Radical polymerization of acrylamide initiated by ceric ammonium nitrate-methionine redox initiator system

The polymerization of acrylamide, initiated by a cerium (IV) [Ce(IV)] ammonium nitrate-methionine redox initiator system, was carried out in an aqueous solution at different reaction conditions. The dependence of molecular weight and polymerization yield on the concentration of Ce(IV), polymerization time, and temperature was determined. The molecular weight distributions (MWD) of the resulting polymers were examined using the HPLC method. Based on the HPLC results, optimum reaction conditions were determined that provided an opportunity to obtain a polymer that had a narrow MWD. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1643–1648, 1997     

Electroinduced copolymerization of acrylonitrile–polyethylene glycol compared with chemical copolymerization

Electroinduced copolymerization of acrylonitrile (AN)–polyethylene glycol (PEG‐400) initiated by Ce(IV) was performed in aqueous solution and compared with chemical copolymerization, which allowed Ce(III) to be converted to Ce(IV) electrochemically during the polymerization. The polymer that was insoluble in water was formed in the cathodic compartment. The effect of Ce(IV), H₂SO₄, monomer, PEG‐400 concentration, temperature, time, and potential on the yield were studied and compared with similar effects under nonelectrolytic conditions. The role of Ce(IV) salt on the copolymerization was followed by spectrophotometric methods during the reaction period. Polymers were characterized by FTIR, UV‐visible spectrophotometry, and NMR. Intrinsic viscosities of polymers were determined. Possible polymerization mechanisms are suggested in the case of electrolytic and nonelectrolytic conditions. The electrolytic process has a demonstrable advantage over the nonelectrolytic method. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1410–1419, 2001     

Structure and properties of cerium phosphate and silicophosphate glasses

We report on the fabrication, properties, and structure of cerium pyrophosphate glasses and partially substituted cerium silicophosphates. In those glasses, cerium occurs predominantly as Ce(III). A combination of dynamic nuclear magnetic resonance and electrical impedance spectroscopy is used to overcome the problem of assessing cerium speciation. While optical spectroscopy is unable to quantify the ratio of Ce(III)/Ce(IV) due to spectral overlap, proxy observations of the effect of silica-for-cerium substitution on optical extinction and the shape and width of the UV band gap corroborate vibrational spectroscopic data of the structural roles of cerium and silica. While silica bonding to phosphate units appears to stabilize Ce(IV), it also impedes the polaron transport, leading to higher polaron activation energy and lower electronic conductivity. On the other hand, Ce(III) is stabilized by coordinating to P = O.     

Electrochemically induced redox polymerization of acrylamide

Polymerization of acrylamide (AA) has been studied in aqueous solution in the presence of a Ce(IV) salt–oxalic acid initiator system in an electrochemical cell with and without separation of anolyte and catholyte. For reactions that required the cathode and anode sections to be analyzed individually, a cell whose compartments were divided by a sintered glass disk of the medium porosity was employed. Polymerization was initiated by a free radical that is formed by the fast reaction of oxalic acid and Ce(IV). The electrolysis of the reaction solution results in regeneration of Ce(IV), which can oxidize oxalic acid to produce radicals. The effect of sulfuric acid and cerium (IV) salt concentration and temperature on the yield of electroinitiated polymerization in different cell designs and structural identification of products were performed. Reaction was also followed by cyclic voltametric measurements, and a mechanism was proposed. Results indicated that the electrolysis method with a divided cell (85% conversion) shows advantages, compared with nonelectrolytic (5% conversion) and with undivided electrochemical cell (25% conversion) methods where a high concentration of initiator was used. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 861–869, 1999     

Electrochemical regeneration of ceric sulphate in an undivided cell

Ceric sulphate (0–0.5 m) was generated electrochemically from cerous sulphate slurries (0.5–0.8 m total cerium) in 1.61 m sulphuric acid, at 50 °C, using a bench scale differential area undivided electrochemical cell with an anode to cathode ratio of eleven. A cell current efficiency for Ce(IV) of 90% was obtained at an anode current density of 0.25 A cm^–2. An empirical model illustrates an increase in overall current efficiency for Ce(IV) with an increase in electrolyte velocity, an increase in total cerium concentration, and a decrease in the cell current. From separate kinetic studies on rotating electrodes, both, anode and cathode kinetics were found to be affected by cerium sulphate adsorption processes. Anode adsorption of cerous sulphate species leads to inhibited mass transfer and negatively affected current efficiencies for Ce(IV). Cathode adsorption of cerium sulphate is thought to be responsible for high cathode current efficiencies for hydrogen (93–100%). The dissolved cerous sulphate concentration increased with increasing ceric sulphate and total cerium sulphate concentrations resulting in slurries with a stable dissolved cerous sulphate concentration of as high as 0.851 m in 1.6 m H₂SO₄ at room temperature.     

Preparation of polydimethylaminoethyl methacrylate grafted attapulgite via ceric ion‐induced redox polymerization

Hybrid nanocomposites consisting of polydimethylaminoethyl methacrylate (PDMAEMA) and attapulgite (ATP) were prepared by using a surface thiol‐Ce (IV) redox initiation system via graft from approach. Initially, ATP was chemically modified with γ‐mercaptopropyltrimethoxysilane (MTS) to anchor thiol groups on the surface (ATP‐MTS). Subsequently, surface‐initiated polymerization of dimethylaminoethyl methacrylate was performed by using ATP‐MTS and cerium (IV) ammonium nitrate (CAN) in aqueous nitric acid (HNO₃) to afford hybrid particles (ATP‐g‐PDMAEMA). Evidence of grafting of PDMAEMA was confirmed by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and Thermogravimetric Analysis (TGA). The crystal structure of PDMAEMA grafted ATP was characterized by X‐ray diffraction (XRD) analysis. Morphology of ATP‐g‐PDMAEMA was observed by transmission electron microscopy (TEM). The effects of concentration of Ce (IV), HNO₃, and reaction temperature were examined by determining the percentage of grafting (PG). With other condition kept constant, the optimum conditions were obtained as follows: the reaction temperature was 50°C, Ce (IV) and HNO₃ concentrations were 12.5 mmol/L and 1 mol/L, respectively, when 0.2 g of ATP‐MTS, 1 mL of DMAEMA, and 4 mL of aqueous solution were used. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42762.     

Polyaminocarboxylic acids–Ce(IV) redox systems as an initiator in acrylamide polymerization

Acrylamide polymerization by Ce(IV)-polyaminocarboxylic acids, i.e., EDTA, DTPA, EGTA, and NTA, which have strong chelating properties, have been studied at different [H⁺], initiator concentration, and reaction time. Initiation of polymerization proceeds through the formation of the free radical after decarboxylation of the carboxyl group of polyaminocarboxylic acid. Results also indicate that the termination of the polymerization reaction is mainly mutual termination. Decrease of the rate of disappearance of the cerium(IV) is in the order of DTPA ≥ EDTA > NTA > EGTA. © 1993 John Wiley & Sons, Inc.     

Mediated electrosynthesis with cerium (IV) in methanesulphonic acid

Methanesulphonic acid has been found to solubilize the Ce(III)/Ce(IV) couple. This makes cerium mediated electrosynthesis practical for commercial production of several carbonyl compounds. Results are presented for the electrochemical generation of Ce(IV) in methanesulphonic acid and for naphthalene oxidation to 1,4-naphthoquinone using Ce(IV).     

Aqueous polymerization of methyl methacrylate initiated by the redox system Ce(IV)-D-Glucose. II: Effect of reaction conditions on polymer molecular weight

The dependence of molecular weight of poly(methyl methacrylate) on reaction conditions, as polymerized in aqueous nitric acid with the redox system ceric ammonium nitrate-glucose, has been studied. The average molecular weights and molecular weight distributions were determined by size-exclusion chromatography. The degree of polymerization was found to increase in the course of a run and was also affected by changes of Ce(IV) and glucose concentrations in the range where the rate of polymerization increased, but not where the rate was independent of Ce(IV) concentration and decreased with glucose concentration. The average molecular weights can be controlled by variations in monomer concentration and in temperature. The polymerization rate was found to attain a maximum with nitric acid concentration whereas the rate of ceric ion consumption increased. A fall in the degree of polymerization was observed on increasing the acid concentration. The effect of nitrate ion concentration as well as of that of certain water-miscible solvents on the above-mentioned parameters has also been studied.     

Studies on cerium oxidation in catalytic ozonation process: A novel approach for organic mineralization

A novel regenerative catalytic system has been developed using cerium and ozone in nitric acid medium. It was found that cerium(III) was oxidized to cerium(IV) by ozone in nitric acid medium with good conversion yields. The conversion rate of Ce(III) was measured under various parameters viz. ozone–air flow rate, initial concentration of Ce(III), and concentration of nitric acid at 25 °C. It was found that the conversion of Ce(III) increased with increasing ozone flow rate and concentration of nitric acid while decreased with increasing Ce(III) concentration. The pseudo first order kinetic constants were evaluated for Ce(III) oxidation. The efficiency of this hybrid system comprising of ozone and cerium redox pair towards organic mineralization was evaluated taking phenol as the model organic pollutant and compared with Ce(III) catalyzed and uncatalyzed ozonation processes. The presence of Ce(III) catalyst increased the destruction efficiency of phenol compared to uncatalyzed ozonation whereas a synergetic effect was observed between the cerium redox pair (Ce(III) and Ce(IV)) and ozone towards phenol mineralization and a maximum TOC removal was obtained in the latter case. Kinetic interpretations have been made with some simplifying assumptions owing to the much complex nature of ozone and metal ion interactions. This hybrid catalytic ozonation process may find its suitability for continuous organic destruction at room temperature.     

Aqueous polymerization of methyl methacrylate initiated by ceric ion reducing agent systems in sulfuric acid medium

Polymerization of methyl methacrylate (MMA) was carried out in aqueous sulfuric acid medium at 30°C using ammonium ceric sulfate (ACS)/methyl ethyl ketone (MEK) and ammonium ceric sulfate/acetone as redox initiator systems. A short induction period was observed with both the initiator systems, as well as the attainment of limiting conversion for polymerization reactions. The rate of ceric ion consumption, R_ce, was first order with respect to Ce(IV) concentration in the concentration range (0.5–5.5) × 10⁻³M, and 0.5 order with respect to reducing agent concentration in the concentration ranges (0.0480–0.2967M) and (0.05–0.3912M) for Ce(IV)–MEK and Ce(IV)–acetone initiator systems, respectively. A fall in R_ce was observed at higher reducing agent concentrations. The plots of R_ce versus reducing agent concentrations raised to the half power yielded straight lines passing through the origin, indicating the absence of complex formation between reducing agents and Ce(IV). The addition of sodium sulfate to maintain constant sulfate ion concentration in the reaction medium could bring down the R_ce values in the present reaction systems. The rate of polymerization of MMA, R_p, increased with increase in Ce(IV), reducing agent, and monomer concentrations for the Ce(IV)–MEK initiator. The rate of polymerization of MMA is independent of Ce(IV) concentration and increased with an increase in reducing agent and monomer concentrations for the Ce(IV)–acetone initiator. At higher concentrations of reducing agent (0.4–0.5M), a steep fall in R_p values was observed with both the initiator systems. The orders with respect to Ce(IV), MEK, and MMA using the Ce(IV)–MEK initiator were found to be 0.23, 0.2, and 1.29, respectively. The orders with respect to Ce(IV), acetone, and MMA using the Ce(IV)–acetone initiator were found to be zero, 0.42, and 1.64, respectively. Maintaining constant [SO²⁻₄] in the reaction medium could bring down R_p values for the Ce(IV)–MEK initiator system. On the other hand, a rise in R_p values with an increase in [Na₂SO₄] could be observed when constant [SO²⁻₄] was maintained in the reaction medium for the Ce(IV) on reducing agent, production of radicals, initiation, propagation, and termination of the polymeric radicals by bimolecular interaction is proposed. An oxidative termination of primary radicals by Ce(IV) is also included. © 1996 John Wiley & Sons, Inc.     

苯酚废水的铈掺杂钛基电极处理工艺

采用热分解方法制备了铈掺杂钛基电极,并以铈掺杂钛基电极为阳极,纯钛板为阴极组成电解池,以苯酚为目标有机污染物进行降解,采用高效液相色谱法检测苯酚的含量。讨论了Ce的掺杂量、电解池中电极间距、电解电压、电解质溶液的pH、电解质浓度、目标物的浓度以及电解时间对苯酚去除率的影响。结果表明该电解池降解苯酚废水的最佳条件：SnCl4·5Hz0、SbCl3、Ce（NO3）,物质的量比为100：10：1、电极间距为4．0cm、电解电压为9V、pH为6．55、电解质NaSO。浓度为10g／L、苯酚浓度为100mg／L、电解时间为6h。在最佳试验条件下苯酚去除率达到100％,完全符合排污标准GB8978--1996,该电极持续使用10d,对苯酚的去除率仍然可以达到85％,降解苯酚的机理趋于直接燃烧。     

Ce(III)/Ce(IV) in methanesulfonic acid as the positive half cell of a redox flow battery

The characteristics of the Ce(III)/Ce(IV) redox couple in methanesulfonic acid were studied at a platinum disk electrode (0.125 cm²) over a wide range of electrolyte compositions and temperatures: cerium (III) methanesulfonate (0.1–1.2 mol dm⁻³), methanesulfonic acid (0.1–5.0 mol dm⁻³) and electrolyte temperatures (295–333 K). The cyclic voltammetry experiments indicated that the diffusion coefficient of Ce(III) ions was 0.5 × 10⁻⁶ cm² s⁻¹ and that the electrochemical kinetics for the oxidation of Ce(III) and the reduction of Ce(IV) was slow. The reversibility of the redox reaction depended on the electrolyte composition and improved at higher electrolyte temperatures. At higher methanesulfonic acid concentrations, the degree of oxygen evolution decreased by up to 50% when the acid concentration increased from 2 to 5 mol dm⁻³. The oxidation of Ce(III) and reduction of Ce(IV) were also investigated during a constant current batch electrolysis in a parallel plate zinc–cerium flow cell with a 3-dimensional platinised titanium mesh electrode. The current efficiencies over 4.5 h of the process Ce(III) to Ce(IV) and 3.3 h electrolysis of the reverse reaction Ce(IV) to Ce(III) were 94.0 and 97.6%, respectively. With a 2-dimensional, planar platinised titanium electrode (9 cm² area), the redox reaction of the Ce(III)/Ce(IV) system was under mass-transport control, while the reaction on the 3-dimensional mesh electrode was initially under charge-transfer control but became mass-transport controlled after 2.5–3 h of electrolysis. The effect of the side reactions (hydrogen and oxygen evolution) on the current efficiencies and the conversion of Ce(III) and Ce(IV) are discussed.     

Graft copolymerization of vinyl monomers with modified cotton. II. Grafting of acrylonitrile and methyl methacrylate on acetylated cotton

Ce(IV)-induced polymerization of acrylonitrile and methyl methacrylate with acetylated cotton having different acetyl contents was investigated. The extent of interaction between the cotton and monomer is dependent upon the acetyl content of the former as well as on the reaction conditions. Increasing the acetyl content caused a significant decrease in the graft yield. Increasing the acrylonitrile concentration was accompanied by a substantial increase in the graft yields. The same effect was found with the initiator up to a certain concentration, but beyond it there was a reversal. The rate of grafting increased by rising the temperature and follow the order 60° > 40° > 30°C. The Ce(IV) consumption during grafting is greater than that consumed during oxidation. The consumption of Ce(IV) by the cellulosic materials was favorably influenced by the concentrations of monomer and initiator, time, and temperature. Rates of grafting and Ce(IV) consumption during oxidation of acetylated cottons having different acetyl contents strongly support the postulated mechanism of grafting using the Ce(IV)–cellulose redox system. Ce(IV) oxidation had practically no effect on the acetyl groups (expressed as per cent combined acetic acid) of the modified cotton.     

Kinetic study of aqueous polymerization of methyl methacrylate initiated by Ce(IV)-maltose redox system

Polymerization of methyl methacrylate initiated by ceric ammonium nitrate-maltose has been investigated in aqueous nitric acid under nitrogen in the temperature range 20.5-35°C. The dependence of the initial rate of polymerization and the initial rate of ceric ion consumption on maltose, Ce(IV), and monomer concentrations has been determined. The reaction orders were found to depend on ceric ion concentration. At a moderately high Ce(IV) concentration (1 × 10^?3mol litre^?1) the orders were 1/2 and 3/2 with respect to maltose and monomer concentration, respectively, and independent of Ce(IV) concentration. But at a low Ce(IV) concentration (4 × 10^?4mol litre^?1) the orders with respect to monomer and Ce(IV) changed to 1 and 1/2, respectively. The effect of temperature was also examined. The average molecular weight, as determined by size-exclusion chromacography, was found to depend on maltose, Ce(IV), and monomer concentrations, as well as on temperature.     

Electroinduced dispersion polymerization of acrylonitrile in the presence of poly(acrylic acid) and catalytic amount of CE(IV)

Electroinduced dispersion polymerization of acrylonitrile initiated by Ce(IV) was performed in an electrolytic cell in the presence of poly(acrylic acid) (PAA). Micron‐size polyacrylonitrile (PAN) particles were stabilized with PAA by electrostatic interaction or by a PAA–Ce(III)–PAN ternary complex formation. A PAA–PAN stable polymer was formed in the cathodic compartment, and the reduced initiator was reoxidized in the anode, thus allowing for the continuation of the process. A possible mechanism of polymerization is suggested. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 723–728, 2002; DOI 10.1002/app.10076     

Graft copolymerization of vinyl monomers onto chitin with cerium (IV) ion

Graft copolymerization of vinyl compounds onto chitin was studied, and an efficient and reproducible procedure has been established, cerium (IV) being used as the initiator. The reactions with acrylamide and acrylic acid onto powdery chitin were carried out under various conditions to elucidate the polymerization behavior in terms of grafting percentage. The amount of cerium (IV) affected the polymerization most strikingly, and grafting percentages showed maxima with suitable amounts of initiator for both the monomers. As a solvent water proved to be superior to aqueous nitric acid except the reaction with a small amount of initiator. Under appropriate conditions, around 240 and 200% grafting percentages were achieved for acrylamide and acrylic acid, respectively. The resulting graft copolymers showed much improved affinity for solvents and hygroscopicity compared to the original chitin.     

Aqueous polymerization of methyl methacrylate initiated by the redox system Ce(IV)—D-glucose. I: General features and kinetics

The polymerization of methyl methacrylate initiated by the ceric ammonium nitrate-D-glucose redox system has been studied in aqueous nitric acid under nitrogen in the temperature range 20-5 to 35°C. The initial rate of polymerization was determined gravimetrically whereas the initial rate of ceric ion disappearance was determined by titration of ceric ion. The relationships between conversion and D-glucose, Ce(IV), and monomer concentrations were determined. The dependence of the rates on D-glucose, Ce(IV), and monomer concentrations was evaluated. The effect of temperature was also examined.     

水溶液中电沉积Ni-Ce-P合金

报道了从含有混合配体：柠檬酸和氯化铵,稳定剂Ｈ３ＢＯ３的水溶液中电沉积出Ｎｉ－Ｃｅ－Ｐ合金镀层。讨论了镀液成分和电镀工艺条件（镀液的ｐＨ值、电流密度、温度、搅拌方式、阳极材料等）的选择。采用ＳＥＭ和ＸＰＳ对镀层的结构和组分进行分析,结果表明镀层是Ｎｉ－Ｃｅ－Ｐ合金。     

Electrochemical study of cerium(IV) in the presence of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetate (DTPA) ligands

The electrochemical behaviour of the complexation of cerium(IV) with EDTA and DTPA was studied using both cyclic voltammetry (CV) and rotating disc electrode (RDE). The Ce(IV)–DTPA complex at various scan rates gave a linear correlation between the peak potential (E _p ) and square root of scan rate, showing that the kinetics of the overall process was controlled by mass transport. However, when the EDTA ligand was added to the Ce(IV) there was no specific change to the potential peak, i.e. the Ce(IV)–EDTA complex has the same redox potential as the Ce(IV)/(III) couple. Kinetic parameters such as potential, limiting current, diffusion coefficients, transfer coefficient and rate constants were studied. The results from RDE experiments confirmed that the parameters measured by CV are similar under hydrodynamic conditions and can be used to determine the kinetic parameters of the redox couples. The use of DTPA as a ligand for complexation of Ce(IV) gaves more favourable results compared to the Ce–(EDTA) complex reported previously. The results of kinetic studies of Ce(IV)–DTPA complex shows promise as an electrolyte for redox flow battery.