Calix[4]pyrrole macrocycle: Extraction of fluoride anions from aqueous media

Abstract

KEYWORDSSolid-phase extraction of fluoride anions by calixpyrrole macrocycle (CP) from aqueous media has been studied using the batch method. Various significant extraction parameters like initial concentration of the anion, extraction time, concentration of the calixpyrrole, pH and temperature were evaluated. Langmuir, Freundlichand, Dubinin-Redushkevish (D-R) isotherms and coefficients were used to analyze the equilibrium data. The amount of fluoride anion extracted per unit of the CP was found to be 0.40 mg/g at 298 K from 19 mg/L aqueous solution of fluoride anions. The mean free energy calculated from D-R model for the removal of fluoride anions by the CP was found to be 10.0 kJ/mol, indicating that chemisorption is involved in the extraction process. The data were also fitted to kinetic models such as pseudo first order and pseudo second order. The removal of fluoride anions increased with increasing temperature indicating the endothermic nature of the extraction process. The present method has been compared with the previous methods.

Stabilization and Extraction of Fluoride Anion Using a Tetralactam Receptor

“…The extraction efficiency is much better than most other reported examples of fluoride extraction using an uncharged hydrogen bonding receptor. Typically, 60%–80% of receptor saturation has been obtained when the starting water layer contained molar or submolar concentrations of fluoride. ,,,− The high extraction efficiency is due in large part to the core–shell architecture of the extracted dimeric complexes that contain one or two F – ions surrounded by two copies of self-associated 2 . All of the polar functional groups are buried within the dimer core, whereas nonpolar functionality dominates the exterior surface.…”

Stabilization and Extraction of Fluoride Anion Using a Tetralactam Receptor

“…The extraction efficiency is much better than most other reported examples of fluoride extraction using an uncharged hydrogen bonding receptor. Typically, 60%–80% of receptor saturation has been obtained when the starting water layer contained molar or submolar concentrations of fluoride. ,,,− The high extraction efficiency is due in large part to the core–shell architecture of the extracted dimeric complexes that contain one or two F – ions surrounded by two copies of self-associated 2 . All of the polar functional groups are buried within the dimer core, whereas nonpolar functionality dominates the exterior surface.…”

Naked-eye detection of inorganic fluoride in aqueous media using a new azo-azomethine colorimetric receptor enhanced by electron withdrawing groups

“…6, there is a drastic drop in the intensity of the absorption band in highly acidic conditions, this is probably due to the protonation of uoride ion, to form weakly ionized hydrouoric acid, thereby lowering the affinity of uoride anion to bind to the receptor active sites. 16 As the pH rises, the intensity of the characteristic band increases, this is probably due to an increase in the accessibility of the deprotonated uoride to form strong hydrogen bonds with the receptor. These pH responses of 1 are not surprising since similar ndings have been reported for other colorimetric uoride sensors.…”

Kinetics and thermodynamics of chromate and phosphate uptake by polypyrrole: batch and column studies

“…However, these techniques have some disadvantages such as high cost, low efficiency, low selectivity, high-energy requirements, and sludge generation [11]. Compared to other methods, uptake is simple and effective [12][13][14]. Several kinds of materials were used as adsorbent for removal of chromate and phosphate pollutants [15,16].…”

“…Among these are fly ash [17], blast furnace slag [18], iron oxide tailing [19], red mud [20], Ca-based adsorbents, and iron-based compounds [21]. Since the last decade, polymers [22][23][24] and macrocyclic derivatives of pyrrole [14] have attracted more attention as adsorbents of anionic and cationic pollutants from water because of their nontoxicity, good environmental stability, low cost and ease of preparation [25][26][27]. In this context, polypyrrole-coated sawdust [28] and Fe 3 O 4 coated polypyrrole magnetic nanocomposite [22] were used to remove phosphate and chromium (VI) ions from water respectively.…”

Stabilization and Extraction of Fluoride Anion Using a Tetralactam Receptor

“…The extraction efficiency is much better than most other reported examples of fluoride extraction using an uncharged hydrogen bonding receptor. Typically, 60%–80% of receptor saturation has been obtained when the starting water layer contained molar or submolar concentrations of fluoride. ,,,− The high extraction efficiency is due in large part to the core–shell architecture of the extracted dimeric complexes that contain one or two F – ions surrounded by two copies of self-associated 2 . All of the polar functional groups are buried within the dimer core, whereas nonpolar functionality dominates the exterior surface.…”

Naked-eye detection of inorganic fluoride in aqueous media using a new azo-azomethine colorimetric receptor enhanced by electron withdrawing groups

“…6, there is a drastic drop in the intensity of the absorption band in highly acidic conditions, this is probably due to the protonation of uoride ion, to form weakly ionized hydrouoric acid, thereby lowering the affinity of uoride anion to bind to the receptor active sites. 16 As the pH rises, the intensity of the characteristic band increases, this is probably due to an increase in the accessibility of the deprotonated uoride to form strong hydrogen bonds with the receptor. These pH responses of 1 are not surprising since similar ndings have been reported for other colorimetric uoride sensors.…”

Kinetics and thermodynamics of chromate and phosphate uptake by polypyrrole: batch and column studies

“…However, these techniques have some disadvantages such as high cost, low efficiency, low selectivity, high-energy requirements, and sludge generation [11]. Compared to other methods, uptake is simple and effective [12][13][14]. Several kinds of materials were used as adsorbent for removal of chromate and phosphate pollutants [15,16].…”

“…Among these are fly ash [17], blast furnace slag [18], iron oxide tailing [19], red mud [20], Ca-based adsorbents, and iron-based compounds [21]. Since the last decade, polymers [22][23][24] and macrocyclic derivatives of pyrrole [14] have attracted more attention as adsorbents of anionic and cationic pollutants from water because of their nontoxicity, good environmental stability, low cost and ease of preparation [25][26][27]. In this context, polypyrrole-coated sawdust [28] and Fe 3 O 4 coated polypyrrole magnetic nanocomposite [22] were used to remove phosphate and chromium (VI) ions from water respectively.…”

Stabilization and Extraction of Fluoride Anion Using a Tetralactam Receptor

“…The extraction efficiency is much better than most other reported examples of fluoride extraction using an uncharged hydrogen bonding receptor. Typically, 60%–80% of receptor saturation has been obtained when the starting water layer contained molar or submolar concentrations of fluoride. ,,,− The high extraction efficiency is due in large part to the core–shell architecture of the extracted dimeric complexes that contain one or two F – ions surrounded by two copies of self-associated 2 . All of the polar functional groups are buried within the dimer core, whereas nonpolar functionality dominates the exterior surface.…”

Naked-eye detection of inorganic fluoride in aqueous media using a new azo-azomethine colorimetric receptor enhanced by electron withdrawing groups

“…6, there is a drastic drop in the intensity of the absorption band in highly acidic conditions, this is probably due to the protonation of uoride ion, to form weakly ionized hydrouoric acid, thereby lowering the affinity of uoride anion to bind to the receptor active sites. 16 As the pH rises, the intensity of the characteristic band increases, this is probably due to an increase in the accessibility of the deprotonated uoride to form strong hydrogen bonds with the receptor. These pH responses of 1 are not surprising since similar ndings have been reported for other colorimetric uoride sensors.…”

Kinetics and thermodynamics of chromate and phosphate uptake by polypyrrole: batch and column studies

“…However, these techniques have some disadvantages such as high cost, low efficiency, low selectivity, high-energy requirements, and sludge generation [11]. Compared to other methods, uptake is simple and effective [12][13][14]. Several kinds of materials were used as adsorbent for removal of chromate and phosphate pollutants [15,16].…”

“…Among these are fly ash [17], blast furnace slag [18], iron oxide tailing [19], red mud [20], Ca-based adsorbents, and iron-based compounds [21]. Since the last decade, polymers [22][23][24] and macrocyclic derivatives of pyrrole [14] have attracted more attention as adsorbents of anionic and cationic pollutants from water because of their nontoxicity, good environmental stability, low cost and ease of preparation [25][26][27]. In this context, polypyrrole-coated sawdust [28] and Fe 3 O 4 coated polypyrrole magnetic nanocomposite [22] were used to remove phosphate and chromium (VI) ions from water respectively.…”