Rate Of Acid Neutralization Research Articles

Real-time acid production and extracellular matrix formation in mature biofilms of three Streptococcus mutans strains with special reference to xylitol

BackgroundAcidogenicity and production of an extracellular matrix (ECM) are important virulence factors for the dental caries-associated bacteria, such as Streptococcus mutans, that live in biofilms on tooth surface. The ECM protects the bacteria from the flushing and buffering effects of saliva resulting in highly acidic microenvironments inside the biofilm. Materials and methodsIn this in vitro study, we applied real-time assays to follow biofilm formation and pH decrease in a growth medium and saliva by three S. mutans strains, as well as acid neutralization inside the mature biofilm. Results were compared with the biofilm composition. Effects of a non-fermentable polyol, xylitol, on acid production and acid neutralization in mature biofilms were evaluated by real-time pH measurements and confocal microscopy. ResultsCombination of real-time pH measurements with biofilm accumulation assays revealed growth media dependent differences in the pH decrease and biofilm accumulation, as well as strain differences in acid production and biofilm formation but not in the buffer diffusion through ECM. The presence of xylitol reduced the pH drop during biofilm formation of all strains. In addition, with strain Ingbritt xylitol reduced the amount of ECM in biofilm, which increased the rate of acid neutralization inside the biofilm after buffer exposure. ConclusionOur results stress the importance of biofilm matrix in creating the acidic environment inside a S. mutans biofilm, especially in the presence of saliva. In addition, our results suggest a novel mechanism of xylitol action. The observed increase in the permeability of the S. mutans ECM after xylitol exposure may allow acid-neutralizing saliva to reach deeper layer of the biofilms and thus, in part, explain previous clinical observations of reduced plaque acidogenicity after frequent xylitol use.

Ethanol's effects on acid neutralization by motor oils

Sulfuric-acid neutralization by motor oils in the presence of ethanol was investigated for the first time by quantitatively visualizing the fate of acid drops in five off-the-shelf commercial motor oils via capillary video-microscopy. For all the oils at room temperature, there was neutralization when ethanol was absent, whereas little neutralization was exhibited when ethanol was present. A very different behavior was exhibited at 100 °C, with rate of acid neutralization being much faster in the presence of ethanol than in absence. With 1% ethanol and temperature of 100 °C, acid droplets were neutralized in 2 min, whereas at room temperature droplets expanded ∼35% in diameter after 60 min with little neutralization. The reported phenomena may affect engine behavior and tribology.

Simultaneous Hydrogen Generation and Waste Acid Neutralization in a Reverse Electrodialysis System

Waste acid streams produced at industrial sites are often co-located with large sources of waste heat (e.g., industrial exhaust gases, cooling water, and heated equipment). Reverse electrodialysis (RED) systems can be used to generate electrical power and hydrogen gas using waste heat-derived solutions, but high electrode overpotentials limit system performance. We show here that an ammonium bicarbonate (AmB) RED system can achieve simultaneous waste acid neutralization and in situ hydrogen production, while capturing energy from excess waste heat. The rate of acid neutralization was dependent on stack flow rate and increased 50× (from 0.06 ± 0.04 to 3.0 ± 0.32 pH units min–1 m–2 membrane), as the flow rate increased 6× (from 100 to 600 mL min–1). Acid neutralization primarily took place due to ammonium electromigration (37 ± 4%) and proton diffusion (60 ± 5%). The use of a synthetic waste acid stream as a catholyte (pH ≈ 2) also increased hydrogen production rates by 65% (from 5.3 ± 0.5 to 8.7 ± 0.1 m3 H...

Recent Mechanical Cultivation of Lawns Enhances Lime Application Efficacy

While the relationship between soil acidity and thatch accumulation in maintained lawns has been reported, interacting effects of cultivation and surface lime applications on soil acidity have not. The experimental objective was to determine how antecedent mechanical cultivation of mature turfgrasses interacts with surface application of liming agents to neutralize soil acidity within the upper and lower depth segments of a hectare furrow slice (2.24 × 106 kg soil). Various liming agents were applied to three lawn systems, each afflicted with soil acidity and thatch accumulations, at rates from 0 to 200% of soil test lime recommendations (LR). In Experiment 1, resulting active acidity (pHw) was measured in the 0 to 5 (thatch excluded) and 5 to 10 cm soil depths over 23 mo. In Experiments 2 and 3, described lime applications followed mechanical cultivation treatments; core aeration, vertical mowing, or none. Resulting pHw and exchangeable acidity (pHKCl) were measured in 0 to 6 (thatch excluded) and 6 to 12 cm soil depths after 1 or 2 yr. Application of the prescribed LR (100%) to uncultivated surfaces did not increase 5 to 10 or 6 to 12 cm pHw levels above unlimed plot levels. One or 2 yr following either lime application rate, statistically higher pHKCl values corresponded to either cultivation treatment in the 6 to 12 cm soil depth. Mechanical cultivation, conducted before surface application of the LR, accelerated the rate of acid neutralization throughout the 0 to 12 cm soil depths of mature lawn systems.

Temperature and acid droplet size effects in acid neutralization of marine cylinder lubricants

Temperature and acid droplet size effects on the rate of acid neutralization by Marine Cylinder Lubricants were investigated by using a heating-capillary video microscopy. The neutralization experiments were performed inside a ∼200-μm capillary micro-reactor and the progress of reaction was recorded in real time. Increasing temperature dramatically impacted on the neutralization rate. While the effect of acid droplet size was negligible initially, it might affect the rate as well when a droplet got smaller than a certain level.

Using Rate of Acid Neutralization to Characterize Aluminum Phosphate Adjuvant

Five aluminum phosphate adjuvants having P/Al molar ratios ranging from 0.74 to 0.26 were prepared. The adjuvants were characterized by both protein adsorptive capacity and rate of acid neutralization at pH 2.25, 25°C. The protein adsorptive capacity was not a useful parameter to compare the initial properties of the adjuvants, as differences in surface charge of the adjuvants required the use of different proteins. In contrast, the rate of acid neutralization allowed a comparison of the freshly precipitated adjuvants and revealed that the rate of acid neutralization was directly related to the P/Al molar ratio. The protein adsorptive capacity decreased slightly during 39 weeks of aging at room temperature. The changes in the rate of acid neutralization were much greater and indicated that a P/Al molar ratio of at least 0.5 was required to minimize the aging of the adjuvants. Thus, the rate of acid neutralization was found to be the most sensitive parameter to characterize aluminum phosphate adjuvants.

Aluminium phosphate adjuvants prepared by precipitation at constant pH. Part II: physicochemical properties

The impact of the pH of precipitation on the physicochemical properties of aluminium phosphate adjuvants was investigated by precipitating aluminium phosphate adjuvants under constant pH conditions at pH values from 3.0 to 7.5 at intervals of 0.5. The pH of precipitation did not affect the morphology, but the point of zero charge (PZC) and rate of acid neutralization varied directly with pH of precipitation. Aggregation and protein adsorption capacity exhibited a parabolic relationship to the pH of precipitation. Minimum protein adsorption and maximum aggregation were observed at pH 5.5. In contrast to adjuvants precipitated from the same reactants but under uncontrolled pH conditions, the pH of all of the adjuvants precipitated under constant pH conditions remained constant for a 3-month aging period at room temperature.

Stability of aluminium-containing adjuvants to autoclaving

Aluminium phosphate adjuvant remained amorphous when autoclaved for 30 or 60 min at 121°C. However, deprotonation and dehydration reactions occurred as evidenced by a decrease in the pH. The protein adsorption capacity, rate of acid neutralization at pH 2.5 and point of zero charge also decreased indicating that the deprotonation/dehydration reactions resulted in a decreased surface area. Autoclaving aluminium hydroxide adjuvant increased the degree of crystallinity as measured by the width at half height of the major band in the X-ray diffractogram. The pH decreased during autoclaving suggesting that the same deprotonation/dehydration reactions which reduced the surface area of aluminium phosphate adjuvant were responsible for the increased degree of crystallinity. These reactions also resulted in a reduced surface area as both the protein adsorption capacity and viscosity decreased following autoclaving.

Acid Mine Drainage Treatment with Armored Limestone in Open Limestone Channels

Much attention has been devoted to developing inexpensive, limestone-based systems for treating acid mine drainage (AMD) with little or no maintenance. Treatment of AMD with limestone results in a surface coating of metal hydroxides, a process known as limestone armoring. Once armored, limestone is assumed to cease dissolution and acid neutralization. Laboratory and field experiments determined acidity changes in AMD when contacted by armored and unarmored limestone and investigated the implications of armoring on the construction of open limestone channels for treating AMD. Results of a laboratory titration study indicated armored limestone was only 2 to 45% less effective in neutralizing a hydrochloric acid solution as unarmored limestone. A laboratory container study showed that armored limestone was 90% as effective in neutralizing AMD as unarmored limestone. The field study surveyed 2- to 8-yr-old, rock-lined channels constructed of sandstone or limestone, and measured water quality changes down the length of the channel. Open limestone channels, though armored, reduced more acidity in AMD (4-62%) than the sandstone channel (2%). The results from open limestone channels were compared to an acid neutralization kinetics model that predicts the rate of acid neutralization for a specified channel size, and AMD flow and acidity concentration. The open limestone channels in the field neutralized more acidity than the model predicted. Open limestone channels show promise for neutralizing AMD in watershed restoration projects and abandoned mine land (AML) reclamation projects where one-time installation costs are incurred, little to no maintenance is required, and systems do not have to meet specific water quality standards.

The Effect of Humidity on the Physical and Chemical Stability of Spray-Dried Aluminum Hydroxycarbonate

The moisture sorption isotherm of amorphous spray-dried aluminum hydroxycarbonate (SDAHC) at 25°C revealed that moisture sorption increased sharply when the relative humidity exceeded 80%. The physical and chemical stability of SDAHC was studied for 1 year at 25°C and 0, 11, 54, 84, or 100% RH. The results were interpreted to reveal that two mechanisms affect the properties of SDAHC at 25°C. The sample stored at 0% RH did not exhibit any significant changes during the 1-year study period. The surface area and rate of acid neutralization decreased when samples were stored at 11 or 54% RH, but the material remained amorphous. This change is believed to be due to aggregation and cementation of particles. Much larger changes in surface area and the rate of acid neutralization occurred in the samples aged at 84 or 100% RH. Under these humidity conditions, polymorphic transformations occurred in addition to aggregation and cementation. X-ray diffraction indicated that microcrystalline boehmite was an intermediate phase. The stable polymorph was bayerite, which is believed to form due to the high surface pH produced by water sorption at 84 or 100% RH. The moisture sorption isotherm was useful in identifying the humidity conditions which resulted in high moisture sorption. Polymorphic transformations were only detected when the SDAHC was aged under these humidity conditions.

Characterization of antacid compounds containing both aluminum and magnesium. II. Codried powders.

The composition and antacid properties of six samples of codried antacids containing both aluminum and magnesium were determined. Aluminum hydroxide-magnesium carbonate codried gel and aluminum hydroxide-magnesium hydroxide codried gel were non-homogeneous, as the samples contained combinations of hydrotalcite, amorphous aluminum hydroxide, magnesium hydroxide, magnesium hydroxycarbonate, and magnesium carbonate. All samples passed the preliminary antacid test and had high acid neutralizing capacities. However, the rate of acid neutralization varied between samples. In some cases the rate of acid neutralization at a dose of 400 mg was too slow to raise the pH to 3.0 as required by the Rossett-Rice test.

Characterization of antacid compounds containing both aluminum and magnesium. I. Crystalline powders.

The composition and antacid properties of 10 samples of crystalline antacids containing both aluminum and magnesium were determined. The composition was found to vary significantly, even within the same type of antacid. For example, three of four hydrotalcite samples exhibit evidence of the presence of a minor phase of amorphous aluminum hydroxide. Almagate and almagcit, which are claimed to be unique compounds, were found to be composed of hydrotalcite, magnesium hydroxycarbonate, and/or magnesium carbonate and amorphous aluminum hydroxide. All three magaldrate samples examined contained a minor phase of amorphous aluminum hydroxide. All 10 samples passed the preliminary antacid test and had high acid neutralizing capacities. However, the rate of acid neutralization varied between samples. In some cases the rate of acid neutralization at a dose of 400 mg was too slow to raise the pH to 3.0 as required by the Rossett-Rice test.

Spectrum of injury produced in the duodenum by perfusion with luminal acid in the rat

The dose and time dependence of duodenal mucosal injury by luminal acid perfusion was studied. Saline, 0.01, 0.05, 0.15, and 0.3N HCl, were perfused through the proximal duodena of rats for 5, 15, or 30 minutes and then harvested for histological examination. In a second set of studies, after a 30-minute perfusion, duodena were harvested either immediately or 2, 4, 8, or 24 hours after the perfusion to study the recovery from injury. Acid disappearance (acid delivered minus acid recovered) was measured in all groups. Duodena were examined grossly, then fixed, stained, and scored histologically. Whereas no gross mucosal injury was noted, there was graded histological injury proportional to acid concentration. Injury occurred early in the perfusion and changed little with increased perfusion durations. The initial injury lead to an acid disappearance rate that was proportional to acid concentration and, therefore, the degree of injury. After the initial injury occurred, the rate of acid neutralization was unchanged by increased duration of acid perfusion. This acid neutralization protected against further injury despite the continued presence of acid. Recovery from injury was complete with physiological (0.01 and 0.05N HCl) but not pharmacological (0.15 and 0.3N HCl) concentrations of acid. It is concluded that acid-induced duodenal injury occurs within 5 minutes of exposure, is proportional to the acid concentration, and results in acid neutralization that protects against extension of the injury with continued acid exposure.

Neutralization of Soil Acidity and Release of Phosphorus and Potassium by Wood Ash

AbstractWood ash is a residual by‐product being produced at an annual rate of 1.5 to 3.0 million t by wood burning power plants in the USA. Currently, much of this ash is being landfilled. Landspreading of wood ash, which is an alternative liming agent, on both agricultural and forest soils is being proposed as a means of disposal that is both environmentally and economically attractive. As with any soil amendment, there is a potential of adverse environmental impact from the landspreading of wood ash. An experiment was conducted to evaluate the initial rate of soil acidity neutralization by wood ash and the release of P and K into suspensions of 10 acid soils. The wood ash had a CaCO3 equivalence of 480 g kg−1. Changes in soil suspension pH, which were used to quantify the rate of acid neutralization by wood ash, and concentrations of P and K of wood ash‐amended soil suspensions were measured at reaction periods ranging from 30 to 300 s. Soil acidity neutralization rates were strongly correlated with soil pH and decreased 41% per unit pH increase in the pH 3.8 to 6.2 range. After the initial release of P into suspension, sorption of released P resulted in decreasing P concentration in the suspension with increasing reaction time for 7 of the 10 soils. Sorption of released P was greater at lower soil pH values, suggesting precipitation as Al and Fe phosphates. In contrast, the solubility of wood ash K was very high. The increase of suspension K levels resulted from the release of wood ash K as well as from the displacement of K on soil exchange sites by Ca and other exchangeable cations released directly from wood ash into the soil suspension. The increase in suspension K was equivalent to 55% of the total K content of the wood ash. The net K content of the suspensions remained near the same level during the reaction period suggesting that soil solution levels of K would immediately increase upon landspreading of wood ash.

Role of Water in the Aging of Aluminum Hydroxide Suspensions

The rate of acid neutralization of anhydrous suspensions of amorphous aluminum hydroxide in methanol did not change during aging. At low water content, when all of the water was adsorbed, an initial decrease in the rate of acid neutralization was observed but no further change occurred during aging. When enough water was present to exceed the adsorptive capacity and produce water in the bulk methanol, the initial rate of acid neutralization decreased and a decrease in the rate of acid neutralization also occurred during aging. The decrease in rate of acid neutralization during aging is believed to be due to polymorphic transformation of the amorphous aluminum hydroxide and aggregation. The change caused by aggregation could be reversed by dehydration or sonication, but the change due to polymorphic transformation could not be reversed.

Adsorption of Phosphate by Aluminum Hydroxycarbonate

Phosphate is specifically adsorbed by aluminum hydroxycarbonate by anion ligand exchange. IR analysis indicated that phosphate exchanged with specifically adsorbed carbonate. Adsorption is favored by low pH and is inversely related to particle size. Adsorption of phosphate decreases the rate of acid neutralization of aluminum hydroxycarbonate. The results are applied to the treatment of hyperphosphatemia and hypophosphatemia.

Mechanism of Freeze–Thaw Instability of Aluminum Hydroxycarbonate and Magnesium Hydroxide Gels

□ The effect of freeze-thaw cycles on the physical stability of aluminum hydroxycarbonate and magnesium hydroxide gels was studied. Coagulation following a freeze-thaw cycle, leading to the formation of visible aggregates, affected the content uniformity of both gels. The freeze-thaw cycles did not affect the crystal form or surface characteristics of the gels as determined by X-ray powder diffraction and point of zero charge, but caused a slight reduction in the rate of acid neutralization and a large increase in the rate of sedimentation. The greatest effect was observed after the first freeze-thaw cycle. While the duration of freezing was not a factor, the rate of freezing was important and was inversely related to the aggregate size. The aggregates which formed following a freeze-thaw cycle were not redispersed by shaking, but were reversed by ultrasonic treatment or homogenization. The adsorption of polymers or surface-active agents prior to freezing reduced and, in some cases, prevented the formation of aggregates. The physical instability produced by a freeze-thaw cycle was explained by the modified DLVO theory. The force exerted on the particles by the growing ice crystals forced the particles into the primary minimum, producing strong interparticle attraction. On thawing, simple agitation did not provide enough force to overcome the attractive force of the primary minimum. Adsorption of polymers or surface-active agents increased the steric repulsive force and prevented the particles from reaching the primary minimum.

Effect of Precipitation Temperature, pH and Agitation on the Acid Reactivity of Aluminum Hydroxycarbonate Gel

AbstractA completely randomized 23-factorial design study of the precipitation of aluminum hydroxycarbonate gel by the reaction of aluminum chloride with sodium carbonate and sodium bicarbonate showed that the precipitation temperature and end-point pH were significant in terms of the rate of acid neutralization at the 0.01 level and that stirring speed was significant at the 0.05 level. No significant interactions occurred between the parameters. The most reactive gels were precipitated at 25°, pH 6.5 and either 15 or 500 rpm. After aging for 105 days at 25° these gels exhibited a twelvefold greater rate of acid neutralization than the least reactive gel which was precipitated at 4°, pH 5.8 and 15 rpm. The results are analyzed in terms of the effect of each parameter on the particle size and structure of aluminum hydroxycarbonate gel

Mechanism of Interaction Between Polyols and Aluminum Hydroxide Gel

IR spectroscopy and changes in the rate of acid neutralization were used to study the interaction between various polyols and aluminum hydroxide. Hydrogen bonding is responsible for this interaction, although structural requirements limit the polyols that interact with aluminum hydroxide. Mannitol and sorbitol, both linear polyols, interacted with sulfate-containing aluminum hydroxide gel and aluminum hydroxycarbonate gel, while inositol, a cyclic polyol, did not interact The adsorbed polyol has the favorable effect of inhibiting the polymerization reaction that occurs on aging and the negative effect of reducing the rate of acid neutralization. Thus, the specific polyol and concentration must be carefully selected to maximize the desired effect of stabilizing the gel structure. The presence of mannitol in the reaction medium during precipitation did not significantly enhance gel structure stability, probably because the mannitol was desorbed during the washing process as a consequence of the weak adsorption forces.

Kinetics of Acid Neutralization by Aluminum Hydroxide Gel

The rate of acid neutralization by an aluminum hydroxide gel prepared by the reaction of aluminum chloride solution and strong ammonia solution was studied. The decrease in acidconsuming capacity during aging as measured by the USP test is due to a decrease in the rate of reaction rather than to a decrease in equilibrium reactivity. The reactivity profile has three phases, which are shown to be related to the structure of the gel. The rate of loss of reactivity is directly related to the extent of washing.