Biosorption of uranyl ions from aqueous solutions by soluble renewable polysaccharides.

Polysaccharides derived from natural sources have been offered as environment friendly sorbents for the adsorption of heavy metals. We present a simple technique to remove uranyl ions from aqueous solutions by using representative polysaccharides. The adsorption efficiency of UO22+ decreased in the following order: xanthan gum > kappa > iota/guar gum, for instance, the efficiencies after sorption of 30 min with 500 mg per L uranyl acetate and 0.03 g of the corresponding polysaccharide were: 89.7%, 85.2%, 79.1% and 77.1%. Lowering the acidity in the system decreased the sorption efficiency with all the polysaccharides, and reducing the ratio between the amount of uranyl ions and the amount of polysaccharide increased the sorption efficiencies, e.g., using 500 mg per L uranyl acetate and 0.05 g of the corresponding polysaccharide (xanthan gum, kappa, iota, guar gum) yielded after 30 min sorption efficiencies of 94.3%, 91.5%, 89.0% and 87.7%, respectively. FTIR, SEM-EDS and TGA analyses verified the presence of uranium in the polysaccharides and showed that the uranyl ions were interacting with the different functional groups. Moreover, the addition of uranyl ions to the polysaccharides caused a sharp decrease in viscometry measurements. In addition, the measurements showed that the addition of uranyl lowered both modules, G' and G'', and made the solution more liquid.

Selective Sorption of Heavy Metals by Renewable Polysaccharides.

Renewable and biodegradable polysaccharides have attracted interest for their wide applicability, among them their use as sorbents for heavy metal ions. Their high sorption capacity is due mainly to the acidic groups that populate the polysaccharide backbone, for example, carboxylic groups in alginate and sulfate ester groups in the iota and lambda carrageenans. In this study, these three polysaccharides were employed, alone or in different mixtures, to recover different heavy metal ions from aqueous solutions. All three polysaccharides were capable of adsorbing Eu3+, Sm3+, Er3+, or UO22+ and their mixtures, findings that were also confirmed using XPS, TGA, and FTIR analyses. In addition, the highest sorption yields of all the metal ions were obtained using alginate, alone or in mixtures. While the alginate with carboxylic and hydroxyl groups adsorbed different ions with the same selectivity, carrageenans with sulfate ester and hydroxyl groups exhibited higher adsorption selectivity for lanthanides than for uranyl, indicating that the activity of the sulfate ester groups toward trivalent and smaller ions was higher.

Green Procedure for Aerobic Oxidation of Benzylic Alcohols with Palladium Supported on Iota-Carrageenan in Ethanol.

The search for selective heterogeneous catalysts for the aerobic oxidation of alcohols to ketones and aldehydes has drawn much attention in the last decade. To that end, different palladium-based catalysts have been proposed that use various organic and inorganic supports. In addition, supports that originate from a biological and renewable source that is also nontoxic and biodegradable were found to be superior. We heterogenized palladium chloride or acetate complexes with triphenylphosphine trisulfonate on iota-carrageenan xerogel by simple mixing of the complex and the polysaccharide in water. The resulting polysaccharide-catalyst mixture then underwent deep freeze and lyophilization, after which the catalyst was characterized by TEM, XPS and SEM-EDS and tested in aerobic oxidation. The new heterogeneous catalysts were successfully used for the first time in the aerobic oxidation of benzylic alcohols. Moreover, they were easily removed from the reaction mixture and recycled, yielding an increase in activity with each subsequent reuse. As determined by TEM and XPS, the reduction in palladium and the formation of nanoparticles during the reaction in ethanol yielded more active species and, therefore, higher conversion rates. A SEM-EDS analysis indicated that the palladium was thoroughly dispersed in the xerogel catalysts. Moreover, the xerogel catalyst was observed to undergo a structural change during the reaction. To conclude, the new heterogeneous catalyst was prepared by a simple and straightforward method that used a non-toxic, renewable and biodegradable support to yield an active, selective and recyclable heterogeneous system.

Environmental sustainability assessment of seawater reverse osmosis brine valorization by means of electrodialysis with bipolar membranes.

The integration of electrodialysis with bipolar membranes (EDBM) with seawater reverse osmosis (SWRO) process influences the two main environmental burdens of SWRO desalination process: climate change, accounted here as carbon footprint (CF) and associated to the high-energy consumption, and the environmental alteration of the vicinities of the facility, due to brine disposal. EDBM powered by photovoltaic (PV) solar energy is able to meet the above-mentioned challenges that arise in SWRO desalination. In addition, HCl and NaOH, both employed in the desalination industry, can be produced from the brines. Hence, environmental benefits regarding the potential self-supply can be achieved. The environmental sustainability assessment by means of life cycle assessment (LCA) of a SWRO and EDBM has been carried out considering four different scenarios. The percentage of treated brines and the influence of the grid mix used for electric power supply has been taken into account. The three different electric power supplies were 100.0% renewable energy (PV solar energy), 36.0% renewable energy (average Spanish grid mix), and 1.9% (average Israeli grid mix). The results showed that the CF per unit of volume produced freshwater for SWRO and the self-supply reagent production scenario for the three Spanish grid mix, the Israeli grid mix, and the PV solar energy were 6.96 kg CO2-eq·m-3, 12.57 kg CO2-eq·m-3, and 2.17 kg CO2-eq·m-3, respectively.

Renewable Polysaccharides as Supports for Palladium Phosphine Catalysts.

The investigation of the use of polysaccharides derived from natural sources to support metal catalysis has been the focus of several studies. Even though these molecules seem to be attractive materials, their full potential for use in support of heterogeneous catalysis still needs to be revealed. To that end, we developed a new preparation technique for polysaccharide-based palladium catalysts by immobilizing the palladium phosphine complexes on various renewable polysaccharides. The Suzuki cross-coupling in ethanol, using PdCl2(TPPTS)2 supported by various polysaccharides, was determined by gas chromatography and compared to homogeneous free-catalyst support. The PdCl2(TPPTS)2, that was immobilized on red algae supports, was successfully used as a heterogeneous catalyst in the Suzuki cross-coupling reaction, yielding high activity, higher than that of the homogeneous complex, without leaching. The FTIR spectrometry of representative heterogeneous polysaccharide-based TPPTS⁻PdCl2 catalysts was compared to that of native polysaccharide and polysaccharide-based TPP⁻PdCl2 catalysts, indicated on new bands, suggesting that the heterogenization occurs via interactions between the sulfonate group on the TPPTS and the hydroxyl groups on the polysaccharides. EDS and XPS analysis were also performed, confirming that the Pd complex was embedded within the i-carrageenan. A comparison of SEM images of i-carrageenan preparations also shed light on the interaction occurring between the polysaccharides and the TPPTS.

Study of Pd-based catalysts within red algae-derived polysaccharide supports in a Suzuki cross-coupling reaction.

Simple palladium complexes were heterogenized into red algae derived polysaccharide supports, and the effects of polysaccharide, catalyst and solvent types on the performances in a Suzuki cross-coupling reaction were tested. It was found that using palladium salts with sodium triphenylphosphine trisulfonate (TPPTS) as a ligand supported on ι-carrageenans and ethanol as the solvent yielded the best systems. Moreover, the conversion rates of these heterogeneous systems were higher than their homogeneous analogues, and they were easily recycled five times. SEM-EDS analysis of Pd(OAc)2(TPPTS)2 that was immobilized on ι-carrageenan support was also performed, demonstrating that the system has a porous structure composed of Pd complex that was embedded within the ι-carrageenan. In addition, both ι-Pd(OAc)2(TPPTS)2 and ι-Pd(OAc)2 systems, were composed of nanoparticles, as proven by TEM analysis.

Efficient synthetic protocols in glycerol under heterogeneous catalysis.

The massive increase in glycerol production from the transesterification of vegetable oils has stimulated a large effort to find novel uses for this compound. Hence, the use of glycerol as a solvent for organic synthesis has drawn particular interest. Drawbacks of this green and renewable solvent are a low solubility of highly hydrophobic molecules and a high viscosity, which often requires the use of a fluidifying co-solvent. These limitations can be easily overcome by performing reactions under high-intensity ultrasound and microwaves in a stand-alone or combined manner. These non-conventional techniques facilitate and widen the use of glycerol as a solvent in organic synthesis. Glycerol allows excellent acoustic cavitation even at high temperatures (70-100 °C), which is otherwise negligible in water. Herein, we describe three different types of applications: 1) the catalytic transfer hydrogenation of benzaldehyde to benzyl alcohol in which glycerol plays the dual role of the solvent and hydrogen donor; 2) the palladium-catalyzed Suzuki cross-coupling; and (3) the Barbier reaction. In all cases glycerol proved to be a greener, less expensive, and safer alternative to the classic volatile organic solvents.

Glycerol triacetate as solvent and acyl donor in the production of isoamyl acetate with Candida antarctica lipase B.

Glycerol triacetate was successfully used as a green solvent and as the acyl donor in the transesterification of isoamyl alcohol to produce isoamyl acetate using free and immobilized Candida antarctica lipase B. Immobilized lipase was more catalytically active than free lipase and could be easily separated from the reaction mixture by filtration. In addition, it was found that increasing either the reaction temperature or the enzyme to substrate ratio increased the conversion of isoamyl alcohol. Using triacetin as the solvent also enabled the separation of product by simple extraction with petroleum ether and catalyst recycling.

A first-order simulator to control dioxin emissions: NMCRC-ATMOS.

Dioxins are highly toxic halogenated organic compounds formed as an unintentional by-product of many industrial processes involving chlorine and combustion. At the Negev Monte Carlo Research Center (NMCRC) and the Green Processes Center at the Shamoon College of Engineering (SCE), Israel, we have developed a code for the first-order estimation of dioxin emissions from waste incinerators and the subsequent atmospheric dispersion. The NMCRC-ATMOS (Atmospheric Evaluator) program will allow public planners and facility operators to estimate and predict the effect of current and potential waste incineration facilities on nearby population centres. This information can also be used by plant operators to decide whether to run the facilities at maximum capacity based on weather conditions. With the NMCRC-ATMOS tool, the user has the ability to easily establish location-based fallout from the average conditions (both facility and atmospheric) surrounding the waste incineration plant. This program currently focuses on dioxin emissions from waste incinerators, but can eventually be expanded to include other emission sources and atmospheric effects, as well as internet connectivity for real-time data acquisition. NMCRC-ATMOS is a Windows program that has been tested on Windows XP Service Pack 2 with the .NET Framework 2.0 installed.

Aqueous enantioselective hydrogenation of methyl 2-acetamidoacrylate with Rh-MeDuPHOS occluded in PDMS.

A new chiral heterogeneous catalytic system obtained by occlusion of the Rh-MeDuPHOS complex in a polydimethylsiloxane film was tested in the asymmetric hydrogenation of methyl 2-acetamidoacrylate in aqueous medium.