Organic Ion Exchange Resins Research Articles

Removal of Zwitterionic PFAS by MXenes: Comparisons with Anionic, Nonionic, and PFAS-Specific Resins.

Zwitterionic per- and polyfluoroalkyl substances are increasingly detected in aquatic environments. The magnitude of their concentration and increased frequency of detection worldwide raise questions on their presence in drinking water and associated health risk. Scientific knowledge on the identification of treatment technologies to effectively capture such zwitterionic PFAS from contaminated water sources remains largely unknown. In this study, we investigated the application of anionic organic scavenger ion exchange (IX) resins (A860), nonionic IX resins (XAD 4 and XAD 7), PFAS-specific resins (A694 and A592), and Ti3C2 MXenes (novel two-dimensional metal carbides) for the removal of select fluorotelomer zwitterionic PFAS from natural waters. The cumulative removal of zwitterionic PFAS at pH ∼ 7 follows the order: Ti3C2 MXenes > A694 > A592 > A860 > XAD 4 ∼ XAD 7. Ti3C2 MXenes were able to capture >75% of the total influent zwitterionic PFAS and the performance remained consistent in natural and synthetic water. Ti3C2 MXenes also exhibited efficient regeneration (>90% recovery) with 0.4 M Na2SO3 solution, while the regeneration efficacy of other IX resins generally remained below 20%. Treatment with ∼180 J/cm2 UV dosage in the 0.4 M Na2SO3 regenerant brine solution yielded >99.9% reduction in the zwitterionic PFAS concentration indicating that UV-sulfite systems exhibit promising potential for the treatment of zwitterionic PFAS concentrates.

Gasification-based thermal treatment of Low and Intermediate Level Waste containing organic matter

VTT has developed a gasification-based technology for processing low- and intermediate-level waste (LILW) rich in organic matter. VTT’s process is based on well-controlled thermal fluidised-bed gasification followed by efficient gas cleaning, gas conditioning/oxidation, wet scrubbing of the oxidised gas (flue gas), and finally, filtering through a high efficiency particulate air (HEPA) filter, which acts as a backup cleaning system. In the case of an organic ion exchange resin (IXR) the primary product from thermal gasification is fine filter dust. In addition, the process produces some bottom ash, which consists mainly of the bed material. The wet scrubber liquid may also contain some activity. Demonstration trials were carried out using unspent organic IXR containing a small amount of added stable Cs in order to simulate Cs content in spent IXR. Gasification tests confirmed the capability of the process to remove organic matter from the IXR and clean the resulting off-gas as required. Simulated waste IXR was reduced to approximately 1 wt-% of its original mass before immobilisation. Filter dust and bottom ash have to be immobilised before final disposal. VTT has previously developed an advanced immobilisation technology based on geopolymerisation and this has been applied to samples from the THERAMIN test trials. VTT’s technology has been designed as a compact process, which can be operated at the nuclear power plant site. Until now, all development and verification test trials have used simulated waste materials. The next step is the demonstration of the process using real radioactive waste.

Interactions between Organic Model Compounds and Ion Exchange Resins.

Ion exchange (IEX) can successfully remove natural organic matter (NOM) from surface water. However, the removal mechanism is not well understood due to the complexity and variability of NOM in real source waters as well as the influence of multiple parameters on the removal behavior. For example, this includes the physicochemical properties of the NOM and IEX resin, and the presence of competing anions. Model compounds with a range of physical and chemical characteristics were therefore used to determine the mechanisms of NOM removal by IEX resins. Fifteen model compounds were selected to evaluate the influence of hydrophobicity, size, and charge of organic molecules on the removal by ion exchange, both individually and in mixtures. Three different resins, comprising polystyrene and polyacrylic resin of macroporous and gellular structure, showed that charge density (CD) was the most important characteristic that controlled the removal, with CD of >5 mequiv mgDOC-1 resulting in high removal (≥89%). Size exclusion of compounds with high MW (≥8 kDa) was evident. The hydrophobicity of the resin and model compound was particularly important for removal of neutral molecules such as resorcinol, which was best removed by the more hydrophobic polystyrene resin. Relationships were identified that provided explanations of the interactions observed between NOM and IEX resin in real waters.

Combined Plasma, Electromagnetic, and Laser Technologies for Creating Waste-Free Industries of a New Technological Structure

The paper considers directions for the development of waste-free, large-scale industrial technologies by setting up new technological routs, including wide use of electrical technologies of a new generation and excluding formation of any industrial waste as a matter of principle. The electrical technologies of a new generation are technologies based on the use of generators and flows of technological plasmas in chemical and metallurgical industries, electromagnetic fields of various frequency ranges for the synthesis and processing of metal and ceramic materials, and technological lasers for, for instance, separation of isotopes and for making micro articles for nanotechnology and micrometallurgy applications. All these technologies have become theoretically and technically feasible in combination with purification technologies for liquid and gaseous raw material preparation for the nuclear fuel cycle (NFC), specifically, ion-exchange sorption on synthetic organic ion-exchange resins, fluid extraction, rectification, or sorption on granular fluoride sorbents, which all provide a tool for attaining any level of purification of raw materials. In many processes discussed in the paper, extraction, sorption and rectification can be directly incorporated in electrical technologies, i.e. this means combined technologies for the synthesis, separation, and purification of the products, such as plasma rectification, plasma sorption, etc. The paper considers a series of such scientifically and technically advanced but still uncommercialized electrical technologies which should form the basis for new environmentally friendly, waste-free industries of a new technological structure. As examples, we focus on several plasma, electromagnetic, and laser technologies, operating on raw materials refined by the above-mentioned purification technologies, including the new technology for the purification of gaseous industrial emissions. These waste-free electrical technologies for the production and processing of inorganic materials were developed for the nuclear industry in the USSR. These are mostly physical technologies insensitive to the chemical formula of the produced or processed materials, and, therefore, they can be used without any problems in other branches of industry.

Development of Chemical and Biological Decontamination Technology for Radioactive Liquid Wastes and Feasibility Study for Application to Liquid Waste Management System in APR1400

A decontamination technology for radioactive liquid wastes was newly developed and hypothetically applied to the liquid waste management system (LWMS) of the nuclear power plant (NPP) to evaluate its decontamination efficacy for the purpose of the fundamental reduction of spent resins. The basic principle of the developed technology is to convert major radionuclide ions in the liquid wastes into inorganic crystal minerals via chemical or biological techniques. In a laboratory batch experiment, the biological method selectively removed more than 80% of cesium within 24 hours, and the chemical method removed more than 95% of cesium. Other major nuclides (Co, Ni, Fe, Cr, Mn, Eu), which are commonly present in nuclear radioactive liquid wastes, were effectively scavenged by more than 99%. We have designed a module including the new technology that could be hypothetically installed between the reverse osmosis (R/O) package and the organic ion-exchange resin in the LWMS of the APR1400 reactor. From a technical evaluation for the virtual installation, we found that more than 90% of major radionuclides in the radioactive liquid wastes were selectively removed, resulting in a large volume reduction of spent resins. This means that if the new technology is commercialized in the future, it could possibly provide drastic cost reduction and significant extension of the life of resins in the management of spent resins, consequently leading to delay the saturation time of the Wolsong repository.

Antifouling Ion-Exchange Resins.

Large quantities of organic ion-exchange resins are used worldwide for water decontamination and polishing. Fouling by microorganisms and decomposition products of natural organic matter severely limits the lifetime of these resins. Much research has thus been invested in polymer-based antifouling coatings. In the present study, poly(4-styrenesulfonate) (PSS) and a co-polymer of PSS and a zwitterionic group were used to spontaneously coat commercial Dowex 1X8 anion-exchange resin. UV-visible spectroscopy provided a precise measure of the kinetics and amount of PSS sorbed onto or into resin beads. When challenged with Chlamydomonas reinhardtii algae, uncoated resin was rapidly fouled by algae. Coating the resin with either the homopolymer of PSS or the co-polymer with zwitterion eliminated fouling. Using narrow- and wide-molecular-weight distribution PSS, a cutoff molecular weight of about 240 repeat units was found, above which PSS was unable to diffuse into the resin. Thus, only one monolayer of added PSS was sufficient to confer a highly desirable antifouling property on this resin while consuming less than 0.1% of the exchanger capacity. Radioactive sulfate ions were used to probe the kinetics of (self)exchange, which were virtually unaffected by the PSS coating. This resin treatment is a fast, ultra-low-cost step for potentially enhancing the lifetime of ion exchangers.

Smart release corrosion inhibitor pigments based on organic ion-exchange resins

Novel calcium(II) and zinc(II)-exchanged pigments based on cross-linked sulphonated polystyrene (CSP) are used in model polymer coatings to inhibit cathodic disbondment on galvanised steel surfaces. An in situ scanning Kelvin probe (SKP) technique is used to quantify coating delamination rates as a function of pigment volume concentration after applying aqueous sodium chloride to a penetrative coating defect. Both in-coating cation types significantly retard delamination rates compared with the un-pigmented case. The performance of CSP is compared with pigments prepared from inorganic cation exchangers and shown to be less effective when incorporating Zn(II) cations, but superior when Ca(II) is present.

Influence of antioxidant extraction on fermentability of olive biomass hydrolysates

Olive tree biomass has been proposed as raw material for ethanol production by means of a biochemical process. The pretreatment is one of the key steps which results in a celluloseenriched pretreated solid and a liquid fraction (hydrolysate) containing most of the hemicellulosic derived sugars, as well as degradation products from sugars and lignin and other minor components. It is of great interest the presence in these hydrolysates of compounds with antioxidant capacity, because their exploitation could affect positively the economy of the global process. This work deals with the fermentation of olive tree biomass hydrolysates by Pichia stipitis. Hydrolysates were prepared from biomass submitted to steam explosion and liquid hot water pretreatments, at different temperatures (170–240 ◦ C). Hydrolysates were further submitted to a process aimed at separating compounds with antioxidant capacity and improve fermentation results by eliminating yeast inhibitors. The fermentability of the hydrolysates before and after separation of these compounds is compared. Separation procedures include organic solvent extraction (e.g., ethyl acetate, which separates phenolic compounds) and ion exchange resins, which allow interesting compounds to be obtained, mainly hydroxytirosol. In the latter case, the process described in the patent procedure (US 2004/0102657A1) is followed, including the use of an anionic resin for retaining certain polyphenolic compounds, and then elution with water.

Treatment of detonation carbon in supercritical water

Experimental data on the treatment of detonation carbon in supercritical water are given. DOI: 10.1134/S1070427210070074 At present much attention is given to the study of carbon nanostructures. Among various synthesized carbon nanomaterials it is necessary to set aside so-called superdispersed nanodiamonds (UDD) obtained on the detonation of solid carbon-containing explosives with a negative oxygen balance [1–4]. Their applicability can be rather wide. Despite of high effi ciency of such procedure, the resulting product, detonation black or a diamond charge includes various structures and forms of carbon containing about 35–45 wt % of a diamond phase. Moreover, depending on the preparation technology, detonation carbon can contain sorbed admixtures in the form of metals, their oxides, and carbides. To isolate a diamond phase and remove water-insoluble admixtures, the initial charge, as a rule, is treated by liquid or gaseous oxidizing agents [3, 6, 7]. Mixtures of sulfuric and nitric acids, sulfurous and chromic anhydrides are used as liquid oxidizing agents. Oxygen or ozone is applied as a gaseous thermal oxidizer. In practice the method of charge treatment with concentrated nitric acid in thermobaric conditions, in a vulcanizer at enhanced pressure and temperature, has found the greatest application. Such method makes it possible to oxidize non-diamond carbon and to remove metals, their oxides, and some other admixtures. To remove surface functional groups (NH, C=O, C=N, NO3, and SO3H) or to change their composition, the initial charge is treated also by organic solvents, alcohols, or ion-exchange resins [3]. Thus purifi ed detonation carbon can contain up to 90–97% of various forms of nanodiamonds and 3–10% of non-diamond carbon and other admixtures. However chemical refi ning with the use of strong acids can lead, on the one hand, to the oxidation of the diamond phase itself and to the contamination of diamond surface by various functional groups, and on the other, to the evolution of abundant aggressive wastage. Therefore, despite of satisfactory quality of removing non-diamond phases and admixtures upon the application of the acid refi ning, it is necessary to study also other methods of the treatment of diamond-containing charge and of UDD isolation, which can result in the formation of new properties of superdispersed diamonds that can play the main role while creating new materials and controlled-quality compounds on their basis. New treatment methods can be used both independently and in combination with existing traditional methods, and(or) can supplement them. It is necessary to note that when creating new methods it is necessary to pay attention to possibilities of decreasing the amount of harmful and aggressive wastage. The authors of the present work studied the treatment of the detonation carbon charge obtained at “Altai” FSPC (Federal Scientifi c-Production Center, Biisk) both in pure supercritical water (SCW) and with hydrogen peroxide or acetic acid added to it. The variation of morphology and structure of carbon forms was studied, and the composition of a supercritical fl uid and also process conductions were selected. It is necessary to note that the work was not directly aimed at the determination of conditions and parameters providing the maximum effi ciency of UDD purifi cation and also on the detailed studying of properties of its surface, phase composition, and microstructure, as these problems receive much attention in the modern literature [3, 4, 8–11].

Sorption of Th, U, and Am on phosphorus-containing ion-exchange materials

Sorption of Th, uranyl, Am, Fe, and Al ions from nitric acid solutions on various phosphorus-containing ion-exchange materials (organic ion-exchange resins, SE-UPO solid extractant) was studied. The highest selectivity to quadruple-charged metal cations is exhibited by S-957 cation exchanger (Purolite) with phosphonic and sulfonic acid groups. The capacity of this resin for Th is essentially independent of the HNO3 concentration in the range 1–7 M and amounts to 80–95 mg ml−1. The uranyl, Am, Fe, and Al ions are sorbed on S-957 resin considerably worse than Th. The internal diffusion coefficient of Th4+ ions in S-957 resin from 3 M HNO3 was determined to be (5.3 ± 0.5) × 10−13 m2 s−1. The IR spectra of S-957 resin in the hydrogen and thorium forms were recorded. S-957 resin shows promise for selective recovery of tetravalent actinides from multicomponent nitric acid-salt solutions.

The effect of an organic ion-exchange resin on properties of heterogeneous ion-exchange membrane

This case study deals with relationships between characteristic properties of organic ionexchange resins and heterogeneous ion-exchange membranes. At first chemical and temperature stability, humidity and particle size distribution of different types of ion-exchange resins was analyzed. Subsequently, membranes were prepared by using different filler/polymer matrix ratio or by using milled resins with different particle size distribution. Finally, different ion-exchange resins were used for preparing of heterogeneous ion-exchange membranes at fixed filler/polymer matrix ratio. We analyzed many characteristic properties of raw materials, intermediate and final products and we paid attention to process parameters during preparing of membranes too. It was proved that there are important relationships between properties of a membrane and the type of resin used for its preparation and the process of membrane preparation. The results show that most of ion-exchange resins can be used for ion-exchange membranes preparation but with different impact on characteristic properties of membranes. We also proved that increasing of filler/polymer matrix ratio or using very fine particle size distribution of milled resin improve electrochemical properties of membranes at the expense of worst mechanical properties and more complicated membrane preparation. On the basis of these results we are able to modify composition of heterogeneous ion-exchange membranes to reach required properties.

Radiation-Induced Degradation in Ion Exchange Resins for a Water Detritiation System

The combined electrolysis and catalytic exchange process has been selected for the water detritiation system for the ITER. In the front-end process of tritiated water electrolyzer composed of a solid polymer electrode, ion exchange resin beds are installed for processing effluent ions in the enriched tritiated water from the catalytic exchange column to avoid the deterioration of the solid polymer electrode. The tritium concentration in the circulation resin bed is evaluated to reach 1.09x1015Bq/m3. It is thus important to note the radiation-induced degradation in ion exchange resins. We studied the degradation effects in Amberlite[registered] and Diaion[registered] organic ion exchange resins caused by the irradiation with electron beam up to the integrated dose of 1500kGy. The procedures D2187-94 of the American Society for Testing and Materials were adopted for the evaluation of the water retention capacity, the backwashed and settled density, the salt splitting capacity, and the total exchange capacity of particulate ion exchange resins. A 20% decrease of total exchange capacity of the cation exchange resin, when irradiated up to 1500 kGy at room temperature, has been observed.

Treatability of resin effluents by electrochemical oxidation using batch recirculation reactor

Electro oxidation processes are developed throughout the world for ambient temperature destruction of organic wastes. Several of these processes are based on mediated electrochemical oxidation. This article presents the experimental results of electro chemical study based on mediated electrochemical oxidation process conducted for synthetic organic ion exchange resin materials. Investigation was carried out using the traditional noble metal oxide coated anode, ruthenium oxide-titanium and the mediator used for the experiment was ferrous sulphate, with sodium chloride as supporting electrolyte. The concentration of sodium chloride was maintained at 5, 8, 12 gm/L. The experiment was carried out in batch recirculation reactor with varied current densities for various flow rates. The study highlighted that in batch reactor set up the best effect of total organic content reduction was found to occur at 3.75 A/dm 2 with flow rate of 20 L/h. The simulated studies were carried out for different volumes of effluent and current densities. A graphical analysis was made between the experimental and simulated values and it was found that both the values are very close.

Removal of Pertechnetate from Simulated Nuclear Waste Streams Using Supported Zerovalent Iron

The application of nanoparticles of predominantly zerovalent iron (nanoiron), either unsupported or supported, to the separation and reduction of pertechnetate anions (TcO4-) from complex waste mixtures was investigated as an alternative approach to current waste-processing schemes. Although applicable to pertechnetate-containing waste streams in general, the research discussed here was directed at two specific potential applications at the U.S. Department of Energy's Hanford Site: (1) the direct removal of pertechnetate from highly alkaline solutions, typical of those found in Hanford tank waste, and (2) the removal of dilute pertechnetate from near-neutral solutions, typical of the eluate streams from commercial organic ion-exchange resins that may be used to remediate Hanford tank wastes. It was envisioned that both applications would involve the subsequent encapsulation of the loaded sorbent material into a separate waste form. A high surface area (>200 m2/g) base-stable, nanocrystalline zirconia was used as a support for nanoiron for tests with highly alkaline solutions, while a silica gel support was used for tests with near-neutral solutions. It was shown that after 24 h of contact time, the high surface area zirconia supported nanoiron sorbent removed about 50% (Kd = 370 L/kg) of the pertechnetate from a pH 14 tank waste simulant containing 0.51 mM TcO4- and large concentrations of Na+, OH-, NO3-, and CO32- for a phase ratio of 360 L simulant per kg of sorbent. It was also shown that after 18 h of contact time, the silica-supported nanoiron removed >95% pertechnetate from a neutral pH eluate simulant containing 0.076 mM TcO4- for a phase ratio of 290 L/kg. It was determined that in all cases, nanoiron reduced the Tc(VII) to Tc(IV), or possibly to Tc(V), through a redox reaction. Finally, it was demonstrated that a mixture of 20 mass % of the solid reaction products obtained from contacting zirconia-supported nanoiron with an alkaline waste solution containing Re(VII), a surrogate for Tc(VII), with 80 mass % alkali borosilicate based frit heat-treated at 700 °C for 4 h sintered into an easily handled glass composite waste form.

Evaluation of Elution Parameters for Cesium Ion Exchange Resins

Cesium ion exchange is one of the planned processes for treating and disposing of waste at the U.S. Department of Energy Hanford Site. Radioactive supernatant liquids from the waste tanks will undergo ultrafiltration, followed by cesium ion exchange using a regenerable organic ion exchange resin. Two resins, SuperLig®644 and a resorcinol‐formaldehyde resin, are being evaluated for cesium removal and cesium elution characteristics. The main purpose of this study is to optimize the cesium elution to provide a resin that, after undergoing elution, would meet the U.S. Department of Energy/Office of River Protection Project‐Waste Treatment Plant processing and resin disposal criteria. Columns of each resin type were loaded to greater or equal to 90% breakthrough with a Hanford waste stimulant and eluted with nitric acid. The temperature, flow rate, and nitric acid concentration were varied to determine the optimal elution conditions. Temperature and eluant flow rate were the most important elution parameters. As would be predicted based upon kinetic consideration alone, decreasing the eluant flow rate and increasing the temperature provided the optimal elution conditions. Varying the nitric acid concentration did not have a significant effect on the elution completion; however, elutions performed using both high acid concentration (1 M) and elevated temperature (45°C) resulted in resin degradation, causing gas generation and resin bed disruption.

Improved separation methods for the recovery of 82Sr from irradiated targets

82Rb is a short-lived positron-emitting isotope ( T 1 / 2 = 7 5 s ) that is increasingly being used in PET to study blood flow through the heart and brain. This isotope is supplied to physicians in the form of a generator where the parent isotope, 82Sr, is immobilized onto an ion exchange column allowing the 82Rb to be eluted with isotonic saline as required. 82Sr is manufactured by the proton irradiation of molybdenum, rubidium chloride or rubidium metal targets followed by complex separations to recover the 82Sr. A number of inorganic ion exchange materials were evaluated for their ability to remove 82Sr from simulated target solutions and compared with currently used organic ion exchange resins. Sodium nonatitanate was identified as a replacement for current resins as a potential material that would simplify target processing and improve the yield of 82Sr from each target.

Molten Salt Oxidation of Ion-exchange Resins Doped with Toxic Metals and Radioactive Metal Surrogates

Ion-exchange resins doped with toxic metals and radioactive metal surrogates were test-burned in a bench-scale molten salt oxidation (MSO) reactor system. The purposes of this study are to confirm the destruction performance of the two-stage MSO reactor system for the organic ion-exchange resin and to obtain an understanding of the behavior of the fixed toxic metals and the sulfur in the cationic exchange resins. The destruction of the organics is very efficient in the primary reactor. The primarily destroyed products such as carbon monoxide are completely oxidized in the secondary MSO reactor. The overall collection of the sulfur and metals in the two-stage MSO reactor system appeared to be very efficient. Over 99.5% of all the fixed toxic metals (lead and cadmium) and radioactive metal surrogates (cesium, cobalt, strontium) remained in the MSO reactor bottom. Thermodynamic equilibrium calculations and the XRD patterns of the spent salt samples revealed that the collected metals existed in the form of each of their carbonates or oxides, which are non-volatile species at the MSO system operating conditions.

Chemical degradation of an ion exchange resin processing salt solutions

This paper describes the results from an investigation into the chemical degradation of an organic ion exchange resin, SuperLig ® 644, over 25 repeated cycles separating cesium from an alkaline solution of sodium salts with subsequent elution. Battelle Pacific Northwest Division (PNWD) tested the resin with a salt solution simulating the radioactive wastes currently stored at Hanford, Washington, USA generated from plutonium production activities. Battelle PNWD used a simulated waste consisting predominantly of nitrate, nitrite and hydroxide salts of sodium for a sodium concentration of ∼120 g/L. We tested the resin in a column with a bed volume of ∼10 mL. Battelle PNWD linked probes positioned on the column feed and effluent lines to a spectrometer that analyzed for dissolved oxygen. A cycle test commenced with converting the resin to the sodium form by pumping 0.25 M sodium hydroxide solution through the bed. Battelle PNWD then processed the simulated waste followed by column rinses with 0.1 M sodium hydroxide solution and de-ionized water. We then eluted the resin with 0.5 M nitric acid solution and the cycle finished with a de-ionized water rinse. The resin bed lost 34% of its mass over the 25 cycles of operation. Some resin appeared to dissolve in the 0.25 M sodium hydroxide regeneration solution since we observed the regeneration effluents of every cycle to be colored deep red-brown. Some regeneration effluents also contained resin fines that settled after ∼1 day. In addition, examination of the resin showed the used resin to have apparently higher porosity than the fresh material. The resin appeared to lose approximately 60% of its effective capacity for cesium over the course of the 25 cycles. However, ∼34% of the resin mass was also lost over this period. Battelle PNWD hypothesizes the difference of 26% to represent a loss in capacity and is presumably due to chemical alteration of the ion exchange sites. In addition, though the weight of resin decreased with each cycle, Battelle PNWD used the same volume of eluant to elute the resin in each cycle, indicating a reduction in elution efficiency. Battelle PNWD assumed resin oxidation to be the major degradation mechanism since oxygen dissolved in the feedstock was consumed upon processing.

Oxidative pyrolysis of organic ion exchange resins in the presence of metal oxide catalysts

Pretreatment of the organic ion exchange resins by oxidative pyrolysis is effective for volume reduction before vitrification. In this work, pyrolysis of two nuclear-grade resins, Purolite NRW100 (cationic) and NRW400 (anionic), was examined using a laboratory-scale theromgravimetric analyzer (TGA) in air. It was shown that the cationic resin was harder to degrade and was less volatile compared to anionic resin. Off-gas data revealed the presence of SO 2, CO 2, CO, and H 2O during oxidative pyrolysis of cationic resin from 30 to 800 °C. Trimethylamine, CO 2, CO, and ethyl formate were found in the case of anionic resin. In addition, oxidative pyrolysis of the mixed resins (50/50 wt.%) showed the existence of the gases nearly at the temperatures where the gases would evolve if the results of two different resins were superimposed. Several metal salts including CuSO 4·5H 2O, CuO, and FeSO 4·7H 2O, as well as the ions Cu 2+ pre-loaded on the resins had a catalytic effect on the oxidative pyrolysis of cationic resins, in which the decomposition of functional groups and polymer matrices was enhanced. Such catalytic effect was highlighted by a large decrease in activation energy calculated according to a degradation mechanism involving four consecutive reactions.

Alkene epoxidation with iodosylbenzene catalysed by polyionic manganese porphyrins electrostatically bound to counter-charged supports

Manganese(III) complexes of tetra-anionic and tetra-cationic porphyrins have been immobilised on counter-charged, surface-modified silica supports and on organic ion-exchange resins. The reactions of these supported manganese(III) porphyrin systems and analogous uncharged homogeneous systems have been examined using cyclooctene and (E)- and (Z)-4-methylpent-2-ene epoxidations, with iodosylbenzene (PhIO) as the oxygen donor. Comparisons using the manganese porphyrin systems as catalysts for the epoxidation of cyclooctene in acetonitrile reveal that, in low turnover reactions (maximum 136 turnovers), they all give an essentially quantitative yield of epoxide although the heterogeneous reactions are significantly slower than the homogeneous analogues. In large scale repeat-use experiments, however, the supported catalysts are clearly superior, giving markedly better yields. The epoxidations of (E)- and (Z)-4-methylpent-2-ene with all the catalysts show a very high stereoretention, with the (Z)-alkene reacting faster than the (E)-isomer. The sterically hindered manganese(III) 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrin (MnTDCSPP) shows the highest selectivity for the (Z)-isomer; by contrast the supported manganese(III) 5,10,15,20-tetrakis[2,3,5,6-tetrafluoro-4-(trimethylammonio)phenyl]porphyrin on Dowex (MnTF4TMAPP–Dowex) reacts with the two alkenes at effectively the same rate. The mechanism of the epoxidations and the influence of the porphyrin ligand and support on the substrate selectivity are discussed.