Query: calcium fluoride hydrofluoric acid

Candidate papers:

abstract: An innovative method for utilizing synthetic calcium fluoride (CaF2) recovered from fluoride containing semiconductor wastewater, and waste sulfuric acid (H2SO4) to produce hydrofluoric acid (HF) was investigated. The research was set to study the low temperature production of HF via reaction of synthetic CaF2 and waste H2SO4. The impact of four factors, including H2SO4 concentration, total volume (H2SO4 H2O)/CaF2 ratio, drying temperature of synthetic CaF2, and reaction carried out under different temperature, on HF productivity was investigated in this study. HF yield increased with increasing H2SO4 concentration and total volume/CaF2 ratio under room temperature. Generally, reactions carried out under low temperature 100 degC) had a positive impact on HF yield. The higher temperature led to an increase in absorbed HF but a decrease in total HF. The reaction of commercial CaF2 and 70% H2SO4 had a higher absorbed HF yield of 61.7% than synthetic CaF2 and 70% waste H2SO4, which had a yield of 36% This was due to the higher purity of the commercial CaF2 and fewer interference ions in H2SO4. HF productivity was lowered by CaSO4, which hindered the reaction of reactants and also the generation of fluorosulfuric acid.
author_names: Min-Fa Lin

Jhong Lin Wu

Ken-Lin Chang

Wen-Jhy Lee

Chih-Ping Chang

Yung-Chang Lin

Po-Han Chen
title: Recycle of synthetic calcium fluoride and waste sulfuric acid to produce electronic grade hydrofluoric acid
venue: Environmental Science and Pollution Research
year: 2020

author_names: Min-Fa Lin

Chih-Ping Chang

Ken-Lin Chang

Wen-Jhy Lee

Jhong Lin Wu

Po-Han Chen
title: A study on the low temperature wet synthesis of hydrofluoric acid from synthetic calcium fluoride and waste sulfuric acid
year: 2020

abstract: The fluoride ions of the industrially largely irreplaceable, locally corrosive hydrofluoric acid (HF) can scavenge cations in biological tissues, which explains their high toxic potential, and also leads to local acidification through proton release. The influence of three complexing agents, calcium (Ca2+ gluconate (as 2.5% Ca2+gel and individually (2.84% or commercially (10% formulated Ca2+solution) magnesium (Mg2+ gluconate (2.84% solution and aluminium (Al3+ solution (Hexafluorine(r) pure and diluted) on the absorption of fluoride following HF exposure (1 3 min, 100 ml, 30%/0.64 cm2) through human skin was investigated in an ex vivo diffusion cell model. Fluoride absorption was assessed over 6 24 h and analysed with a fluoride electrode. Decreasing the contamination time reduced the fluoride absorption distinctly which was further reduced by the application of fluoride binding decontamination agents (Ca2+ Mg2+ Al3+ or water alone without being significantly different. Ca2+ appeared slightly more effective than Mg2+ in reducing fluoride absorption. Moreover, the addition of pH adjusting buffer promoted the decontamination efficacy. Fluoride binding agents can facilitate the decontamination of dermal HF exposure. However, prompt decontamination appeared to be the key to successful limitation of fluoride absorption and pushes the choice of decontamination agent almost into the background.
author_names: Suvarna Mini Vijayan

Thomas Goen

Kathrin Dennerlein

Raymund E Horch

Ingo Ludolph

Hans Drexler

Sonja Kilo
title: Calcium, magnesium and aluminium ions as decontaminating agents against dermal fluoride absorption following hydrofluoric acid exposure.
venue: Toxicology in vitro an international journal published in association with BIBRA
year: 2020

abstract: Introduction After dermal contact to occupational hazardous substances the cleaning of exposed skin areas is an important first aid measure to reduce adverse health effects. Due to possible severe systemic intoxication following dermal exposure to hydrofluoric acid (HF) the decontamination of skin should focus on the inactivation of free fluoride ions. The present ex vivo study investigated the effects of exposure duration and different antidotes on the potential systemic uptake of fluoride. Methods The transdermal penetration of HF (c=30% through excised human skin was investigated by using static diffusion cells. After dermal application of the acid (100 ul/0.64 cm2) for 1 min the excess was removed using one dry cotton swab. Subsequently, the skin was cleaned with water, calcium gluconate (CaGl) polyethylene glycol (PEG) 400 or hexafluorine(c) using a standardised protocol. In a further study, the application time was extended to 3 min to assess the effect of exposure duration. Chemical analyses of fluoride were carried out by GC MS or via a fluoride sensitive electrode. Result Extension of the exposure time from 1 to 3 min led to an enhancement in the transdermal penetration of fluoride, however with similar penetration kinetics. At the end of experiments (6 hour) a 7 fold higher fluoride amount was detected in the receptor fluid (16 vs 114 ug) In all test series maximum flux was achieved within the first hour past exposure. Decontamination of the skin reduced the cumulative penetrated amount of fluoride by 28% (PEG 400) 49% (water) and 64% (CaGl/hexafluorine(c) compared to control. Discussion The results indicate that the systemic uptake of fluoride ions and therefore possible systemic intoxication after exposure to hydrofluoric acid can be diminished by shortening the exposure duration. Reduction was further increased by decontamination of skin most by substances which are known to supply the complexation of fluoride ions.
author_names: Kathrin Dennerlein

T Hahn

Thomas Goen

Hans Drexler

Sonja Kilo
title: 914 Hydrofluoric acid effects of skin decontamination on the bioavailability of fluoride
year: 2018

abstract: ABSTRACT The production of phosphoric acid generates an enormous amount of phosphogypsum with emission of toxic fluorine acid gas. To remedy these environmental problems, a novel and a simple procedure permits converting phosphogypsum waste by recycled fluorine acid into valuable products. The obtained results confirm the efficiency of this procedure, which synthesises at room temperature the calcium fluoride in the form of nano crystalline powder and the ammonium bisulphate salt from the exact stoichiometric proportions of phosphogypsum, hydrofluoric acid and ammonia. The total conversion of phosphogypsum is achieved after reaction time equal to one hour and a half. Generally, this novel procedure offers not only a solution for reducing phosphogypsum waste and fluorine gas emission, but also gives rise to valuable products, useful to industry and agriculture.
author_names: Yassine Ennaciri

Mohammed Bettach

Hanan El Alaoui-Belghiti
title: Recovery of nano calcium fluoride and ammonium bisulphate from phosphogypsum waste
year: 2020

abstract: The phosphoric acid production in the world generates a large amount of phosphogypsum with the emission of toxic acid fluorine gas into the atmosphere, which forms a significant source of environmental contamination. In this work, a novel and a simple procedure allows converting phosphogypsum waste by using hydrofluoric acid and sodium fluoride into valuable products. The obtained results confirm well the efficiency of this procedure, which permits to synthesize at room temperature, the sodium hydrogen sulfate monohydrate and a relatively pure nano calcium fluoride from the exact stoichiometric proportions of the phosphogypsum, hydrofluoric acid, and sodium fluoride. The total phosphogypsum conversion is achieved after reaction time equal to 1.5 h. Generally, this procedure offers not only a solution for reducing phosphogypsum waste but also permits to obtain valuable products, which interest several sectors of industry.
author_names: Yassine Ennaciri

Mohammed Bettach

Hanan El Alaoui-Belghiti
title: Conversion of Moroccan phosphogypsum waste into nano calcium fluoride and sodium hydrogen sulfate monohydrate
year: 2020

abstract: Waste has been identified as one of the main sources of greenhouse gas (GHG) emissions resulting from global population growth. Climate change and resource scarcity have emerged as pressing environmental issues in recent years. Resource recycling and recovery have been proven effective ways of implementing circular economy and GHG reduction to maintain sustainable resource use. Calcium fluoride sludge and hydrofluoric acid are the primary wastes generated from the electronics industry, such as from semiconductors, liquid crystal displays, light emitting diodes, solar cells and other optoelectronic sectors. The accumulation of such waste has become a major problem of Taiwan's electronics industry. If not properly treated or managed, electronic waste would cause serious health and environmental problems; however, if recycled, they can be recovered and transformed into artificial fluorite (CaF2) and sodium fluorosilicate (NaSiF6) which have economic and environmental benefits. For example, CaF2 can be applied as fluxing agent to replace raw fluorite in the steel industry. Moreover, both materials can be used as substitutes for cement in construction. The main objective of this study is to evaluate carbon footprint of renewable material from calcium fluoride sludge to understand the carbon emission of waste reuse method from a life cycle perspective. The scope and system boundary of the assessment will be determined on the basis of literature review and expert consultation. Data for calculating carbon footprints will be collected by in situ inventory and from the literature. The commercial software SimaPro 8.2.0 will be used for calculations. The results of carbon footprint may be used to develop strategies for life cycle management of waste reuse to realize sustainable usage.
author_names: Allen H Hu

Chien-Hung Kuo

Ciao-Sin Hong

Lance Hongwei Huang
title: Carbon Footprint Assessment of Recycling Fluorspar from Waste Calcium Fluoride (CaF 2 Sludge
year: 2019

abstract: Hydrofluoric acid was discovered in 1771 by Swedish pharmaceutical chemist Carl Wilhelm Scheele when he was investigating the mineral called fluorite (Calcium fluoride) Hydrogen fluoride (HF) has several synonyms: Hydrofluoric acid, Fluoric acid, Hydrofluoride, Fluorine monohydride, Fluorane. Hydrofluoric (HF) acid is an extremely powerful inorganic acid and a vigorous dehydrating agent that is used in many industrial branches including production of aluminum, stainless steel and hydrofluorocarbons, glass etching, stevedoring and transportation industries, inorganic and organic chemical manufacturing, mineral processing, petroleum oil refineries, fire extinguishers manufacturing, steel mills, cleaning HVAC systems, and as the precursor to all fluorine compands in the pharmaceutical industry. [1][2][3][4] Consumer products containing hydrofluoric acid include rust removers, detergents, marble, brick and stone cleaning, toilet bowl clearners, insecticides, automobile wheel cleaners and air conditioner cleaners. [4][5] Hydrofluoric acid is comprised of a diatomic compound of hydrogen and fluoride atoms as a gas, while in the liquid state it has strong hydrogen bonds between the chains forming a polymeric compound. [6] Anhydrous hydrofluoric acid and hydrofluoric acid in aqueous solutions range in appearance from colorless to slightly tinted based upon the concentration and impurities. It has a boiling point of 20 degrees celcius (68 degrees fahrenheit) at 760 mmHg, vapour density greater than air and readily dissolves in water that when diluted (exothermal reaction) is visibly indistinguishable from water. Hydrofluoric acid has a disagreeable, pungent odor at concentrations of 0.04 ppm which is way below the OSHA PEL (Permissible Exposure Limit) of 3 ppm and is extremely corrosive and has the ability to dissovle a number of materials especially oxides. [4] The Major source of production of hydrofluoric acid is by treating fluorite with concentrated sulfuric acid at temperatues of 265 degrees fahrenheit to produce hydrofluic acid and calcium sulfate. Alternate production is a by product in the production of phosphoric acid from the mineral apatite. Hydrofluoric acid is also produced by the release from industrial and welding processes and environmental activities such as volcanoes. HF production exceeds one million tons world wide by a number of manufactors and is transported and stored under high pressure as a highly concentrated liquid. [7] In the United States of America, the Department of Transportation Hazard Label and National Fire Protection Assocation (NFPA) 704 lists the health value of 4 (can be lethal) flammability value of 0 (will not burn under typical fire conditions) instability value of 2 (readily undergoes violent chamical changes at elevated temperatures and pressures) and special value of W with line through (reacts violently or exposevely with water) Domestic concentrations of hydrofluoric acid is typically around 0.5% with industrial concentrations approaching 100% Primary health consequences including dermal burns, eye injury, acute respiratory symptoms, gastrointestinal symptoms and cardiac abnormalities can occur from direct skin eye contact, ingestion of solutions or inhalation of fumes and vapors with unintentional and intentional exposures. Unintentional exposure of hydrofluoric acid in and out of the workplace include inappropriate operations, mechanical failure of equipment, explosions of containers and tanks containing HF, during traffic incidents with leakage of HF, inadequate protective equipment and children accidentally exposed through ingestion of domestic cleaners. [4][8][9][10] Intentional cases of ingestion, with suicidal and homicidal intent, of hydrofluoric acid have been documented.[4][11] Hydrofluoric acid is highly toxic and damaging to humans due to the "double danger" properties of the corrisive nature of the hydrogen ions and toxic effect due to the ability of fluoride ions to penetrate into deep tissue causing liquefactive necrosis and release of cellular products. Hydrofluoric acid burns present with a unique concern for systemic fluoride toxicity including cardiovascular, pulmonary, renal and neuromuscular symptoms, electrolyte imbalance and enzyme inhibition which can lead to cardiac arrhythmias and death. [12] Chronic symptoms may occur or persist for months after HF ingestion or respiratory exposure. [3][9]
author_names: Daniel L Schwerin

J Hatcher
title: Hydrofluoric Acid Burns
year: 2019

abstract: Occupational injuries to digits due to hydrofluoric acid (HFA) are frequently encountered. They have distinctive features, including intense pain, progressive tissue necrosis, and possible bone erosion. To minimize tissue damage, it is of great importance to execute prudent preoperative assessment and determine the correct surgical modality to reconstruct and maintain the function of the hand. However, proper protocols for fingers have not been presented in previous studies. Eight cases with HFA burn to digits were presented to the emergency room. Wounds were immediately irrigated with saline, calcium gluconate was applied topically to block destructive effects of fluoride ions. Blisters that could lead to progressive tissue destruction were debrided. A fish mouth fasciotomy was performed and prostaglandin was administered intravenously to maintain maximal distal circulation. Wounds were evaluated daily for apparent demarcation for 6 or 7 days. Digits were reconstructed with free sensate second toe pulp free flap to provide sufficient padding for the fingertip. All patients showed excellent recovery with stable flaps with acceptable external contour, durable soft tissue padding, and full range of motion of affected joints. In conclusion, when a patient is admitted due to HFA exposure to the finger, early treatment including irrigation, topical neutralizers, and fasciotomy are of great importance to minimize tissue damage. In addition, a physician should wait at least 7days until the degree of damage to the tissue can be classified so that the physician can decide whether aggressive debridement should be proceeded. In case of deep layer injuries of weight bearing portions such as finger pulp, reconstruction techniques utilizing durable tissues such as partial second toe pulp free flap should be employed.
author_names: Hyun Ho Han

Byung Yeun Kwon

Sung-No Jung

Suk-Ho Moon
title: Importance of initial management and surgical treatment after hydrofluoric acid burn of the finger.
venue: Burns journal of the International Society for Burn Injuries
year: 2017

abstract: Recent experimental in vivo studies have shown that aqueous solutions of stannous fluoride (SnF2) and hydrofluoric acid (HF) can reduce enamel solubility after 5 min. The aim of this study was to evaluate the longer term protective effect of SnF2 (0.78% pH 2.9) and HF (0.2% pH 2.0) (both ~0.1 mol/l F) using the same experimental model. Labial surfaces of healthy anterior teeth (all four surfaces when possible, otherwise a pair of surfaces) in 103 subjects (n 399 teeth) were exposed to citric acid (0.01 mol/l, pH 2.7) The acid was applied using a peristaltic pump (5 ml, 6 ml/min) and was collected in coded test tubes (etch I) The test solutions were then applied to the same surfaces of the teeth (1 min, 6 ml/min) After either 1, 7, 14 or 28 days, citric acid was again applied to the same surfaces and subsequently collected (etch II) Enamel solubility was examined by assessment of calcium concentration in etch I and etch II solutions using atom absorption spectroscopy. Median values were calculated for all time periods and statistical analysis was carried out using the Wilcoxon signed ranks test. Results showed that HF reduced enamel solubility by 54 and 36% after 1 and 7 days, respectively. After 14 and 28 days, there was no longer any effect. SnF2 showed no protective effect after the first day. Given these results, repeated application of HF and especially SnF2 may be necessary to improve the protective effect of these fluorides, and this requires further testing.
author_names: Carl Hjortsjo

Grazyna Jonski

Per Stanley Thrane

Erik Saxegaard

Alix Young
title: Effect of Stannous Fluoride and Dilute Hydrofluoric Acid on Early Enamel Erosion over Time in vivo
venue: Caries Research
year: 2009