Third Phase Formation in the Extraction of Inorganic Acids by TBP in n‐Octane

Abstract

The extraction of HNO₃, HClO₄, H₂SO₄ and H₃PO₄ by 20% (v/v) TBP (0.73 M) in n‐octane was measured under identical conditions up to and beyond the critical point of third phase formation (Limiting Organic Concentration, or LOC condition). The data, together with those obtained previously for HCl, allowed us to establish the following lyotropic series of effectiveness with respect to third phase formation in the extraction of acids by TBP: HClO₄>H₂SO₄>HCl>H₃PO₄>HNO₃. This series correlates with the amount of water present into the organic phase at the point of phase splitting. This result reinforces the validity of the reverse micellar model developed previously for the extraction of metal salts by TBP. The measurements of LOC values as a function of temperature revealed major differences among the acid‐TBP systems investigated. For HClO₄, the strong increase of the LOC value with increasing temperatures is accompanied by a large favorable entropy change. The opposite is true for HCl, while H₂SO₄ and H₃PO₄ represent intermediate cases. Measurements of the LOC values for the extraction of HClO₄ by TBP dissolved in a series of diluents confirmed that topological parameters, such as the Connectivity Index, CI, are useful for predicting the critical condition for phase splitting in different diluents. Based on the linear correlation between LOC values for HClO₄ and CI values of diluents, the effective Connectivity Index of the French nuclear reprocessing diluent, HTP, a complex mixture of highly branched alkanes, was determined.     

Graft copolymerization to cellulose in the presence of hydrogen peroxide with ultraviolet irradiation

The decomposition of hydrogen peroxide in the presence of cellulose with ultraviolet irradiation and graft copolymerization occurring upon addition of methyl methacrylate to this system was investigated. Graft copolymerization barely began in the hydrogen peroxide system without ultraviolet irradiation, but was markedly accelerated by ultraviolet irradiation. Ultraviolet light is capable of initiating the graft copolymerization even without addition of hydrogen peroxide, and this capability is enhanced further with the use of hydrogen peroxide. However, an increase in the hydrogen peroxide concentration was observed to exercise a zero or negative effect on the number of grafts. Such a phenomenon is absent in the ceric ion initiator system and, in the present study, is believed to be brought about by a characteristic enhancement of the stabilization of grafting sites effected by hydroxyl radicals. The number of grafts of copolymers obtained in the present initiator system is only approximately 0.085 mmole/100 g of cellulose at its maximum and is within the range of results obtained for the hydrogen peroxide initiator system in general.     

Ceric salt-initiated graft copolymerization of methyl methacrylate on preoxidized cellulose samples

The effects of preoxidation of cellulose samples on graft copolymerization in the presence of ceric salt (Ce⁴⁺) as an initiator were investigated. The use of Ce⁴⁺ as oxidizing agent inhibited the formation of grafts, and the number of grafts decreased as the concentration of Ce⁴⁺ in the pretreatment rose. In contrast, the samples oxidized with periodic acid (HIO)₄ or hydrogen peroxide (H₂O₂) tended to show improved initiation characteristics and gave a larger number of grafts than the unoxidized samples. The reactivity of oxidized samples toward Ce⁴⁺ was examined and the following results were obtained: The part of easy reactivity decreased in the Ce⁴⁺-oxidized samples but it increased in the HIO₄-oxidized samples; on the other hand, it did not vary greatly in the H₂O₂-oxidized samples. Cellulose is probably oxidized to different states by different oxidizing agents, and the reactivity of Ce⁴⁺ toward these oxidized samples, as one index, seems to be reflected in the graft copolymerization. It was consequently recognized that the graft copolymerization characteristics of cellulose samples could be improved significantly by proper selection of oxidiation conditions.     

Pentavalent vanadium ion-induced grafting of methyl methacrylate onto cotton cellulose

Graft polymerization of methyl methacrylate (MMA) onto cotton cellulose using vanadium pentanitrate as initiator was studied under a variety of conditions. The graft yield increased with increasing initiator concentration up to 8 mmole/l. and then decreased upon further increase in initiator concentration. Increasing MMA concentration from 1 to 5% was accompanied by a significant increase in the degree of grafting. The latter was also affected by the kind and concentration of the acid incorporated in the polymerization medium. Based on graft yields, the efficiency of the acids follows the order H₂SO₄ > HNO₃ > HClO₄. Replacement of the acid with isopropyl alcohol was also examined. An isopropyl alcohol concentration of 10% constitutes the optimal concentration for grafting. Maximum graft yield depends upon the polymerization temperature; it follows the order 50°C ≥ 60°C > 40°C > 30°C > 70°C. Reaction mechanisms for grafting in the presence of acid as well as in the presence of isopropyl alcohol are proposed.     

Spectroscopic,transport, and morphological studies of polyaniline doped with inorganic acids

A conducting polymer, polyaniline, was synthesized by chemical polymerization using different inorganic acids, such as HCl, H₂SO₄, HClO₄, HNO₃, and H₃PO₄, as protonic acid media. The synthesized polymers were characterized using UV‐visible and FT‐IR spectroscopy. A granular type of morphology was observed under SEM for HCl, HNO₃, and H₃PO₄ doped polyanilines. However, HClO₄ doped polyaniline shows the folded lamellar structure derived from the fibers. The thermal stability of these polymers was investigated with the help of thermogravimetric (TG/SDTA) analysis. The formation of a greater fraction of the conducting emeraldine salt phase is observed in HClO₄ as a protonic acid media. The thermal stability of H₃PO₄ doped material is found to be better as compared with other acids. An increase in conductivity with an increase in temperature was observed in all the samples except for HClO₄ doped polyaniline. Polym. Eng. Sci. 44:1676–1681, 2004. © 2004 Society of Plastics Engineers.     

Liquid-Liquid Extraction of Acids and Water by a Malonamide: I-Anion Specific Effects on the Polar Core Microstructure of the Aggregated Malonamide

In a solvent extraction process, the compositions of the phases in thermodynamic equilibrium (described as a Winsor-II regime) must be determined to obtain the extraction isotherms of ions as well as co-extracted water. By comparing the extractions of a series of acids by the malonamide DMDOHEMA (N,N’-dimethyl-N,N’-dioctyl hexylethoxy malonamide) in n-heptane, the specific anion effects regarding third phase formation and the strength of the acid-extractant interaction were investigated. It is shown that third phase formation is driven by hydration enthalpy of acid, while the polar core microstructure is controlled by the pKa of the acids. Upon acid extraction, the promotion of third phase formation follows the series H₂SO₄ ≈ H₃PO₄ ≈ HClO₄ > HNO₃ > HCl > HCOOH, which correlates to hydration enthalpy of acid in the case of monoacids. The combination of IR spectroscopy and DFT calculations revealed two different modes of acid extraction, either by hydrogen bonding (extraction of non-dissociated acid: HA) or by protonation of the extractant (extraction of dissociated acid: H⁺A^?). The strength of the amide-acid interaction (protonation vs. hydrogen bonding) is correlated to the pKa of the acid and is responsible for the microstructure of the solution.     

Aminolysis reaction of poly(N-4-methylphenylitaconimide) and its graft copolymerization

Polyitaconimide and copolymers of itaconimide were transformed to macromolecules having diamido pendent groups via an aminolysis reaction. The polymers obtained were cast into films, which were then graft copolymerized with acrylamide (AAM) using ceric ion as an initiator. Radical homopolymerization and copolymerization of N-4-methylphenylitaconimide with methyl acrylate or ethyl acrylate were carried out at 60°C in benzene; high molecular weight polymer and copolymers (M?_n = 10⁴–10⁵) were obtained. The resulting polymer and copolymers were reacted with n-butylamine in order to produce polymers possessing a pendent 4-tolylcarbamoyl group (4-CH₃C₆H₄NHCO-), which can significantly promote the acrylamide (AAM) graft copolymerization initiated with ceric ion. Transparent films of the polymers were graft copolymerized with AAM in the presence of ceric ion at 45°C. The formation of graft polymers was verified by water absorption percentage, XPS and SEM.     

Grafting of vinyl acetate–methyl acrylate mixture onto cellulose. Effect of inorganic salts

The effect of the addition of NaNO₃ and NaCl on the graft copolymerization of a mixture of vinyl acetate–methyl acrylate onto cellulose, using ceric ion as initiator, is examined. Several grafting parameters were measured. Presence of NaNO₃ affects the graft copolymerization by enhancing the cellulose oxidation, but it leaves almost unaffected the homopolymerization reaction. NaCl works similarly to NaNO₃. As a consequence of salt presence, ligand changes in the ceric ion complexes, as well increase in the ionic strength of the medium, are expected.     

Acid-catalyzed condensation of oleic acid into estolides and polyestolides

Oleic acid, when treated with 1.0 equivalent of perchloric acid at 50°C, produced a 76% yield of polyestolide. The concentration of mineral acid greatly affected the rate of estolide formation, with increased rates under high acid concentrations. Over a range of temperatures from room temperature to 100°C, reaction rates increased at higher temperatures. However, high acid concentrations and temperatures produced undesirable side products, primarily lactones. Other acids catalyze the condensation of oleic acid to form estolide with the following relative rates: HClO₄ >H₂SO₄>p-toluenesulfonic>BF₃·Et₂O> montmorillonite K-10>HCl>H₃PO₄, HNO₃. Addition of water impedes the formation of estolide.     

Effect of metallic ions in photo-induced graft copolymerization onto cellulose

In photo-induced graft copolymerization of methyl methacrylate onto cellulose, the effect of metallic ions as sensitizer was investigated. Some metallic ions were effective in their adsorbed states and accelerated the formation of grafts in the order Fe²⁺ > Ag⁺ > Fe³⁺. However, Cu²⁺ acted negatively, and little effect was observed for Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺, and Cr³⁺. In the systems in which aqueous metallic salt solutions were added, the formation of grafts was generally depressed, but Fe³⁺ was an exception. The effect of metallic ions on the scission reaction of cellulose main chains did not necessarily agree with the effect on the formation of grafts. This is attributed to the varied interaction between cellulose and the different active species produced by irradiation, depending on the type of metallic ions used.     

Coatings of Conducting Polymers for Corrosion Protection of Mild Steel

The investigation of electrochemical behavior of different conducting polymers, polythiophene (PTh), polypyrrole (PPy) and polyterthiophene (PTTh) on a mild steel (MS) electrode were done. Moreover, the combinations of the conducting polymers PTh and PPy was investigated. The synthesis of all polymeric coatings was done by the cyclic voltammetry technique. The electrochemical impedance spectroscopy (EIS) measurements were used to evaluate the corrosion performance of coated mild steel by different polymers in 0.5 M of different acid solutions (HCl, HClO₄, H₂ C ₂ O ₄, H₃PO₄ and HNO₃). The protection of all polymeric coatings against corrosion of the substrate was promising and the bilayer coating PPy/PTh gave the best protection efficiency in all used acids. The order of efficiency for the different coatings in HCl and HNO₃ solutions was MS/PPy/PTh > MS/PPy > MS/PTTh > MS/PTh but the order in HClO₄, H₃PO₄ and H₂ C ₂ O ₄ solutions was MS/PPy/PTh > MS/PTTh > MS/PPy > MS/PTh.     

Graft copolymerization of methyl acrylate onto sago starch using ceric ammonium nitrate as an initiator

The graft copolymerization of methyl acrylate onto sago starch was carried out by a free radical initiating process. The free radicals were produced by the chemical initiation method in which ceric ammonium nitrate was used as an initiator. It was found that the percentages of grafting, grafting efficiency, and rate of grafting were all dependent on the concentration of ceric ammonium nitrate (CAN), methyl acrylate (MA), sago starch (AGU), mineral acid (H₂SO₄), and reaction temperature and period. The variables affecting the graft copolymerization were thoroughly examined. The optimum yield of grafting was obtained when the concentration of CAN, MA, AGU, and H₂SO₄ were used at 8.77 × 10⁻³, 0.803, 0.135, and 0.175 mol L⁻¹, respectively. The optimum reaction temperature and period were 50°C and 60 min, respectively. The rate of graft polymerization was explored on the basis of experimental results and reaction mechanism. The evidence of grafted copolymers was investigated by using FTIR spectroscopy, TG, and DSC analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 516–523, 2000     

Effect of lignin in graft copolymerization of methyl methacrylate on cellulose by ceric ion

The effect of lignin contained in cellulosic materials in graft copolymerization of methyl methacrylate on such materials using ceric ion as initiator was studied. It was found that the percent grafting and the average molecular weight of grafts became lower in samples having a larger lignin content but the number of grafts formed increased proportionally up to lignin content of about 2.5%. Ceric ion reacted at a faster rate with lignin than with cellulose in wood pulp, and the results indicating that the active sites formed on lignin by oxidation with ceric ion accelerate the formation of grafts and increase the number of grafts were obtained. But on the other hand, the active sites participated in the termination reaction of the growing graft polymer radicals to cause lowering of the average molecular weight of grafts.     

Grafting onto wool. XXVIII. Effects of acids on gamma-radiation induced graft copolymerization of ethylmethacrylate onto wool fiber

Graft copolymerization of ethylmethacrylate (EMA) onto Himachali wool fiber has been investigated in aqueous medium by mutual gamma irradiation from a Co⁶⁰ source in air and in nitrogen atmosphere. Percentage of grafting has been evaluated as a function of (i) total dose, (ii) concentration of monomer, and (iii) effect of concentration of different acids such as hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, and acetic acid. Maximum percentage of grafting has been obtained in the presence of sulfuric acid. Following reactivity order of different acids towards grafting has been observed: H₂SO₄ > HCI > HNO₃ > HCIO₄ > CH₃COOH. A plausible mechanism to explain the effect of acids on percentage of grafting of EMA has been suggested.     

Relationship between photo-induced scission of cellulose chains and graft copolymerization

Studies were carried out on the relationship between the scission of cellulose chains and the initiation of photo-induced graft copolymerization of methyl methacrylate. The photo-induced scission of cellulose chains was sharply accelerated by the application of irradiation with light shorter than 300 nm, the use of photosensitizer such as ferric ion, the swelling of cellulose samples, and so on. On the other hand, the scission reaction was markedly suppressed by blocking the carbonyl groups contained in the samples by oximation. A linear increase in the number of grafts was indicated with the number of scissions of cellulose chains in the graft copolymerization. However, a number of scissions not contributing to any formation of grafts was also noticed during the induction period of copolymerization. The factors such as short wavelength light, photosensitizer, and swelling, which contribute to the rises in the rate of graft formation and the scission of cellulose chains, worked also to shorten the induction period. As might be expected, appreciable increases of per cent grafting and shortening of induction period were achieved by preirradiation the cellulose samples with light. From the above, it was concluded that the scission of cellulose chains should be a main factor for the initiation of graft copolymerization in the system.     

Ion Flotation and Solvent Extraction of Ferric Thiocyanate Complexes

Abstract

The influence of thiocyanate and accompanying mineral acids concentration on the effectiveness of Fe(III) ion flotation, Fe(III) precipitation in cetyl-trimethylammonium ferric-thiocyanate form (as sublate), and Fe(III) extraction using ethyl acetate was studied. The effectiveness of these processes improves with the extent of Fe(III) complexation by thiocyanates. In the presence of acids, flotation and precipitation are increased as follows: HC1O₄ < HC1 < HNO₃ < H₂SO₄. The position of H₃PO₄ in this series changes with changing thiocyanate concentration. Extraction effectiveness is increased in the series: H₃PO₄ < H₂SO₄ < HNO₃, HC1O₄ HCl. The following points are discussed: (a) the influence of acid anions competing with thiocyanate anions in Fe(HI) complexation; (b) the influence of the competition between acid anions and complex ferric-thiocyanate anions in sublate formation; (c) the influence of hydrogen ion concentration increase in thiocyanate medium on the results of Fe(III) flotation, precipitation, and extraction; and (d) the influence of anion affinity for a collector on the solution surface properties and on Fe(III) flotation.     

Electrochemical Behavior of Polyaniline,Poly(o-Anisidine) and Their Copolymer Thin Films in Inorganic and Organic Supporting Electrolytes

Abstract

The influence of inorganic and organic supporting electrolytes on electrochemical, optical, and conducting properties of polyaniline, poly(o-anisidine), and poly(aniline-co-o-anisidine) thin films were investigated. Homo- and copolymer thin films were synthesized electrochemically, under cyclic voltammetric conditions in aqueous solutions of inorganic acids, viz., H₂SO₄, HCl, HNO₃, H₃PO₄, and HClO₄ and organic acids, viz., benzoic acid, cinnamic acid, oxalic acid, malonic acid, succinic acid, and adipic acid, at room temperature. The films were characterized by cyclic voltammetry, ultraviolet (UV)–Visible spectroscopy, and conductivity measurements using four probe technique. The optical absorption spectra indicated that the formation of the conducting emeraldine salt (ES) phase took place in all the inorganic supporting electrolytes used whereas, inorganic supporting electrolytes ES phase formed only with oxalic acid. It was also observed that the current density and conductivity of thin films are greatly affected by the nature and size of the anion present in the electrolyte. The formation of copolymer has also been confirmed by differential scanning calorimetry.     

ESR study of reactions of cellulose initiated by the ceric ion method

The ESR spectra of microcrystalline cellulose and purified cotton cellulose reacted with ceric ammonium nitrate in nitric acid were determined. The effects of the concentration of ceric ion, atmosphere, temperature, and graft copolymerization with acrylonitrile on the rates of formation and decay of radicals in the cellulose molecule were determined under both static and dynamic conditions. Under static conditions, after the desired conditions of reaction, the samples were frozen at –100 or –160°C., and then the concentration of free radicals was determined. Under dynamic conditions ceric ion solution was continuously flowed through the celluloses while these determinations were being made at 25°C. In the presence of oxygen the rate of decay of free radicals was decreased. On initiation of copolymerization reactions with acrylonitrile, there was an increase in radical concentration, then a decrease. Apparently, during graft copolymerization the radical site initially on the cellulose molecule was retained on the end of the growing polymer chain. Then additional ceric ion coordinated with the hydroxyl groups of the cellulose, leading to the formation of additional radical sites. An Arrhenius interpretation of the effect of temperature on the formation of these additional radical sites gave apparent activation energies for radical formation on cotton cellulose as 34 kcal./mole and on microcrystalline cellulose as 29 kcal./mole.     

Synthesis of polyamidoxime chelating ligand from polymer‐grafted corn‐cob cellulose for metal extraction

A conventional free‐radical initiating process was used to prepare graft copolymers from acrylonitrile (AN) with corn‐cob cellulose with ceric ammonium nitrate (CAN) as an initiator. The optimum grafting was achieved with corn‐cob cellulose (anhydroglucose unit, AGU), mineral acid (H₂SO₄), CAN, and AN at concentrations of 0.133, 0.081, 0.0145, and 1.056 mol/L, respectively. Furthermore, the nitrile functional groups of the grafted copolymers were converted to amidoxime ligands with hydroxylamine under basic conditions of pH 11 with 4 h of stirring at 70°C. The purified acrylic polymer‐grafted cellulose and polyamidoxime ligand were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy analysis. The ligand showed an excellent copper binding capacity (4.14 mmol/g) with a faster rate of adsorption (average exchange rate = 7 min), and it showed a good adsorption capacity for other metal ions as well. The metal‐ion adsorption capacities of the ligand were pH‐dependent in the following order: Cu²⁺ > Co²⁺ > Mn²⁺ > Cr³⁺ > Fe³⁺ > Zn²⁺ > Ni²⁺. The metal‐ion removal efficiency was very high; up to 99% was removed from the aqueous media at a low concentration. These new polymeric chelating ligands could be used to remove aforementioned toxic metal ions from industrial wastewater. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40833.     

Studies on the ability of cellulosic materials to initiate graft copolymerization

The activity to initiate graft copolymerization was investigated for various cellulose samples. Oxidation of the sample with hydrogen peroxide or sodium hypochlorite indicated a remarkable increase in the per cent grafting as well as the number of grafts. This phenomenon must be attributed to the formation of special reactive groups in cellulosic materials. However, the treatment with hot water caused a definite decrease in the per cent grafting or the number of grafts for the graft copolymerization on the sample, indicating a lower activity to initiate graft copolymerization. Accordingly, the reactive groups, once formed on the sample by oxidation, seemed to be easily decomposed by hot water. The ferric ion adsorbed on cellulose increased the per cent grafting and accelerated the formation of grafts, and the contribution of metallic ions to the initiation was recognized as one of the important factors of graft copolymerization.