Solubility Of Calcium Carbonate Research Articles

Differences in the solubility of CaCO3 from blood clam shells and Ca(OH)2 as a candidate pulp capping material

Background: Calcium hydroxide (Ca(OH)2) is the gold standar in pulp capping treatment because the biocompatibility and capability to stimulate hard tissue formation and also antibacterial effect. However, this compound has the disadvantage of being easily soluble in saliva which will increase the risk of leakage in the cavity. Another alternative pulp capping material is calcium carbonate from blood clam shells. Blood clam shells contain 98% CaCO3, CaCO3 has low solubility and is difficult to dissolve in water due to the large ions on Ca2+ and CO32- so that the attractive force between these ions is very strong and finally H2O is not able to break down the CaCO3 compound to be dissolved. Purpose: Explained the differences in the solubility of calcium carbonate from blood clam shells and calcium hydroxide as candidates pulp capping materials. Methods: This research is a laboratory experimental study with a pretest-posttest control group design method. The samples consisted of 12 pieces of Ca(OH)2 and CaCO3 then divided into 2 groups and given treatment. Group 1 CaCO3 immersed in 1 day, group 2 Ca(OH)2 immersed in 1 day, group 3 CaCO3 immersed in 7 days, and group 4 Ca(OH)2 immersed in 7 days. Solubility is calculated according to the solubility formula. Data testing with Anova-Welch. Results: There was a significanly difference in the solubility rate between the CaCO3 dan Ca(OH)2 groups immersed for 1 day and 7 days on the Anova-Welch results (p<0.05). Conclusion: The solubility of CaCO3 in blood clam shells is lower than the solubility in Ca(OH)2.)

Clogging mechanisms of biological aerobic filter in a petro-chemical wastewater treatment plant: A field study

Clogging reduces the treatment capacity of the Biological Aerobic Filter(BAF). Revealing the cause of clogging is the key to maintaining normal treatment of BAF. In a petrochemical wastewater treatment plant, two identical structure BAF exhibit different clogging situations. Pre-BAF was clogged with slurry while Posterior-BAF was clogged with medium hardening. SEM showed the medium granular of Posterior-BAF were glued by crystal scale. The crystal scale was detected as calcite by XRD. Water quality analysis illustrated that the raw water contained high concentrations of Ca2+ and HCO3−, the calcium carbonate solubility products of the Pre-BAF and Posterior-BAF water were 6.5 × 10−8 and 3 × 10−8, both are over deposition value. The concentration of TOC in the Pre-BAF influent water was 67.8 mg/L, 7 times higher than that in the Posterior-BAF. The calcium content in the Posterior-BAF scaling along the flow direction shows the proportions were 8.2 %, 19.1 % and 30.7 % in the front, middle and back sections respectively. Thermal gravimetric analysis of the crystalline scale illustrated there were organic weight loss peaks in the front section while only calcite peaks in the back section. It is concluded the organic content is the main reason for the clogging difference in the two BAFs. The organic substance exerts an effect on the scale composition and the calcite crystal perfect in the Posterior-BAF.

CaCO3 solubility in the process water of recycled containerboard mills

Abstract Water system closure in recycled containerboard mills may have reached a technical limit due to the accumulation of organic and inorganic contaminants in the process water. The specific water chemistry characteristics of recycled containerboard mills with restricted water systems were analyzed and a computer model was developed to simulate calcium carbonate solubility in the presence of volatile fatty acids under relevant mill conditions. A strong linear correlation between VFAs and calcium ions was found. The calcium carbonate dissolution mechanism, solubility, and precipitation were investigated. The reaction of VFAs with calcium carbonate results in the formation of bicarbonate and carbonic acid. By binding hydrogen ions, the carbonate has a pH buffering effect. The carbonic acid dissociates into water and CO2. Gaseous CO2 escapes from the water and leads to decarbonization. This mechanism is responsible for the uncoupling of pH from the concentration of VFAs, as well as from the concentration of dissolved calcium ions. The resulting lack of carbonates prevents the precipitation of calcium carbonate. The introduction of CO2 contained in the biogas produced in anaerobic biological water treatment reverses the dissolution mechanism and causes the precipitation of calcium carbonate. Concentrating technologies such as membrane filtration and evaporation may therefore meet the specific requirements for complete water system closure in recycled containerboard mills better than current commonly used biological treatment.

Mechanism of densification of calcium carbonate by cold sintering process

In general, carbonates cannot be easily hardened by the conventional ceramic sintering process due to their thermal decomposition during heating. However, when the cold sintering process (CSP) is selected, carbonates can be hardened at lower temperatures. It has been demonstrated that calcium carbonate can be hardened by CSP, but the detailed densification mechanisms of cold sintering at various temperatures have not been fully clarified. In this study, the vaterite phase of calcium carbonate was selected as the starting material. As the cold sintering temperature for calcium carbonate powder increased, the bulk density of the hardened calcium carbonate body increased. The compressive strength was maximized when cold sintered at 80 °C due to the balance between the solubility of calcium carbonate and the reactivity of cold sintering. Almost no crystal phase transformation from vaterite to calcite occurred during cold sintering, and reprecipitation of the vaterite phase though dissolution-precipitation densified the body.

Carbonation of EAF Stainless Steel Slag and Its Effect on Chromium Leaching Characteristics

EAF stainless steel slag (EAF slag) is one kind of chromium-bearing metallurgical solid waste, which belongs to alkaline steel slag, and contains a large number of alkaline mineral phases. The carbonation activity of these minerals gives EAF slag the capability to effectively capture CO2. In this paper, EAF slag samples with different carbonation degrees were prepared by the slurry-phase accelerated carbonation route. The mineralogical identification analysis was used to qualitatively and semi-quantitatively determine the types and contents of the carbonatable mineral phases in the EAF slag. The sequential leaching test was used to study the chromium leachabilities in EAF slags with different carbonation degrees. The results showed that the main minerals with carbonation activity in EAF slag were Ca3Mg(SiO4)2 and Ca2SiO4, with mass percentages of 56.9% and 23%, respectively. During the carbonation process, Ca2SiO4 was the main reactant and calcite was the main product. As the degree of carbonation increased, the pH of the EAF slags’ leachate gradually decreased while the redox potential (Eh) gradually increased. At the same time, a large amount of Ca2+ in the EAF slag combined with CO2 to form slightly soluble calcium carbonate, which led to a significant decrease in the conductivity of the leachate. With the gradual increase in carbonation ratio, the leachability of chromium in the EAF slag first decreased and then increased, and reached its lowest value when the CO2 uptake ratio was 11.49%.

Ex vivo study: is it possible to overcome the blurriness caused by holmium laser fragmentation of kidney stones?

Better endoscopic vision is mandatory for successful ureteroscopic stone operations to achieve shorter operating time. However, an important impairing factor for a good endoscopic view is the cloudiness of vision which was formed during laser fragmentation. Holmium laser fragmentation of calcium oxalate stones produces calcium carbonate solubility of which is dependent on pH, citrate, and phosphate. In this ex vivo research, the solubility of calcium carbonate has been investigated in solutions composed of various concentrations of citrate and phosphate buffered at different pH levels after laser fragmentation of calcium oxalate stones. Calcium oxalate stones were placed into the laboratory tubes filled with various concentrations of citrate-phosphate buffers with different pH values. Laser energy in dusting mode was applied to the stones and spectrophotometric measurement for optical density (OD) was calculated for each buffered solution for clarity comparison. In the first phase, solutions composed of four different molar concentrations of citrate-phosphate buffer (0.2, 0.3, 0.4 and 0.5 molars) at various pH levels were used. Then, the next phase of the study was designed to compare solutions demonstrating the lowest OD values with an isotonic saline solution. The results were most convenient at 0.5 molarity (pH = 6) followed by 0.4 molarity (pH = 7) in the first phase (OD values of 0.054 and 0.065, respectively). In the next phase, OD values of both buffered solutions were significantly lower than those of isotonic saline solution (p = 0). Two specific buffers have provided better optic visibility values after laser fragmentation supporting their use as an irrigation solution for the favor of less cloudiness.

Key to Indigo Naturalis' oral effectiveness: in vivo and in vitro verification of bile action

Indigo Naturalis( IN) is mainly composed of 10% organic matter and 90% inorganic matter,with a poor wettability and strong hydrophobicity. Indigo,indirubin and effective ingredients are almost insoluble in water. And how it exerts its effect after oral administration still needs to be revealed. For this reason,this study put forward the hypothesis that " Indigo Naturalis forms a slightly soluble calcium carbonate carrier in a strong acid environment of gastric fluid,and organic substances are solubilized in the bile environment of intestinal fluid",and then verified the hypothesis. First,the dissolution apparatus was used to simulate the change process of IN in different digestive fluid,and the effects of low-dose and normal bile on the dissolution of inorganic substances and the release of organic substances were compared. After the surface morphology and element changes of IN in different digestive fluid were observed,it was found that bile is the key to promoting the dissolution of organic and inorganic substances in IN. Furthermore,the rat fever model induced by 2,4-dinitrophenol was used to study the antipyretic effect of IN in normal rats and bile duct ligation rats. It was found that the antipyretic effect of IN on normal rats was better than that of bile duct ligation rats. The above results indicated that after oral administration of IN,the calcium carbonate carrier was transformed into a slightly soluble state in acidic gastric fluid,and a small amount of organic matter was released. When IN entered the intestinal fluid mixed with bile,the carrier dissolved in a large amount,and indigo and indirubin were dissolved in a large amount,so as to absorb the blood and exert the effect. This study has a certain significance for guiding clinical application of IN. For patients with insufficient bile secretion( such as bile duct resection),oral administration with IN may not be effective and shall be paid attention.

A Bivalve Biomineralization Toolbox.

Mollusc shells are a result of the deposition of crystalline and amorphous calcite catalyzed by enzymes and shell matrix proteins (SMP). Developing a detailed understanding of bivalve mollusc biomineralization pathways is complicated not only by the multiplicity of shell forms and microstructures in this class, but also by the evolution of associated proteins by domain co-option and domain shuffling. In spite of this, a minimal biomineralization toolbox comprising proteins and protein domains critical for shell production across species has been identified. Using a matched pair design to reduce experimental noise from inter-individual variation, combined with damage-repair experiments and a database of biomineralization SMPs derived from published works, proteins were identified that are likely to be involved in shell calcification. Eighteen new, shared proteins likely to be involved in the processes related to the calcification of shells were identified by the analysis of genes expressed during repair in Crassostrea gigas, Mytilus edulis, and Pecten maximus. Genes involved in ion transport were also identified as potentially involved in calcification either via the maintenance of cell acid–base balance or transport of critical ions to the extrapallial space, the site of shell assembly. These data expand the number of candidate biomineralization proteins in bivalve molluscs for future functional studies and define a minimal functional protein domain set required to produce solid microstructures from soluble calcium carbonate. This is important for understanding molluscan shell evolution, the likely impacts of environmental change on biomineralization processes, materials science, and biomimicry research.

Electrochemical enhancement and inhibition of calcium carbonate deposition

Abstract Calcium carbonate is by far the most widespread scaling material. Its deposition in pipes and flowlines has been a long-standing problem for many industries. Hence, a lot of research is devoted to scale inhibition. One of the calcium carbonate scale management methods relies on removal of calcium ions from scaling solution by electrochemically enhanced deposition. Application of potential between two electrodes may result in oxygen reduction and water electrolysis. Both processes change the local pH in close proximity to the electrodes. Solution close to the anode is becoming acidic while that close to the cathode alkaline. Solubility of calcium carbonate is pH dependent. The alkaline pH in the vicinity of the cathode promotes precipitation of calcium carbonate. On the other hand, the acidic environment near the anode prevents anode from scaling. In this paper we show how the cathodic and anodic processes, respectively, accelerate and prevent scale deposition on graphite electrode surfaces. The growth of calcium carbonate at different calcium ion concentrations and different voltage magnitudes applied were followed using X-ray computed tomography. The morphology of the deposited calcium carbonate was studied using the scanning electron microscopy. The polymorphic forms of calcium carbonate deposited at different voltage magnitudes were identified using X-ray powder diffraction. A strong correlation between the scaling rate, the average crystallite size and the voltage applied was observed.

Novel Cake Washer for Removing Oil-Based Calcium Carbonate Filter Cake in Horizontal Wells

An impermeable layer “filter cake” usually forms during the overbalanced drilling technique. Even though it helps in protecting the formation from a further invasion of drilling fluids, the removal of this layer is essential for a proper cement job and to avoid any reduction in wellbore deliverability. The design of the removal process is complicated and depends on the filter cake composition and homogeneity. This paper presents an experimental evaluation on the usage of a novel cake washer (NCW) in the removal of a filter cake formed by an invert emulsion oil-based drilling fluid that contains calcium carbonate as a weighting material while drilling a horizontal reservoir. The proposed NCW is a mixture of organic acid, mutual solvent and nonionic surfactant. It is designed to enable restored wellbore permeability for a sustainable production. Since the filter cake mainly consists of the weighting material, the solubility of calcium carbonate in NCW at different ranges of temperature, duration and concentration was investigated. An actual casing joint was used to test the corrosion possibility of the treating solution. High-pressure and high-temperature (HPHT) filtration tests on ceramic discs and Berea sandstone core samples were conducted to measure the efficiency of the filter cake removal and the retained permeability. Ethylene glycol mono butyl ether (EGMBE) was used as a mutual solvent and the solubility was higher compared to when the mutual solvent was not used in the washer formulation. A significant increase in calcium carbonate dissolution with time was observed for a duration of 24 h. The solubility was found to be proportional to the concentration of NCW with optimum results of 99% removal at a temperature of around 212 °F. At those conditions, no major corrosion problems were detected. Permeability of the core retained its pristine value after the treatment.

Correction to “The Effect of Monoethylene Glycol on Calcium Carbonate Solubility at High Temperatures”

Correction to “The Effect of Monoethylene Glycol on Calcium Carbonate Solubility at High Temperatures”

Evaluation of Nanofiltration Membrane Process for Smartwater Production in Carbonate Reservoirs From Deoiled Produced Water and Seawater

SummaryThis research focuses on membrane-separation efficiencies by adjusting the ionic composition of deoiled produced water (PW) and evaluates the possibility for smartwater production from PW for enhanced oil recovery (EOR) in carbonate reservoirs. Key characteristics of smartwater for carbonate reservoirs are increased concentrations of divalent ions and low concentrations of monovalent ions compared with seawater.In this research, PW was pretreated with media filters, which resulted in 96 to 98% oil removal. This deoiled PW was used as feed for nanofiltration (NF) membranes. Combinations of NF retentate with seawater as feed and NF permeate from PW were considered. PW NF permeate, mixed with seawater spiked with multivalent ions, sulfate (SO42−), or phosphate (PO43−), is expected to alter the wettability of oil reservoirs.NF-membrane performance was evaluated in terms of flux and the separation efficiencies of the key scaling ions calcium (Ca) and barium (Ba). The tested membranes removed 60% of Ca2+ and 53% of Ba2+, thereby reducing the scaling tendency. No membrane fouling was observed during the experiments.NF-treated PW was analyzed for solubility of calcium carbonate (CaCO3). The results showed no Ca dissolution, which could affect chalk-reservoir compaction. This research also reflects the use of nonprecipitating PO43− for smartwater production, simultaneously decreasing the Ba concentration and the scaling potential of PW. The results obtained conclude that spiking PO43− below 12 mM showed no indication of chalk dissolution during equilibration tests at room temperature. Experiments performed with 44 mM of PO43− resulted in calcium phosphate [Ca3(PO4)2] precipitation.A process scheme is proposed for smartwater production by ionic selection from seawater and PW at an operating pressure of 18 bar. Energy-consumption analysis for smartwater production before membrane treatment concluded NF to be economic over other desalination technologies. The power consumed by NF membranes for smartwater production at 18 bar is calculated at 0.88 kW·h/m3, whereas the power consumed is 51.22 and 103.52 kW·h/m3 for reverse osmosis (RO) and multistage flash distillation (MSF), respectively.

Effect of Carbon Nanoparticles on the Crystallization of Calcium Carbonate in Aqueous Solution.

Nanofluids have great application prospects in industrial heat exchange systems because they can significantly improve the heat and mass transfer efficiency. However, the presence of nanoparticles in the fluid might also affect the formation and attachment of inorganic scales, such as calcium carbonate, on the heat exchange surface. The effects of carbon nanoparticles on the crystallization of calcium carbonate in aqueous solution were studied by the scale inhibition test, solution analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results showed that carbon nanoparticles had an excellent surface scale inhibition performance for calcium carbonate, which could effectively prevent the adhesion of scale on the heat exchange surface. The carbon nanoparticles did not affect the solubility of calcium carbonate in water, but changed the crystal form of the precipitated calcium carbonate, making it difficult to adsorb on the heat exchange surface and achieving a surface scale inhibition effect. Carbon nanofluids effectively inhibit the adhesion of calcium carbonate to heat exchange surfaces.

The Effect of Monoethylene Glycol on Calcium Carbonate Solubility at High Temperatures

This study presents the solubility of calcium carbonate in monoethylene glycol (MEG)/water solution at high temperatures and high MEG concentrations. The conditions simulate the water removal proce...

Characterization of soil of Jijiga plain in the Somali regional state of Ethiopia

Low soil fertility and poor soil fertility management practices constrain crop production in Ethiopia. Diagnosing soil fertility problems and characterizing soils are a prerequisite for formulating appropriate soil fertility management practices. However, most soil fertility problems in Ethiopia are not diagnosed, and the soils are not characterized. This invariably leads to lack of documented information for judicious application of soil ameliorative measures to increase crop yields. This study was, therefore, aimed at characterizing soil of Jijiga Plain in the Somali Regional State of Ethiopia on which wheat is commonly grown. The study was conducted during the main cropping season of 2012/2013. The study area was stratified in to three altitude categories 1650 - 1700, 1750 - 1800, 1850 - 1900 meters above sea level prior to sampling. Then, a total of 3 x 2 x 30 x 3 = 540 disturbed soil samples were collected from the surface (0-15 cm) and subsurface (15-30 cm) layers across the altitude categories. The samples were composited treatment-wise to 3 x 6 = 18 sub-samples. The composite soil sub-samples were analyzed for selected soil physico-chemical properties. The data were analyzed using descriptive statistics. The results indicated that both the surface and subsurface soils are clayey in texture. The pH of the soil at the layer of 0 - 30 cm ranged from 8.37 to 8.82 and is rated as strongly alkaline. The exchangeable Ca 2+ contents of the soil at the surface and subsurface soil layers were 24.52 and 30.52 cmol+/kg, respectively, which is rated as very high in both soil layers; the exchangeable Mg 2+ content is 7.36 cmol+/kg in the surface soil layer, which is rated as high, but 10.21 cmol+/kg in the sub-surface soil layers, which is rated as very high. The exchangeable Na+ content of the soil ranges from 0.33 to 2.16 cmol+/kg, which is rated as medium to high. The exchangeable K+ contents of the surface and subsurface soil layers are 1.1 and 1.4 cmol+/kg, respectively, which are rated as high and very high in the surface and sub-surface soil layers. The cation exchange capacity of the soil ranges from 37.17 to 40.49 cmol+/kg, which is rated as high to very high. The percent base saturation in the surface soil is 89.63% whereas that in the sub-surface soil is 109.23%, which is rated as very high. The contents of soil organic carbon (1.81%) and total nitrogen (0.13%) in the surface soil layer were found to be medium whereas those of the sub-surface soil layer were found to be low. However, the available phosphorus contents of both the surface (2.4 mg kg -1 soil) and sub-surface (1.87 mg kg -1 soil) soil layers were found to be very low. It could, thus, be concluded that, the soil of the study area is characterized by strong alkalinity with high contents soluble calcium carbonate, very low content of plant-available phosphorus, and medium contents of soil organic matter as well as total nitrogen. However, the texture and other chemical properties of the soil do not appear to limit crop production. Therefore, there is a need to take ameliorative measures aimed at lowering the pH and increasing availability of soil phosphorus, soil organic carbon, and total nitrogen to improve wheat and other crop yields in the study area. Keywords: Available phosphorus; Cation exchange capacity; Soil organic carbon; Soil organic matter; Soil texture; Soil pH

Crystallization of calcium carbonate and magnesium hydroxide in the heat exchangers of once-through Multistage Flash (MSF-OT) desalination process

In this paper, a dynamic model of fouling is presented to predict the crystallization of calcium carbonate and magnesium hydroxide inside the condenser tubes of Once-Through Multistage Flash (MSF-OT) desalination process. The model considers the combination of kinetic and mass diffusion rates taking into account the effect of temperature, velocity and salinity of the seawater. The equations for seawater carbonate system are used to calculate the concentration of the seawater species. The effects of salinity and temperature on the solubility of calcium carbonate and magnesium hydroxide are also considered. The results reveal an increase in the fouling inside the tubes caused by crystallization of CaCO3 and Mg(OH)2 with increase in the stage temperature. The intake seawater temperature and the Top Brine Temperature (TBT) are varied to investigate their impact on the fouling process. The results show that the (TBT) has greater impact than the seawater temperature on increasing the fouling.

Thermodynamics and kinetics of methane hydrate formation and dissociation in presence of calcium carbonate

Huge amount of gas hydrate deposits are identified in deep marine sediments, which may be considered as a future source of energy. Since carbonate is one of the major components of marine sediments, in the present study attention has been given to characterize methane hydrate formation and dissociation in presence of calcium carbonate. Experiments were performed with 0%, 2%, 4%, 6% and 10% by weight of calcium carbonate in distilled water. Extensive investigations have been done on pressure-temperature equilibrium behavior of hydrate formation and dissociation at varying concentrations of calcium carbonate. Hydrate formation rate was found to vary with concentration of calcium carbonate as the solubility of calcium carbonate in water is controlled by the presence of simultaneous chemical equilibria involving a high number of species like Ca2+, CO32−, HCO3−, CO2, etc. Induction time for hydrate formation has also been measured at different concentrations of carbonate. Nucleation point for the hydrate formation was observed to be slightly higher at higher concentration of calcium carbonate due to increased heat absorption. Dissociation enthalpy of hydrates was calculated by using Clausius-Clapeyron at different measured conditions. Moles consumption of methane gas during hydrate formation at different concentrations of carbonate was measured using real gas equation and found to be minimum at 10 wt%.

Control of temperature and aqueous Mg2+/Ca2+ ratio on the (trans-)formation of ikaite

The calcium carbonate hexahydrate mineral ikaite (CaCO3⋅6 H2O) has been documented in aquatic environments at near-freezing temperatures. An increase of the prevailing temperature in the depositional environment, results in the transformation of natural ikaite into less soluble calcium carbonate phases occasionally leaving calcite pseudomorphs in the sediments, which are considered asan indicator for primary cold water temperatures. Detailed understanding on the physicochemical parameters controlling ikaite (trans-)formation however, such as temperature and reactive solution chemical composition, are still under debate. In order to study the formation of ikaite, we conducted precipitation experiments under controlled physicochemical conditions (pH = 8.3±0.1; T=6, 12, and 18±0.1°C) at defined aqueous molar Mg/Ca ratios. The transformation of ikaite into anhydrous calcium carbonate polymorphs was investigated in solution and at air exposure. The obtained results reveal the formation of ikaite at temperatures up to 12°C, whereas Mg-rich amorphous calcium carbonate precipitated at 18°C. In contact with the reactive solution ikaite transformed into aragonite at aqueous molar Mg2+/Ca2+ ratios of ≥14. In contrast, ikaite separated from the Mg-rich solution and exposed to air transformed in all cases into calcite/vaterite. The herein obtained temperature limit of ≤12 for ikaite formation is significantly higher than formerly expected and most probably caused by (i) the high saturation degree of the solution with respect to ikaite and (ii) the slow dehydration of the aqueous Ca2+ ion at low temperatures. This result questions the suitability of calcite pseudomorphs (i.e. glendonites) as a proxy for near-freezing temperatures. Moreover, our findings show that the CaCO3 polymorph formed from ikaite is strongly controlled by the physicochemical conditions, such as aqueous molar Mg2+/Ca2+ ratio of the reactive fluid and H2O availability throughout the transformation process.

Measurement of Physical Properties and Correlation of the Solubility of Calcium Carbonate in Ammonium Sulfate Aqueous Solution at T = (298.15, 323.15, and 348.15) K in the Process of Preparing Calcium Carbonate Products by the Desulfurization of Gypsum

As a continuation of our previous study in which the basic data about the NH4Cl–CaCO3–H2O ternary system was measured, the solubility and physical properties (density, viscosity, and refractive index) of calcium carbonate in ammonium sulfate aqueous solution at (298.15, 323.15, and 348.15) K have been investigated by using the isothermal dissolution method in this work. The results showed that the solubility of calcium carbonate increased as the molality of ammonium sulfate aqueous solutions and temperature increased. The solubility of calcium carbonate in ammonium sulfate aqueous solutions and the viscosity of aqueous solutions were correlated with the second-order polynomial equation and semiempirical exponential model equation, respectively. By comparing the calculated values with experimental data, the second-order polynomial equation and semiempirical exponential model equation provide accurate mathematical representations of the experimental results. The obtained experimental data in this work could provide available data for the industrial production of calcium carbonate products and further theoretical studies.

Ash behavior during hydrothermal treatment for solid fuel applications. Part 2: Effects of treatment conditions on industrial waste biomass

This second half of our work on ash behavior concentrates on the effects of hydrothermal treatment conditions on paper sludge. Ash composition and solubility were determined based on treatment temperature, reactor solid load and liquid pH using experimental design and univariate regression methods. In addition, ash properties for combustion were evaluated based on recent developments on ash classification. Based on the results, all experimental variables had a statistically significant effect on ash yields. Only reactor solid load was statistically insignificant for char ash content, which increased based on increasing treatment temperature due to the decomposition of organic components. Ash dissolution and ash yield were governed by liquid pH and the generation of acids mainly due to the solubility of calcium carbonate identified as the main mineral species of paper sludge. Dissolution of calcium carbonate however decreased ash fusion temperatures more likely causing problems during char incineration. This indicated that decreasing the ash content of sludge during hydrothermal treatment can actually weaken ash properties for solid fuel applications.