Papers at 5th World Congress on Particle Technology

5th World Congress on Particle Technology - WCPT5 - Orlando 2006

Use of multisample analytical centrifugation for evaluation of separation of fine particle slurries in the centrifugal field

T. Sobisch, D. Lerche, T. Detloff

Dispersion Stability & Particle Analysis, L.U.M. GmbH

Rudower Chaussee 31, 12489 Berlin, Germany,

info@lum-gmbh.de, www.lum-gmbh.com

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 gather kinetic information as function of the processing conditions, particle interaction and particle concentration.

The separation behaviour of quartz (stable dispersions) and limestone suspensions (moderately and strongly flocculated) was investigated as function of solid concentration and centrifugal acceleration using a multisample analytical photocentrifuge. The new multisample approach uses the STEP-technology. Space and time resolved extinction profiles quantify the alteration of particle concentration, the velocity distribution of particles and packing behaviour during centrifugation. Particle interactions are characterized by the packing density determined under defined conditions and by its variations under alternating centrifugal load.

Multisample analytical batch centrifugation with optical detection proved to be a versatile tool for the characterization of the separation of fine grained materials. This holds for information on the type of sedimentation behaviour (free sedimentation of individual particles, hindered settling, zone settling) on the sedimentation velocity distribution inside the centrate and on the packing, compression and elasticity behaviour, on the nature of particle interactions and the degree of flocculation as well.

The results of multisample analytical centrifugation with optical detection were in good agreement with the results derived by other methods (velocity distribution determined by manometric detection and average packing density obtained during compression in a disc centrifuge).

Characterization of interparticle forces in aqueous and nonaqueous dispersions using multisample analytical centrifugation

T. Sobisch, D. Lerche

info@lum-gmbh.de, www.lum-gmbh.com

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 present work reports on the use of multisample analytical centrifugation for investigation of the packing and compression behaviour to characterize the colloidal stability and microstructure in aqueous and nonaqueous dispersed systems.

Packing density, obtained after compression, is related to the total interparticle potential energy. By using different additives interaction between particles can be shifted from nearly hard sphere behaviour to strong attraction which results in flocculated systems. Additional information could be obtained about the strength and elasticity of particle networks by analysing the relative change in sediment volume after increasing/decreasing the excess pressure in multiple cycles.

The multisample technique applied implies the potential for more systematic studies for targeted colloidal stability.

The new multisample approach uses the STEP-technology. Space and time resolved extinction profiles quantify the alteration of particle concentration and packing behaviour during centrifugation without the need for sample dilution. The latter is a necessary prerequisite for ensuring that the liquid dispersions maintain their original properties.

The paper further covers the influence of the nature of interparticle forces on segregation and deliquoring of common polydisperse fine particle slurries in the centrifugal field.

KEYWORDS: Multisample Analytical Centrifugation, Interparticle Forces, Particle Interactions, Packing Behaviour, Dispersion Stability, Consolidation, Compressibility

Characterization of liquid nanoparticle dispersions by multisample analytical centrifugation

Particle interaction, colloidal crystallization

T. Sobisch, D. Lerche

info@lum-gmbh.de, www.lum-gmbh.com

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 multisample analytical centrifugation proved as an efficient tool.

The new multisample approach uses the STEP-technology. Space and time resolved extinction profiles quantify the alteration of particle concentration but also packing behaviour and phase separation during centrifugation.

Examples are presented for the detection of the presence of flocculation in nanoparticle suspensions, for examination of microgels and colloidal crystallization. The behaviour of microgels was characterized as function of centrifugal acceleration, temperature and concentration. Further, the effect of initial volume concentration and sediment pressure on the speed and extend of the crystallization process was studied.

KEYWORDS: Multisample Analytical Centrifugation, Nanoparticles, Microgels Interparticle Forces, Particle Interactions, Packing Behaviour, Colloidal Crystallization

PAH in clothing

mail from Joseph Mc Donald

I am hoping you may be able to answer a question that seems to have everyone staring into space. It appears we are all focused on what pollutants are in the air , water and soil but no one seems to know what happens to them when they come into contact with our clothing.

Living in a area where coal burning is still common practice for domestic heat and power generation it is quite common for clothing to be exposed to various levels of Coal soot and it's bi- products on a daily basis. ( just a note we burn oil but have many neighbors that burn coal and one of the power plants is 2 miles away) Seeing soot on the cars etc. is part of daily living and we always assumed once our clothes were machine washed with a brand name detergent any soot contamination would be removed. However approximately 15 months ago a family member became ill and it was determined PAH or heavy metal exposure were contributing factors. Since this individual worked in an office environment as did the rest of the family we frantically searched for the potential source and had various tests completed.

To our surprise we found various trace heavy metals and PAH evidence still present in freshly washed clothes which was shocking and the urine analysis for heavy metals on all three family members followed the same pattern, including a 13 year old. All clothes were also machine dried indoors. It appeared Sulfur, Barium, Beryllium, Thallium, Uranium, Magnesium, Strontium and Nickel for example were in the clothes after washing and also over the normal ranges in our bodies. Yet lead, mercury, etc were all perfect. We did not have the resources to do any extensive testing on PAHs but did find 1-oh-pyrene in urine ( benzene). I could not afford to have any further testing completed.

My question is has anyone completed any detailed testing in this area after removal of the tri sodium phosphates from the detergents to ensure no traces of PAH or heavy metals were being left behind. The detergent manufactures will not give anything other than a generic answer and I have tried them all. There are thousands of individuals that work in various heavy industry that are exposed to PAHs and heavy metals daily , those on the street levels of the larger cities, etc. who like us wash our clothes in the household machine assuming all of these potential toxins are being removed. But are they really or are we wearing a toxic patch.

From your experiences with PAHs / heavy metals over the years how would you say they should behave when on clothing and are exposed to a machine wash and modern detergent, would they stay in place since they do not dissolve in water, would they eventually break down on the clothing even though they are not being exposed to direct sunlight or microorganisms in soil. Would they ever break down in an indoor environment. Do they just sit there on the clothes until we eventually come into contact with them and absorb them.

Answer

Contaminants in clothes are an issue. There are also related investigations (at least determining contaminant levels). However, these are related to pesticide residues, heavy metals (black coloured clothes) and cancer causing dye compounds. We have here a monthly journal 'oekotest', which deals with issues like contaminations in various consumer products.
However, I would argue that PAH in clothes is not an issue of concern.

Points to consider

# PAH will not be removed by washing, only partly. However, the part easily available for further transport into the body will be removed.
# one should focus on the main routes of transport into the body - which is transport through the lungs (diesel particulates, road dust, tobacco smok, of course soot from coal burning).

That is uptake by routes other than clothes is far more likely!

Similar to contamination of soil, also in clothes only a part of the PAH is readily available for transport.
This is due to differences in physical properties (PAH group is a mixture of compounds with different solubilities, partition coefficients etc.) and differences in the nature of bonding and location inside the fibers. PAH located on the surface are very much more available for transport than PAH which have penetrated into the fibres.
By the way, phosphates are not an issue here. The main action of removing the contamination is due to surfactants. In detergents the phosphates have been replaced by other ingredients, which at least have similar positive effect on removal of PAH as the phosphates.

So there are essentially only two alternatives - move to a location in a pristine environment or raise the issue of environmental contamination.

I am very sorry about the health problems experienced in your family.

international reputed chemists thread to US homeland security?

As written in the Washington Post, the president of the International Council for Science, Indian organic chemist Goverdhan Mehta, was recently refused entry to the USA two weeks because his chemical expertise was deemed a threat to US security.

Liquid food shelf life prediction based on multisample analytical centrifugation

The International Symposium on Food Rheology and Structure (ISFRS 2006)

SHELF LIFE PREDICTION OF LIQUID FOOD PRODUCTS BASED ON MULTISAMPLE ANALYTICAL CENTRIFUGATION

Dietmar Lerche, Titus Sobisch and Stefan Kuechler

L.U.M. GmbH, Rudower Chaussee 29, 12489 Berlin, Germany

A considerable fraction of food products are dispersions (emulsions, suspensions, suspoemulsions). Therefore, not only the microbiological and chemical stability matters, but the separation stability has also to be characterized.

Centrifugation is the only method truly to accelerate physically sedimentation or creaming processes of food dispersions. Multisample analytical centrifugation with photometric detection is a tool for efficient screening of dispersions based on determination of creaming/sedimentation velocity.

It was evaluated how to deduce the separation stability using measurements under centrifugal acceleration based on the analysis of the velocity versus g-force (RCF relative centrifugal acceleration) relation.

Multisample analytical centrifugation is an efficient tool to measure the physical separation stability of liquid food products at different RCF values which enables one to deduce the behaviour under normal gravity, i.e. the calculation of physical shelf life.In addition these studies reveal important information about the structural (rheological stability) of food products.

Geschwindigkeitsverteilung polydisperser Feinstpartikeldispersionen

Echzeituntersuchungen zur Geschwindigkeitsverteilung polydisperser Feinstpartikeldispersionen für technische Abscheideprozesse

D. Lerche, T. Sobisch, T. Detloff, LUM GmbH, Berlin

Zentrifugalfelder werden in technischen Verfahrensoperationen häufig zur Abscheidung und Klassierung von Feinstpartikeln genutzt. Für die Auslegung der entsprechenden Trennprozesse ist die Modellierung des Bewegungsverhaltens von feinsten Teilchen in Suspensionen erforderlich. Da bisher zuverlässige Methoden zur Vorausberechnung der Abtrenngeschwindigkeit bzw. deren Verteilung in realen Systemen fehlen, ist dies beim gegenwärtigen Stand der Technik mit einem hohen Maß an Empirie verbunden. Dies führt zu einem hohen Aufwand bei der Einrichtung der Trennaggregate (umfangreiches Programm an Betriebsversuchen) und beim Betrieb der Anlagen unter nicht optimalen Bedingungen. Die Auslegung der Trennprozesse bezüglich Trennschnitt oder Resttrübung erfordert die direkte Messungen in Zentrifugen. Eine Übertragbarkeit von Ergebnissen aus Untersuchungen ohne Einfluß des Zentrifugalfeldes ist nicht gegeben.

Die analytische Zentrifugation mit Multiprobenrotor und photometrischer Detektion ermöglicht bei hohem Probendurchsatz die Analyse der Geschwindigkeitsverteilung im Suspensionsüberstand sowohl orts- als auch zeitaufgelöst. Diese Parameter sind für die Optimierung von Wehrhöhe und Verweilzeit entscheidend.

Die photometrische Detektion erlaubt es, die Geschwindigkeitsverteilung von Dispersionen bis hin zu sehr kleinen Aufgabekonzentrationen zu bestimmen. Dies ist besonders bei der Klärung von Trüben von Bedeutung.

Die stabile Quarzsuspension zeigt erwartungsgemäß eine breite Geschwindigkeitsverteilung.

What is the photoelectrocatalytic fuel cell? - The Clean Water Project What is the photoelectrocatalytic fuel cell?

The Clean Water Project - Articles - 01 - What is the photoelectrocatalytic fuel cell?

PECF:
It combines photocatalytic oxidation and the direct methanol fuel cell to oxidise organic pollutants (break down to smaller fragments) including pathogens on catalyst.

EPA calls to eliminate Teflon precursor

The Environmental Protection Agency (EPA) on Jan. 25 announced a global stewardship program that calls for voluntary withdrawal of use of toxic compound perfluorooctanoic acid (PFOA).

" PFOA is the key ingredient used to manufacture Teflon or fluoropolymers, which are used in the manufacture of a wide range of non-stick and stain-resistant surfaces and products."

' DuPont responded quickly to the invitation. In a statement released on Jan 27, the company said it "has committed to virtually eliminate the sources of exposure to PFOA from our manufacturing operations and products by 2015." '

Source US EPA

Floating floc - Discussion at the Waterandwastewater Help Forum

Question

We are using a new parts washer detergent (mainly Sodium hydroxide, tkpp, soda ash), and have started to have floating flocs.
Some white residue got past the sedimentation tanks, sand filters, 1 micron cartridges, and finaly clogged the RO membranes.

After cleaning the membranes we removed a white solution, that when floculent was aded produced white strings.

Any ideas what this could be?
Is there a chemical that can de-emulsify the oil from the detergent?

Answer

as you said, you have an alkaline cleaner without or with low content of surfactant. Probably part of the oil/grease (mineral oil?) is saponified and precipitated as unsoluble soaps by water hardness? Soaps will be also precipitated by cationic flocculants.

By neutralization or shifting the pH to slightly acidic conditions the emulsions should be demulsified.

Reply
It changed everything!

I reduced the PH to 7. The foam disapeared and small oil particles started to float, however flocculation ceased, I played arround with the qty of floc/coag.and could not fix this situaton.

I returned PH to 9 and continued to produce white floating flocs.

Answer
as your contamination is oil removal by flotation or an oil/water separator is much more efficient than sedimentation. Sedimenting flocs can only be achieved by heavy ballasting, maybe using bentonites or a high dosage of precipitated iron salts.

The situation with demulsification and flocculation is the following.

The emulsion droplets are stabilized by negativ surface charges at high pH. Adding cationic polyelectrolytes or iron/aluminum ions flocculation or coagulation is achieved.
At neutral pH emulsion droplets are destabilized and coalescence, but will not interact with cationic additives. (Question - is the coalescence efficient enough to remove the oil by an oil-water separator or oil skimmer?).
If destabilization is not efficient enough you might either readjust the pH to alkaline and add a low amount of cationic flocculant to enhance separation or adjust the pH to slightly acidic and add an anionic flocculant (low amount). In both cases the oil droplets will float.

New Study Raises Questions About Sustainability Of Metal Resources

Pollution Online SOURCE: The National Science Foundation

'Researchers studying supplies of copper, zinc and other metals have determined that these finite resources, even if recycled, may not meet the needs of the global population forever.'

The problem might only be resolved by improving recycling and develope new technologies with less demand on these resources

Study: Storing Carbon To Combat Global Warming May Cause Other

Durham, N.C. — Growing tree plantations to remove carbon dioxide from the atmosphere to mitigate global warming -- so called "carbon sequestration" -- could trigger environmental changes that outweigh some of the benefits, a multi-institutional team led by Duke University suggested in a new report. Those effects include water and nutrient depletion and increased soil salinity and acidity, said the researchers.

SOURCE: Duke University

Removal of sulfate and phosphate by flocculation

SpringerLink - Article http://www.springerlink.com/content/3323738214278l71/:
Removal of sulphate and phosphate from aqueous solutions using a food grade polysaccharide as flocculant
by Anuradha Mishra and Malvika Bajpai
Department of Chemistry, University Institute of Engineering and Technology, CSJM University, Kanpur, 208 024, India