El nuevo molino ultracentrífugo ZM 200 de RETSCH es un molino de rotor no sólo extremadamente rápido y cuidadoso con el material molido, sino también de uso universal gracias a su amplia gama de accesorios.
Planeten-Kugelmühlen haben seit jeher einen festen Platz in der täglichen Laborpraxis zur Feinzerkleinerung unterschiedlichster Materialien. Neben dem Mischen und Zerkleinern hat sich in den letzten Jahren auch im mechanischen Legieren z.B. thermoelektrischer oder hochkoerzitiver Materialien ein weiteres Anwendungsgebiet ergeben.
Nanoteilchen, d.h. Partikel mit einem Durchmesser von weniger als 100 Nanometer, werden seit vielen Jahren von Wissenschaftlern erforscht. Zum einen lassen sie sich im „Bottom-up“ Verfahren aus Atomen oder Molekülen synthetisieren. Im “Top-Down“ Verfahren hingegen werden größere Partikel, z.B. mit Hilfe von Labormühlen, zerkleinert. Kleine Partikel weisen durch das extrem vergrößerte Verhältnis von Oberfläche zu Volumen erhöhte Oberflächenladungen auf, so dass die Partikel elektrostatisch zueinander gezogen werden. Daher können Nanopartikel nur durch Nassvermahlung (Kolloidvermahlung) erzeugt werden.
Die Zerkleinerung als wichtiger Verfahrensschritt der Probenaufbereitung hat einen erheblichen Einfluss auf die nachfolgende Analytik. So können zu grobe Partikelfeinheiten oder auch Inhomogenitäten insbesondere dann zu unbrauchbaren oder falschen Analyseergebnissen führen, wenn es sich um kleinste Probenvolumina handelt die repräsentativ für die Gesamtprobe sind.
Freizeitaktivitäten in der Natur wie Wandern, Radfahren oder Klettern erfreuen sich großer Beliebtheit. Die Textilindustrie bietet hierfür eine große Bandbreite an Funktionskleidung aus synthetischen High-Tech Materialien, die in der Regel wind- und wasserfest sind sowie atmungsaktiv. Wie Greenpeace in einer Studie von 2013 nachweisen konnte, finden sich in wetterfesten Textilien immer wieder Gefahrstoffe wie per-oder polyfluorierte Chemikalien (PFC), welche z. B. zum Schutz vor Wasser und Schmutz in die Kleidung eingearbeitet werden.
Bestimmung von anorganischen Inhaltsstoffen in Bodenproben
In Industrienationen mit hoher Besiedlungsdichte und einem begrenzten Angebot an Industrie- und Gewerbegebieten unterliegt die Nutzung von Gebäuden und Flächen einem dauerhaften Wandel. Daher sind Bodenuntersuchungen für Investoren, Behörden und Privatpersonen unumgänglich. Umweltanalytische Untersuchungen bilden die Basis, um Gefährdungen aufzuzeigen und damit Menschen und eingesetztes Kapital zu schützen. Bei SGS Institut Fresenius in Herten werden bis zu 400 Bodenproben am Tag aufgearbeitet und analysiert. Hierbei wird sehr genau darauf geachtet, dass geltende Normen und Verordnungen eingehalten werden. In Deutschland gilt die BbodSchV, wobei die Analytik auch auf die Vorschriften anderer Länder angepasst wird.
Die Vermeidung von Umweltverschmutzung ist eines der zentralen Themen in den Industriegesellschaften des 21. Jahrhunderts. Eines der wichtigsten Instrumente in diesem Zusammenhang ist die regelmäßige Kontrolle mit modernen analytischen Methoden. Neben Luft- und Wasseranalytik stehen Altlastensanierungen und Deklarationsanalysen ebenso im Fokus wie die Analytik von Boden, Bauschutt, Sedimenten, Altholz, Sekundärbrennstoffen u.v.m..
Für nahezu sämtliche chemische und physikalische Analysenmethoden ist es notwendig, die Analysenprobe in einem möglichst hohen Grad zu homogenisieren und sie auf eine definierte Feinheit zu zerkleinern. Hierbei erstreckt sich die notwendige Probenvorbereitung auf alle Proben der unterschiedlichen Matrizes. Die Probenvorbereitung hat somit neben der Probenahme einen entscheidenden Einfluss auf das Analysenendergebnis, denn: Probenvorbereitungsfehler können das Endergebnis um mehr als 50% beeinflussen!
In zahlreichen Labors werden täglich viele unterschiedliche Probenmaterialien aufbereitet. Für die Zerkleinerung von Feststoffproben auf Analysenfeinheit wird eine Mühle benötigt, die nicht nur vielseitig einsetzbar und leicht zu reinigen ist, sondern die auch eine reproduzierbare Probenvorbereitung – und damit zuverlässige Analysenergebnisse - garantiert. Mit der Ultra-Zentrifugalmühle ZM 200 bietet RETSCH eine Rotormühle an, die nicht nur sehr schnell, sondern auch äußerst materialschonend zerkleinert und, dank einer umfangreichen Zubehörpalette, universell einsetzbar ist. Mit ihrem kraftvollen Powerdrive-Antrieb vermahlt die ZM 200 weiche bis mittelharte und faserige Materialien extrem schnell auf Endfeinheiten bis unter 100 µm und steigert so den Probendurchsatz im Labor.
Kryomühle im Einsatz an der BTU Cottbus Bei vielen Materialien ist es vorteilhaft eine Kryomühle für die Zerkleinerung einzusetzen, statt einer Labormühle, die bei Raumtemperatur arbeitet. Die Probe wird durch den eingesetzten flüssigen Stickstoff versprödet und kann darum besser durch Schlag, Druck und Reibung zerkleinert werden; außerdem bleiben leicht flüchtige Bestandteile erhalten. An der Brandenburgischen Technischen Universität (BTU) Cottbus ist eine Kryomühle in den Bereichen Kunststoffrecycling und Biomaterialien im Einsatz.
A solid sample material should always be sufficiently prepared by size
reduction and homogenization before it is subjected to chemical or physical analysis. Care should be taken that the analysis sample fully represents the original material and that the sample preparation process is carried out reproducibly. Only then are meaningful results guaranteed. Most sample materials can be reduced to the required analytical fineness at room temperature by choosing a mill with a suitable size reduction principle (impact, pressure, friction, shearing, cutting).
The use of pesticides in agriculture makes it possible to plant extensive mono cultures and often leads to substantial yield increases of food and feed crops. Demand and application have grown steadily over the years, leading to increased contamination of the soil due to the toxic nature of pesticides. Soils save the toxins and their decomposition products so that wildlife is also affected by them. Among the undesired side effects are damages to useful plants and insects like bees. The wind carries pesticides to uncontaminated areas such as fields used for organic farming. Rain also transports the chemicals away from their original area of application to waters and groundwater. Although in most cases the limit values for particular pesticides and their decomposition products are not exceeded, the cumulative effect on humans and animals has not been thoroughly investigated so far. The possible accumulation of pesticides in the food chain could be a source of health hazards; therefore strict quality control of soils is indispensable.
Representative sampling of large sample volumes is an integral part of the physical and chemical analysis of bulk goods and has a decisive influence on the quality of the results. Extraction of a sample from the bulk is not always carried out in a way to ensure representativeness. This is a widespread flaw in the quality control process with a negative impact on the subsequent analysis results. Therefore, more attention should be paid to the correct sampling procedure. Sample division is often considered as a labor-intensive process which not always leads to representative results. RETSCH provides some convenient solutions which help to improve working conditions and thereby the quality of the sampling process.
Modern analytical methods increase precision and push detection limits to make even the smallest traces of sample components detectable. Despite this development sample preparation, which is carried out prior to the actual analysis, is frequently neglected. Errors caused by lacking accuracy in sample preparation have a much bigger impact than errors made during analysis. Just like an iceberg which is mostly hidden under water, only a small part of the sum of errors is perceived whereas the major part of potential errors is not taken into account (fig. 1). One of the reasons may be the fact that sampling and sample preparation have always been done in a traditional way which has become a routine over the years and is no longer considered as having a critical influence on the subsequent analyses.
How are nano particles produced? The “Bottom-Up” method synthesizes particles from atoms or molecules. The “Top-Down” method involves reducing the size of larger particles to nanoscale, for example with laboratory mills. Due to their significantly enlarged surface in relation to the volume, small particles are drawn to each other by their electrostatic charges. Nano particles are produced by colloidal grinding which involves dispersion of the particles in liquid to neutralize the surface charges. Both water and alcohol can be used as dispersion medium, depending on the sample material. Factors such as energy input and size reduction principle make ball mills the best choice for the production of nanoparticles.
Plastic is an inherent part of our everyday lives; it is used in a huge variety of things such as, for example, packaging, furniture, clothing or electronic devices. Though the utility of the material is undoubted, consumers are increasingly unsettled by recurring news about hazardous substances detected in plastics. Substances such as plasticizers, which are not firmly bound in the material, are absorbed via the skin and can influence the hormonal balance. Plasticizers contained in food packaging, for example, penetrate into the food and thus into the human body when the food is eaten. Plasticizers in toys are a particularly serious problem; children tend to take toys into their mouths thus absorbing the dangerous chemicals. Equally hazardous are polycyclic aromatic hydrocarbons (PAH). The family of PAH comprises more than 100 compounds most of which have been found to be carcinogenic.
The Emax is an entirely new type of ball mill which was specifically designed by RETSCH for high energy milling. The impressive speed of 2,000 min-1, so far unrivaled in a ball mill, in combination with the special grinding jar design generates a vast amount of size reduction energy. The unique combination of impact, friction and circulating grinding jar movement results in ultrafine particle sizes in the shortest amount of time. Thanks to the new liquid cooling system, excess thermal energy is quickly discharged preventing both sample and mill from overheating, even after long grinding times.
Sample preparation of vegetable-based raw materials with laboratory mills
Thanks to the increasing usage of biomass as a source of energy, the analysis of these materials in the context of R&D and quality control gains importance, too. Due to the complex properties of plant materials, adequate sample preparation can be rather a challenge.
Today, recycled glass is the most important resource for the glass industry. The processed glass can be reintroduced to the melting process any number of times and made into new products. In Germany, currently up to 95 % of recycled glass is used for producing glass, which has various advantages: energy saving, less consumption of primary raw materials (such as lime and silica sand) and the reduction of landfill costs for waste glass.
The prevention of environmental pollution is a prime issue of today’s industrialized societies. Important instruments in this context are regular checks using the latest analytical methods. Beside air and water analysis the focus is also on environmental remediation and declaration analyses as well as examination of soils, construction waste, sediments, secondary fuels and many more. Prevention and ecological recycling and disposal are the key words of a modern environmental policy. If the production of waste cannot be prevented, the primary objective is its material or energetic recycling. Residuals which cannot be recycled have to be disposed of in an ecologically friendly way.
A faultless and comparable analysis is closely linked to an accurate sample handling. Only a sample representative of the initial material can provide meaningful analysis results. Rotating dividers and rotary tube dividers are an important means to ensure the representativeness of a sample and thus the reproducibility of the analysis. Correct sample handling consequently minimizes the probability of a production stop due to incorrect analysis results. Thus correct sample handling is the key to effective quality control.
Some sample materials have properties which make size reduction at ambient temperature impossible. If, for example, very elastic materials need to be ground or volatile components have to be preserved for further analysis, it is essential to carry out cryogenic grinding. The use of liquid nitrogen helps to embrittle the sample, thus improving its breaking properties, and preventing volatile substances from escaping due to the frictional heat produced by the grinding process.
The EU directive 2000/53/EG stipulates that as of 2015 95 % of the weight of a car that has reached the end of its life span have to be recycled. The work of ARN is strongly focused on this objective. Together with partner companies they make sure that old cars are processed in an environmentally compliant way. The recycling chain begins with the companies that dismantle the car and remove raw materials and liquids. Waste management companies collect these materials and deliver them to the processing companies who reuse the materials in accordance with high production standards.
Semiconductors are used for a variety of electronic applications such as integrated circuits (microprocessors, microcontrollers etc.), optical detectors and radiation sources (e. g. light emitting diodes), but particularly for photovoltaics where solar energy is transformed into electrical power. For the majority of applications, silicon is the semiconductor material of choice.
Due to decreasing resources and increasing market prices for primary fuels like oil, gas or coal, it is paramount for the cement industry to search for alternative energy sources. With regard to the CO2 emissions trading, a switch to energy sources which have a neutral CO2 balance can be rather profitable. Usually, these are non-fossil fuels. Industries with high energy consumption have made increasing use of alternative fuels during the last years. Accordingly, the use of so called secondary fuels (also waste derived fuels/wdf or refuse derived fuels/rdf) has gained importance. These are mostly combustible fractions of domestic or industrial waste which cannot be recycled.
The SM 300 excels especially in the tough jobs where other cutting mills fail. It has a freely selectable speed range from 700 to 3,000 rpm with high torque. The mill is convenient to operate and easy to clean. Reliable and extremely efficient sample preparation in the laboratory is now guaranteed with the SM 300.
Wood residues from forestry work and wood processing are usually processed to wood chips. These can be used in different ways, depending on the type of wood, bark and residual moisture, for example as raw material for chipboards or as substrate for the cultivation of mushrooms. The major part, however, is used for energy generation. The quality of the wood chips can vary significantly, depending on their origin and condition. Trade and industry are interested in the percentage of dry matter and in the calorific value of the chips as the price calculation depends on the water contents of the product. With the analysis result representing an important economic factor, the representative and reproducible sample preparation gains importance, too.
With ever increasing socio-economic and geo-political demands, the use of secondary fuels in cement manufacture is a well-established practice for reducing both costs and CO2 emissions. The depletion of resources, combined with an increasing demand for primary fuels such as oil, gas or coal, make it paramount for energy consuming industries to search for alternative energy sources.
Polycyclic aromatic hydrocarbons, short PAH, are usually a by-product of combustion and can be found, for example, in cigarette smoke or oil-based products. Mineral oil containing PAH is often used in rubber products as plasticizer, especially in black-coloured products such as car tyres, rubber grips of tools or rubber shoe soles. It was discovered that some polycyclic aromatic hydrocarbons are carcinogenic, so that maximum permissible values have been determined for the concentration of PAH in consumer products.
For the size reduction of many materials it is more suitable to use a cryogenic mill than a laboratory mill which operates at room temperature. The sample is embrittled by liquid nitrogen which improves its breaking behavior when submitted to impact, pressure and friction; moreover, volatile components of the sample are preserved. The RETSCH CryoMill is not only the most modern and safest cryogenic mill in the market, it also provides excellent grinding results.
Cutting mills are used in many different areas of sample preparation for subsequent analyses. Typical applications include the size reduction of secondary fuels, the processing of biomass for renewable energy research, the control of products in the context of RoHS and WEEE regulations or the recovery of precious metals – the variety of sample materials is huge.
The preparation of a mixture of organic and inorganic samples holds some difficulties: whereas sand, clay and stones can usually be ground to homogeneous samples with suitable laboratory mills, the high energy input can cause samples with organic components such as fat or starch to cake. Carsten Bunn, a laboratory technician at the waste water treatment laboratory BRW, has to deal with this problem every day. He treats samples which are taken from the sand traps of the wastewater treatment plants and consist of exactly that mixture. The sediments of household and industry waste water not only contain sand, clay or leaves but anything that people nowadays dispose of through the sewer system: cellulose, hair and especially food residues.
To produce high-quality cement, the mineralogical and chemical composition of raw materials as well as intermediate and finished products has to be determined. At each stage of the production, samples have to be taken, processed and analysed to ensure quality control without gaps. Retsch offers a range of instruments that are used for sample preparation during the complete production process, from the quarrying of the raw materials to the final product. The typical sample preparation process involves preliminary size reduction, sample division and fine size reduction before the sample can be submitted to further analyses....
Mechanochemistry is a very effective method to carry out syntheses without solvents and by-products. The technical literature describes a great number of reactions where a conversion of 100% is achieved. A precondition for the establishment of mechanochemistry in the industrial sector is the availability of suitable laboratory mills. A decisive factor is that – similar to conventional preparative chemistry – ambient parameters such as pressure and temperature can be documented and monitored. The Planetary Ball Mills and Mixer Mills from Retsch fulfill these requirements.
Preparing electronic waste for obtaining representative analytical samples. A solution for converting an electrical appliance into a meaningful analytical sample is described using a remote-controlled toy car as an example.
The elemental analysis of plastics has become more and more important. EC directive 91/338/EWG regulates the ban of cadmium in PVC, EC directive 94/62/EC defines limits for cadmium, lead, chromium and mercury in packing materials and EC directive 2000/53/EC defines limits for the same elements in end-of-life vehicles. This has created a strong need for a rapid and reliable testing method.
An efficient sample preparation procedure for rapid, reliable and reproducible analytical results is becoming increasingly important today. Ever more stringent requirements are being set both in research and production, e.g. for product monitoring and quality control.
X-Ray fluorescence is one of the most versatile methods to determine elements in a sample. The material is exposed to x-rays that cause each element to emit its own unique fluorescent x-ray. The subsequent analysis of the results is based on comparisons to standard samples with given chemical composition.
Now that a certain environmental awareness has developed in the population over the past few years, our efforts are geared not only to avoiding waste, but also to reducing the mountains of waste which still arise by means of raw material recovery and the reintroduction of secondary raw materials into the industrial cycle.
The following situation is typical for many production plants: After a routine quality check, the production process is stopped or an already produced batch is suspended, because the analysis results were not within the relevant critical values. But does the tested product really deviate from the specifications? The quality control managers are convinced of this because modern analysis instruments provide results with very low tolerances. The sample in question was tested several times and the result was confirmed. The question is why the product does not match the specifications although the production parameters have not been changed in any way. The possibility that the tested product is indeed deficient cannot be excluded. However, it is often not the product itself which causes irregular analysis results but a lack of understanding of the steps which come before the analysis.
Air jet sieving is usually the method of choice for dry sieving of materials with particle sizes below 40 microns. However, it is also a faster alternative to vibratory sieving of materials of up to 250 microns.
Particle analysis of large quantities of bulk goods is usually done by vibratory sieving. In most vibratory sieve shakers in the market the sieve stack is mounted on springs which oscillate vertically. However, to evenly distribute the material over the entire sieve surface, the so called 3D vibratory sieving as it is used in the AS 450 control is the most suitable method. This is characterized by a circular motion superimposing the vertical throwing motion so that the sample material is moved over the whole sieve.
Particle size analysis and particle size distribution are important criteria for the quality control of bulk materials. In a running production process, the results of a quality check must be available quickly to allow for immediate adjustment of the production parameters. Depending on the expected particle size and sample volume, different sieving methods and sieving machines are suitable for analysis. The method used for particle size analysis is primarily determined by the fineness of the material to be sieved. For dry sieving of samples with particle sizes below 40 microns, air jet sieving is the method of choice.
Referências de clientes (7)
Sample preparation of soils - Alcontrol Laboratories