Processes for working-up an aqueous fluosilicic acid solution

Touré, Awa Oumar; Sambe, Falilou Mbacké; Koita, Démo; Diop, Codou Mar; Sock, Oumar

doi:10.4102/sajs.v108i11/12.919

Cited by 7 publications

(5 citation statements)

References 5 publications

(5 reference statements)

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“…, water fluoridation and synthesis of low-density AlF 3 ), its market share is rather limited and its related compounds, such as fluorosilicates, are generally considered low added-value products with niche applications. For these reasons, disposal at sea upon neutralization is still common practice for FSA derived from fertilizers, especially in those countries with lax environmental regulations, causing detrimental effects to the environment . Nevertheless, FSA should be acknowledged as a valuable and inexpensive source of both fluorine and silicon.…”

Section: Introductionmentioning

confidence: 99%

“…For these reasons, disposal at sea upon neutralization is still common practice for FSA derived from fertilizers, especially in those countries with lax environmental regulations, causing detrimental effects to the environment. 4 Nevertheless, FSA should be acknowledged as a valuable and inexpensive source of both fluorine and silicon. As far as fluorine is concerned, hexafluorosilicic acid is thought to be an interesting source of this element in the production of important commodities as an alternative to conventional mineral feedstock (CaF 2 ).…”

Section: ■ Introductionmentioning

confidence: 99%

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Hexafluorosilicic Acid (FSA): from Hazardous Waste to Precious Resource in Obtaining High Value-Added Mesostructured Silica

Vacca

Cara

Mameli

et al. 2020

ACS Sustainable Chem. Eng.

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In this work, industrial waste hexafluorosilicic acid (H 2 SiF 6 or FSA) has been proven to be a low-cost alternative to silicate esters for the synthesis of high-quality MCM-41 (high surface area, high degree of order, narrow pore size distribution, high thermal stability) through a head-to-head comparison between the most common silica precursor, tetraethylorthosilicate (TEOS), and FSA. The effect of different parameters such as temperature, time, hydrothermal treatment, and the presence of ethyl acetate has been explored by studying the textural, structural, and morphological features. On the most promising samples, thermal and hydrothermal stability has been assessed, indicating a higher thermal stability for the FSA-derived sample, due to the thicker walls, and comparable hydrothermal stability. The mother solution treatment has allowed the obtainment of nanostructured fluorite as an additional valuable product and a CTAB-rich ammonia solution for successive synthesis with FSA. Recovery processes for the templating agent entrapped in the MCM-41 mesostructure have also been explored for both FSA-and TEOS-derived samples, showing an easier removal in the case of FSA-MCM-41. Moreover, mesostructured silica derived from FSA has also been proven to be an ideal support to design efficient and regenerable mesostructured iron oxide-based sorbents for H 2 S removal from syngas, showing similar performance to that of the corresponding nanocomposite prepared from TEOS.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Hexafluorosilicic Acid (FSA): from Hazardous Waste to Precious Resource in Obtaining High Value-Added Mesostructured Silica

Vacca

Cara

Mameli

et al. 2020

ACS Sustainable Chem. Eng.

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show abstract

“…2 million tons per year [ 64 ]. The main concern regarding FSA production is its disposal, which is mostly performed by neutralization directly into the sea [ 154 ]. In fact, FSA storage is quite expensive and potentially dangerous as FSA violently reacts with bases and water-producing HF, and it is extremely corrosive against metals and glassware [ 155 ].…”

Section: Silica From Industrial Production Waste or End-of-life Productsmentioning

confidence: 99%

Recent Advances on Porous Siliceous Materials Derived from Waste

Montini,

Cara,

D’Arienzo

et al. 2023

Materials

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In recent years, significant efforts have been made in view of a transition from a linear to a circular economy, where the value of products, materials, resources, and waste is maintained as long as possible in the economy. The re-utilization of industrial and agricultural waste into value-added products, such as nanostructured siliceous materials, has become a challenging topic as an effective strategy in waste management and a sustainable model aimed to limit the use of landfill, conserve natural resources, and reduce the use of harmful substances. In light of these considerations, nanoporous silica has attracted attention in various applications owing to the tunable pore dimensions, high specific surface areas, tailorable structure, and facile post-functionalization. In this review, recent progress on the synthesis of siliceous materials from different types of waste is presented, analyzing the factors influencing the size and morphology of the final product, alongside different synthetic methods used to impart specific porosity. Applications in the fields of wastewater/gas treatment and catalysis are discussed, focusing on process feasibility in large-scale productions.

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“…In the worldwide phosphate fertilizer production, more than 2 million tons of hexafluorosilic acid are generated annually as a result of the reaction of phosphate ore and sulfuric acid. , The valorization of this acid remains a global environmental challenge and generates research efforts. ,− For instance, superphosphate plants such as Industries Chimiques du Senegal discharge nearly 276000 m 3 /year of H 2 SiF 6 into the sea for a production of 600000 tons/year of phosphoric acid. In our previous work, we proposed a three-step aqueous process to treat waste solutions containing 250 to 300 g/L of H 2 SiF 6 issued from phosphoric acid production.…”

Section: Introductionmentioning

confidence: 99%

Carbonation of Calcium Silicate Hydrates as Secondary Raw Material from the Recovery of Hexafluorosilicic Acid

Ndiaye

Pisch

Touré³

et al. 2022

ACS Sustainable Chem. Eng.

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This work focuses on the carbonation reaction of calcium silicate hydrates (CaO)(SiO 2 )(H 2 O) (CSH) powders synthesized by an aqueous process using fluorosilicic acid waste and lime as main reactants. We investigated whether these CSH could constitute a secondary raw material to produce building materials that harden at low temperature by reaction with CO 2 , according to a process that is commonly based on the use of minerals such as natural wollastonite (CaSiO 3 ). CSH and wollastonite powders were placed in a gas stream consisting either of pure CO 2 or of a 15 vol % CO 2 −85 vol % air mixture, saturated with water, at atmospheric pressure and 40 °C. Based on thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy of the products, we proved the occurrence of the carbonation reaction and we calculated the carbonation degree α for various reaction times. The structural water contained in the CSH played a beneficial role in the carbonation reaction since their carbonation degree is much higher than that of wollastonite: for a reaction time of 120 min at 40 °C, α = 75% for CSH against 12% for CaSiO 3 . Furthermore, carbonation promotes the formation of calcite with only 15 vol % CO 2 , allowing the direct use of cement plant fumes.

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Processes for working-up an aqueous fluosilicic acid solution

Cited by 7 publications

References 5 publications

Hexafluorosilicic Acid (FSA): from Hazardous Waste to Precious Resource in Obtaining High Value-Added Mesostructured Silica

Hexafluorosilicic Acid (FSA): from Hazardous Waste to Precious Resource in Obtaining High Value-Added Mesostructured Silica

Recent Advances on Porous Siliceous Materials Derived from Waste

Carbonation of Calcium Silicate Hydrates as Secondary Raw Material from the Recovery of Hexafluorosilicic Acid

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