Influence of Hydrofluoric Acid Concentration and pH on Corrosion of Porous Multi-Oxide Engineering Ceramics

2010 ◽  
Vol 64 ◽  
pp. 7-12
Author(s):  
Marju Mannila ◽  
Antti Häkkinen
Keyword(s):  
Hydrofluoric Acid ◽  
Aqueous Media ◽  
Fluoride Concentration ◽  
Ion Concentration ◽  
Aluminum Silicate ◽  
Ceramic Plate ◽  
Weight Losses ◽  
Technical Ceramics ◽  
Full Factorial ◽  
Dissolved Components

The object of the research was to compare the corrosion resistance of three types of multioxide technical ceramics in hydrofluoric acid containing aqueous media according to a full factorial experimental plan with pH and fluoride ion concentration as variables. The samples were a silicon carbide doped aluminum silicate material, and two membrane coated aluminum silicates with one containing a membrane on both sides of the ceramic plate. The substrates contained more additives on alumina, while the membrane coats were of higher grade aluminum oxide. The samples were shaken in containers for up to two weeks, and their remaining hardness and weight losses were measured. Daily samples drawn from the liquid phase were analyzed for dissolved components. With respect to all measured properties, fluoride concentration affected the materials more detrimentally than alterations in pH.

scholarly journals Numerical Analysis of Thermophoresis of a Charged Spheroidal Colloid in Aqueous Media

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 224
Author(s):  
Yi Zhou ◽  
Yang Yang ◽  
Changxing Zhu ◽  
Mingyuan Yang ◽  
Yi Hu
Keyword(s):  
Numerical Analysis ◽  
Aqueous Media ◽  
Concentration Field ◽  
Ion Concentration ◽  
Spherical Particles ◽  
Hydrodynamic Effect ◽  
Oblate Spheroids ◽  
Thermodiffusion Coefficient ◽  
Arbitrary Electric Double Layer ◽  
Dimension Ratio

Thermophoresis of charged colloids in aqueous media has wide applications in biology. Most existing studies of thermophoresis focused on spherical particles, but biological compounds are usually non-spherical. The present paper reports a numerical analysis of the thermophoresis of a charged spheroidal colloid in aqueous media. The model accounts for the strongly coupled temperature field, the flow field, the electric potential field, and the ion concentration field. Numerical simulations revealed that prolate spheroids move faster than spherical particles, and oblate spheroids move slower than spherical particles. For the arbitrary electric double layer (EDL) thickness, the thermodiffusion coefficient of prolate (oblate) spheroids increases (decreases) with the increasing particle’s dimension ratio between the major and minor semiaxes. For the extremely thin EDL case, the hydrodynamic effect is significant, and the thermodiffusion coefficient for prolate (oblate) spheroids converges to a fixed value with the increasing particle’s dimension ratio. For the extremely thick EDL case, the particle curvature’s effect also becomes important, and the increasing (decreasing) rate of thermodiffusion coefficient for prolate (oblate) spheroids is reduced slightly.

scholarly journals Thermodynamic Study on the Dissociation and Complexation of Coumarinic Acid with Neodymium(III) and Dioxouranium(VI) in Aqueous Media

2021 ◽  
Vol 11 (10) ◽  
pp. 4475
Author(s):  
Luana Malacaria ◽  
Giuseppina Anna Corrente ◽  
Emilia Furia
Keyword(s):  
Protonation Constant ◽  
Aqueous Media ◽  
Metal Cations ◽  
Natural Antioxidants ◽  
Ion Concentration ◽  
Basic Salt ◽  
Hydrogen Ion Concentration ◽  
Overall Stability ◽  
Titration Data ◽  
Metal Ratio

In the frame of a systematic study on the sequestering ability of natural antioxidants towards metal cations, the complexation of coumarin-3-carboxilic acid (HCCA) with neodymium(III) and dioxouranium(VI) (uranyl, UO22+), and overall stability constants of the resulting complexes, were evaluated from the pH-potentiometric titration data at 37 °C and in an aqueous solution (i.e., 0.16 mol/L NaClO4). The graphic representation of the complex’s concentration curves is given by the distribution diagrams, which provide a depiction of all the species present in the solution in the selected pH ranges. The protonation constant of HCCA was also determined to evaluate the competition of the ligand for the metal cations and H+. The ligand-to-metal concentration ratio was varied between 1 and 10, and the hydrogen ion concentration was decreased stepwise until the incipient precipitation of a basic salt of the metal, which occurred at different values depending on the specific metal cation and the ligand to metal ratio. Speciation profiles obtained by potentiometric titrations and supported by UV-Vis data show that a complexation occurs at a ligand-to-Nd(III) and to –UO22+ ratio of 1:1 and 2:1, with different degrees of deprotonation: Nd(OH)(CCA)+, UO2(OH)(CCA), UO2(OH)2(CCA)−, and Nd(OH)(CCA)2, UO2(CCA)2 and (UO2)2(OH)2(CCA)2.

Assessment of the drinking water quality for planning endogenic prevention of dental caries

2021 ◽  
Vol 21 (2) ◽  
pp. 88-93
Author(s):  
A. B. Shashmurina ◽  
O. L. Mishutina ◽  
V. R. Shashmurina
Keyword(s):  
Drinking Water ◽  
Dental Caries ◽  
Water Supply ◽  
Fluoride Concentration ◽  
Water Hardness ◽  
Drinking Water Supply ◽  
Ion Concentration ◽  
Normal Range ◽  
Hydrogen Ion Concentration ◽  
Normal Limits

Relevance. Dental caries is a leading dental disease in children. Aim – to study the quality of drinking water in Smolensk and its region to provide evidence for implementing dental caries preventive measures in children.Materials and methods. We took tap water samples from ten water intake points in seven districts of Smolensk and six Smolensk regions. An accredited testing laboratory of the Center for Hygiene and Epidemiology in the Smolensk Region carried out water chemical analysis. The study analyzed standard parameters of drinking water quality: pH 6.5-8.5, fluoride content 0.60-1.2 mg/l; water hardness 7.0-9.0 (Sanitary Regulations and Standards 2.1.4.1116-02). The parameter was considered normal if its 95% confidence interval was within the reference range.Results. In Smolensk, the hydrogen ion concentration in centralized drinking water supply systems is within normal limits and amounts to 7.39 (95% CI: 7.32-7.46; р < 0,05) pH units. The mean fluoride concentration in the Smolensk water is 0.19 (95% CI: 0.14-0.23; р < 0,05) mg/l, which is below the normal range. In most Smolensk districts, water hardness is within normal limits, 8.21 mmol/l (95% CI: 7.03-9.39; р < 0,05). However, the upper limit of the confidence interval of 9.39 mg/l and the maximum of 12.0 mg/l exceed the normal range. In the Smolensk region cities, the hydrogen ion concentration is 7.2 (95% CI: 7.02-7.38; р < 0,05) pH units in the centralized drinking water supply. The fluoride concentration in the Smolensk region water is 0.45 mg/l (95% CI: 0.23-0.68; р < 0,05), which demonstrates the fluoride deficiency in water. In the Smolensk region cities, mean water hardness is 6.66 mmol/l (95% CI: 6.00-7.03; р < 0,05), which is below the normal values. However, the CI upper limit of 7.03 mmol/l and the maximum of 7.05 mmol/l are within normal limits.Conclusions. The water of the centralized drinking water supply system in Smolensk and the Smolensk region is low in fluorides. Urgent community and individual preventive measures should be taken to expose children to fluoride.

Application of radiation grafted waste polypropylene fabric for the effective removal of Cu (II) and Cr (III) ions

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Md. Nabul Sardar ◽  
Nazia Rahman ◽  
Shahnaz Sultana ◽  
Nirmal Chandra Dafader
Keyword(s):  
Adsorption Capacity ◽  
Metal Ion ◽  
Aqueous Media ◽  
Thermo Gravimetric Analysis ◽  
Ion Concentration ◽  
Gravimetric Analysis ◽  
Order Kinetic ◽  
Polypropylene Fabric ◽  
Alternative Material ◽  
Waste Polypropylene

Abstract This study focuses on the adsorption of hazardous Cr (III) and Cu (II) ions from aqueous solution by applying modified waste polypropylene (PP) fabric as an adsorbent. Pre-irradiation technique was performed for grafting of sodium styrene sulfonate (SSS) and acrylic acid (AAc) onto the PP fabric. The monomer containing 8% SSS and 16% AAc in water was used. Graft yield at 30 kGy radiation dose was 390% when 4% NaCl was added as additive. The prepared adsorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA) and dynamic mechanical analyzer (DMA). The influences of different parameters including pH, contact time, temperature and initial metal ion concentration were also investigated. The equilibrium adsorption data were better fitted to the Langmuir isotherm model with maximum monolayer adsorption capacity 384.62 mg/g for Cr (III) and 188.68 mg/g for Cu (II) ions. The kinetic data were better explained by pseudo first-order kinetic model having good matching between the experimental and theoretical adsorption capacity. The adsorption process was spontaneous, endothermic and thermodynamically feasible. Furthermore, investigation of desorption of metal ions and reuse of the adsorbent suggesting that the adsorbent is an efficient and alternative material in the removal of Cr (III) and Cu (II) from aqueous media.

scholarly journals A methodological proposal for the analysis of Cladocera (Crustacea, Branchiopoda) subfossils from sediments of temporary aquatic ecosystems

2020 ◽  
Vol 80 (1) ◽  
pp. 97-101
Author(s):  
E. E. Silva ◽  
R. Cassino ◽  
Z. W. Leibowitz ◽  
E. M. Eskinazi-Sant’Anna
Keyword(s):  
Hydrofluoric Acid ◽  
Aquatic Ecosystems ◽  
Aqueous Media ◽  
Climatic Changes ◽  
Kochia Scoparia ◽  
Ecological Relevance ◽  
Taxonomic Analysis ◽  
Standard Methodology ◽  
Sediment Particles ◽  
Silicate Materials

Abstract The main objective of the present study was to promote some adaptations to the standard methodology used in the analysis of Cladocera subfossils. The samples used in this study were collected at Lagoa dos Coutos, a temporary lake located on an outcrop with iron-rich duricrust in the Serra do Gandarela (Minas Gerais, Brazil). The sediment from this pond, typical of temporary ecosystems in the region, is characterized by rigid concretions that are difficult to dissolve in aqueous media, making it difficult to visualize and analyze subfossils taxa. Sediment samples were prepared according to the standard methodology used in paleolimological studies and the methodological adaptations proposed in the present study, which included the addition of 1 mg of Kochia scoparia, a palynological marker used to estimate subfossil density, as well as the addition of hydrofluoric acid (HF) to oxidize silicate materials. The samples prepared according to the new methodological procedure improved Cladocera subfossil visualization, facilitating the taxonomic analysis of the species. The samples submitted to the standard methodological procedure had a significantly higher mean of sediment particles (mean of 84.2 sediment particles) and 70% more residues compared to the samples prepared with the newly proposed methodology (mean of 22.1 sediment particles). Absolute data on the temporal variation of the density of Cladocera subfossils was obtained by using the palinological marker K. scoparia, which showed higher densities of subfossils in more recent, humid periods (112,000 subfossils/cm3 at 5 cm, equivalent to 3,500 years BP). The results indicate that the new methodology can contribute to advances in paleolimnological studies of temporary aquatic ecosystems, whose lake histories are rarely investigated, despite their ecological relevance as ecosystems that indicate environmental and climatic changes.

Effect of Fluoride on the Corrosion Behavior of Ti and Ti6Al4V Dental Implants Coupled With Different Superstructures

2011 ◽  
Vol 37 (3) ◽  
pp. 309-317 ◽  
Author(s):  
Eman M Anwar ◽  
Lamia S Kheiralla ◽  
Riham H Tammam
Keyword(s):  
Corrosion Resistance ◽  
Dental Implants ◽  
Corrosion Behavior ◽  
Artificial Saliva ◽  
Fluoride Concentration ◽  
Ion Concentration ◽  
Fluoride Ion ◽  
All Ceramic ◽  
Metal Ceramic ◽  
Implant Alloys

Abstract The effect of fluoride ion concentration on the corrosion behavior of Ti and Ti6Al4V implant alloys, when coupled with either metal/ceramic or all-ceramic superstructure, was examined by different electrochemical methods in artificial saliva solutions. It was concluded that increased fluoride concentration leads to a decrease in the corrosion resistance of all tested couples. The type of the superstructure also showed a significant effect on the corrosion resistance of the couple.

scholarly journals Simultaneous removal of Cd2+ and Zn2+ from aqueous solution using an upflow Al-electrocoagulation reactor: optimization by response surface methodology

2019 ◽  
Vol 79 (7) ◽  
pp. 1297-1308
Author(s):  
Vianey Ariadna Burboa-Charis ◽  
Eddy Jonatan Moreno-Román ◽  
Juan Antonio Vidales Contreras ◽  
Celestino García-Gómez
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Aqueous Media ◽  
Ion Concentration ◽  
Current Intensity ◽  
Fluid Distribution ◽  
Electrolysis Time ◽  
Reactor Optimization ◽  
Electrocoagulation Process ◽  
Positive Effect

Abstract The presence of heavy metals in the environment has increased, and cadmium (Cd) and zinc (Zn) are considered to be among the most dangerous. An upflow Al-electrocoagulation reactor was used to remove Cd2+ and Zn2+ ions from aqueous media. The system consisted of perforated aluminum circular electrodes for fluid distribution with elimination of external agitation. The effect of different parameters, i.e. current intensity, electrolysis time, concentration of Cd2+ and Zn2+ ions and electrolytic support dose were optimized by response surface methodology. The results indicated that increasing the current intensity and the electrolysis time had a positive effect on the elimination efficiency of the pollutant ions. Likewise, increasing the dose of electrolytic support and decreasing the concentration of the pollutants improved the efficiency of the system. The optimal results were: current intensity of 0.4 A, electrolysis time of 40 min, ion concentration of 44.6 mg·L−1 and electrolytic support dose of 0.56 mg·L−1, with the maximum elimination percentages of 96 ± 3.8% and 96 ± 2.7% for Cd2+ and Zn2+, respectively. This study showed that the electrocoagulation process in an upflow electrocoagulation reactor could be successfully applied to remove pollutants from water.

scholarly journals Photoreversible stretching of a BAPTA chelator marshalling Ca2+-binding in aqueous media

2019 ◽  
Vol 15 ◽  
pp. 2801-2811 ◽  
Author(s):  
Aurélien Ducrot ◽  
Arnaud Tron ◽  
Robin Bofinger ◽  
Ingrid Sanz Beguer ◽  
Jean-Luc Pozzo ◽  
...  
Keyword(s):  
Calcium Concentration ◽  
Dissociation Constants ◽  
Aqueous Media ◽  
Ion Concentration ◽  
Free Calcium ◽  
Biological Processes ◽  
Secondary Messenger ◽  
Synthetic Receptor ◽  
Free Calcium Concentration ◽  
Calcium Ion Concentration

Free calcium ion concentration is known to govern numerous biological processes and indeed calcium acts as an important biological secondary messenger for muscle contraction, neurotransmitter release, ion-channel gating, and exocytosis. As such, the development of molecules with the ability to instantaneously increase or diminish free calcium concentrations potentially allows greater control over certain biological functions. In order to permit remote regulation of Ca2+, a selective BAPTA-type synthetic receptor / host was integrated with a photoswitchable azobenzene motif, which upon photoirradiation would enhance (or diminish) the capacity to bind calcium upon acting on the conformation of the adjacent binding site, rendering it a stronger or weaker binder. Photoswitching was studied in pseudo-physiological conditions (pH 7.2, [KCl] = 100 mM) and dissociation constants for azobenzene cis- and trans-isomers have been determined (0.230 μM and 0.102 μM, respectively). Reversible photoliberation/uptake leading to a variation of free calcium concentration in solution was detected using a fluorescent Ca2+ chemosensor.

scholarly journals Selective Removal of Sodium Ions from Aqueous Media Using Effective Adsorbents: Optimization by RSM and Genetic Algorithm

2021 ◽  
Vol 68 (4) ◽  
pp. 791-803
Author(s):  
Lei Yao ◽  
Chao Hong ◽  
Hani Dashtifard ◽  
Hossein Esmaeili
Keyword(s):  
Genetic Algorithm ◽  
Activated Carbon ◽  
Sorption Capacity ◽  
Removal Efficiency ◽  
Contact Time ◽  
Aqueous Media ◽  
Ion Concentration ◽  
Order Kinetic ◽  
Adsorbent Dosage ◽  
Sorption Efficiency

This study aimed to determine the best adsorbent among Moringa oleifera-derived activated carbon (AC), eggshell-derived CaO nanoparticles and CaO/Fe3O4 for sodium (Na+) removal from aqueous media. In the first step, the appropriate adsorbent for sodium adsorption was determined among the three adsorbents, which the results showed that the AC had the highest sorption efficiency. Then, response surface methodology (RSM) was used to evaluate the impact of different factors on the Na+ ion sorption efficiency using the AC. The highest removal efficiency was obtained to be 95.91% at optimum conditions such as pH of 11, contact time of 45 min, temperature of 25 °C, sodium ion concentration of 900 mg/L, and adsorbent dosage of 5 g/L. Also, the best conditions using the genetic algorithm was obtained at contact time of 94.97 min, adsorbent dosage of 3.52 g/L, Na+ ion concentration of 939.92 mg/L and pH value of 10.92. Moreover, the maximum sorption capacity using the Langmuir model was obtained to be 249.67 mg/g, which was a significant value. Besides, the equilibrium and kinetic studies indicated that the experimental data of sodium adsorption process were fitted well with the Langmuir isotherm model and the pseudo-second-order kinetic model, respectively. Furthermore, the thermodynamic study indicated that the sorption process was endothermic. Generally, among the three adsorbents used, activated carbon with a high removal efficiency and significant sorption capacity can be considered as a promising adsorbent for the removal of sodium from wastewater on an industrial scale.

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