High Acid Neutralizing Capacity Research Articles

Distribution and Characteristics of Blackwater Rivers and Streams of the Contiguous United States

AbstractBlackwater rivers and streams have stained or tea‐colored water from tannins released by decaying plant matter. Natural conditions in these waters often differ from non‐blackwater systems. For example, the pH and oxygen levels in waters can be very low, but completely natural. We examined an existing USEPA data set and found that blackwaters existed across the contiguous United States but were most common in the east. Water chemistry showed differences between blackwater and non‐blackwater sites, but differences were not consistent across ecoregions making national scale generalizations difficult. Physical habitat data analysis did not show dramatic differences between blackwater and non‐blackwater sites. Blackwater typically arises from streams that drain tannin‐rich bogs/muskeg and wetlands, so as expected blackwater sites had a shorter Euclidean distance to wetlands than non‐blackwater sites and existed in watersheds with a higher percentage of wetland habitat. Blackwaters in Northern and Temperate Plains tended to have higher acid neutralizing capacity, conductivity, and lower True Color; a visual color scale used for water purity. We posit that differences were because Color and Dissolved Organic Carbon at these sites were from buried wetland deposits rather than contemporary wetland habitats. Research needs that may increase our understanding and management of blackwaters include development of an operational definition that includes a classification framework and reference conditions for different blackwater types, identification of stressors and their associated dynamics that negatively impact blackwater systems, and development of data‐driven, consistent, and repeatable assessment methods, including development of targets, protective of unique conditions in blackwater rivers and streams.

Utilization of municipal solid waste incineration fly ash as construction materials based on geopolymerization

Incineration has been widely used to dispose municipal solid wastes (MSWs) with heat recovery. The generation of fly ash (FA, around 3∼5 wt% of the fed amount) that is normally defined as hazardous wastes remains a serious problem. It is ideal to work out a way to reutilize FA for valuable use instead of landfilling. As a novel utilization technology for municipal solid waste incineration (MSWI) fly ash, geopolymerization can produce geopolymer as construction materials with the advantages of low energy consumption, low pollution and high utilization rate. In this paper, metakaolin (MK) and washed fly ash (WFA) were used to prepare MSWI fly ash-based geopolymer (FAG) with alkali activator. Besides, the strength, heavy metals immobilization and acid resistance of FAG were in detail studied. Under the proper formulation, all the prepared FAGs exhibited strength higher than MU15 level (≥15 MPa) and the maximized one reached MU30 (≥30 MPa). Heavy metals including Cr, Mn, Cu, As, Pb, Zn and Cd had a immobilization rate of more than 92%, and others like As, Pb and Zn were nearly fully immobilized. As for the simulated testing for acid rain scenario, FAG could still fix up the heavy metals well indicating a controllable risk for the environment, which could be ascribed be its high acid neutralization capacity. In a word, this work reports a feasible method for treatment and resource reutilization of MSWI fly ash.

Formulation Studies to Develop Low-Cost, Orally-Delivered Secretory IgA Monoclonal Antibodies for Passive Immunization Against Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a common cause for diarrheal infections in children in low- and middle-income countries (LMICs). To date, no ETEC vaccine candidates have been approved. Passive immunization with low-cost, oral formulations of secretory IgA (sIgA) against ETEC is an alternative approach to protect high-risk populations in LMICs. Using a model sIgA monoclonal antibody (anti-LT sIgA2-mAb), the stability profiles of different formulations were assessed during storage and in in vitro digestion models (mimicking in vivo oral delivery). First, by employing various physicochemical techniques and a LT-antigen binding assay, three formulations with varying acid-neutralizing capacity (ANC) were evaluated to stabilize sIgA2-mAb during stress studies (freeze-thaw, agitation, elevated temperature) and during exposure to gastric phase digestion. Next, a low-volume, in vitro intestinal digestion model was developed to screen various additives to stabilize sIgA2-mAb in the intestinal phase. Finally, combinations of high ANC buffers and decoy proteins were assessed to collectively protect sIgA2-mAb during in vitro sequential (stomach to intestine) digestion. Based on the results, we demonstrate the feasibility of low-cost, ‘single-vial’, liquid formulations of sIgA-mAbs delivered orally after infant feeding for passive immunization, and we suggest future work based on a combination of in vitro and in vivo stability considerations.

Effect of Exchanged MgAl-Hydrotalcite with Carbonate on Increases of Acid Neutralizing Capacity: A Good Candidate as an Antacid

Background: In this study, we determined the acid-neutralizing capacity (ANC) of Mg/Al-Hydrotalcite-like compounds. The MgAl-hydrotalcites were synthesized by the co-precipitation method at room temperature using Mg/Al molar ratios 2:3. The synthesized bioactive nanomaterials were characterized by various physicochemical techniques such as TG/dTG, XRD, FT-IR spectroscopy, BET/BHJ, and SEM/EDX. The antacid activity assay was done by converting both synthesized samples into liquids, 1 g of which was added to 50 ml of deionized water at 37°C under vigorous agitation. The acid-neutralizing capacity (ANC) was evaluated with 0.1N HCl. The pH was constantly measured using a pH meter and values were recorded every minute up to 35 min. In order to improve the neutralizing power of the samples, we performed an exchange of chlorides by carbonates on the MgAl-HT3 synthesized. The exchanged Mg/Al-Hydrotalcite (MgAl- HTE) showed high acid neutralization capacity (up to 13.5 mEq/g). Objective: This study aimed to synthesize MgAl-hydrotalcite-like compounds and evaluate their acid-neutralizing capacity. In order to can be good candidates for pharmaceutical applications as antacid drugs. Methods: Following methods are used in this study: - Preparation of MgAl-hydrotalcite-like compounds was done by coprecipitation methods. - Characterization of samples was done by physico-chemical techniques such as TG/dTG, XRD, FT-IR spectroscopy, BET/BHJ and SEM/EDX. - Evaluation of acid-neutralizing capacity was done by titration procedure (Dose-titration). Results: This protocol describes the preparation of MgAl-hydrotalcite-like compounds using the classical coprecipitation method. The synthesized samples were characterized by various physicochemical techniques such as TG/dTG, XRD, FT-IR spectroscopy, BET/BHJ, and SEM/EDX. The as-synthetized samples were used for the evaluation of their acid-neutralizing capacity (ANC). Further, an exchanged of MgAl-Hydrotalcite with carbonate was done for the purpose to increase the acid-neutralizing capacity. Conclusion: In summary, this study describes a simple synthesis of MgAl-Hydrotalcites compounds by a co-precipitation method at constant pH around 10, with a ratio Mg/Al = 3:2 (referred to as MgAl-HT3 and MgAl-HT2). An exchange of the chlorides (not eliminated by washing) by the carbonates was carried out on hydrotalcite with a ratio Mg/Al = 3, and the solid obtained was named MgAl-HT3E. The materials MgAl-HT2, MgAl-HT3, and MgAl-TH3E were used to evaluate antacid activity. To this end, a study was conducted to determine the acid-neutralizing capacity (ANC). As result, the MgAl-HT3E was able to increase acid-neutralizing capacity and maintain an ideal pH. These results could be interesting to prepare novel antacid drugs (due to the low cost of synthesized materials) essentially the hydrotalcite of mg/Al ratio equal to 3 because of its relatively slow kinetics of releasing basic species and therefore of its beneficial action as an antacid.

The Physico-Chemical and Mineralogical Characterization of Mg-Rich Synthetic Gypsum Produced in a Rare Earth Refining Plant

The physical, chemical and mineralogical characterization of the constituents of magnesium-rich synthetic gypsum produced in a rare earth-refining plant located in Gebeng, Pahang, Malaysia was conducted through elemental chemical analysis, scanning electron microscopy with Energy Dispersive X-ray (EDX)-analyzer, thermal analysis, X-ray fluorescence and X-ray diffraction. The crystalline nature of the by-product was studied using FTIR spectroscopy. Elemental analysis confirmed the presence of Ca and Mg, which are essential macronutrients required by plants and this Ca alongside the high pH (9.17) of MRSG may confer on the material a high acid neutralization capacity. From the result, it was observed that the studied by-product is a heterogeneous crystalline material comprising of gypsum (CaSO4.2H2O) and other major components such as calcium (magnesium) compounds (hydroxide, oxide, silicates, and carbonate) and sulfur. These aggregates may contribute to give an acid neutralization capacity to MRSG. The XRD study of MRSG indicated a high content of gypsum (45.4%), shown by the d-spacing of 7.609 Å (2-theta 11.63) in the diffractogram. The infrared absorption spectra of MRSG indicate close similarities to mined gypsum. The results of the characterization indicated that MRSG has valuable properties that can promote its use in amending soil fertility constraints on nutrient-deficient tropical acid soils.

Evaluation of acid neutralizing and buffering capacities of selected antacids in Ghana

This study has evaluated the acid neutralizing and buffering capacities (BC) of nine selected antacid brands (“L1-L9”) in Ghana. The active acid neutralizing ingredients were recorded and the preliminary antacid test (PAT) determined with 0.5 N HCl after 10 min. The acid neutralizing capacity (ANC) was evaluated with 1 N HCl by neutralizing the excess with 0.5 N NaOH after 15 min stirring. Buffering capacity (BC) was estimated with 0.1 N HCl and titrated with 0.1 N NaOH at 5 min interval up to 50 min. All determination were at 37±3 °C using a pH meter. All brands had as part of their active ingredients dried aluminum hydroxide and magnesium hydroxide, with 67% containing simethicone as antifoam. The PAT declared all brands to be antacids with pH range of 4.38 ± 0.21–6.43 ± 0.06. The ANC of all brands were in the range 13.16 ± 0.55–20.70 ± 0.18 mEq/g with “L4” and “L9” having the lowest and highest values respectively. “L9” further demonstrated a considerably higher BC up to 40 min whiles “L6” had the least BC up to 15 min. The ability of an antacid to have a high ANC and to resist significant changes in pH (longer BC) is crucial in assuring quality and efficacy of the brand.

Almagate: A clinical and biochemical review

Almagate is a crystalline hydrated aluminum-magnesium hydroxycarbonate containing antacid with a unique rigid lattice structure. The observations from preclinical and clinical studies have shown that almagate has a higher acid-neutralizing capacity (ANC) with a buffering capacity in pH 3–5 making it effective for longer duration compared to aluminum hydroxide, magnesium hydroxide, and magaldrate. Almagate achieves pH 4 within 2 min as reported by in vitro studies. It was reported to have longer Rossett–Rice time and buffering capacity with bile acid adsorption capacity at pH 3. It also has inhibition activity against pepsin. It does not cause overalkalization and the risk of rebound acidity is low. Almagate was found to have the lowest intrinsic sodium content of 25 ppm compared to aluminum hydroxide (1200 ppm), magnesium hydroxide (1100 ppm), and magaldrate (360 ppm). Unlike aluminum hydroxide, magnesium hydroxide, and magaldrate, almagate maintains capacity to dilute acid even at increasing gastric pH. This review presents the clinical, nonclinical, and biochemical properties of almagate.

Utilization of alkaline silicate wastes for removal of cadmium ions from aqueous solution: Comparative performances and removal mechanisms

In this work, alkaline silicate wastes including blast furnace slag (BFS), coal fly ash (CFA), straw ash (SA) and lithium slag (LS) were used to remove Cd2+ from aqueous solution. The removal performances of Cd2+ by silicate wastes were compared in batch experiments, and the removal mechanisms by SA were proposed. All of four silicate wastes showed high acid neutralization capacity with solution pH increasing from 2.0 at initial to 6.27–9.70 at equilibrium. The removal of Cd2+ by four wastes followed the pseudo‒second‒order kinetic model and the equilibrium data were well described by the Langmuir isotherm. The maximum removal capacity of Cd2+ for four wastes had the sequence of SA > BFS > CFA > LS. The SA with the maximum removal capacity of 88.75 mg/g was the best adsorbent for Cd2+ removal. The XRD tests showed that Cd2+ could be chemically precipitated as Cd(OH)2 on the SA surface. The FTIR and XPS analysis exhibited that oxygen functional groups of SA could undergo surface complexation with Cd2+. Hydration products such as calcium silicate hydrate derived from SA could immobilize Cd2+ ions through ion exchange. In summary, the removal of Cd2+ by straw ash had a complicate involvement of chemical precipitation, ion exchange and surface complexation with oxygen functional groups.

Treatment of the acidic effluent from a copper smelter by flotation tailings

Since commissioning in 1961, the copper mine Majdanpek, a part of the Mining and Smelting Complex Bor (RTB Bor), produced approximately 378 million tons of flotation tailings. Semi-quantitative mineralogical analysis of the flotation tailings revealed significant content of carbonate minerals (approximately 20-25 %), indicating high acid neutralization capacity. Also, approximately 70 % of copper is in the form of the oxide mineral cuprite (Cu2O). Copper can be easily leached from cuprite by using sulphuric acid. The RTB Bor copper smelter generates 8.7 m3h-1 of extremely acidic waste effluent (142.4 kgm-3 of sulphuric acid, pH -0.464) with relatively high concentrations of dissolved metals and metalloids (Cu, Fe, Zn, Pb and As). The effluent is currently treated with hydrated lime. The present study focused on application of flotation tailings as a neutralizing agent for acidic effluents. Laboratory experiments followed by computer simulation of the industrial process showed that 99% of the acid can be neutralized with flotation tailings in a series of six reactors resulting in the final copper concentration of 1.55 gL-1. Benefits of the proposed process are: lower environmental impact of the process and reduced costs of neutralization of the acidic effluent from the copper smelter.

Thirty‐year trends in acid deposition and neutralization in two headwater catchments, northwestern Massachusetts, USA

AbstractLong‐term decreases in acidic precursors have changed the chemistry of precipitation and streamflow in two moderately to well‐buffered, forested headwater catchments in the Taconic Range of western New England, USA. We report 30‐year geochemical trends from Birch Brook and annual and seasonal variations from Birch Brook and adjacent Ford Glen, which drain phyllitic and carbonate bedrock. Median pH of precipitation has increased irregularly since 1983, consistent with regional trends. Increases in precipitation pH and decreases in sulfate (SO42−) correspond with increasing stream pH and decreasing SO42− concentration and flux over at least the past 30 years. Calcium (Ca2+) concentration and acid‐neutralizing capacity (ANC) in Birch Brook began to increase about 2005, in contrast to geochemical indicators from some poorly buffered catchments in the NE USA. Point and longitudinal sampling over a range of flows show that Birch Brook chemistry is a mixture of upstream source waters (throughfall, soil water, and ground water) with different chemistries. Acidic precipitation and shallow soil water affect stream chemistry directly only in the upper reaches of Birch Brook and during periods of extremely high flow, such as snowmelt. Ford Glen has high ANC and is near saturation with calcite at most flows. Long‐term trends measured at Birch Brook and at other streams in western Massachusetts show that stream chemistry reflects changes in acidic deposition in upland catchments, even where ecosystem geochemistry is well buffered by bedrock composition.

Present status of water chemistry and acidification under nonpoint sources of pollution across European Russia and West Siberia

Acidic deposition has caused severe surface water acidification in Europe and North America, but surface water acidification has not been systematically studied in Russia. Here we present the first detailed study on regional surface water acidification in European Russia (ER) and Western Siberia (WS) based on a survey of 367 lakes in a transect from the tundra to the steppe, which were investigated to explore the status and mechanism of surface water acidification. The variability of water chemistry is documented and discussed. High pH and acid-neutralizing capacity (ANC) were observed for lakes in the southern region, indicating that surface water acidification does not occur here. Anthropogenic acidification occurs in the humid areas of both regions, being observed in 4.4% of ER and 8.2% of WS lakes. These tundra and taiga lakes are characterized by high transparency, low pH, and ANC with a high concentration of strong acid anions. The main factor leading to acidification in the ER lakes is sulfur emission from metal smelters whilst that in WS is acidification, likely associated with gas burning by oil production facilities. In the ER acid lakes, SO42− is dominant; this is in contrast to WS, where NO3− and Cl− are dominate. The influence of strong technogenic acids on the structure of organic components and their possibility to form a proton is discussed. The phenomenon of the increase in water acidification by organic acids and strong acids is explained. These results clearly show the effect of a number of factors that strengthen the acidity of water. Differences in the chemical composition of lakes of both regions, as well as differentiation by their acid properties, were statistically proved. Results of our research indicate the need to reduce emissions of acidic gases into the atmosphere.

Formulation and Evaluation of Sustained and Raft Forming Antacid Tablet

Antacids have been widely used in the treatment of various gastric and duodenal disorders such as heartburn, reflux esophagitis, gastritis, irritable stomach, gastric and duodenal ulcers. A pH-responsive of bi-polymer of sodium alginate and pectin have been studied as raft-forming polymers using sodium bicarbonate and calcium carbonate as gas-generating and calcium ion sources. The aim of study was to formulate and evaluate mono and bilayer tablets of floating and sustained release antacid delivery systems using sodium carboxy methyl cellulose as a gel forming substance, calcium and magnesium carbonate as sources of acid neutralizing and carbon dioxide gas generators agents upon contact with acidic solution. The effect of the formulation contents on the buoyancy has been investigated. In addition to, the antacid activities of intact and pulverized tablets have been studied. The result obtained showed that the buoyance is remarkably affected by the percentages of sodium carboxy methyl cellulose and carbonates salts. All formulas of mono and bilayer tablets revealed sustained action of acid neutralization and raft formation. Besides, bilayer tablets showed a significant and higher level of acid neutralizing capacity than monolayer tablets. Moreover, the pulverized of bilayer tablets exhibited significant and higher acid neutralizing capacity at raft than that at bulk of artificial gastric juice medium. Keywords: Raft forming agent, Antacid, floating drug delivery, Acid neutralizing capacity, Sodium carboxy methyl cellulose.

Formulation and Evaluation of Sustained and Raft Forming Antacid Tablet

Antacids have been widely used in the treatment of various gastric and duodenal disorders such as heartburn, reflux esophagitis, gastritis, irritable stomach, gastric and duodenal ulcers. A pH-responsive of bi-polymer of sodium alginate and pectin have been studied as raft-forming polymers using sodium bicarbonate and calcium carbonate as gas-generating and calcium ion sources. The aim of study was to formulate and evaluate mono and bilayer tablets of floating and sustained release antacid delivery systems using sodium carboxy methyl cellulose as a gel forming substance, calcium and magnesium carbonate as sources of acid neutralizing and carbon dioxide gas generators agents upon contact with acidic solution. The effect of the formulation contents on the buoyancy has been investigated. In addition to, the antacid activities of intact and pulverized tablets have been studied. The result obtained showed that the buoyance is remarkably affected by the percentages of sodium carboxy methyl cellulose and carbonates salts. All formulas of mono and bilayer tablets revealed sustained action of acid neutralization and raft formation. Besides, bilayer tablets showed a significant and higher level of acid neutralizing capacity than monolayer tablets. Moreover, the pulverized of bilayer tablets exhibited significant and higher acid neutralizing capacity at raft than that at bulk of artificial gastric juice medium.
 Keywords: Raft forming agent, Antacid, floating drug delivery, Acid neutralizing capacity, Sodium carboxy methyl cellulose.

Is surface water acidification a serious regional issue in China?

Acidic deposition used to cause severe surface water acidification in Europe and the North America, but no damage of surface water acidification was reported under continuous heavy acid deposition in China. We present the first detailed study on regional surface water acidification in southern and northeastern China based on a survey of 255 forested headwater streams, which were investigated during 2010-2015 to explore the status and mechanism of surface water acidification. South China has a subtropical climate with high acid deposition, whereas northeast China is located in a cold temperature zone with relatively low acid deposition. High pH and acid neutralizing capacity (ANC) were observed for almost all of the streams, indicating that surface water acidification may not be a serious regional issue in China both at present and in the future. In northeast China, where soil types are similar in low weathering rate to those in Northern Europe and North America, the ANC of surface waters was lower than that in South China, indicating a higher acid-sensitivity of the surface water. In comparison, the high pH and ANC of streams in southwest China resulted from high soil weathering and atmospheric calcium (Ca) deposition, despite elevated atmospheric acid inputs due to the high sulfur (S) and nitrogen (N) deposition. Comparison of stream nitrate (NO3-) and sulfate (SO42-) concentrations with modeled N and S deposition showed significant N and possible S sinks in the catchments in south China, probably due to denitrification of NO3- in groundwater discharge zone and SO42- adsorption by acid soils respectively, which may also buffer the acidifying effect of S and N depositions. It seems that considerable NO3- leaching to stream waters does not occur in China unless N deposition is higher than 1.8keq·ha-1·yr-1 (2.50g N·m-2·yr-1) (or greater values in certain regions).

Calcium content in pond sediment and its effect on neutralizing capacity of water and fish production

This paper deals with the assessment of the available insoluble calcium compounds in pond sediment and their conversion into soluble bicarbonate; its impact on the acid neutralizing capacity (ANC) or alkalinity of water and the influence of bioturbation by fish stock. The objective of the study was the assessment of the influence of different Ca contents in pond sediments of two groups of ponds: LCa (with a low content of available Ca) and HCa (with a high content of available calcium) on acid neutralizing capacity of water, conductivity and pH. In our experiments, the turbidity of water, content of chlorophyll, nutrients and natural gain of fish in general have been observed as well. The results revealed that ponds with a higher content of calcium with a mean concentration of 27.45 ± 7.9 mmol Ca/kg in dry matter reported a higher ANC (alkalinity; mean value of 2.31 ± 0.33 mmol/l); pH with smaller fluctuations (7.69 ± 0.37; p < 0.05) and higher average values of turbidity (30.9 ± 17.4 NTU) and conductivity of water (291 ± 40.5 μS/cm−1; p < 0.01). Tight relations of the content of Ca in sediments and acid neutralizing capacity, conductivity and water pH during the growing season have been proven. The natural gain of fish was higher in the ponds with a higher content of available Ca in the sediment and a higher value of acid neutralizing capacity of water. The natural gain of fish was positively influenced also by a higher content of nutrients and chlorophyll, which was observed particularly in HCa ponds.

Effect of ageing on the availability of heavy metals in soils amended with compost and biochar: evaluation of changes in soil and amendment properties.

Remediation strategies using soil amendments should consider the time dependence of metal availability to identify amendments that can sustainably reduce available pollutant concentrations over time. Drying-wetting cycles were applied on amendments, soils and soil+amendment mixtures, to mimic ageing at field level and investigate its effect on extractable Cd, Cu, Ni, Pb and Zn concentrations from three contaminated soils. The amendments investigated were municipal waste organic compost and biochars. The amendments, soils and mixtures were characterised by their physicochemical properties at different ageing times. The amendments were also characterised in terms of sorption capacity for Cd and Cu. The sorption capacity and the physicochemical properties of the amendments remained constant over the period examined. When mixed with the soils, amendments, especially the compost, immediately reduced the extractable metals in the soils with low pH and acid neutralisation capacity, due to the increase in pH and buffering capacity of the mixtures. The amendments had a relatively minor impact on the metal availability concentrations for the soil with substantially high acid neutralisation capacity. The most important changes in extractable metal concentrations were observed at the beginning of the experiments, ageing having a minor effect on metal concentrations when compared with the initial effect of amendments.

Evaluation of heavy metal leaching from coal ash-versus conventional concrete monoliths and debris

Application of coal ash in construction materials is constrained by the potential risk of heavy metal leaching. Limited information is available on the comparative heavy metal leaching from coal ash-versus conventional concrete. The current study compared total and leached heavy metal concentrations in unbound coal ash, cement and sand; and investigated the effect of initial leachant pH on heavy metal leaching from coal-ash versus conventional concrete monoliths and their debris. Total Pb, Mn and Zn in coal ash were lower than or similar to that of other materials, while Cu and Fe showed the opposite trend. Leached concentrations of Zn, Pb, Mn, Cu and Fe in unbound coal ash, its concrete and debris were comparable and in some cases even lower than that for conventional concrete. In all cases, leached concentrations accounted for just <1% of the total concentrations. Log–log plots of concentration and cumulative release of Fe versus time based on tank leaching data showed that leaching was dominated by diffusion. Overall, the risk of Zn, Pb, Mn, Cu and Fe leaching from coal ash and its concrete was minimal and comparable to that of conventional concrete, a finding in contrast to widely held public perceptions and earlier results reported in other regions such as India. In the current study the coal ash, and its concrete and debris had highly alkaline pH indicative of high acid neutralizing and pH buffering capacity, which account for the stabilization of Zn, Pb, Mn, Cu and Fe. Based on the low risk of Zn, Pb, Mn, Cu and Fe leaching from the coal ash imply that such coal ash can be incorporated in construction materials such as concrete without adverse impacts on public and environmental health from these constituents.

Acid neutralization capacity and cost-effectiveness of antacids sold in various retail pharmacies in the United Arab Emirates

The objective of this research was to determine the acid neutralization capacity (ANC) at 37°C±2°C (as per United States Pharmacopeia 30 and the National Formulary 25) of antacid preparations sold in various retail pharmacies in the United Arab Emirates. Another important objective was to quantify the sodium and calorific content of antacids, as well as overall monthly consumption, and cost of therapy of different antacids from different manufacturers. The tablet and liquid antacids fall into four statistically different ANC groups. Three of the tablet antacids have an ANC similar to that of liquid antacid medications described as being in the high-ANC class. Of the five liquid antacids tested, only two were found to have a high ANC between four production lots at 5% level of significance. The ANC of the most effective liquid antacid was twice that of the lowest. However, this variation in capacity for neutralization is not observed in the product description of antacid brands. A standard dose is one to two teaspoons: one teaspoon will neutralize 20.2–35.92mEq and two teaspoons will neutralize 40.44–71.84mEq depending on the antacid selected. It is apparent from the results of quantification that maximum ANC combined with a minimum dosage volume–weight ratio is achieved by antacids from the high- or intermediate/high-ANC group. Consumption of these categories of antacids is beneficial as they contain less sodium and fewer calories and they are less expensive for pharmacists and/or the public. The monthly cost of daily high-dose therapy is much lower for high-ANC tablet antacids than for low-ANC tablet antacids. In conclusion, if antacids are to be used optimally, it is imperative that the ANC is specified on the product label.

Solidified structure and leaching properties of metallurgical wastewater treatment sludge after solidification/stabilization process

ABSTRACTThe presented study investigates solidification/stabilization process of hazardous heavy metals/arsenic sludge, generated after the treatment of the wastewater from a primary copper smelter. Fly ash and fly ash with addition of hydrated lime and Portland composite cement were studied as potential binders. The effectiveness of the process was evaluated by unconfined compressive strength (UCS) testing, leaching tests (EN 12457-4 and TCLP) and acid neutralization capacity (ANC) test. It was found that introduction of cement into the systems increased the UCS, led to reduced leaching of Cu, Ni and Zn, but had a negative effect on the ANC. Gradual addition of lime resulted in decreased UCS, significant reduction of metals leaching and high ANC, due to the excess of lime that remained unreacted in pozzolanic reaction. Stabilization of more than 99% of heavy metals and 90% of arsenic has been achieved. All the samples had UCS above required value for safe disposal. In addition to standard leaching tests, solidificates were exposed to atmospheric conditions during one year in order to determine the actual leaching level of metals in real environment. It can be concluded that the EN 12457-4 test is more similar to the real environmental conditions, while the TCLP test highly exaggerates the leaching of metals. The paper also presents results of differential acid neutralization (d-AN) analysis compared with mineralogical study done by scanning electron microscopy and X-ray diffraction analysis. The d-AN coupled with Eh-pH (Pourbaix) diagrams were proven to be a new effective method for analysis of amorphous solidified structure.

Electrokinetic remediation of metal-polluted marine sediments: experimental investigation for plant design

This paper presents the results of an extensive set of laboratory experiments performed to design a demonstrative electrokinetic plant for extracting heavy metals from marine sediments dredged from the Livorno marine harbour. The investigated sediments displayed a high salinity, a high acid neutralization capacity, a low electrical resistivity (0.5Ωm), a high alkalinity (pH≈8) and a large fraction of fine particles. The target metals were Cd, Cr, Cu, Ni, Pb and Zn at relatively weak and inhomogeneous concentrations with high non-mobile fractions. After an accurate characterization, several screening and full electrokinetic tests were performed using cells of two different sizes, several conditioning agents (HNO3, HCl, H2SO4, citric acid, oxalic acid, ascorbic acid, EDTA), different applied current intensities and durations. The tests highlighted the need for long treatment times in order to obtain a significant pH reduction, with some appreciable metal removal being attained only after several weeks. The best results were obtained with strong acids used as the conditioning agents, with significant specific effects of each acid, including pronounced resistivity increase (from 0.5 up to 10Ωm) and a high electroosmotic flow (EOF) with H2SO4, or a reversed EOF (electroendosmosis), and minor resistivity changes with HNO3. The use of the obtained data to design a demonstrative plant is also presented in the paper, with considerations on operating parameters such as energy and reagent consumption, characteristics of plant components and required safety measures.