
Titus SobischIndependent Researcher
Titus Sobisch
Dr.
retired since 2021 10 21, but still interested in field of colloid and interface science
About
82
Publications
375,965
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1,194
Citations
Introduction
Studies in chemical engineering at the Technical University Budapest 1975 –1980
Research scientist at the Academy of sciences in Berlin 1980 – 1991 with research on surfactant adsorption, solubilization and micellization.
PhD in 1989, Adsorption of surfactants on polar solid surfaces
Current position – Senior Application Specialist at L.U.M. GmbH
Professional Background
1980 – 1992 physico-chemical characterization of surfactants, their adsorption, micellization and solubilization behaviour
1992 – 1997 R&D with focus on surfactant applications, especially for soil remediation purposes.
Since 1998 senior application specialist at L.U.M. GmbH, applied research related to stability of colloidal dispersions.
Cooperation in R&D with several industrial partners
active at the Help Forum at http://www.waterandwastewater.com
Additional affiliations
March 1998 - present
LUM GmbH
Position
- senior application specialist
Description
- Characterization of dispersion properties and dispersion stability
September 1980 - February 1992
Academy of Sciences Berlin
Position
- scientific coworker
Description
- adsorption of surfactants on polar surfaces, characterization of micellization and solubilization
January 1992 - present
AUF mbH, AERES GmbH
Position
- surfactant formulations for enhanced soil remediation
Description
- surfactant formulations for physico-chemical ex- and in-situ treatment surfactants for enhancement of biodegradation
Education
September 1975 - June 1980
Technical University Budapest
Field of study
- Chemical engineering
Publications
Publications (82)
Basically, separation processes can be described by extended Stokes law taking into account volume concentration of disperse phase (hindrance) and rheological behaviour of continuous phase. To deduce separation behaviour under high gravity in centrifuges one can assume that separation velocity scales linearly with acceleration in Newtonian liquids....
In first approximation, settling may be easily described by Stokes law taking into account dynamic viscosity η and in case of high solids concentration a suitable hindrance function. In centrifugal field centrifugal acceleration has to be used instead of gravitational acceleration. Settling studies based solely on visual inspection have been increa...
Dispersibility of agglomerated/aggregated particles, i.e. complex solids is of key interest for application in various suspension based formulations. Dispersibility in a given matrix obviously depends on chemical nature of the primary nanoparticles. Surface modification allows to tune dispersibility characteristics specifically. It was presumed tha...
Delayed sedimentation, e.g. collapse of transient gels [1] is an interesting phenomenon. Despite its relevance for storage of complex formulations this topic is only sparsely researched. "In a transient gel the particles aggregate, by the depletion interaction, to form a space-spanning network which maintains its structural integrity for a finite p...
Dispersing particulate matter into a liquid continuous phase is common to produce suspension-based products in many industrial fields.
Hansen Solubility Parameters (HSP) have gained growing interest for selection, optimization and prediction of suitable continuous phase. Hansen parameters are widely used to predict good liquids (continuous phases)...
Use of instrumental methods for analysis of sedimentation kinetics of dispersions (LUMiSizer/LUMiReader) in connection with the newly defined standardized RST is a versatile approach to determine optimum solvents and HDP of solids as exemplified for complex agglomerated/aggregated carbon black.
In case of complex agglomerated/aggregated solids, e....
Most finished products have coated surfaces for various reasons. Building constructions have to withstand manifold external influencés, eg temperature and humidity, UV radiation or erosion caused by rain. Cutting tools like drills are exposed to high mechanical stress. To extend the work life, their surfaces are often modified with protective coati...
For most particle-based applications, formulation in the liquid phase is a decisive step, and thus, particle interactions and stability in liquid media are of major importance. The concept of Hansen solubility parameters (HSP) was initially invented to describe the interactions of (polymer) molecules and their solubility in different liquids and is...
The Hansen Solubility Parameters (HSP) are powerful descriptors to evaluate interactions of (polymer) molecules and their solubility in different liquids. Although approaches do exist to transfer the HSP-concept to the question of dispersibility of particles, HSP determination of slowly sedimenting (nano)particles (NPs) is time consuming and depend...
The article introduces a novel method for accelerated analysis of membrane fouling during ultrafiltration of colloids: centrifugal ultrafiltration with a stepwise change of centrifugal rotation speed. The method allows simultaneous analysis of membrane fouling for different colloidal samples in a single analytical centrifugation experiment. The ana...
Dispersibility of agglomerated/aggregated, i.e. complex solids is of key interest for application in various dispersion based formulations. Hansen Solubility Parameters (HSP) have gained growing interest for selection, optimization and prediction of suitable dispersion media. Applying the HSP concept to dispersions and for characterization of surfa...
Dispersion based formulations have a broad and diverse range of uses, e.g. for construction materials, paints, cosmetics, food and pharmaceuticals. Gravity driven processes potentially may affect their spatial and temporal composition and this way their appearance and functionality. Therefore physical stability has to be evaluated and predicted in...
The article is devoted to the application of analytical centrifugation for the measurement and analysis of centrifugal ultrafiltration kinetics. The model of centrifugal ultrafiltration of colloids accounting for the cake formation, compression and possible decompression is proposed. The method for the determination of filter cake properties (press...
Current development of analytical centrifugation methods facilitates the experimental characterizationof dispersion stability and optimization of separation processes (such as centrifugation and filtration).Nevertheless, theoretical analysis of the centrifugal data remains rather complex. In addition, differentside effects can influence the centrif...
Separation processes basically can be described by extended Stokes law taking into account volume concentration of disperse phase (hindrance) and rheological behaviour of continuous phase. To deduce separation behaviour under high gravity in centrifuges one can assume that separation velocity scales linearly with acceleration in Newtonian liquids....
Flocculation is often used in solid-liquid separation processes to ensure removal of fines. Average packing density in sediments and degree of clarification are easily accessible by optical detection with light. For a more comprehensive understanding of separation process and packing behaviour of sediments more detailed information on local particl...
No abstract is available for this article.
Biopolymers like pectins are frequently used in food industry to build texture and adjust the rheological profile of liquid and semisolid products. These products tend to change starting from the moment of production over the time of storage until the final consumption. In a dynamic process structuring proceeds continuously on a slow scale though....
A method and a device for the automatic determination of selected physical and colloidal chemistry parameters by determining the attenuation of radiated waves through monodisperse or polydisperse dispersion samples subjected to gravitation or centrifugation, wherein during the segregation by means of centrifugation or gravitation, the instantaneous...
Hansen Solubility Parameters (HSPs) have been widely used in coating industry and in diverse scientific disciplines, such as surface science [1]. They are used for predicting the solubility of materials in different solvents and for characterization of pigment dispersibility and wettability of various surfaces as well as of adsorption properties of...
Paper making and recycling processes are very complex. In this regard one important aspect is the complex composition of dispersions used. Beside water and cellulose fibres they contain inorganic particles (mainly clay and lime) and various process additives. During processing various separation processes have to be controlled. Detailed evaluation...
To match a desired shade of colour often mixtures of inorganic and organic pigments are used. Due to the considerable difference in density there is always a risk of pigment segregation. This may happen in pigment concentrates or in the final formulation. Ongoing pigment segregation processes are difficult to trace and even more difficult to predic...
Short communication based on part of the work done by Nadine Urbansky during her master thesis at LUM.
During emulsification droplet break-up and coalescence proceed simultaneously. To supress the latter process fast adsorbing emulsifiers and eventually formation of an adsorption layer with optimum (maximum) emulsifier coverage are needed. For a gi...
The kinetics of free and hindered sedimentation of a suspension of titanium dioxide (anatase) under the action of a high-molecular-weight cationic acrylamide copolymer and of hybrid polymer-inorganic nanosystems was studied. The influence of the content of the cationic acrylamide copolymer in hybrid systems and of the particle size on the TiO2 aggr...
Phase transition and ordering in an electrostatically stabilized colloidal system
In-situ characterization by Small Angle X-ray Scattering and X-ray Photon Correlation Spectroscopy
Fabian Westermeier, Birgit Fischer, Michael Spung, Gerhard Grübel
Characterization of the packing behaviour as function of excess pressure and measurement of concentra...
This technical note describes the theoretical background of a newly introduced Instability Index and its calculation. It is based on the particle concentration decrease (progress of transmission profiles, clarification) in emulsions and suspensions. Its use in SEPView® and the applicability for stability ranking is demonstrated for technical suspen...
Dispersion based products have applications in every area of life. During formulation of new products the dispersion properties have to be adjusted to obtain the desired stability, textural and rheological properties. Most often stable colloidal dispersions are required, sometime however, weak flocculation is purposely induced to adjust structural...
Carbon nanotubes are considered as nano materials with a broad application potential, e.g. as filler, in electronic devices and batteries. The relatively good dispersibility in ionic liquids is an interesting approach.
For efficient application generally a high degree of dispersion is required. Unfortunately, carbon nanotubes tend to form extended...
To optimize silica-iron oxide magnetic nanoparticles with surface phosphonate groups decorated with 25-kD branched polyethylenimine (PEI) for gene delivery.
Surface composition, charge, colloidal stabilities, associations with adenovirus, magneto-tranduction efficiencies, cell internalizations, in vitro toxicities and MRI relaxivities were tested f...
Formulation of products as well as process and quality control is in need of fast and efficient measurement techniques of the state of dispersion products. We review the basics of experimental techniques of stability assessment of suspensions and emulsions, procedures of accelerated stability testing, and discuss the relationship between results of...
Modern high performance ceramics, such as dental or artificial bone materials, tiles and technical ceramics are often based on complex suspensions. Composition and pre-processing of the suspension are essential for a consistent high quality of the final product. The evaluation of the sedimentation behaviour of dispersed particles delivers important...
Modern high performance ceramics, such as dental or artificial bone materials, tiles and technical ceramics are often based on complex suspensions. Composition and pre-processing of the suspension are essential for a consistent high quality of the final product. The evaluation of the sedimentation behaviour of dispersed particles delivers important...
Carefully designed colloidal properties are the prerequisite for successful diagnostic and therapeutic applications of magnetic fluids (MF). A high degree of dispersion (small particle size, absence of agglomeration) and stability is required. Multisample analytical centrifugation with high resolution photometric detection was applied to characteri...
Asphaltenes occur naturally in crude oil emulsions and its derivatives having different volume
fraction, composition and physico-chemical properties. Their unexpected precipitation is creating a
lot of technical and economical trouble. Especially the flocculation of asphaltenes in heavy fuel oils
may cause severe problems, including reservoir plugg...
Polymeric thickeners are important ingredients to adjust flow properties and stability of formulations. The effect of polymeric additives on dispersion properties is rather complex (viscosity of the continuous phase, adsorption and depletion effects, interaction with other ingredients). Therefore optimum formulation requires extensive experimental...
Emulsion-based products are found within the chemical and agrochemical, cosmetic, pharmaceutical,
and food industries. As emulsion structures are thermodynamically unstable, shelf-life stability is a main
aspect in product and process development. The objective of this work was to evaluate multisample analytical
centrifugation with STEP-technology...
Das Verhalten von Dispersionen, gekennzeichnet durch Entmischungs-, Fließ- und Packungsverhalten, wird durch Art und Stärke der interpartikulären Wechselwirkungskräfte bestimmt. Dies ist von grundlegender Bedeutung für die Anwendung von Dispersionen auf verschiedensten Gebieten aber auch für Fest/Flüssig-Trennverfahren. Der folgende Beitrag bericht...
The paper reports on labscale column studies for in situ surfactant washing of oil-contaminated soils. The displacment efficiency
of nonionic surfactants and their blends was tested on small columns. The kinetics of oil displacement and surfactant sorption-desorption
were studied. Further, the viscosity behavior of emulsions of varying compositions...
The consolidation behavior of suspensions was experimentally analyzed by means of a multisample analytical photocentrifuge. Experiments were conducted covering a broad range of volume concentrations and centrifugal accelerations. The obtained material functions allow to simulate batch sedimentation, filtration and consolidation. For only hydrodynam...
The particle size distributions of dispersions of fine particles were determined by an analytical photocentrifuge, which allows to measure space and time resolved extinction profiles (STEP™-Technology) during the centrifugation of up to 12 samples simultaneously. This type of centrifuge provides a powerful tool for the characterisation and quality...
Unit processes using centrifugal fields are often applied for the separation, deliquoring and classification of fine grained materials. Modelling of these processes requires information about the separation behaviour of the suspensions to be processed. To this end, direct measurements in centrifuges are obligatory. Moreover, these measurements have...
A common goal in the formation of stable emulsions during a homogenisation process is to obtain the smallest possible particle size distribution of the dispersed phase. The choice of emulsification process and process parameters (e.g. type of homogeniser, temperature, energy input, time, and homogenisation cycles) used to achieve this goal depends...
The particle size distribution of suspensions of fine particles was determined by a photocentrifuge from transmission/extinction profiles. Photocentrifuges provide a useful tool for the characterization and quality control of suspensions. While the variation of the light extinction curves caused by centrifugal segregation allows a qualitative descr...
Porous bead celluloses have wide ranging applications as separation media and carrier systems. Physicochemical characterization of these materials and related suspensions is essential for quality control and technical applications. This includes their surface properties, porosities and mechanical properties.
The paper describes the application of m...
The particle size distributions of dispersions of fine particles were determined by an analytical photocentrifuge, which allows to measure space and time resolved extinction profiles (STEP™-Technology) during the centrifugation of up to 12 samples simultaneously. This type of centrifuge provides a powerful tool for the characterisation and quality...
Unit processes using centrifugal fields are often applied for separation, deliquoring and classification of fine grained materials. Modelling of these processes requires information about the separation behaviour of the suspensions to be processed. To this end direct measurements in centrifuges are obligatory. Moreover, these measurements have to g...
The behaviour of dispersions in liquid media, i.e. dispersion stability, flow, separation and packing behaviour, is determined by the nature and degree of interparticle forces. This is of fundamental importance for their application in diverse fields such as nanomaterials, coating, paper making, ceramics, sludge dewatering, to name just a few. The...
Unit processes using centrifugal fields are often applied for separation, deliquoring and classification of fine grained materials. Modelling of these processes requires information about the separation behaviour of the suspensions to be processed. To this end direct measurements in centrifuges are obligatory. Moreover, these measurements have to g...
Reducing particle dimensions to nanoscale leads to qualitatively new properties. This holds also for liquid dispersions, which are the most often used form of application of nanoparticles. For characterization of nanoparticle dispersions techniques are preferable, which avoid dilution, thus don't modify dispersion properties. To this end multisampl...
Surface active additives are often applied to stabilize dispersions (emulsions, suspensions) and to modify surface properties. Selection of optimum additive concentration and composition is a crucial step in formulation and in design of technical applications. To this end, a lot of different laboratory methods have been developed, which are in part...
In the 90-ies surfactant combinations have been developed for enhanced degradation of recalcitrant compounds like polyaromatic hydrocarbons (PAH).
A principle formulation approach was invented delivering a range of closely related surfactant products, from which the most appropriate can be chosen by lab degradation tests.
Details on surfactants use...
Motivation
Der HLB-Wert repräsentiert die Gesamtpolarität des Emulgators, unabhängig von der Zusammensetzung - egal ob Einzeltensid, Mischung zweier Tenside oder Gemisch mit breiter Verteilung. Andererseits ist bekannt, daß die Geometrie der Tensidmoleküle und ihre Packungsdichte in den Adsorptionsschichten einen deutlichen Einfluß auf Typ und Sta...
The paper reports on a new laboratory method for evaluation of solid-liquid separation in decanter centrifuges based on analytical centrifugation. The method allows to determine the two critical parameters for sludge dewatering – separation rate of sludge flocs and the compressibility (dewaterability) of the sludge cake. The initial separation rate...
Nanostructuring of liquids and sorption layers has a very important influence on the behaviour of solid/liquid disperse systems and processes at the solid/liquid interface. Studies in this area often employ very sophisticated methods of characterization, i.e. surface force measurements. Analytical centrifugation is a relatively simple but efficient...
This paper reports on lab-scale investigations in relation to pre-selection of flocculants for sludge dewatering with decanter centrifuges. Results obtained were compared with CST-measurements and discussed in relation to findings under field conditions. Experiments were carried out with sewage sludges of different origin and characteristics and a...
In a series of experiments with soil samples of contaminated sites we investigated the effect of special surfactant combinations and other additives on the kinetics and extent of solubilization and degradation of PAH. Biodegradation tests showed a positive effect of adding surfactant combinations T10 and T15. The effect was more pronounced when sam...
The performance of a newly developed separation analyzer is demonstrated by characterization of the sedimentation kinetics
and the swelling behavior of organoclays in binary solvent mixtures (toluene/cyclohexane) as well as by investigation of oil-in-water
and water-in-oil emulsions stabilized by clay derivatives. The automatic measuring system – L...
overview over results of 10 years of own research. No time for actively continuing research in this field but happy to share details and discuss approaches.
paper in German only - outdated (my first trial to compile a short overview on use of analytical centrifugation (LUMiFuge) for evaluation of separation processes solid-liquid and liquid-liquid before getting a more detailed insight)
Soils contaminated with tar products are difficult to clean by soil washing technologies. It is widely expected that the performance of the washing process can be enhanced by the application of surface-active additives. Therefore investigations were carried out to search for additives effective in the clean-up of tar contaminated soils.
The solubilization capacity of aqueous solutions of surfactant mixtures was determined with n-nonane as model oil. The main objective was to investigate the effect of mixing ethoxylated fatty alcohols (polyoxyethylene-alkylether with C16/18-alkyl chain and polyoxyethylene-oleylether). The influence of commercial anionic surfactants on the solubiliz...
The adsorption of a series of ethoxylated p-tert-octylphenols on various silica substrates has been investigated to yield experimental data on the selectivity of adsorption. Therefore the oligomer distribution before and after adsorption has been determined, A comparison of the adsorption under static and dynamic conditions has also been included.T...
This paper is intended to contribute to the understanding of the complex action of additives on the model system toluene/water/non-ionic surfactant. The temperature dependence of the solubilization capacity for toluene was investigated for different systems of this type by measuring the cloud points. Short-chain aliphatic alcohols were used as addi...
As has been shown for the system poly(ethylene glycol) (PEG-600) — H2O, a gradual change in the number of water molecules per oxyethylene (EO) unit leads to a corresponding change of the wavelength
of the absorption maximum of methyl orange (MO). This effect has been used to investigate the alterations of the hydration
state of oligoether chains in...
Questions
Questions (21)