Water and Carbon Dioxide: A Unique Solvent for the Catalytic Polymerization of Ethylene in Miniemulsion

The catalytic polymerization of ethylene is performed in water pressurized with CO₂ . The size of the initial monomer droplets and of the resulting polymer particles can be varied by simply changing the CO₂ pressure. Furthermore, at identical ethylene partial pressure, the polymerizations performed in the presence of CO₂ are significantly faster than in its absence. Thus, the combination of CO₂ and water is a promising green solvent for catalytic emulsion polymerizations.

Radical polymerization of miniemulsions induced by compressed gases

Pressurization of a macroemulsion comprising a vinyl monomer/water/surfactant can result in formation of a transparent miniemulsion without use of high energy mixing, suitable for synthesis of polymeric nanoparticlesviaminiemulsion polymerization.

Synthesis of crosslinked polymeric nanocapsules using catanionic vesicle templates stabilized by compressed CO2

The synthesis of polymeric nanocapsules in the approximate diameter range 40-100 nm (TEM/SEM) using catanionic surfactant vesicle templates stabilized by subcritical CO2 is demonstrated. Near equimolar aqueous solutions of the surfactants sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) experienced immediate vesicle destabilization and precipitation in the absence of CO2. However, pressurization with CO2 (5 MPa) dramatically enhanced the stability of the initial vesicles, and enabled swelling of the bilayers with hydrophobic monomers via diffusion loading (loading of monomers into preformed bilayers). Subsequent radical crosslinking polymerization of the monomers n-butyl methacrylate/tert-butyl methacrylate/ethylene glycol dimethacrylate contained within the bilayers was conducted at room temperature using UV-initiation under CO2 pressure. The hollow structure of the resultant nano-objects was confirmed by successful encapsulation and retention of the dye Nile Blue. It is demonstrated that using this method, polymeric nanocapsules can be successfully prepared using diffusion loading of up to 94 wt% monomer (rel. to surfactant) stabilized by CO2.

Polymerization induced self-assembly: tuning of nano-object morphology by use of CO2

A novel method for synthesis of polymeric nano-objects via polymerization-induced self-assembly in a CO₂-expanded medium has been developed.

Evaluating the impact of recycled fiber content on effluent recycling in newsprint manufacture

This paper investigates the effect of using recycled fiber (RCF) in newsprint production on the effluent quality and its treatability using membrane operations for internal and external recycling and reuse. Increased chemical usage in RCF for deinking had significant impact on the silica and sodium content of the effluent which in turn limits the membrane's operation. Increasing the RCF content from 0% to 50% is estimated to increase the silica content from 4 to 119mgL(-1) and sodium content from 135 to 500mgL(-1). A process model was developed to calculate the impact of these excess chemicals on the greenhouse gas (GHG) emission and brine disposal for an integrated membrane plant design producing 4MLday(-1) of recycled water. As the ratio of RCF increased from 0% to 50% in the mill process, the operating pressure increased for nanofiltration (NF) and reverse osmosis (RO). Additionally, organics presence in the feed increased the NF operating pressure above the simulated value and reduced the silica removal efficiency by 15%. Incorporation of lime coagulation pretreatment was found to be essential to operate RO at high recoveries with relatively GHG emissions. Without pretreatment, as RCF content increased from 0% to 50%, RO recovery decreased from 80% to 22% and the expended GHG increased from 0.9 to 3.5kgCO2m(-3). Although the excess sodium concentration limits the brine disposal for irrigation purposes, a partial blending of the treated wastewater with other process streams resulted in the reduction of sodium absorption ratio by 20%.

Separation of biomolecules using supercritical fluid extraction

Supercritical fluids are increasingly being used as a replacement for more conventional organic solvents in the extraction of biomolecules from a range of matrices. Supercritical fluid extraction of essential fatty acids from fish oils is discussed. Supercritical CO2 was used to fractionate two fatty acids, EPA and DHA from fish oil ethyl esters. EPA and DHA were obtained with a purity of 58% and 67% respectively from Sardine oil with an original composition of 17% and 12%.