stevia sutanto | University of Twente (original) (raw)

Papers by stevia sutanto

Journal of Membrane Science, 2009

Two multi-channel defect-free high-silica MFI membranes have been tested for the removal of ethan... more Two multi-channel defect-free high-silica MFI membranes have been tested for the removal of ethanol from a 7 mol% and 3 mol% aqueous solution under pervaporation conditions. One membrane is detemplated by calcination at 773 K, and one is ozonicated at 473 K. The flux and ethanol separation factor were determined at 348 K, 360 K, and 373 K. The ethanol separation factors of both membranes were similar and ranged from ∼20 at 373 K to ∼40 at 348 K. The ethanol and water fluxes through both membranes in this temperature range are proportional to the component fugacity difference over the membranes. The calcined membrane showed an 80% higher flux than the ozonicated membrane, showing the ozonication could not completely remove the template. After the ozonicated membrane was calcined at 723 K, the flux increased to a similar value as the initially calcined membrane, while the separation factor did not change. Both membranes showed an increase in flux by a factor of two after a subsequent calcination at 823 K, also without affecting the separation factor. The high calcination temperature required for complete detemplation indicates the presence of aluminum in the zeolite framework of the membrane. The membrane stability was monitored for 40 h and 177 h of operation for the initially calcined and ozonicated membrane, respectively. At 348 K the membranes showed stable performance, but the stability of the membranes at elevated temperatures is limited, showing a decrease in both flux and selectivity during operation at 373 K. The effect of the exposure to a water/ethanol mixture on the zeolite membrane is investigated by permporometry measurements of the membranes and by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, magic angle spinning nuclear magnetic resonance (MAS NMR), thermogravimetric analysis (TGA), and nitrogen adsorption experiments using several MFI-type zeolite powders. The most plausible mechanism causing the instability of the membrane is ethoxy formation of the ethanol with the silanol groups and Brønsted acid sites in the zeolite framework combined with the formation of hydrophilic extra-framework pathways by hydrolysis.

Proceedings of the 8th International Symposium on Cavitation, 2012

Tenside Surfactants Detergents, 2013

Cleanability of well-characterised textile materials of different types -cotton, polyester and wo... more Cleanability of well-characterised textile materials of different types -cotton, polyester and wool -in liquid carbon dioxide (CO 2 ) have been systematically investigated under different process conditions. It was found that the soil removal, which is represented with the soiling additional density (SAD), strongly depends on the kind of investigated textile materials. The use of a commercial detergent ClipCOO significantly improved the cleanability of all textile materials under study and slightly reduced the re-deposition of soil in the case of wool fabric. In addition, by using optical roughness analysis, some topographical changes in the fabric structure after cleaning were studied.

The Journal of Supercritical Fluids, 2014

ABSTRACT High pressure carbon dioxide (CO2) is a potential solvent for textile dry cleaning. Howe... more ABSTRACT High pressure carbon dioxide (CO2) is a potential solvent for textile dry cleaning. However, the particulate soil (e.g. clay, sand) removal in CO2 is generally insufficient. Since cavitation has been proven to be beneficial in other CO2 cleaning applications, this study aims to investigate the possibility of improving the performance of CO2 textile dry cleaning by using ultrasound or other mechanisms to induce the mechanical action such as bubble spray and jet spray. In the experiments, several types of textiles soiled with a mixture of motor oil and soot were cleaned using 1 Land 90 L CO2 dry cleaning set-ups. Using either ultrasound, stirring, liquid spray or bubble spray does not give a significant improvement on particulate soil removal from textile. It was also found that the additional use of ClipCOO detergent does not give a significant improvement on particulate soil removal either. The cleaning performance of CO2 is 50% lower than that of PER and thus another method to increase the particulate soil removal in CO2 textile dry cleaning still needs to be developed.

The Journal of Supercritical Fluids, 2013

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Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2012

ABSTRACT In this paper we propose, characterize and test a surfactant formulation, consisting of ... more ABSTRACT In this paper we propose, characterize and test a surfactant formulation, consisting of a branched polyoxyethylene type commercial non-ionic surfactant (Igepal CA520), n-hexane and water, for use in CO2 dry-cleaning to enhance the removal of particulate soil. In the formulation lamellar mesophases Lα coexist in an L2 microemulsion (reverse micellar) phase. We hypothesize that enhanced soil removal would be possible due to the adsorption of lamellar liquid crystalline phases at the fabric–soil interface, the presence of water pools, the improvement of the solvent quality of liquid CO2 by the presence of n-hexane, and the enhanced viscosity due to the presence of the lamellar mesophases. We have characterized the formulation by optical microscopy with crossed polarizers, confocal microscopy, dynamic light scattering and shear viscometry to determine the phase behaviour, the size of the reverse micelles and the flow behaviour. AFM force measurements in n-hexane show that large adhesion forces between a model soil particle (silica) and fabric surface (cellulose) in water-saturated hexane can be reduced by the action of the surfactant mesophases. In the presence of the surfactant formulation the interaction forces were found to be decreased from ∼15 nN to 0.5 nN. The formulation, applied as a pre-treatment on standard soil test monitors and followed by washing in liquid CO2, showed a five times better soil removal ability than the control.

Advances in Colloid and Interface Science, 2012

Liquid CO 2 is a viable alternative for the toxic and environmentally harmful solvents traditiona... more Liquid CO 2 is a viable alternative for the toxic and environmentally harmful solvents traditionally used in drycleaning industry. Although liquid CO 2 dry-cleaning is being applied already at a commercial scale, it is still a relatively young technique which poses many challenges. The focus of this review is on the causes of the existing problems and directions to solve them. After presenting an overview of the state-of-the-art, we analyze the detergency challenges from the fundamentals of colloid and interface science. The properties of liquid CO 2 such as dielectric constant, density, Hamaker constant, refractive index, viscosity and surface tension are presented and in the subsequent chapters their effects on CO 2 dry-cleaning operation are delineated. We show, based on theory, that the van der Waals forces between a model soil (silica) and model fabric (cellulose) through liquid CO 2 are much stronger compared to those across water or the traditional dry-cleaning solvent PERC (perchloroethylene). Prevention of soil particle redeposition in liquid CO 2 by electrostatic stabilization is challenging and the possibility of using electrolytes having large anionic parts is discussed. Furthermore, the role of different additives used in dry-cleaning, such as water, alcohol and surfactants, is reviewed. Water is not only used as an aid to remove polar soils, but also enhances adhesion between fabric and soil by forming capillary bridges. Its role as a minor component in liquid CO 2 is complex as it depends on many factors, such as the chemical nature of fabrics and soil, and also on the state of water itself, whether present as molecular solution in liquid CO 2 or phase separated droplets. The phenomena of wicking and wetting in liquid CO 2 systems are predicted from the Washburn-Lucas equation for fabrics of various surface energies and pore sizes. It is shown that nearly complete wetting is desirable for good detergency. The effect of mechanical action and fluid dynamic conditions on dry-cleaning is analyzed theoretically. From this it follows that in liquid CO 2 an order of magnitude higher Reynold's number is required to exceed the binding forces between fabric and soil as opposed to PERC or water, mainly due to the strong van der Waals forces and the low viscosity of CO 2 at dry-cleaning operational conditions.