WO2002081385A2

WO2002081385A2 - Means for separating off of heavy metals from polluted water

Info

Publication number: WO2002081385A2
Application number: PCT/DE2002/001188
Authority: WO
Inventors: Eiko Hermann; Frank Dullies; Ingeborg Griebel; Gunter Kieszig
Original assignee: Wismut Gesellschaft Mit Beschränkter Haftung
Priority date: 2001-04-05
Filing date: 2002-04-03
Publication date: 2002-10-17
Also published as: AU2002302335A1; DE10116951A1; DE10116951B4; WO2002081385A3

Abstract

The invention relates to a means for the separating off of heavy metals, metals, arsenic, uranium and radium from polluted water, by means of a reactive material, comprising several components in the form of a titanium oxide hydrate granulate. The separation of heavy metals, metals, arsenic, uranium and radium from polluted water is achieved by means of an agent comprising the components titanium oxide hydrate, bonding agent made from vinyl acetate and hydrogen peroxide. The homogeneous titanium oxide granulate, made from the components, is characterised by a high mechanical and chemical stability and a good permeability to the water for purification and a sufficiently large free surface. The aim of the invention is to produce an effective and economical agent which securely meets, and guarantees or betters legal requirements, regulatory conditions and permitted water conditions regarding the reduction of the concentration of heavy metals, metals, arsenic, uranium and radium over a serviceable life which is as long as possible, removes or adds no other ions from or to the drinking and/or mineral water for removal of toxic contaminants and causes low volumes and costs on the necessary removal and disposal.

Description

Agent for the separation of heavy metals, metals, arsenic, uranium and radium from polluted water

The invention relates to a means for separating heavy metals, metals, arsenic, uranium and radium from contaminated water by a reactive material consisting of several components in the form of a titanium oxide hydrate granulate.

The removal of pollutants, primarily uranium, radium, arsenic, molybdenum and nickel, from groundwater, surface water and seepage water as well as drinking and mineral water is usually carried out according to the same basic principles of precipitation and adsorption. The removal of pollutants from drinking and mineral waters is subject to the requirement that the water composition must not be changed when the pollutants are removed; H. no additional ions have to be introduced or removed into the water to be treated. The contaminated water is treated in special water treatment systems before being discharged into the hydrographic network.

The required setting and cleaning of these waters is a costly, device-intensive and often long-term process. A discharge of the cleaned water into the hydrographic network is only possible if, in addition to water law requirements or specific legal and official regulations and requirements, the requirements of radiation protection (activity concentrations for radionuclides of the natural decay series, especially for uranium and radium) or the limit values of the concentrations relevant heavy metals are observed. For these reasons, high demands are placed on the treatment of contaminated water with radioactive components as well as toxic components containing heavy metals and metals. Radioactively contaminated waters contain radium on the one hand as a natural decay product of uranium in the form of dissolved radium ions and on the other hand it is bound to fine mineral suspended matter. Uranium exists at pH values well above 4.2 in the form of its pH-specific uranyl carbonate complexes. Other metals are present as ions, arsenic as arsenate under oxidative conditions.

The precipitation of the pollutants from the contaminated waters is known to be carried out in several stages, the higher stages of uranium in the order of several milligrams per liter being precipitated as the first stage. The second stage is followed by the Separation of the radium from arsenic is carried out analogously to the removal of phosphate from water with iron salts or adsorbed on the iron hydroxide which forms

According to EP 0071810, the removal of pollutants from contaminated water by means of an ion exchange resin is known. The disadvantages of the process are the necessary regeneration or disposal of the ion exchange resin after the removal of the pollutants and the change in the water composition due to the production-related release of absorbable organochlorine halogens (AOX) of the ion exchange resin in the water to be cleaned

According to US Pat. No. 4,654,200 or US Pat. No. 4,454,097, a further known procedure for separating pollutants from contaminated water is the addition of organic complex-forming reagents, such as EDTA or D2EHPA (DAPEX process). The procedure corresponds to a conventional liquid-liquid extraction The recovery of the organic complexing agents from the treated water is generally difficult, with residual amounts of the organic liquids remaining in the water, since the degree of separation can never be 100%. There is also the disposal problem for the contaminated organic liquids. In the patents US Pat. No. 4,323,007, US 4,636,367, US 4,423,007 and US 4,265,861 describe the use of water-soluble barium salts, in particular barium chloride, for precipitating the radium from contaminated water. In addition to the extensive procedural requirements for the removal of the radium, volumes adapted to the throughput are de r Containers for precipitation and sedimentation, the addition of a polymeric flocculant to bind the very fine Ba (Ra) SO ₄ particles as well as the separation, treatment and disposal of the radioactive fall products obtained Disadvantages of the process

The use of so-called permeable reactive walls (PRW) is known for the in situ treatment of contaminated water.The PRW consist of layers of one or more water-permeable reactive or adsorption-active media.The pollutants are adsorptively bound, oxidized, reduced or precipitated when flowing through (rigid, RC , Cherry, JA, In-situ remediation of contaminated Ground Water The Funnel-and-Gate System - Ground Water 32 (3) S 465 - 476)

In Melzer, R, Weth, D, use of a reactive wall for the remediation of a LHKW damage in North Rhine-Westphalia - status report on the progress of the refurbishment project, in IWS-series, Vol 28, S 357 - 361 the use of metallic iron as PRW for in situ removal of Pollutants from groundwater for organic pollutants, e.g. B. described in LHKW dehalogenation.

The effectiveness of the passive systems used depends on their implementation costs, essentially the costs for the reactive material and the service life, i.e. H. the time in which the system eliminates the pollutants from the water. The service life is determined by the type of ions to be eliminated and the level of pollutants in the water to be cleaned. If the pollutants are separated off by precipitation, the precipitation products displace the pores of the reactive material, as a result of which, after a given time, it becomes impermeable to water and thus ineffective for the task to be performed.

If the separation of the pollutant ions is carried out by adsorption on a suitable adsorption-active medium, the free surface available, i. H. the grain size distribution of the material used is of crucial importance. The precipitation of water-insoluble carbonates or sulfates in the reactive material usually represents a limitation that questions the use of the material. On the one hand, if the fineness of the reactive material is too low, the flowability is no longer guaranteed after a short time, or on the other hand, if the pore volume is too small, the absorption capacity of the reactive material for the pollutant ions is unacceptably low. It is therefore necessary to find a compromise between the free surface of the adsorption-active medium available for the adsorption and the available pore volume for the flow through the adsorption-active medium.

A similar problem with very special boundary conditions occurs when removing pollutants from drinking and / or mineral water. The special conditions are that no additional ions may be introduced or removed. This basically eliminates all precipitation processes and only adsorption onto a reactive medium is conceivable, which acts as a quasi-mechanical filter without other ions being taken up or released. The addition of barium chloride is not suitable for the removal of radium from drinking and / or mineral water. An alternative is the use of natural mineral barium sulfate (barite). Although it is generally known that the radium precipitation with inclusion in the barium sulfate takes place immediately after the addition of the barium chloride, the kinetics of an experimental radium precipitation with a deficit of barium chloride (only part of the radium is also precipitated) shows that the precipitation is completed in the seconds range the specific activity of radium in the solution was further reduced over a period of several hours. This is due to adsorption of the radium on the barium sulfate precipitate. Natural, inexpensive barium sulfate (barite) is obtained from barite ore by crushing the ore to an upper grain size of less than 0.5 mm and usually has an upper grain size of less than 0.3 mm. This dust-fine material is almost impossible for water to flow through. The production of coarser, flowable barite fractions is associated with considerable additional costs and the surface is reduced in the second power with the diameter of the particles. Since the absorption of radium on barite takes place very slowly, a large free surface is naturally necessary, so that this material is not suitable for the removal of radium.

Furthermore, methods are known for removing pollutants from contaminated waters, which generally remove only individual pollutants or heavy metals from the waters.

In Langmuir, D., Geochim. Cosmochim. Aca 42, 547-569 (1978) and Venkataramani, B .; Ventatswarlu, K. S .; Shankar, J. III. J. Colloid Interf. Be. 67 (2), 187-194 (1978) describes investigations for the in situ remediation of radionuclide-containing water, which are, however, only carried out on a laboratory scale. The transfer to specific applications only took place in the 1990s. According to Morrison, S. J .; Spangler, R.R., Environ. Be. Technol. 26 (10), 1922-1931 (1992) various industrial products, e.g. B. hydrated lime, fly ash, titanium oxide, lignite, peat and hematite, used to separate pollutants in waste water from uranium ore processing.

Also known are studies on the use of organic materials in "biological" reaction barriers for the remediation of contaminated groundwater in the field of uranium mining (Shiprock, NM, USA) by Thombre, M. S .; Thomson, B. M .; Barton, L.L., Int. Conf. On Containment Technology, St. Petersburg, Abstract, p. 71, Florida, (Feb. 1997). Cellulose, wheat straw, alfalfa hay, sawdust and soluble starch compounds are tested as the reactor material. For the purification of acidic mine water, biotechnological approaches exist as on-site technology (Somlev, V .; Tishov, S., Geomicrobiology Journal, 12 (1), 53 - 60, (1994)). With a reaction material made of an easily degradable organic substance and Fe (0) as the carrier material, degradation or fixation of heavy metals is achieved.

After Blowes, DW; Ptacek, CJ; Benner, S.G. Waybrant, KR; Bain, JG, Uranium Mining an Hydrogeology II, Proceedings of the Unt. Conference, Freiberg, Germany, (1998) are investigations of mixtures of different organic materials for the treatment of acid mine- known water. The mixtures of compost, leftover wood and limestone used caused a decrease in the concentration of heavy metals in the downstream. Disadvantages of the materials described last are:

- the restricted use of the materials on individual pollutants or heavy metals,

- No suitability for the simultaneous cleaning of the contaminated water and unproblematic separation of heavy metals, metals, arsenic, uranium and its natural decay products, so there is a need to use other conventional methods and materials for cleaning the contaminated water.

The object of the invention is to provide an effective and inexpensive means for separating heavy metals, metals, arsenic, uranium and radium from contaminated water,

- which has a very high mechanical and chemical stability and a very large internal surface area, as well as a high absorption capacity for these pollutants,

- that safely meets and guarantees or undercuts the legal requirements, official requirements and water law requirements with regard to the reduction of the concentrations of heavy metals, metals, arsenic, uranium and radium,

- that the concentrations of heavy metals, metals, arsenic, uranium and radium are reduced to values that allow the water to be discharged into the receiving water with official approval,

- that reliably removes heavy metals, metals, arsenic, uranium and radium over the longest possible service life,

- that if contaminants are removed from drinking and / or mineral water to be purified, no additional ions are absorbed or released into the water after pretreatment,

- That eliminates the additional use of other conventional processes and materials for the necessary separation of other pollutants and

- That causes small amounts and costs when disposal and landfill are required.

According to the invention, the object is achieved by a means for separating heavy metals, metals, arsenic, uranium and radium from water contaminated with pollutants by means of a reactive material consisting of several components, which comprises a homogeneous mixture in the form of a titanium oxide hydride. rat granules from titanium oxide hydrate with a mass fraction of 80% to 95%, adhesive based on vinyl acetate with a mass fraction up to 15% and hydrogen peroxide with a mass fraction up to 5%. First the components are mixed, then the homogeneous mixture is filled into flat containers for drying at 50 ° C. to 95 ° C. for 10 to 30 hours and then annealed at 110 ° C. to 140 ° C. for up to 2 hours. After cooling, the raw material is broken and classified.

The agent produced according to the invention has a structure which ensures good flow-through for the water to be cleaned as well as a sufficiently large free surface. Titanium oxide hydrate, which would be infinitely diluted and rinsed out of the water in the state of a suspension, is brought into a water-resistant structure by the described means, which ensures a maximum capacity of the reactive material and the flowability. By adding hydrogen peroxide, the titanium oxide hydrate mixture is foamed, an additional enlargement of the outer surface is achieved and a highly porous solid is produced.

By subsequently breaking the tempered titanium oxide hydrate mixture and classifying it, depending on the application, granules can be produced with any grain size or grain size distribution. The oversize particles that occur during classification are broken again and the undersize particles are returned to the production of the titanium oxide hydrate mixture. In this way, no significant material losses occur during the manufacture of the agent. To separate pollutants from the polluted waters, the homogeneous mixture in the form of titanium oxide hydrate granules is introduced into naturally existing and / or technically created cavities in the flow paths of the waters and / or in technical facilities to which the waters are supplied.

Before the removal of pollutants from drinking and / or mineral waters, the homogeneous mixture in the form of a titanium oxide hydrate granulate is washed in a water bath and adjusted to a pH value of the titanium oxide hydrate granulate of 7 before drying in order to release measurable ion concentrations in to prevent the treated water.

The described means produces an effective and inexpensive material that has significant environmental and economic advantages over known means. These advantages are that: the agent has a high mechanical and chemical stability and a large inner surface,

- the medium has a high absorption capacity for heavy metals, metals, arsenic, uranium and radium and therefore has a long service life,

- there is a granular agent classified in a narrow grain class range, the grain size of which is adapted to the flow conditions in the naturally existing and / or technically created cavities and / or in the technical facilities and any precipitations of neutral salts (e.g. sulfates, carbonates) that occur Choice of a suitable grain size distribution can be compensated,

the strength of the structural material and the previous classification ensure that no abrasion occurs when the granular agent is installed, which can lead to a displacement of the pore spaces,

- that no additional ions are taken up or released into the water to be treated,

- that the legal requirements, official requirements and water law requirements with regard to the reduction of the concentrations of heavy metals, metals, arsenic, uranium and radium are safely met and guaranteed or undercut,

- due to the high absorption capacity of the agent with regard to heavy metals, metals, arsenic, uranium and radium, the volume of the material layer to be introduced can be kept significantly lower than with other materials that are also suitable for the separation of pollutants or the service life can be increased significantly with the same material layer thickness,

- the additional use of other conventional means and processes can be omitted and

- The volume or the mass of the agent used in the case of necessary disposal and landfill, because of the significantly higher absorption capacity of the agent compared to comparable materials, has significantly lower volumes and costs

embodiment

The example describes a laboratory test of treating a water in a glass column with a titanium oxide hydrate granulate. The water has an arsenic concentration of 1000 μg / l The titanium oxide hydrate granules used in this experiment have the following composition and grain size class:

- Titanium oxide hydrate with a mass fraction of 90%

- Vinyl acetate-based adhesive with a mass fraction of 9%

- hydrogen peroxide with a mass fraction of 1%

- Grain size class of the granules used 0.5 mm to 2.0 mm. The following parameters were set during the test:

- Weight of the titanium oxide hydrate granules 43 g

- Volume of the titanium oxide hydrate granules 94.5 ml

- Height of the flowed layer 16.5 cm

- Diameter of the glass column used 2.7 cm

- Arsenic concentration in raw water 1000 μg / 1

- water temperature 20 C.

The following results were achieved:

- 458 days until fully loaded

- Average arsenic loading of the granules 21 mg / g

- total treated water volume 1098 liters

- Exceeding 5 μg / 1 arsenic in the course of 154 days or 368 liters

- Exceeding 50 μg / 1 arsenic in the course of 238 days or 570 liters

- Exceeding 500 μg / 1 arsenic in the course of 354 days or 846 liters.

The results show very impressively that with an arsenic concentration of 1000 μg / 1 in raw water, the limit value for arsenic in drinking water of 50 μg / 1 is only reached after a run of 570 liters. Converted this means that under the selected test conditions (raw water with 20 times the arsenic concentration of the drinking water limit) approx. 13.3 m ^{3 of} water with arsenic concentrations lower than the drinking water limit can be cleaned with 1 kg of titanium oxide hydrate granules.

Claims

claims

1 means for the separation of heavy metals, metals, arsenic, uranium and radium from polluted water by a reactive material consisting of several components, characterized in that a homogeneous mixture in the form of a titanium oxide hydrate granules of titanium oxide hydrate with a mass fraction of 80% to 95%, Vinyl acetate-based adhesive with a mass fraction of up to 15% and hydrogen peroxide with a mass fraction of up to 5% are produced, the components being mixed first, after which the homogeneous mixture is dried for 10 to 30 hours at 50 ° C. to 95 ° C. flat containers filled, then annealed for up to 2 hours at 110 ° C to 140 ° C and finally broken and classified after cooling

2 Means according to claim 1, characterized in that the homogeneous mixture in the form of a titanium oxide hydrate granules in naturally existing and / or technically created cavities in the flow paths of the water and / or in technical facilities to which the water is supplied to separate pollutants contaminated water is introduced

3 means according to claims 1 and 2, characterized in that before the removal of pollutants from drinking and mineral water, the homogeneous mixture in the form of a titanium oxide hydrate granules washed in a water bath and to a pH of the titanium oxide hydrate granules of 7 before drying is set