Total Aluminum Research Articles

In situ monitoring of the Sinos River, southern Brazil: water quality parameters, biomarkers, and metal bioaccumulation in fish.

The Sinos River is an important water supply in Southern Brazil and receives industrial, agricultural, and domestic effluents which may affect aquatic biota. Water physicochemical and microbiological analyses, biomarker responses (scaled mass index (SMI), gill histopathology, and micronucleus and nuclear abnormality (MN and NA) frequencies), and metal bioaccumulation in muscle were assessed in the fish species Bryconamericus iheringii (Characidae) captured at three sampling sites (S1, S2, and S3) in four sampling periods. The mean values of five parameters (total phosphorus, thermotolerant coliforms, aluminum, iron, and lead) exceeded the limits established by the Brazilian legislation at the three sampling sites. Although physicochemical analysis indicated higher impacts at S3, in some samples, significantly higher MN frequencies and bioaccumulation of manganese in fish muscle were observed at S1, whereas low SMI and higher concentrations of aluminum and zinc in fish muscle were found at S2. Histopathological alterations in gills were observed in fish collected at the three sampling sites; however, no spatial differences were observed, indicating similar environmental conditions with respect to this biomarker. Moreover, temporal variation of biomarker responses and metal bioaccumulation were found at all sampling sites. Furthermore, the consumption of fish from the Sinos River should be avoided given the concentrations of chromium (all samples), cadmium, and lead in fish muscle above the threshold for safe human consumption.

Aluminum exposure in premature babies related to total parenteral nutrition and treatments.

Aşut E, Köksal N, Dorum BA, Özkan H. Aluminum exposure in premature babies related to total parenteral nutrition and treatments. Turk J Pediatr 2018; 60: 385-391. This study aimed to measure aluminum contamination of parenteral nutrition (PN) solutions and aluminum contents of parenteral products given to newborn infants for nutrition or treatment. In this study, the aluminum content of the first products used to prepare PN solutions for premature neonates, of the final parenteral products prepared therefrom, and of the parenteral drugs frequently used in newborn units was measured using the inductively coupled plasma mass spectrometry. The aluminum contamination of all parenteral nutritional products evaluated, except for one, was detected to be over the recommended doses. Of all the first products analyzed within the scope of the study, trace-element preparation, preparation containing fat-soluble vitamins, 20% dextrose solution, calcium gluconate ampoule and sodium phosphate ampoule indicated high aluminum contamination. The total aluminum content of the prepared final products was identified to be at least 40% higher than the total aluminum content of the ingredients added to the compound. Accordingly, the minimum amount of aluminum content was measured as 233 μg/kg/day in nutrition solutions prepared for a baby weighing 1,000 g. Contamination was detected in 9 of the 18 drugs evaluated. This study indicated that the rate of aluminum exposure of the premature babies receiving parental nutrition is still much higher than the safe doses recommended as 5 µg/kg/day by the FDA. Products with lower aluminum content should be preferred in the care of premature infants.

Determination of anthocyanin content of two forms of Brassica oleracea

The present study was carried out to determine the total anthocyanin content of two cultivars of Brassica oleraceae belongs to the family Cruciferae. Total phenolics and total flavonoid content were also determined. pH differential method was used to determine total anthocyanins present and aluminium chloride and Folin-Ciocalteu reagents were used for the determination of flavonoids and phenolics, respectively. Comparatively, anthocyanin flavonoid and phenolic contents were varied between white and red cabbage. Red cabbage showed high amount of these phytochemicals when compared to white cabbage. Thus depending on results we say that red cabbage variety may serve as a potential source of nutraceuticals and functional food development.

Stability, Deactivation, and Regeneration of Chloroaluminate Ionic Liquid as Catalyst for Industrial C4 Alkylation

Alkylation of isobutane and 2-butene was carried out in a continuous unit using triethylamine hydrochloride (Et3NHCl)-aluminum chloride (AlCl3) ionic liquid (IL) as catalyst. The effects of impurities such as water, methanol, and diethyl ether on the stability of the catalytic properties and deactivation of the ionic liquid were studied in the continuous alkylation. In the Et3NHCl-2AlCl3 ionic liquid, only one half of the aluminum chloride could act as the active site. With a molar ratio of 1:1, the active aluminum chloride in the ionic liquid was deactivated by water by reaction or by diethyl ether through complexation while the complexation of aluminum chloride with two molecular proportions of methanol inactivated the active aluminum chloride in the ionic liquid. The deactivation of chloroaluminate ionic liquid was observed when the active aluminum chloride, i.e., one half of the total aluminum chloride in the ionic liquid, was consumed completely. The regeneration of the deactivated ionic liquid was also investigated and the catalytic activity could be recovered by means of replenishment with fresh aluminum chloride.

A methodology for the assessment of inhalation exposure to aluminium from antiperspirant sprays.

Inhalative exposure can occur accidentally when using cosmetic spray products. Usually, a tiered approach is applied for exposure assessment, starting with rather conservative, simplistic calculation models that may be improved with measured data and more refined modelling. Here we report on an advanced methodology to mimic in-use conditions for antiperspirant spray products to provide a more accurate estimate of the amount of aluminium possibly inhaled and taken up systemically, thus contributing to the overall body burden. Four typical products were sprayed onto a skin surrogate in defined rooms. For aluminium, size-related aerosol release fractions, i.e. inhalable, thoracic and respirable, were determined by a mass balance method taking droplet maturation into account. These data were included into a simple two-box exposure model, allowing calculation of the inhaled aluminium dose over 12min. Systemic exposure doses were calculated for exposure of the deep lung and the upper respiratory tract using the Multiple Path Particle Deposition Model (MPPD) model. The total systemically available dose of aluminium was in all cases found to be less than 0.5µg per application. With this study it could be demonstrated that refinement of the input data of the two-box exposure model with measured data of released airborne aluminium is a valuable approach to analyse the contribution of antiperspirant spray inhalation to total aluminium exposure as part of the overall risk assessment. We suggest the methodology which can also be applied to other exposure modelling approaches for spray products, and further is adapted to other similar use scenarios.

Flame propagation through heterogeneous combustion of hybrid aluminum-boron poly-disperse particle suspensions in air

In this paper, flame propagation through heterogeneous hybrid aluminum-boron dust cloud including the effect of particle Poly-dispersion was simulated. Particles were distributed randomly within a three-dimensional domain. A discrete thermal model based on heat transfer between distinct metallic particles was developed to estimate flame propagation speed in the mixture. The flame propagation speed of the hybrid dust cloud in air was calculated for a range of total particle concentrations and different aluminum and boron partial concentrations. The presented results showed that the flame front velocity increases as the weight percentage of aluminum particles increase. In addition, adding aluminum to boron dust cloud can improve the flame propagation speed. To investigate the roles of conduction and radiation as well as radiative heat loss, time variations of particle temperatures when only one of the heat transfer mechanisms is present were evaluated and discussed. Careful examination of the numerical results showed that conduction heat transfer had the dominant role in aluminum and boron aero-suspension combustion.

Study of the aluminium content in AGB winds using ALMA

(abbreviated) We aim to constrain the dust formation histories in the winds of oxygen-rich AGB stars. We have obtained ALMA observations with a spatial resolution of 120x150 mas tracing the dust formation region of a low mass-loss rate and a high mass-loss rate AGB star, R Dor and IK Tau. Emission line profiles of AlO, AlOH and AlCl are detected and are used to derive a lower limit of atomic aluminium incorporated in molecules. We show that the gas-phase aluminium chemistry is completely different in both stars, with a remarkable difference in the AlO and AlOH abundance stratification. The amount of aluminium locked up in these 3 molecules is small, <=1.1e-7, for both stars, i.e. only <=2% of the total aluminium budget. This leaves ample of room for aluminium to be incorporated in grains. A fundamental result is that AlO and AlOH, being the direct precursors of alumina grains, are detected well beyond the onset of the dust condensation proving that the aluminium oxide condensation cycle is not fully efficient. The ALMA observations allow us to quantitatively assess the current generation of theoretical dynamical-chemical models for AGB winds. We discuss how the current proposed scenario of aluminium dust condensation for low mass-loss rate AGB stars at a distance of ~1.5 Rstar, in particular for the stars R Dor and W Hya, poses a challenge if one wishes to explain both the dust spectral features in the spectral energy distribution (SED), in interferometric data, and in polarized light signal. In particular, the estimated grain temperature of Al2O3 is too high for the grains to retain their amorphous structure. We propose that large gas-phase (Al2O3)n-clusters (n>34) can be the potential agents of the broad 11 micron feature in the SED and in the interferometric data and we explain how these large clusters can be formed.

Detection of microorganisms, endotoxins and aluminum in mobile dialysis services

Hemodialysis water and dialysates are fundamental in the treatment of kidney disease. During just one hemodialysis session, 120 liters of dialysate are consumed. Thus, it is essential that the parameters of chemical and microbiological quality of the fluids used in dialysis systems are carefully observed. In this study, water samples were collected at 12 hospitals in the state of Rio de Janeiro. The samples were obtained at three points of fluid reservoirs: pre-, post-osmosis and dialysis solution. After collection, colony forming units (CFU), total coliforms and Escherichia coli 100 mL -1 were quantified. Later, isolated colonies and endotoxin content were identified by biochemical assays. Data about total aluminum levels per sample (mg L -1 ) were also obtained. Samples of all mobile dialysis services and points of collection were contaminated above the levels set out by national laws, in particular by Pseudomonas aeruginosa . Endotoxin levels were also above the recommended by current legislation (> 0.25 EU mL -1 ). Only three samples contained detectable levels of aluminum, which were found to be above the recommended values for the corresponding resolution (0.01 mg L -1 ). Finally, there were no observable amounts of total coliforms and E. coli 100 mL -1 sample. The data from this study are an important step forward in the standardization and control of chemical/microbiological quality of mobile dialysis services.

Is exposure to aluminium adjuvants associated with social impairments in mice? A pilot study

BackgroundOur group has shown that significant correlations exist between rates of Autism Spectrum Disorder (ASD) and total aluminum adjuvants given to children through vaccines in several Western countries. These correlations satisfied eight out of nine Hill criteria for causality. Experimental studies have demonstrated a range of behavioural abnormalities in young mice after postnatal exposure to aluminium. To build on our previous work, the current study will investigate the effect of aluminium adjuvants on social behaviour in mice. Anomalies in social interaction are a key characteristic of those with ASD. MethodsNeonatal CD-1 mice pups were injected with either a total of 550μg of aluminum hydroxide gel (experimental group) or saline (control) spread out during the first two weeks of postnatal life. The mice were then subjected to behavioural tests for social interest and social novelty at postnatal week 8, 17 and 29. p-Values were calculated using the Mann-Whitney and Kruskal Wallis tests. ResultsAluminum injected mice showed diminished social interest compared to controls at week 8 (p=0.016) and 17 (p=0.012). They also demonstrated abnormal social novelty from controls at week 8 (p=0.002) and week 29 (p=0.042). ConclusionThis is the first experimental study, to our knowledge, to demonstrate that aluminum adjuvants can impair social behaviour if applied in the early period of postnatal development. The study, however, is insufficient to make any assertive claims about the link between aluminium adjuvants and ASD in humans.

Evaluating Differences in Aluminum Exposure through Parenteral Nutrition in Neonatal Morbidities.

Aluminum is a common contaminant in many components of parenteral nutrition, especially calcium and phosphate additives. Although long-term effects have been described in the literature, short-term effects are not well-known. Currently, the Food and Drug Administration recommends maintaining aluminum at <5 mcg/kg/day. This was a single center, retrospective case-control study of 102 neonatal intensive care unit patients. Patients were included if they had a diagnosis of necrotizing enterocolitis, rickets/osteopenia, or seizures and received at least 14 days of parenteral nutrition. Patients were matched 1:1 with control patients by gestational age and birth weight. Mean total aluminum exposure for the 14 days of parenteral nutrition was calculated using manufacturer label information. Differences in mean aluminum exposure between cases and controls, as well as subgroup analysis in those with renal impairment or cholestasis, was conducted. Aluminum exposure in patients meeting inclusion criteria closely mirrored the aluminum exposure of control patients. The difference in aluminum exposure was not found to be statistically significant, except in patients with cholestasis. Although the study found no difference in aluminum exposure in short-term complications with neonates, long-term complications are well established and may warrant the need to monitor and limit neonatal aluminum exposure.

An advanced dynamic process model for industrial horizontal anode baking furnace

• Advanced dynamic process model for industrial horizontal anode baking furnace. • Coupling of fluids, gas and solid parts through an interface at the brick surface on the flue side. • Model prediction of bi-dimensional behaviour of the flue gas. • Pseudo tridimensional prediction of the solids behaviour. • Anode baking performance study to reduce energy consumption. The global aluminum industry is facing new challenges due to new technological developments. Carbon anodes, consisting of mainly petroleum coke and coal tar pitch, are used in the electrolytic production of aluminum. High amperage utilization in the electrolytic cells with the objective of increasing production requires high quality carbon anodes. The anode quality depends both on raw material quality, anode recipe as well as forming and baking conditions of anode manufacturing process. The cost of the baking process constitutes 15 to 25% of the total aluminum production cost [1] . The industrial challenge is to produce better quality anodes consuming less energy, and reducing environmental emissions. A transient two dimensional (2D + ) process model for horizontal anode baking furnace was developed during this study. The main objective was to develop an efficient furnace model with low computation load and time, using the transient Finite Difference Method and simplified furnace geometry. The model represents several phenomena involved during the anode baking process such as heat transfer (convection, radiation and conduction), fuel combustion, volatile matter (tar, methane and hydrogen) generation and combustion, air infiltration and energy loss to the atmosphere from the walls, the top of the furnace and the foundation. The model was developed using two coupled sub-models; the first one describes the thermal conduction through the solid materials (brick refractory wall, packing coke and anode block) as well as the volatile release, and the second one describes the gas flow, heat and mass transfer as well as the combustion of fuel and volatiles in the flue. Compared to the existing process models (where the gas flow in flue is assumed as unidirectional along the horizontal furnace direction), the present model also considers the gas flow in vertical direction and uses four vertical planes per pit section to predict the temperature of the solids. The model predicts 2D temperature distribution within the flue gas (xy plane) and the pit solid materials (yz plane) allowing then the prediction of the pseudo tridimensional distribution of the solid temperature. This model is a useful tool for the continuous monitoring of anode temperature and studying of the horizontal anode baking furnace behaviour. The effect of any change in operational parameters and the energy consumption on the furnace operation can be predicted.

Study on the Effect of [Al&lt;sub&gt;13&lt;/sub&gt;]&lt;sup&gt;7+&lt;/sup&gt; over the Free Swelling Ratio of Expansive Soil

The hydroxy-aluminum solution is prepared by alkali neutralization titration and the subsequent cross-linking tests are designed by mixing the hydroxy-aluminum solution and expansive soil, followed by the discussion on the influence of the molar ratio of OH- to Al3+ and ratio of total aluminum to expansive soil on the swelling behavior of the cross-linked soil. The free swelling ratio of the cross-linked soil decreased significantly, indicating that the main aluminum species that changes the expansion properties of the cross-linked soil is [Al13]7+.

Influence of environmental factors on absorption characteristics of suspended particulate matter and CDOM in Liaohe River watershed, northeast China.

Absorption characteristics of optically active substances, including non-algal particles, phytoplankton, and chromophoric dissolved organic matter (CDOM), were measured in conjunction with environmental factors in five rivers within the Liaohe River watershed. Spectral absorption of non-algal particles [a NAP(λ)] was similar to that of total particles for most samples, suggesting that the absorption of the total particles [a p(λ)] was dominated by a NAP(λ). The CDOM absorption spectra [a CDOM(λ)] of West Liaohe and Taizihe rivers were easily distinguished from those of Hunhe, Liaohe, and East Liaohe rivers. Redundancy analysis indicated that absorption by optically active substances and anthropogenic nutrient disturbances probably resulted in the diversity of water quality parameters. The environmental variables including dissolved organic carbon, total alkalinity (TAlk), and total nitrogen (TN) had a significant correlation with CDOM absorption at 440nm [a CDOM(440)]. There was almost no correlation between a p(λ) and chlorophyll a, TN, total phosphorus, and TAlk. Moreover, total copper ion concentration and mercury ion concentration had a strong correlation with a p(440), a p(675), a NAP(440), and a NAP(675). The concentration of total aluminum ions exhibited a positive correlation with a p(675) and a NAP(675) (p<0.05), and a significant correlation was observed between total arsenic concentration and a CDOM(440). Furthermore, the interaction between metal ions and optically active substances provided an insight into particulates and CDOM properties linked to water quality characteristics for rivers in semiarid areas.

Ammonium sulphate and/or ammonium bisulphate as extracting agents for the recovery of aluminium from ultrafine coal fly ash

We recently showed that the selective extraction of aluminium from the amorphous phase of a South African ultrafine coal fly ash can be achieved via thermochemical treatment with ammonium sulphate for 1h followed by aqueous dissolution, as an alternative to conventional hydrometallurgical processes. In this study, insight gained from the previous work was applied to investigate and compare total vs selective aluminium extraction efficiencies using ammonium sulphate or ammonium bisulphate either on its own, or as a mixture of the two salts as extracting agents during a 2h thermal treatment process. The effects of (i) ash-to-extractant mass ratio and (ii) temperature during thermal treatment on extraction efficiency was investigated. While a maximum, but non-selective, recovery of 46.6% total aluminium was achieved using ammonium bisulphate at 400°C, the most technically appropriate results for selective recovery yielded 37.3% aluminium, with only 0.3% silicon, 0.1% titanium and 3.9% iron having been co-extracted when using ammonium sulphate at a processing temperature of 600°C. Extraction of most of the calcium and magnesium could not be prevented. Using mixtures of ammonium salts as extracting agents during thermochemical treatment may however introduce technical difficulties on large scale. Our results indicate that any of the two ammonium salts could be used on their own during thermochemical treatment. Thermochemical treatment of coal fly ash using ammonium salts may therefore represent a promising technology for extracting aluminium from South African coal fly ash.

Residual aluminum control for source water with high risk of overproof coagulant residue: A novel application of principal component analysis

This study first applied the principle component analysis (PCA) and multivariate linear regression analysis (MLRA) to estimate the level of aluminum residue in two full-scale clarifiers, i.e. Densadeg and mechanical clarifier, potentially providing a predictive approach for aluminum residue and operation cost control. For Densadeg, effective relationships were established between aluminum residue and factors including FeCl3 dose, water temperature and turbidity (R2=0.802 and 0.774 for total and soluble Al, respectively). These three factors facilitated the control of aluminum residue, and FeCl3 dose was the most important. More factors were needed to effectively evaluate the residual total aluminum in mechanical clarifier, including the dose of FeCl3 and polyaluminum chloride (PACl), turbidity and tryptophan-like protein similarly contributing to the presumption result (R2=0.817). And water temperature also showed important impact on soluble aluminum besides the four factors aforementioned (R2=0.793). FeCl3 dosage and turbidity enhanced aluminum removal for both clarifiers, while water temperature showed distinct effects: negative for Densadeg but positive for mechanical clarifier. Tryptophan-like protein was associated with an undesirable increase in aluminum residue, as showed by the evaluation of aluminum residue in mechanical clarifier. Aluminum residue in Densadeg was less vulnerable to the fluctuation of PACl dose and organic matters.

Aluminum fractionation in acidic soils and river sediments in the Upper Mero basin (Galicia, NW Spain).

This study aims to determine aluminum fractions in the fine earth of acidic soils under different land uses (forest, pasture and cultivation) and in the river bed sediments of the headwater of the Mero River in order to identify and quantify Al-bearing phases to assess Al mobility and potential bioavailability (environmental availability) in the monitoring area. Sequential extraction is used to evaluate the Al partitioning into six fractions operationally defined: soluble/exchangeable/specifically adsorbed, bound to manganese oxides, associated with amorphous compounds, aluminum bound to oxidizable organic matter, associated with crystalline iron oxides, and residual fraction (aluminum within the crystal lattices of minerals). The mean concentration of total aluminum (24.01gkg-1) was similar for the three considered uses. The mean percentage of the aluminum fractions, both in soils and sediments, showed the following order: residual fraction≫amorphous compounds≈crystalline iron oxides>water-soluble/exchangeable/specifically adsorbed>bound to oxidizable organic matter≈Mn oxides. However, in the soils, the amorphous compounds and water-soluble/exchangeable/specifically adsorbed fraction showed considerable differences between some types of uses, the percentage of aluminum linked to amorphous compounds being higher in forest soils (16% of total Al) compared to other uses (mean about 8% of total Al). The highest values of water-soluble/exchangeable/specifically adsorbed Al were also found in forest soils (mean 8.6% of the total Al versus about 4% of pasture and cultivation), which is consistent with the lower pH and higher organic matter content in forest soils. Nevertheless, the potentially bioavailable fraction (sum of the first three fractions) is low, suggesting very low geoavailability of this element in both soils and sediments; hence, the possibility to affect the crops and water quality is minimal.

The Potential of Fermentation and Contamination of Teff by Soil to Influence Iron Intake and Bioavailability from Injera Flatbread.

The high phytic acid (PA) concentration in the diet based on teff injera is a likely contributing cause of iron deficiency in Ethiopia. We monitored PA during teff injera fermentation in 30 households in Debre Zeyit, Ethiopia and evaluated its influence on iron bioavailability, considering contaminant soil iron in teff flour. After fermentation (48h), mean PA concentration in injera batter decreased from 0.87 to 0.58 g/100 g dm (P < 0.001). Low phytase activity in teff flour (0.44 μmol phosphate/min/g) and a rapid drop in pH, indicated that PA degradation was driven by microbial phytases. The iron concentration in injera batter among the households ranged widely from 14.5-160.4 mg/100 g dm (mean: 34.7 mg/100 g dm) principally due to contamination with soil. Estimated intrinsic iron concentration of teff based on the strong correlation between total iron and aluminium concentrations (P < 0.001; aluminium concentrations in injera batter: 28.7-184.9 mg/100 g dm) was 4.4 mg/100 g dm, indicating that 86-97 % is extrinsic iron from soil. The median daily iron intakes from 3-day weighed food records in 10 young children were 18.9 mg/day including soil iron vs. 4.9 mg/day without soil iron (P < 0.01). The PA:iron molar ratios indicated low iron bioavailability from teff injera, particularly when soil iron was excluded. Traditional fermentation thus has a modest influence on PA levels and more complete degradation is needed to improve iron bioavailability. There is an urgent need to better understand the bioavailability of contamination iron from soil before considering national fortification or biofortification strategies in Ethiopia.

Study on the effects of organic matter characteristics on the residual aluminum and flocs in coagulation processes

Characteristics of organic matter may affect the residual aluminum after the coagulation process. This study reported the results of a survey for one drinking water treatment plant and measured the concentration of residual aluminum species with different molecular weights. Survey results indicated that humic acid or organic matter whose molecular weight was smaller than 1500Da had significant effects on residual aluminum. All the treatment processes were ineffective in removing dissolved organic matter whose molecular weight was smaller than 1500Da. These results also indicated that the addition of sand or polyacrylamide in the coagulation process could greatly decrease the concentration of humic acid, and the concentration of residual aluminum also decreased. These results revealed that for all water samples after filtration, the majority of total residual aluminum existed in the form of total dissolved aluminum, accounting for 70%–90%. The concentration of residual aluminum produced in bovine serum albumin solutions indicated that when the DOC was larger than 4.0mg/L, there were still significant differences when the solution pH value varied from 4.0 to 9.0.

Thermal transformations up to 1200 °C of Al-pillared montmorillonite precursors prepared by different OH–Al polymers

Aluminum-pillared montmorillonites are useful materials for their application as catalysts, adsorbents and ceramic composites. The precursor is a pillared montmorillonite that is not thermally stabilized. The precursor preparation methods, textural properties and catalytic activity have been extensively investigated, but comparatively, studies concerning their thermal transformations at high temperature are limited. In this work, precursors were prepared using two types of montmorillonites, Cheto (Ch) and Wyoming (W), and using two different OH–Al polymer sources: hydrolyzed (H) and commercial (C) solutions. Structural and thermal transformations of the precursors with heating up to 1200 °C were determined by X-ray diffraction and thermogravimetric analysis. Thermal analysis of these precursors below 600 °C revealed the influence of OH–Al polymers from the two solutions. The major phases developed at 1200 °C from the original montmorillonites were mullite for W and cordierite for Ch. The content of these phases depended on the aluminum in the octahedral sheet of the pristine montmorillonites. Amorphous phase, cristobalite, spinel, sapphirine and others phases were also found. The intercalation of OH–Al polymers in montmorillonites caused an increase in amorphous content after treatment at 1030 °C; however, it favored mullite development above 1100 °C. Although total aluminum content of both W and Ch precursors was similar, the transformation to mullite was directly related to the octahedral aluminum/magnesium ratio. The phase composition of the products at 1200 °C was not dependent on the type of intercalated OH–Al polymers. The increase in mullite content of the thermally treated precursors contributes to its possible application as advanced ceramic products.

Mud-Acid Interactions With Sand and Clay-Based Ceramic Proppants Used in Gravel-Packed and Fractured Wells

SummaryProppants are solid particles with specific mechanical strength that are widely used in hydraulic-fracturing operations. Their main purpose is to keep fractures open and increase well production. They can be naturally occurring sand grains or synthetic ceramic proppants. The acid resistance of fracturing proppants is an important property because acids are used during the hydraulic-fracturing process to remove the scale and clays that affect fracture conductivity. These acids affect proppants that are already present in the fracture, as well. Industry measures acid solubility of proppants according to the API RP 19C (2008)/ISO 13503-2 (2006) standard. This measurement produces a solubility number, but gives no guidance on the expected final effect of acid dissolution on the mechanical performance of tested proppants or on how acid-solubility values vary as a function of time, temperature, and dynamic conditions.This study investigates factors affecting the interactions of regular mud acid [hydrofluoric acid (HF)/hydrochloric acid (HCl) = 3:12] with sand and clay-based proppants under downhole conditions. Experiments were conducted by use of an aging cell at temperatures up to 300°F. The effects of varying temperatures, soaking times, and static and dynamic conditions were examined. The supernatant of solubility tests was analyzed with fluorine nuclear magnetic resonance (19F-NMR) to identify the reaction products. Total aluminum, iron, silicon, titanium, and calcium concentrations were measured by inductively coupled plasma optical-emission spectroscopy (ICP-OES). A Zeiss Axiophot microscope was used to acquire images for the proppant particles to study particle shape and effect of acid solubility. Proppants were then analyzed by X-ray fluorescence (XRF) and X-ray diffraction (XRD). After the solubility tests, the proppants and the residual solids were dried and analyzed by use of scanning-electron microscopes (SEMs) with energy dispersive X-ray spectroscopy (EDS) capabilities. Effects of acid dissolution on mechanical performance of the proppants were also tested through use of an automated load frame.The results show that sand proppants are readily soluble in regular mud acid, with a maximum recorded solubility of 10 wt%. The amount dissolved increases with temperature, soaking time, and dynamic conditions. Clay-based proppants are also soluble in mud acid, with much higher acid solubility than that seen in sand proppants. The proppant packs show more compaction for clay-based proppants than for sand proppants before and after acid exposure. Understanding the effects of acid on natural and synthetic proppants will improve production by promoting the design of acidizing regimens used during hydraulic-fracturing operations.