from available CH (carb. ratio CSH/CH) increases.The presence of a well packed net of oxychloride minerals of prismatic and platey shape and growing underneath a crust of cement paste were observed in polarized microscopy after the freezing cycle. The crystallization pressures caused by these minerals below the surface are believed to contribute to concrete scaling.The mechanism is started with the dissolution of calcium bearing minerals from the carbonated concrete paste at the low temperatures occurring during the freezing cycle. The available calcium hydroxide present in the pore solution combines with chloride ions to form temporary oxychloride crystals. The crystal growth caused by these salts causes paste disruption. During the thaw cycle oxychlorides dissolve releasing calcium hydroxide, thus potentially contributing to calcium leaching from concrete in every cycle and also maintaining calcium availability for subsequent oxychloride formation during the next cycle. CO2 equilibrium in the pore solution is crucial for mineral stability; therefore the reactions are temperature and pH dependent.

Inefficacy of osmotic backwash induced by sodium chloride salt solution in controlling SWRO membrane fouling

A study was conducted to evaluate the efficacy of osmotic backwash induced by high salt (NaCl) concentration solution on feed side of seawater reverse osmosis (SWRO) membranes, online and offline, in controlling membrane fouling and therefore minimizing/eliminating the need for chemical cleaning. SWRO membranes were deliberately fouled by feeding seawater from an open intake located on the Arabian Gulf Coast without dosing chemicals. The fouled membranes were subjected to offline cleaning with the salt solution of up to 25 % concentration. Despite the partial removal of foulants from the membrane surface, SWRO membrane performance could not be restored, indicating the ineffectiveness of osmotic backwash in aiding offline salt cleaning. Similarly, online osmotic backwash was found to be not only ineffective in removing foulants from membrane surfaces but actually increased the fouling rate, as indicated by faster fouling rates compared to other cases. Although the driving force required for the osmotic backwash existed, the generated back flow proved to be insufficient to detach foulants from membrane surfaces. During the study period, the average SWRO membrane flux was maintained between 19 and 23 LMH, whereas the average generated back flow flux by high salt concentration solution was only 11 LMH, which was not adequate to remove foulants from membrane surfaces. Moreover, it seems that the membrane configuration as well as inherent microstructure of SWRO membrane places certain constraints on the osmotic backwash process and renders osmotic backwash ineffective in tackling SWRO membrane fouling. Hence, chemical cleaning is essential to restore SWRO membrane performance whenever fouling occurs, and the use of highly concentrated salt solution does not have any significant benefit. Membrane autopsy revealed only an insignificant accumulation of biofouling layer despite the absence of disinfection. However, it was shown that culturable biofilm bacteria species isolated from membranes tolerated exposure to high salt concentrations at pH range of 7–8. In addition, the overall findings of the study indicate that SWRO membranes can be operated in Gulf seawater at a recovery of 30 % without using any chemicals, such as coagulant, disinfectant and antiscalant, for an acceptable period of time without performing membrane cleaning. This is highly likely, if media filters are used in the pretreatment and SWRO membranes are operated at normal flux and recovery ratio.

Investigating a Prototype Heat Exchanger for Steam Storage

A coiled tube single pass counter flow heat exchanger was designed and fabricated using locally available materials and its capacity to transmit heat to water to make steam was tested. The heat exchanger was part of components used in solar thermal power production using a parabolic trough solar concentrator. The design of the heat exchanger storage system was done using Auto CAD 2010 software. Higher temperatures of steam were realized when the heat exchanger was used as a steam storage system. The heat transfer fluids used were locally available and they were water, sunflower oil, Rina oil, used engine oil, unused engine oil, 2 M sodium chloride salt solution, 4 M sodium chloride salt solution and 6 M sodium chloride solution. For each of the heat transfer fluids, heat exchanger operating points were obtained and it was operated between 1 Nm -2 to 1.0 Nm -2 of pressure. In the study the number of heat transfer units of the heat exchanger obtained was 0.61 and the thermal efficiency was found as 0.91. The average rates of heat transfer were 68.4 J for 6M sodium chloride solution, 62.8 J for 4 M sodium chloride solution, 57.9 J for used engine oil. Thermal conductivity of the salt solutions was better than for other heat transfer fluids although they were more corrosive on the system. Thermal efficiencies of the heat transfer fluids were 6 M sodium chloride solution; 0.89, for 4 M sodium chloride solution ; 0.84, for 2 M sodium chloride solution ; 0.80, water ; 0.78, sunflower; 0.69, Rina oil ; 0.66, unused engine oil ; 0.75 and used engine oil; 0.71. Storage of solar thermal energy will address the problem of low solar density and its variability. The heat exchanger storage system achieved a thermal capacity of 3.26 kJ at a maximum temperature of 249.4 o C and at a pressure of 7.2 Nm -2 . The use of heat exchangers in solar thermal storage will increase the overall efficiency of total

Efficacy of Three Denture Cleansers on Candida-Related Denture Stomatitis

Aim: The aim of the study is to evaluate the efficacy of three dentures cleanser on Candida related denture stomatitis through assessing their ability to reduce the number of colony forming unit (CFU) of Candida on palate of the patient for different times. Materials and methods: Group of 12 patients who have denture stomatitis were divided into four groups according to the type of denture cleaners (Protefix, sodium hypochlorite solution 0.02%, saturated sodium chloride salt solution and control wa-ter). The microbiological examination was done to determine the efficacy of the cleansers that used by assessing the number of (CFU) at different times (day before treatment and after 14, 28days of treat-ment). The data were statistically analyzed, (ANOVA) followed by Duncan's multiple Range test to assess the significant difference between the groups at P≤0.05. Results: The results showed that there was a significant effect of three cleansers on reducing number of (CFU) of Candida species in the treatment of denture stomatitis after 14 and 28 days of treatment, but it was not significant for control water group. Sodium hypochlorite showed the highest efficacy. Conclusions: Result showed that there was no significant difference in the efficacy between the three cleansers indicating that all cleansers are effective in the treatment of denture stomatitis .

Dispersion measurement of liquids with a fiber optic probe based on a bi-functional lensed photonic crystal fiber

We report a fiber optic probe suitable for measuring the wavelength dispersion of liquids. The measuring probe is made from an extrinsic fiber-optic cavity formed by a lensed photonic crystal fiber (PCF) and a micro-mirror. The custom-designed lensed PCF plays a dual role of collimator to help realize a long cavity length of the order of millimeters and as an efficient reflector to form the reference beam. The length of the cavity used in the experiment is about 1620 μm. In this article, we present the analytical method of obtaining dispersion of the liquid sample from the spectral interferogram of a single-arm or common path interferometer. Sodium chloride salt solutions with varied concentrations are used as an example to demonstrate the efficacy of the instrument. The index change with concentration is found to be linear at low concentrations and deviates from linearity as it approaches saturation.

Impact of mechanical loading on the corrosion of steel reinforcement in concrete structures

This paper presents results of an experimental investigation on the effect of mechanical loading on the corrosion of steel reinforcement in concrete. Reinforced concrete beams were cast, subjected to mechanical loadings and then exposed to corrosive environment. Successive drying and wetting cycles using 3% sodium chloride salt solution were used to accelerate the corrosion attack. Electrochemical techniques such as macrocell corrosion current, linear polarization resistance (LPR), corrosion potential (E corr ) and electrochemical impedance spectroscopic (EIS), were used to evaluate the corrosion behavior of the reinforcement. Also, chloride penetration profile and visual inspection of the beam rebars were obtained. The results shows that the pre-exposure mechanical load has no influence on the corrosion initiation or corrosion rate thereafter, unless it reaches to some limit where it develops connected cracks through which the chloride ions flow and depassivate the rebars. The load of 25% of the ultimate capacity seems to be the critical load limit where some microcracks onset to be connected, facilitate the chloride ions flow, and initiate the rebar corrosion.

Pool boiling fouling and corrosion properties on liquid-phase-deposition TiO2 coatings with copper substrate

Fouling on the heat transfer surfaces of industrial heat exchangers is an intractable problem, and several techniques have been suggested to inhibit fouling. Surface coatings are of such techniques by which the adhesion force between fouling and heat transfer surface can be reduced with low surface free energy thin films. In this article, liquid phase deposition was applied to coat titanium dioxide thin films on the red copper substrates with film thickness in micro- or nano-meter scale. Coating thickness, contact angle, roughness, surface topography, and components were measured with X-ray diffraction, contact angle analyzer, stylus roughmeter, scanning electron microscopy, and energy dispersive X-ray spectroscopy, respectively. Surface free energy of coating layers was calculated based on the contact angle. Heat transfer and fouling characteristics in pool boiling of distilled water and calcium carbonate solution on coated surfaces were investigated. Heat transfer enhancement was observed on coated surfaces compared with untreated or polished surfaces due to the micro- and nano-structured surfaces which may increase the number of nucleation sites. The nonfouling time on the coated surfaces is extended than that on the untreated or polished surfaces due to the reducing of the surface free energy of coated surfaces. Corrosion behavior of coated surfaces soaked in the corrosive media of hydrochloric acid, sodium hydroxide alkali, and sodium chloride salt solutions with high concentration at room temperature a few hours was also explored qualitatively. Anticorrosion results of the coated surfaces were obtained. The coatings resisted alkali corrosion within 7.2 × 105 s, acidic corrosion within 3.6 × 105 s and salt corrosion within 2.16 × 106 s. The present work may open a new coating route to avoid fouling deposition and corrosion on the heat transfer surfaces of industry evaporators, which is very important for energy saving in the related industries. © 2010 American Institute of Chemical Engineers AIChE J, 2011

APPLICATION OF RESPONSE SURFACE METHODOLOGY FOR THE OSMOTIC DEHYDRATION OF CARROTS

ABSTRACT Osmotic dehydrations of carrot cubes in sodium chloride salt solutions at different solution concentrations, temperatures and process durations were analyzed for water loss and solute gain. The osmotically pretreated carrot cubes were further dehydrated in a cabinet dryer at 65C and were then rehydrated in water at ambient temperature for 8–10 h and analyzed for rehydration ratio, color and overall acceptability of the rehydrated product. The process was optimized for maximum water loss, rehydration ratio and overall acceptability of rehydrated product, and for minimum solute gain and shrinkage of rehydrated product by response surface methodology. The optimum conditions of various process parameters were 11% salt concentration, 30C osmotic solution temperature and process duration of 120 min.

Heat Transfer Characteristics of Ice Melting in Water and Salt Solutions

Ice cubes were placed in identical beakers, one containing tap water and the other containing a sodium chloride salt solution. Both beakers and their original contents were at 20°C. As expected, the ice cubes floated and slowly melted, however, it was found that the ice cube in the water melted 25% faster than in the brine, contrary to expectation. A second series of tests were undertaken in which the ice cubes were made to sink to the bottom by placing them in a coarse string bag with weights attached. It was found that the submerged ice cube in the brine solution melted four times faster than that submerged in tap water. Computational Fluid Dynamics, has shown that the paradoxical experimental findings can all be explained by considering the strength and direction of buoyancy driven currents.

Chemical dilation and the dual porosity of humified bog peat

Hydrochloric acid and calcium and sodium chloride salt solutions were passed through humified bog peat cores of 1 m length to determine values for the material properties governing solute transport: hydraulic conductivity, effective porosity, and dispersivity. Chloride passed through the bulk peat cores about twice as fast as predicted from chloride breakthrough curves measured by selective-ion probes inserted into the peat 30 cm downgradient from the source. With continued experimentation, chloride dispersion increased. Chloride also passed through the peat up to 12 times slower than predicted by conservative advection. The retardation of the chloride fronts, the faster bulk transport, and the asymmetry of the breakthrough curves all indicate that humified bog peat is a dual porosity medium. Solutes both move preferentially through active macropore spaces and diffuse into dead pore space in the peat matrix. Neither the effective porosity nor the dispersivity of the peat could be precisely determined from the breakthrough curves because the hydraulic conductivity and discharge rates through the peat increased as much as five times when the chloride tracer solutions passed through the cores. In initial experiments, the shapes of the breakthrough curves were generally consistent with dispersivities of the order of centimeters, similar to that observed for granular soils at the same length scale (meters), whereas they `flattened' considerably during later experiments, suggesting dispersivities in the range of tens of centimeters. We hypothesize that the interaction of the chloride tracer solutions with organic-acid functional groups may cause macropores to dilate and micropores to close off.