1. Thermal study of APTES-functionalized magnetite nanoparticles with citric acid and polyacrylic acid for advanced forward osmosis systemsMatjaž Kristl, Urška Ostroško, Irena Ban, Irena Petrinić, Janja Stergar, 2024, original scientific article Abstract: Iron-based magnetic nanoparticles (MNPs) have attracted considerable attention as promising draw solutes in forward osmosis processes due to various advantages. In the present study, magnetite (Fe3O4) nanoparticles (MNPs) with diameters in the range of 12±2 nm were synthesized by applying the coprecipitation method and stabilized using (3-aminopropyl) triethoxysilane (APTES). The amino groups of APTES were further functionalized with various amounts of citric acid (CA) and poly(acrylic acid) (PAA) to achieve higher osmotic pressure. The as-prepared and functionalized nanoparticles were characterized using diferent methods: Fourier-transform infrared spectroscopy (FTIR) confrmed the binding of APTES and CA/PAA on the surface of the MNPs, while the size of the particles was determined by transmission electron microscopy (TEM) and X-ray powder difraction. The isoelectric point, zeta potential, and the particle size in suspension were determined by dynamic light scattering (DLS)/zeta potential measuring system. The amount of free –COOH groups was determined by conductometric titrations. The amount of organic matter (APTES, CA, and PAA) bound on the surface was determined by thermogravimetric analysis (TG), giving results between 7.6% for samples stabilized with APTES only and 17.5% for samples functionalized with APTES+PAA. TG provides a simple and efcient method for determining the amount of organic compounds bound to the surface of MNPs. The osmotic pressure measurements of double-layer coated MNPs provided encouraging results of up to 28 bar, enabling using the samples as draw solutions in an experimental forward osmosis system.
Keywords: magnetic nanoparticles, magnetite, citrit acid, poly(acrylic acid), forward osmosis
Published in DKUM: 14.08.2024; Views: 105; Downloads: 5
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2. Process integration of a steam turbineAndreja Goršek, Peter Glavič, 2003, original scientific article Abstract: Cogeneration consists of combined production of electricity and heat using only one fuel which allows remarkable energy savings in comparison with a system producing electricity and heat separately. The possibilities for integrating a cogeneration system with chemical processes has been studied in this paper. Improvement in the systems where high temperature streams exist can be achieved by direct integration of steam turbine with them. Hot reactor utility was used instead of fuel to produce electricity and steam for further process heat requirements. A thermodinamics oriented approach to identify and preliminary design a cogeneration plant that completely satisfies process heat and power demand is highlighted. Pinch analysis with extended grand composite curve enables rational choice of utilities. The acrylic acid process was used to illustrate the procedure proposed. Economic attractiveness based on payback time and net present worth indicated that the steam turbine based cogeneration system would yield return period of less than 3 months, showing that the investment in cogeneration could be of interest for this plant.
Keywords: process energetics, efficient energy use, process industry, cogeneration systems, acrylic acid, technological processes
Published in DKUM: 01.06.2012; Views: 2071; Downloads: 104
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3. Acrylic acid "reversed" polyHIPEsPeter Krajnc, Dejan Štefanec, Irena Pulko, 2005, original scientific article Abstract: An oil-in-water high internal phase emulsion consisting of acrylic acid, water, and a crosslinker (N,N-methylene bisacrylamide) as the water phase, and toluene as the oil phase was successfully stabilised to sustain thermal initiation of radical polymerisation resulting in porous open-cellular monolithic material. The type of initiator used influenced the average pore size ranging from approx. 708 nm to approx. 1 087 nm, as determined by mercury porosimetry.
Keywords: hydrophilic polymers, macroporous polymers, poly (acrylic acid), polyHIPE, supports
Published in DKUM: 01.06.2012; Views: 2588; Downloads: 102
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4. HYBRID PolyHIPE MATERIALSSebastijan Kovačič, 2011, dissertation Abstract: A new class of polyHIPE materials has been prepared using high internal phase emulsions (HIPEs) with monomers in both phases. Resulting materials, namely hybrid polyHIPE materials, are obtained consisting of hydrophobic matrix (consisted of styrene cross-linked with DVB or dicyclopentadiene) filled with hydrophilic polymer gel (polyacrylic acid or polyNIPAM) and exhibit morphology changes according to pH and temperature of the surrounding medium. Our focus with regards to the production of hybrid polyHIPE materials was the responsiveness of such materials used for flow control. This property is beneficial for controlling the flow of the solution through the monolithic polymers. Furthermore, polyHIPE materials have also been prepared by using ring opening metathesis polymerisation of monomers, such as dicyclopentadiene and norbornene. Obtained materials have Young’s moduli in the range of hundred times higher than standard polyHIPE materials with the same level of porosity which represents a very important improvement in the development of highly porous cellular polymeric materials.
Keywords: emulsions, high internal phase emulsions, polymers, polyHIPEs, hybrid, hybrid polyHIPE materials, ROMP, flow-through, styrene, DVB, acrylic acid, NIPAM
Published in DKUM: 04.05.2011; Views: 3490; Downloads: 328
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