Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
  • G01N21/66—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence
  • G01N21/67—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence using electric arcs or discharges
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
  • G01N21/66—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence
  • G01N21/69—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence specially adapted for fluids, e.g. molten metal

Definitions

• the object of the invention is a method and apparatus for measuring the elementary composition of solutions, more particularly a method and apparatus that can be operated as an automatic monitoring device for detecting a specific range of metallic elements in water-based solutions with high contents of oily and greasy pollutants and floating materials, that is, solutions containing high amounts of emulsified/suspended disturbing components (typically wastewaters).
• pollutant elements Taking into account environmental and other factors (e.g. aspects of cleaning technology) the order of importance of pollutant elements is the following: toxic metals (heavy metals), non-toxic metals (Fe, Mn, Na, K, Ca, Mg), other toxic elements (e.g. arsenic, selenium, halogens, etc.)
• toxic metals heavy metals
• non-toxic metals Fe, Mn, Na, K, Ca, Mg
• other toxic elements e.g. arsenic, selenium, halogens, etc.
• This measurement method comprises the main steps of adjusting the conductivity of the water sample to a reasonably high value by means of acidifying or the addition of alkali salts, introducing the sample into an 5-ml overflow vessel with a continuous flow rate of approx. 5-10 ml/min , and connecting it through a contact to the negative pole (electrolyte cathode) of a high-voltage DC power supply, with the positive pole of the discharge being provided by a metallic anode arranged above the sample's surface determined by the overflow rim.
• the surface layer of the sample undergoes sputtering by the generated water vapor glow discharge plasma, with the components leaving the surface being atomized and excited to emit atomic emission lines.
• a condition for ELCAD emission (in case conductivity has been adjusted by means of acidifying) is that the pH of the solution should fall in the interval 1-2, which has to be provided utilizing a mineral acid. Due to the high-energy processes of the discharge
• the small cathode-side bright spot (approx. 0.5 mm in size) of the 3-5 mm glow discharge, the so-called "negative glow", is directed to the spectrometer measuring the atomic spectral lines by means of a quartz glass optics
• a necessary condition of the measurement is that the negative glow region should be projected into the entrance slit of the spectrometer in a stable, flicker-free manner.
• the stability of the surface of the flowing sample heavily affects the signal-to- noise ratio of the light emission detected by the spectrometer, and through it the reliability of the measurement.
• ELCAD emission An important characteristics of ELCAD emission is that the emitted characteristic radiation is relatively weak. This is an especially crucial parameter for detector design. Other important features of ELCAD emission are the special, disc-like geometry of the light-emitting volume and the constraints posed on possible detection directions, the most significant of which being the shading effect of the sample surface.
• ELCAD spectrometry a narrower range of elements can be determined than with the application of ICP. For instance, non-metallic elements (among them As and Se, which are increasingly important from an environmental aspect) cannot be measured. The measuring range is also smaller, spanning at most two orders of magnitude.
• the detection limit for heavy metals for samples free from floating material and organics (with a so-called capillary discharge cell), can reach the concentration value of 10-30 ppb [T.Cserfalvi, P.Mezei, Subnanogram sensitive multimetal detector with atmospheric electrolyte cathode discharge, JAAS, 2003,18(6) 596-602 ].
• These analyzers uitlilize capillary-sized flow systems and are exclusively capable of analyzing clean samples that are free from floating materials.
• the filtering out of floating materials from wastewaters may solve flow disturbance and blocking problems of the different measurement cells, but for the pH values commonly found in wastewaters the larger portion of metallic contaminants are present precisely in these materials.
• the ELCAD method is less sensitive to floating materials, as only materials floating on the surface or in the thin surface layer are "visible" to the discharge plasma glowing at the surface of the electrolyte cathode.
• the instrument is capable of analyzing wastewater samples only for a short time, because oily and floating contaminants getting deposited on the overflow rim obstruct the flow path of the liquid, cause disturbances in the flow profile, the position of the sample surface and the plasma is changed and thus instead of the negative glow the spectrometer will "see” other regions of the plasma. Deposits on the overflow rim will sooner or later short circuit the discharge.
• the instrumental analytical methods detailed above are not capable of being utilized for wastewater monitoring applications because they require the complete removal of floating materials (or other disturbing components) from the sample.
• the discharge cell of the original ELCAD method which comprises an overflow-type cathode vessel, meets most of the requirements set by monitoring applications but its long-term stability is insufficient.
• Fig. 1 illustrates the general flow shape applied in the invention.
• Fig. 2 illustrates the simplest implementation of the invention in the form of a gravity- flow discharge cell in plan view (Fig. 2/a) and side view (Fig. 2/b).
• Fig. 3 shows a possible embodiment of the rotating-body flow guide cathode.
• Fig. 4 shows an embodiment of the rotating-body flow guide cathode applying axial sample infeed.
• Fig. 5 shows details of the ionically conducting cathode contact implemented with the application of electrolyte (Fig. 5/a) and without electrolyte (Fig. 5/b).
• Fig. 6 illustrates the configuration of the cathode applying a hydrophilic membrane, showing the arrangement in side view (Fig. 6/a) and plan view (Fig. 6/b).
• Fig. 7 shows the top plan view (Fig. 7/a) and the side view (Fig. 7/b) of a preferred optical arrangement for the detection device.
• a wastewater analysis method based on electrolyte cathode DC glow discharge can be adapted for long-term monitoring of metal content in highly contaminated wastewaters by such an arrangement of the free-surface flow shape, flow route and the cathodic contact of the sample in the discharge cell where emulsified and suspended components are deposited at the operating area of the ELCAD plasma to a minimal extent, and the formed deposits do not affect flow shape for an extended period of time and can be removed in a fast, simple and easily automatizable manner from the ELCAD plasma area.
• ELCAD electrolyte cathode DC glow discharge
• additives should be used to increase the coagulation stability of components, and/or ultrasonic energy should be introduced into the sample with a specific intensity chosen such that the introduced ultrasound increases the degree of dispersion and thereby works against coagulation processes.
• the position stability of the light-emitting spatial area of he glow discharge can be most preferably provided by forcing the solution that is flowing with uniform velocity to assume a free-surface stationary flow shape by means of a suitable hydrophilic boundary surface.
• the stationary flow shape of the solution is produced on a surface that is disposed at an angle of 10-90 degrees with respect to the horizontal plane utilizing the balance of gravity and surface tension.
• the slanting surface is preferably of 0.5-10 cm in size, with the liquid being introduced from an upper and/or lateral direction.
• the stationary flow shape of the solution can also be produced on a rotating surface, utilizing the balance of centrifugal force and surface tension, where the liquid is introduced into the appliance at an arbitrary point, preferably at the axis of rotation, of the surface, the liquid spreading over the rotating surface and leaving the surface at the rim thereof.
• the rotating surface itself may be any surface of rotation, the only requirement being stable film formation.
• conical, funneled or negative cylindrical surfaces are also suitable, and the negative paraboloid shape can also be utilized.
• the size of the rotating parts is typically a few centimeters.
• the cathodic contact may be located below the base point of the plasma, but it can contact the solution at another point.
• the contact itself can be ionically or electron- conducting.
• a closure comprising a hydrophilic membrane is preferred.
• the contact can be realized in a geometrically advantageous manner by means of a circular electrode or at the solution inlet portion.
• An important feature of our invention is the solution provided for the cleansing of the cathode surface.
• Mechanical cleansing of the cathode surface is made possible by the arrangement where the cathodic contact necessary for the glow discharge is produced at the base point of the plasma through a mechanically slideable separator layer and thus contaminants can be removed from the liquid-contacting portion of the discharge cell, located under the plasma region, as frequently as is necessary.
• the movable ionically conducting layer can for instance be a porous ceramic element with a thickness of 0.5-2 mm that can be cleansed after removing it by sliding from the discharge location.
• the movable ionically conducting layer is a hydrophilic film applied in a tensioned state between two storage rolls. The film can be provided in an endless-loop arrangement.
• a dispersing effect of a specific magnitude of 1-100 W/cm is applied, for instance by means of ultrasonic energy.
• sample preparedness detection is a crucial step in the wastewater monitoring process that involves samples of highly different composition.
• Sample preparedness detection is carried out in the instrument by detecting that the specific conductivity of the sample has reached a given value, a significant increase of the concentration of free charge carriers appearing after the addition of mineral acid to the sample acts as an indicator of the fact that the sample has been saturated with the acid and the mobilizable contaminants have been dissolved.
• the specific conductivity of the samples it can be achieved that cathode-side resistance remains the same (within the margin of error of detection) for different samples, which enhances the stability of the discharge.
• the specific conductivity of the sample is measured by detecting inductivity changes of the sample flowing through a suitably formed flow pipe.
• Detecting sample preparedness in the above described manner provides that the instrument is capable of reliable automatic analysis of the widely varying samples taken from mixed industrial/communal wastewaters.
• the optical axis of the photon-collecting optical element or, in case a complex imaging system is applied, the optical axis of an optical element of the imaging system, should be arranged at an angle other than 90 degrees with respect to the surface normal of the cathode surface. It can thus be achieved that the images of such spatial portions of the light-emitting "disc" which have different positions when projected onto the plane spanned by the optical axis and the surface normal of the sample surface will be at different distances from the optical axis. This characteristics of the image makes it possible to treat separately these image point groups located at different positions, and that way transform them into a form suitable for being processed by the polychromator.
• the new image adapted for being processed by the polychromator can be a plane where the image spots belonging to given object points emit light approximately into the direction of the surface normal with a numerical aperture corresponding to the transformation.
• a transformation can be realized by means of a prism-like optical element/elements preferably having antireflective coating and being most preferably disposed in the light path in the the vicinity of the image generated by the imaging system.
• This prismatic element or elements disposed in the above manner are capable of efficiently changing the real or virtual focal length of image spots. Because the loss-free transmission of this transformed image still requires a slit width greater than the width of the emitting disc, a further transformation corresponding to the aperture of the dispersing element may be applied.
• the numeric aperture of focusing is usually smaller for directions in the plane spanned by the optical axis and the surface normal of the sample than for directions in the plane perpendicular to it.
• the application of a cylindrical lens is preferable in order to utilize the numerical aperture of the dispersing element in both directions.
• the prism and the transforming element can be a single optical element that can be implemented by the axial-direction truncation of a cylindrical body made of glass.
• the resolution can be further increased by applying a further focusing element in the polychromator before the position of the tested wavelength.
• this focusing element is a short-focus cylindrical lens that is preferably disposed, for instance in the Seya-Namioka mounting, in the vicinity of the Rowland circle.
• the solution is forced to flow in a film along a suitable solid substrate surface, where the flow shape is determined by the balance of liquid-solid and liquid-air interfacial tension and the driving force of the flow.
• Interfacial tension values are dependent on the chosen materials.
• the substrate should have a wettable (hydrophilic) surface to provide stable operation. That way flow shape and flow shape stability are determined by the shape of the substrate surface and the magnitude and spatial distribution of the flow driving force.
• Fig. 1 shows the general flow shape of the invention near the ELCAD discharge plasma.
• the wastewater 1 flows along the hydrophilic solid substrate surface 3 with a layer thickness of 0.1-3 mm.
• the substrate surface can be any plane or curved surface or any combination of these, the only constraint on shape being that the flowing wastewater should not separate from the surface in the proximity of the plasma.
• An example of a combination of planes is the V-shaped channel, while curved surfaces can be for instance cylindrical, conical, or spherical surfaces.
• the wastewater is connected through the cathode contact 6 to the negative pole of the power supply applied for sustaining the plasma, the metallic anode 5 connected to the positive pole being disposed 0.5-5 mm above the surface of the solution.
• the plasma 4 gets stabilized after being ignited by spark or any other means at the location of the narrowest inter-electrode gap between the anode 5 and cathode 1.
• the cathode contact connecting to the flowing wastewater film can be made of metal or graphite, but the preferred implementation is an ionic conductor having a conductivity sufficient for carrying the discharge current of 50-100 mA.
• An advantage of establishing the contact through an ionic conductor is that the formation of hydrogen (which would disturb flow stability and deteriorate plasma behaviour) can be avoided.
• a high-conductivity electrolyte solution 5 (preferably a 2-50% solution of a strong acid or its salt) being disposed in a reservoir element 4 behind the cathode contact 7.
• the electrolyte solution 5 is connected to the negative pole of the power supply through a non-corrodible metal electrode 6 (preferably Pt), or a graphite electrode.
• a non-corrodible metal electrode 6 preferably Pt
• a graphite electrode When discharge current passes through the electrode 6 a small amount hydrogen is formed which is vented into the air through port 2 in a safe way.
• the ionically conducting cathode contact 7 can be implemented as a gelatinous closure plug (made e.g. from agar-agar), a solid porous plug (e.g. grass frit, ceramic, etc.), or a hydrophilic membrane saturated with the electrolyte 5.
• the hydrophilic membrane can be a semipermeable membrane (e.g. a cellulose-based membrane, PVC membrane, dialysis membrane), or an ionically conducting membrane containing chemically bonded charged groups.
• 5/b shows an electrolyte-free connection arrangement, where a porous electron-conducting film or mesh 5 (metal or graphite) is mounted on the back of the ion-conducting membrane 7, with the metal electrode 6 being connected to this film or mesh. At the contact of the ion-conducting membrane 7 and electrode mesh 5 hydrogen is formed, which has to be vented out through port 2.
• the advantage of this solution is the electrolyte-free configuration, but it has the drawback of smaller current transfer capability, which makes it necessary to increase conductor cross section.
• the driving force of flow is gravity, in which case no external energy is needed.
• the flow of the flowing film 1 is sustained on the hydrophilic substrate surface 3 (set at an angle ⁇ with respect to the horizontal plane) with the help of continuous infeed 2 by the gravitational force.
• the cathodic contact is established through an ionic conductor 7 and a metallic contact 6 connected thereto.
• the application of the solution utilizing a hydrophilic membrane cover can further lengthen maintenance-free running time by a factor of 10-30.
• the requirement for a hydrophilic substrate surface and the establishment of cathode contact by means of a hydrophilic contact-membrane give a further possibility for providing a quick and automatizable solution for cleansing the discharge area.
• This can be achieved utilizing the arrangement shown in Fig. 6, where the hydrophilic membrane 7 covers the entire flow holding surface of body 3.
• the membrane 7 sticks to the surface of the body 3 due to a slight tensioning, but for the sake of increased safety clamping elements 9 (e.g. spring rollers or rods) can also be applied.
• the wastewater flows along the surface formed by the hydrophilic membrane, which has one of the cathode contacts detailed in Fig. 5 mounted at a suitable location.
• the solution is illustrated in Fig. 6/a by the cathode contact comprising an electrolyte.
• the body 3 need not be made of a hydrophilic material, which means that any chemically resistant and not bulk conducting structural material is suitable.
• the hydrophilic membrane can be slid further into any direction, but preferably into the flow direction of the wastewater sample either in a pre-programmed manner or in case an increase of contamination degree is detected.
• the wastewater sample can be forced to flow in a film-like layer by means of a centrifugal driving force.
• the flow substrate surface is generally a rotationally symmetric surface, with a shape ranging from conical to spherical and even to a rotating disc. Rotating the surface about its axis of symmetry will effectively cause the wastewater introduced at the axis of rotation to spread evenly on the surface, with floating contaminants getting drifted to the periphery of the flow surface due to the significant force acting on them.
• Fig. 3 shows a possible embodiment of the ELCAD cathode with a rotating-body flow guide surface, where wastewater sample is introduced at the top of the rotated conical base body.
• wastewater sample is introduced at the top of the rotated conical base body.
• the wastewater is spread over the entire surface in the form of a liquid film 1, intensively flowing along the surface towards the circumference.
• two solutions are provided, both of which are illustrated by the figure.
• a stationary slip ring 6 made of metal is arranged outside the rim of the surface with a narrow gap in such a way that it is in contact with the entire circumference of the liquid film 1, with the radial-direction flow preventing deposits from getting near the plasma 4 ignited between the anode 5 (disposed leaving a discharge air gap) and the water film. Contaminants building up on the collar electrode 6 can be removed easily.
• a more advantageous (lower-resistance) cathodic contact to the liquid film can be provided utilizing an ionic conductor.
• the ionically conducting liquid-free contact shown in Fig. 5/b is mounted inside a circular channel 7 recessed into the surface of rotating body 3 conforming to the position of the plasma.
• Contact to the electrode is provided through sliding contact 8, with the hydrogen that is formed on the contact being released through bores 9.
• FIG. 4 Another configuration of the ELCAD cathode with rotating-body flow guide surface is shown in Fig. 4.
• the wastewater sample 2 being fed through the rotating tubular axle, is introduced to the top portion of the cone from the interior of the rotating body, with the centrifugal force spreading the sample 2 evenly on the surface in the form of a liquid film.
• the plasma 4 is maintained between the anode 5 disposed axially and the water introduced to the tip of the cone.
• Cathodic contact to the water film can be provided by either one of the two solutions illustrated in the drawing.
• the slip ring 9 is provided to the water passing through the axle tube through a solution-free ionically conducting contact 7 (details of the latter are shown in Fig. 5/b).
• the other solution involves an electrode 8 mounted in the outer surface of the rotating body, with the electrode 8 being connected through a metallic connection to the slip ring 9.
• the main advantage of the arrangement shown in Fig. 4 is that contaminants are removed from the base region of the plasma, and there is no other point on the surface where deposits could be accumulated.
• Fig. 7/a shows preferred position of the slit of the polychromator 3 in the general case when photons emitted by the plasma source 2 are collected by means of an ellipsoid mirror 1. Setting the slit at a non 90 degrees angle with respect to the midline of the light beam requires that the detection slit 5 should be arranged in the polychromator at an oblique position conforming to the image transformation to detect the image provided by the concave grating 6.
• Fig. 7/b shows a preferred arrangement of the prism body 4, indicating light paths. In this case the focusing element and the prism are implemented as a single combined element.

Landscapes

• Health & Medical Sciences (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=89986173

Family Applications (1)

Country Status (3)

Cited By (2)

Families Citing this family (4)

Family Cites Families (9)

• 2005
  • 2005-07-26 HU HU0500715A patent/HUP0500715A2/hu unknown
• 2006
  • 2006-07-26 EP EP06765402A patent/EP1913368A2/de not_active Withdrawn
  • 2006-07-26 WO PCT/HU2006/000061 patent/WO2007012904A2/en active Application Filing

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events