ES2360784T3 - CONTACT GRANULES AND ADSORBENTS. - Google Patents

Abstract

Process for manufacturing an adsorption agent / reaction agent, characterized in that (a) iron oxyhydroxides of the α-FeOOH phase are mixed in solid, semi-solid or suspended form by the addition of Fe (OH) 3 in suspension or in the form of gel with variable water contents, Fe (OH) 3 can also be generated in situ from Fe (lll) and neutralization salt solutions, and then (b1) or the suspension is dried to obtain a solid state and solid material Then, it is mechanically crushed to the desired shape and / or size, or (b2) the suspension, if necessary after a pre-drying in a semi-solid state, is subjected to a mechanical conformation and then (additionally) to drying, obtaining a solid state,

Description

The present invention relates to a process for manufacturing an adsorption agent / reaction agent, characterized in that

(a) iron oxyhydroxide of the α-FeOOH phase is mixed in solid, semi-solid or suspended form by adding Fe (OH) 3 in suspension or in gel form with variable water contents, Fe (OH) can be generated 3 also in situ from Fe (lll) and neutralization salt solutions, and then

(b1) either the suspension is dried to obtain a solid state and the solid material is then mechanically ground into the desired shape and / or size, or

(b2) the suspension, if necessary after pre-drying to a semi-solid state, is subjected to a mechanical conformation and then (additionally) drying, obtaining a solid state,

to the adsorption agents / reaction agents that can be obtained according to the above-mentioned process as such, which are further characterized in that the needles of the α-FeOOH type of amorphous layers are adhered to each other; to apparatus containing the adsorption agents / reaction agents mentioned above, as well as to the use of the adsorption agents / reaction agents and the apparatus mentioned above for the purification of gases and liquids.

Contact granules and adsorbents, also those that are based on iron oxide and / or iron oxyhydroxide, have already been described. They are mainly used in continuous procedures, usually found in tower or column type apparatus through which the medium to be treated circulates, and the chemical reaction or adsorption processes

or physical take place on the inner and outer surface of the granules. To this end, materials in powder form cannot be used, as they are compacted in the direction of flow of the medium and, thereby, increase the resistance to flow until the apparatus is locked. If a device is cleaned by backwashing (see below), large amounts of dust are discharged or lost, or cause an intolerable load of wastewater.

The circulating means also exert, however, forces on the granules, which can cause abrasion and / or movement until the agitation of the granules is intense. Therefore, the granules collide with each other and, as a consequence, unwanted abrasion wear is generated. This causes a loss of contact material or adsorbent and a contamination of the medium to be treated.

They are advantageously used, for example, in the field of water purification or gas purification, adsorption agents / reaction agents containing iron oxide and iron hydroxide. In the case of water purification, this agent is used in absorbent filters or columns with horizontal or vertical circulation or by adding to the water to be treated for the separation of compounds, organic or inorganic, dissolved, suspended or emulsified phosphorus , arsenic, antimony, sulfur, selenium, tellurium, beryllium, cyanocomposites and heavy metal compounds of drinking water, drinking water, industrial and domestic wastewater, mineral water, holy water and medicinal water, as well as in river water, garden pond water and water for agricultural use. It is also possible to use those known as reactive walls for the separation of contaminants from soils and infiltration water pipes from contaminated sites (landfills).

In the case of gas purification, the agent is used in adsorbers for binding to unwanted constituents such as sulfuric acid, mercaptans and cyanhydride acid, as well as phosphorus, arsenic, antimony, sulfur, selenium, tellurium compounds, as well as cyanocomposites and heavy metal compounds in exhaust gases. It is also possible to adsorb gases such as HF, HCl, H2S, SOx, NOx.

It is also possible to eliminate phosphorus, arsenic, antimony, selenium, tellurium compounds, as well as cyano compounds and heavy metal compounds from used oils and other contaminating organic solvents.

Contact granules and adsorbents based on iron oxides and / or iron oxyhydroxides are also used for catalysis of gas or liquid phase chemical reactions.

Methods of different types for removing trace elements and contaminants from aqueous systems using adsorption agents are also known.

Thus, in DE-A 3 120 891 a process is described in which, for the separation, particularly, of surface water phosphates, filtration is carried out through active alumina with a granulation of 1 to 3 mm.

DE-A 3 800 873 describes an adsorption agent based on porous materials such as, for example, hydrophobicized crete with a fine to medium granulation, for the removal of water contaminants.

In DE-A 3 703 169 a process for the manufacture of a granulated filter material for treating natural water is disclosed. The adsorbent is manufactured by granulating an aqueous kaolin suspension with the addition of dolomite in powder form in a fluidized bed. Next, the granules are calcined at 900 to 950 ° C.

From DE-A 40 34 417 a process is known for manufacturing and using reagents with high reactivity for the purification of exhaust gases and wastewater. This document describes mixtures of Ca (OH) 2 with clay additives, rocks in powder, volatile powder and volatile ash, which are manufactured with a porous shape and have an area of approximately 200 m2 / g.

The mentioned procedures or the contact agents used in said document have the general disadvantage that the corresponding components responsible for the selective adsorption of constituents of the media to be purified, that is, the true adsorbents, must be added with high amounts of aggregates, to allow a conformation to granules. This greatly reduces the ability to bond with aqueous contaminants that must be removed. In addition, subsequent processing or reuse of the material is problematic, since the foreign substance used as a binder must first be separated again.

In DE-A 4 214 487 a process and a reactor for removing contaminants from water are described. A funnel-shaped reactor, in which, as a sorbent for aqueous contaminants, iron hydroxide distributed in the form of flakes is used, has a horizontal circulation. The disadvantage in this process is the use of iron hydroxide in flakes, since due to the small difference in density between water and iron hydroxide, it results in a reactor of this type can only operate with flow rates very low and there is a risk that the sorbent, if already loaded with contaminant, is discharged from the reactor along with the water.

JP-A 55 132 633 describes granulated red sludge as a byproduct of aluminum production as adsorbent for arsenic. This is composed of Fe2O3, Al2O3 and SiO2. The stability of the granules and the granulation procedure is not reported in said document. Another disadvantage of these adsorbents is the lack of constancy of the composition of the product, the lack of security of availability and the possible loading with aluminum of the drinking water. Since it is suspected that aluminum favors the onset of Alzheimer's disease, contamination with it should be especially avoided.

A process for manufacturing an adsorption agent containing iron hydroxide is described in DE-A 19 826 186. A polymer dispersion is mixed with iron hydroxide in water in a dispersible form. This mixture dries well, obtaining a solid state, and the solid material is then mechanically ground into the desired shape and / or size or the mixture, if necessary after drying, is subjected to a shaping and, then, it has just dried obtaining a solid state. This results in a material in which iron hydroxide is solidly embedded in the polymer and must have a high binding capacity for contaminants included in wastewater or exhaust gas.

The disadvantage of this procedure is the use of organic binders, which additionally charge the water to be treated by erosion by washing and / or abrasion wear of organic substances. In addition, stability is not guaranteed with the long-term use of the combination of adsorbents. In addition, bacteria and other microorganisms can use an organic binder as a feeding medium, so that there is a risk of colonization of contact with microorganisms and contamination of the medium by them. Basically, the presence of other auxiliary substances necessary for the manufacture of adsorbents in the processing, recycling or reuse of used adsorbents presents a disadvantage, since the use of pure substances is less problematic than the use of substance mixtures As in this case. Thus, for example, polymeric binders in the reuse of iron oxide based adsorbent materials such as concrete coloring pigments have the disadvantage that these binders can prevent the dispersion of the pigment in the liquid concrete.

In DE-A 4 320 003 a process for removing arsenic dissolved in groundwater by means of granulated or colloidal iron hydroxide is described. For the use of fine, suspended iron (II) hydroxide products, it is recommended in said document to introduce the iron hydroxide suspension in solid bed filters, which are filled with the granulated material or other vehicles with high external or internal porosity . This procedure also has the disadvantage that, due to the adsorbent "substrate + iron hydroxide", only reduced specific loading capacities can be achieved. In addition, there is only a weak bond between the substrate and iron hydroxide, so that in a subsequent treatment with arsenic-containing water there is a risk of discharging iron hydroxide

or iron arsenate. This publication also mentions the use of granulated iron hydroxide as an adsorbent material for a solid bed reactor. The manufacture of the granulated iron hydroxide is carried out by means of a freezing (lyophilization) conditioning of iron hydroxide obtained by neutralizing acidic solutions of iron (III) salts at temperatures below 5 ° C. This manufacturing process consumes a large amount of energy and generates a wastewater very charged with salts. In addition, as a result of this manufacturing process only very small particles with reduced mechanical stability are obtained. This causes, in the case of using a solid bed reactor, that the particle spectrum by mechanical abrasion of the particles is clearly reduced over the course of the operation, which again has the consequence that the finely dispersed particles are discharge from the reactor with the adsorption agent charged or not charged. Another disadvantage of this granulate is that the adsorption capacity against arsenic compounds is greatly reduced if the granulate, for example, due to a longer drying period, loses water.

From US-A-5,948,726, adsorbent / binder systems have been disclosed which are obtained by extracting from a mixture of (a) a binder capable of cross-linking from metal oxides or metalloids, (b) oxidizing adsorbents as metalloid oxides and (c) an acid a sufficiently large amount of water, so that components (a) and (b) are crosslinked forming an adsorbent / binder system. As shown in the embodiments, an alumina or colloidal aluminum oxide is used as a binder.

The disadvantage of this composition is that for its manufacture it is necessary to use acid (column 9, row 4) as well as the fact that it is not a pure substance, but heterogeneous, which is undesirable for manufacturing, regeneration , disposal or definitive storage of adsorbents of this type, for example, in a landfill. Adsorbents that are suitable for arsenic adsorption should also be included in the scope of the disclosure of this publication, but no concrete examples are presented. It is known that aluminum oxide is clearly inferior with respect to the adsorption strength for arsenic to iron oxides.

For water treatment, adsorbents that operate continuously, which frequently operate in parallel oriented groups, are preferably used. For example, to release water from organic pollutants, adsorbent of this type is fed with activated carbon. At the time of maximum use, the adsorbents present operate in parallel, to allow the flow rate not to exceed the maximum allowed. During periods of reduced water use, the adsorbents are removed separately from the operation and can be kept on hold, meanwhile, for example, by fixing the adsorbent material at special loads, as explained in detail below. The use of granules has also been considered, which can be generated by compacting, for example, iron oxide in powder form by using high linear forces. Granules of this type have already been described to homogeneously color liquid concrete. The use of high linear forces in compaction consumes a great deal of energy and is expensive and the stability of the compacting is insufficient in case of long-term use of the adsorbent. Therefore, the use of adsorbents of this type is considered, in particular in continuous operation, for example, for water purification, only to a limited extent. In particular, for the maintenance or purification of adsorbent installations by backwashing (see below), granules of this type lose, due to the agitation thereof associated with it, large amounts of substance. The backwash wastewater becomes heavily clouded due to abrasion. This is unacceptable for several reasons: First, adsorbent material is lost, which is heavily loaded with contaminants after a long period of operation and, therefore, is toxicologically worrying. In addition, the wastewater stream is loaded with the material produced by abrasion wear, which can sediment and thus cause a detrimental effect on the conduction system, and finally, the purification facility is physically and undesirably charged. Toxicologically, to mention just a few reasons.

The present invention is based, therefore, on the objective of providing an adsorption agent / reaction agent based on pieces of iron and oxygen in the form of pieces having a high mechanical stability together with a high binding capacity with the Contaminants included in liquids and gases without organic binders or binders of different inorganic types to be used to obtain sufficient mechanical stability or facilities operating with such media.

The contact or adsorption agents / reaction agents according to the invention, their provision, their use, as well as the apparatus that is fed with them, solve this objective complex.

In this regard, it is an iron oxyhydroxide embedded in a polymer of Fe (OH) 3, a material that in the α-FeOOH phase, as experiments have shown, has a high binding capacity with contaminants frequently present in water waste or exhaust gases and without the addition of organic binders or other inorganic substances with binder function already has sufficient mechanical and hydraulic stability.

Because this material is free of binders of another type, it has the advantage of adsorbents of the prior art, in addition, the advantage that if necessary after separation or removal of adsorbed contaminants, it can be removed as a whole or used for other applications, such as after crushing for the coloring of concrete and other building materials, as well as customary uses of pigments in paints, dyes and varnishes or for coloring other substrates such as crust padding or crushed wood.

The material according to the invention is obtained by mixing iron oxyhydroxide of the α-FeOOH phase in solid or suspended form by adding Fe (OH) 3 in suspension or in gel form with variable water contents and of this mixture, then , the water is removed, totally or with maintenance of a certain amount of water, for example, by filtration or evaporation, and the solid or semi-solid material is then mechanically crushed in the desired shape and / or size, or the dispersion it is subjected, if necessary, after drying to a semi-solid state, to a mechanical conformation and then (additionally) to drying, obtaining a solid state. In this regard, iron oxyhydroxide is solidly embedded in the polymer of Fe (OH) 3. Fe (OH) 3 can also be obtained in situ from salt solutions of Fe (lll) and neutralization. Preferably, the base remaining in the manufacturing process of the suspended pigment is reacted for this purpose with an equivalent amount of Fe (III) salt. The iron hydroxide (OH) 3 is, in an initial state, preferably in an aqueous-pasty form, the paste being able to present almost discretionary amounts of water, generally between 10 and 90% by weight, preferably between 40 and 70 % in weigh. Freshly prepared Fe (OH) 3 iron hydroxide can also be used, which has been obtained by precipitation of the iron (III) salt solution. The elimination of water by evaporation is preferably carried out later, if the suspensions from which the water is to be removed are largely free of salt and / or less high demands on the mechanical stability in operation have been established on the final product obtained.

Alternatively, water is removed by filtration. In this regard, it is possible to improve the filtration behavior of the suspensions by applying measures that improve filtration, such as those described, for example in Solid-Liquid Filtration and Separation Technology, A. Rushton, AS, Ward RG., Holdich, 2nd. 2000 edition, Wiley-VCH, Weinheim and Handbuch der Industiellen Fest / Flüssig-Filtration, H. Gasper, D. Öchsle, E. Pongratz, 2nd edition 2000, Wiley-VCH Weinheim. In this way, flocculation agents are added to the suspensions, for example.

The adsorption agents / reaction agents according to the invention can be subjected to air and / or vacuum drying and / or in a drying cabinet and / or in a continuous-pass dryer or in a temperature-spray dryer which are in the range of 5 to 300 ° C. A lyophilization of the material is also possible.

The adsorption agents / reaction agents according to the invention preferably have a residual water content of less than 20% by weight.

The crushing of the material is preferably carried out by grinding to give particles of a size in the range of 0.5 to 20 mm. The mechanical conformation of the semi-solid material preferably takes place in a pelletizing or pelletizing installation or in an extruder, with molded bodies having a size in the range of 0.5 to 20 mm in diameter or length can be obtained.

It has been found that the fragments or granules obtained in this way have a binding capacity with contaminants present in water, liquids or gases and, in addition, have a sufficiently high stability against fluid media with respect to their mechanical or hydraulic stress.

It is particularly surprising that iron oxyhydroxides treated with Fe (OH) 3 are compacted into very hard drying agglomerates, which have high resistance to mechanical abrasion and high hydraulic stability against contact with circulating water without the addition of binders, and that have a high binding capacity with contaminants and trace elements present in the water.

Goethite iron oxyhydroxide pigments are suitable for use according to the invention. The preparation of iron oxide pigments is in the state of the art; they are obtained by precipitation and oxidation reactions and from Penniman from iron (II) salt solutions and iron hydroxide by precipitation from iron (III) salt solutions.

The product has a BET area of 50 to 500 m2 / g, preferably 80 to 200 m2 / g.

The primary particle size was determined by measurements by scanning with the scanning electron microscope, for example, with an increase of 60000: 1 (apparatus: XL30 ESEM FEG, Philips company). If the primary particles are needle-shaped, such as, for example, in the α-FeOOH phase, the width of the needle can be indicated as a measure of particle size. A needle width of 100 nm is observed for α-FeOOH nanoparticles, however, mainly between 4 and 50 nm. The α-FeOOH primary particles usually have a length: width ratio of 5: 1 to 50: 1, typically 5: 1 to 20: 1. By endowment or a special embodiment of the reaction, however, the length: width ratio of the needle shapes can be varied.

By mixing Fe (OH) 3 with iron hydroxides, the existence of the crystalline pigment or germ particles in their known particle morphology, which are held together with each other or is observed in the scanning electron microscope. they are adhered to each other by means of the amorphous Fe (OH) 3 polymer.

Yellow iron oxyhydroxide pigments are generally synthesized by precipitation of hydroxides

or iron (II) carbonates from the corresponding iron (II) salt solutions such as, for example, FeSO4, FeCI2, in pure form or as pickling solutions, in an acidic or basic pH range, and thereafter oxidation in iron (III) oxyhydroxides (see, among others, G. Buxbaum, Industrial Inorganic Pigments, VCH Weinheim, 2nd edition, 1998, page 231 et seq.). The oxidation of divalent or trivalent iron is preferably carried out with air; In this regard, intensive gasification is an advantage. Also oxidation with H2O2 results in iron oxyhydroxides. As the precipitation agent, preferably, NaOH is used. However, other precipitation agents, such as KOH, Na2CO3, K2CO3, CaO, Ca (OH) 2, CaCO3, NH3, NH4OH, MgO and / or MgCO3, can also be used.

By means of the appropriate choice of the precipitation and oxidation conditions, an α phase of iron oxyhydroxide nanoparticles having a high specific surface can be obtained, such that the nanoparticles agglomerate in a dry state and have a high stability in crushed form. against mechanical abrasion and fluid mechanics. To control precipitated pigments in the sense of a necessary high fine distribution, precipitation, for example of yellow α-FeOOH, as described in US-A 2 558 303 and US-A 2 558 304, they perform in the basic pH range with alkali carbonates as precipitating agents and generally adding modifiers, such as, for example, SiO2, zinc, aluminum or magnesium salts, hydroxycarboxylic acids, phosphates, metaphosphates. Products obtained in this way are described in USA 2 558 302. Such crystalline germ modifiers do not prevent further processing, recycling or other use of different types of adsorbents according to the invention. In precipitation procedures in aqueous media, precipitation in basic media results in agglomerated powders less hard than those made in acidic media, according to current knowledge.

However, crystallization germ modifiers have the advantage, among others, that at high reaction temperatures they can achieve a sufficiently fine distribution on their own.

Against the state of the art, in the case of the products described, the procedure for its preparation and its use have an improvement. The adsorption agents / reaction agents according to the invention can be loaded much more than those of the state of the art and therefore have superior abrasion stability against mechanical and hydraulic stresses. They can be used directly as such. In the crushing or grinding of the pure dry substances obtained below, from filter cakes or extruders, a purification of water can be avoided, for example, in the use of adsorbent plants, since the thick pieces are broken down by themselves in case of contact with water. In this case a statistical distribution of grain size appears; however, no particle of a size that is discharged in considerable quantities through the medium in circulation from the adsorber.

In a separate granulation, as would be necessary in the use of conventional oxyhydroxides in powder form (loose), either by using binders other than the substance or high linear forces in compaction, it can be totally avoided.

As another procedure for obtaining a granulate, the effectiveness of granulation of a semi-liquid paste has been tested. In this regard, pellets or bars are formed from a semi-solid paste, for example using a simple perforated sheet, a roller press or an extruder and these are dried either similarly or this extrudate is carried by means of a spheronizer. , additionally, to a ball or granule shape. The still wet pellets or pellets can be subsequently dried to a discretionary moisture content. With this, the granules do not agglutinate, with a residual moisture content <50% being recommended. Such a ball shape may be advantageous for the use of solid bed adsorbents due to the improved loading in this way in adsorbent containers against crushed granules or stick-shaped pellets.

The amounts used in accordance with the invention of iron oxyhydroxides or iron oxides, on the one hand, and iron hydroxide, on the other, are determined by the requirements on the product manufactured according to the invention with respect to its stability Mechanical and abrasion resistance. A high content of pigments (in powder form) certainly reduces, generally, the mechanical stability of the products according to the invention, facilitating, however, the filtration of the suspensions. The expert in the corresponding application sectors can determine the optimal mixing behavior for the application purposes by a few targeted tests.

Particularly preferably, the adsorption agents / reaction agents according to the invention are used for the purification of liquids, in particular for the removal of heavy metals. A preferred application in this technical field is the decontamination of water, in particular drinking water. Some time ago, the removal of arsenic from drinking water gave special attention. The granules according to the invention are very suitable for this, because the limit values established by the United States EPA administration by using the granules according to the invention are not only respected, but can even be lowered.

For this purpose, the adsorption agents / reaction agents can be used in conventional adsorption apparatus, as currently used, for example, fed with activated carbon, for the removal of contaminants of another type. A batch operation is also certainly possible, for example in tanks or similar containers, which if necessary are equipped with stirrers. However, use in continuous operating facilities such as step adsorbers is preferred.

Because the water treated for drinking water usually also contains organic pollutants such as algae and similar organisms, the surface of the adsorbents is covered, in particular the outer surface of adsorbents in the form of granules, during use, with sediments in mostly viscous, which hinder or completely prevent the entry of water and, with it, the adsorption of the components to be removed. For this reason, the adsorber devices are washed countercurrently from time to time with water, which is preferably carried out during periods with reduced water consumption (see above), individually, in the appliances removed from service. In this regard, the adsorbent according to the invention swirls, and by the mechanical stress of the implicit surface, the unwanted coating is removed and discharged against the direction of the fluid in useful operation. Washing water is usually fed to a purification facility. In this regard, the adsorbents according to the invention are preserved in a particularly good way, since their high stability allows a purification in a short period, without significant losses of adsorbent material being recorded or the backwashing water fed to the Waste water is enriched with expelled adsorbent material, if necessary, already heavily loaded with heavy metals.

Because the granules according to the invention are free of binders of a different type, the material is easily removed in a similar manner after use. Thus, the adsorbed arsenic can, for example, in special apparatus, be removed thermally or chemically, obtaining an iron oxide pigment as pure material, which is either recycled for similar application purposes or can be supplied for conventional pigment applications. Depending on the application and legal determinations, the content of the adsorber can also be used without prior removal of heavy metals, for example, as a pigment for coloring long-lasting building materials such as concrete, because the heavy metals extracted from it Drinking water mode are immobilized in the long term and extracted from the water cycle.

Therefore, also the water treatment facilities or the water supply plants, in which it is operated with apparatus coated with the granules according to the invention are also object of the present invention, as well as the procedures for decontamination of water using devices of this type and the devices themselves.

The determination of the specific surface of the products according to the invention according to BET is carried out by means of carrier gas processes (He: N2 = 90: 10) according to the one-point procedure, in accordance with DIN 66131 (1993). For measurement, the sample is heated 1 hour at 140 ° C in a stream of dry nitrogen

To measure the adsorption of arsenic (II) and arsenic (V), a 5-liter PE bottle is treated for a given period of 3 l of an aqueous solution of NaAsO2 or Na2HAsO4 with the corresponding initial indicated concentrations of 2-3 mg / 1 arsenic with 3 g of the sample to be analyzed and, in this regard, the bottle is added to a rotating roller. The adsorption rate of As ions on iron hydroxide during this given period, for example one hour, is indicated with mg (As3 + / 5 +) / g (FeOOH) · from the difference with As3 + / 5 + ions Remnants in solution.

The adsorption of Sb3 +, Sb5 +, Hg2 +, Pb2 +, Cr6 +, Cd2 + ions is measured according to the same sample and, specifically, the desired concentrations are prepared by dissolving the corresponding amounts of Sb2O3, KSb (OH) 6 , PbCI2, NaCrO4, CdCI2 in H2O and the pH value is adjusted to 7-9.

The contents in As, Sb, Cd, Cr, Hg or Pb of the charged iron hydroxide or solutions are determined by mass spectroscopy (ICP-EM) according to DIN 38406-29 (1999) or by optical emission spectroscopy (ICP-OES) according to EN-ISO 11885 (1998) with the corresponding inductive coupled plasma as an activation unit.

The mechanical and hydraulic abrasion resistance is evaluated according to the following procedure: 10 g of the granulate to be analyzed were introduced, with a grain size> 0.1 mm in a 500 ml Erlenmeyer flask with 150 ml of demineralized water in a LabShaker shaker (Modell Kühner, Braun company) for a period of 30 minutes with a rotation of 250 revolutions per minute. Next, the portion> 0.1 mm is isolated from the suspension by means of a sieve, dried and weighed. The weight ratio between the weighing out and the weighing determines the value of abrasion wear in%.

The invention will be explained in detail below by an example. The example should serve as an illustration of the procedure and does not represent any limitation

525 g of a suspension of a needle-shaped pigment powder of α-FeOOH (50 g / l FeOOH, Bayfer-rox® 920, Bayer AG, Leverkusen, Germany) was added to 800 g of a FeCI3 solution ( 100 g / l) and by adding 247 g of an aqueous solution of NaOH (24%) an iron hydroxide was formed on the pigment. The suspension was filtered through a vacuum filter, the filter cake with a residual conductivity of the filtrate of 1 mS / cm was washed and the filter cake was then dried in a drying cabin at 75 ° C. The very hard material was crushed, then giving a granulate with grain sizes between 0.2 and 2 mm. The specific surface area according to BET amounted to 64 m2 / g. By scanning with the scanning electron microscope, for example with an increase of 60000: 1, it was observed that the needles of the α-FeOOH type of amorphous layers are adhered together or agglomerated. The adsorption rate with respect to an aqueous solution of NaAsO2 with an initial concentration of 2.9 mg / l (As3 +) was 1.8 mg (As3 + / g (FeOOH) · h, relative to a solution of Na2HAsO4 with an initial concentration of 2.8 mg / l (As5 +) amounted to 1.6 mg (As5 +) / g (FeOOH) · h.

Claims (13)

1. Process for manufacturing an adsorption agent / reaction agent, characterized in that (a) iron oxyhydroxides of the α-FeOOH phase are mixed in solid, semi-solid or suspended form by adding Fe (OH) 3 in suspension or in gel form with variable water contents, Fe (OH) can be generated 3 also in situ from Fe (lll) and neutralization salt solutions, and then (b1) either the suspension is dried to obtain a solid state and the solid material is then mechanically ground to the desired shape and / or size, or (b2) the suspension, if necessary after pre-drying to a semi-solid state, is subjected to a mechanical conformation and then (additionally) drying, obtaining a solid state, 2. A method according to claim 1, characterized in that in iron a) as iron oxyhydroxides of the α-FeOOH phase, yellow iron oxyhydroxide pigments are used, which are synthesized by precipitation of hydroxides or iron carbonates from (II) from of the corresponding iron (II) salt solutions in pure form or as pickling solutions in an acidic or basic pH range and subsequent oxidation to iron (III) oxyhydroxides.

3.

Process according to claim 1 or 2, characterized in that to precipitate Fe (OH) 3 Fe3 + salts of the series of carbonates, chlorides, fluorides, nitrates, sulfates, sulphites are used.

Four.

Adsorption agent in the form of pieces, manufactured according to one of the methods according to claims 1 to 3, characterized in that the needles of the α-FeOOH type of amorphous layers are bonded together.

5.

Adsorption agent / reaction agent in the form of pieces according to claim 4, characterized in that in the case of the adsorption agent / reaction agent in the form of pieces it is a molded body.

6.

Apparatus through which media can circulate, characterized in that they contain the adsorption agent / reaction agent in the form of pieces according to claims 4 and 5.

7.

Apparatus through which media can circulate according to claim 6, characterized in that in the case of the apparatus it is a passage adsorber.

8.

Water treatment facilities comprising apparatus according to claims 6 or 7.

9.

Water supply plants comprising water treatment facilities according to claim 8.

10.

Use of the adsorption agents / reaction agents in the form of pieces according to claims 4 and 5 and of the apparatus according to claims 6 and 7 to purify gases or liquids.

eleven.

Use of the adsorption agents / reaction agents in the form of pieces according to claims 4 and 5 and of the apparatus according to claims 6 and 7 for water treatment.

12.

Use of the adsorption agents / reaction agents in the form of pieces according to claims 4 and 5 and of the apparatus according to claims 6 and 7 to remove heavy metals, such as phosphorus, antimony, beryllium, selenium, tellurium, cadmium compounds , chromium as well as cyano compounds of water.

13.

Use of the adsorption agents / reaction agents in the form of pieces according to claims 4 and 5, of the apparatus according to claims 6 and 7, of the water treatment facilities according to claim 8, as well as of the supply plants of water according to claim 9 for removing arsenic compounds from water.