WO2018073723A1 - Method for producing a filter material containing iron for the treatment of water and plant for implementing the method. - Google Patents
Method for producing a filter material containing iron for the treatment of water and plant for implementing the method. Download PDFInfo
- Publication number
- WO2018073723A1 WO2018073723A1 PCT/IB2017/056408 IB2017056408W WO2018073723A1 WO 2018073723 A1 WO2018073723 A1 WO 2018073723A1 IB 2017056408 W IB2017056408 W IB 2017056408W WO 2018073723 A1 WO2018073723 A1 WO 2018073723A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- iron
- separator
- salt
- water
- hydroxide
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
- B01J20/28016—Particle form
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/103—Arsenic compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
Definitions
- the present invention relates to a method for producing a filter material containing iron for the treatment of water and plant for implementing the method.
- iron oxide- or hydroxide- or oxyhydroxide-based filter materials are capable of removing undesired pollutants, such as phosphates, arsenic, vanadium, selenium, antimony and other metals, from water.
- a method for making the filter material which envisages the following steps:
- the material in grains thus obtained is taken to the purification system site and inserted in filters to be crossed by the water to be treated.
- the first operation which is performed when the filter is commissioned consists in washing the filtering material.
- the purpose of the washing is to remove the fine particles which could otherwise reach the treated water, with unfavorable consequences of various nature, from coloring the water red to making it non-drinkable due to the excessive iron content.
- removing the fine particles is needed because otherwise these particles would be interposed during filtering between those of larger size and would at least partially prevent the water flow, with consequent increase of the load loss through the filter.
- the presence of fine particles promotes the packing of the material and may damage it beyond repair for this reason.
- the presence of fine particles in the material is inevitable.
- the main production processes employed envisage granulating the material by means of a freeze thawing process, which inevitably forms a fine fraction (granules smaller than 0.2 mm in diameter), which can be estimated in about 10-15% of the total mass.
- the water is made to cross the material from the bottom upwards and once the water has reached the upper outlet of the filter it is discharged.
- the washing water flow rate is regulated so that the speed at which it crosses the material bed is generally comprised between 25 and 28 m/h. This is the falling speed in water of particles of size greater than about 0.2 mm in diameter, while those of smaller size sediment at a lower speed.
- the effect is that particles with sedimentation speed higher than that of the washing water cannot exit from the filter, while those with slower speed are carried away by the water flow.
- This method is continued until the outlet water is clear, and this generally takes at least two hours.
- the water volume containing the fine particles which is generated is at least 50 cubic meters for each square meter of section of the filter.
- a basin obtained in the ground is used, provided with a draining sand layer into which the waste is conveyed. After washing and after the water as percolated into the ground underneath through the sand layer, the layer itself is removed (having retained the fine part removed from the material) and this sand mixed with the oxyhydroxide is taken to a landfill.
- Such object is achieved according to the invention by a method for producing a filter material containing iron for treating water as described in claim 1 .
- the present invention is further explained below with reference to the attached drawing showing a diagrammatic view of a plant for implementing the method according to the invention.
- the method according to the invention envisages the use of a system substantially constituted by:
- a recirculation circuit 6 connected to the separator 4 provided with an on-off valve 8, a recirculation pump 10 and a conductivity meter 12, the meter 12 and the pump 10 being placed respectively downstream and upstream of the ceramic separation membranes 14,
- the reactor 2 is fed with a compound of trivalent iron, i.e. ferric chloride, and a base, e.g. sodium hydroxide.
- the reaction product is an iron hydroxide in colloidal form and sodium chloride.
- bivalent iron compound e.g. ferrous sulfate
- an oxidant such as air or oxygen blown into the reaction environment.
- the iron hydroxide and the sodium chloride are sent into the separator 4.
- valve 18 in closed configuration and valve 8 in open configuration the solution is sent into the ceramic membranes 14 for cross-flow washing.
- a partial separation of the iron hydroxide from the sodium chloride is obtained since the membranes let the water and the sodium chloride through, but not the iron hydroxide.
- the sodium chloride solution is discharged outside, while the iron hydroxide solution still containing sodium chloride is reintroduced into the separator 4 and is recirculated with the addition of water coming from the washing of the water contained in the tank 24 until the conductivity meter 12 detects the near absence of sodium chloride. Indeed, by gradually replacing the water downstream of the membranes (which contains sodium chloride) with water fed upstream of the membranes free from sodium chloride, the suspension progressively loses sodium chloride and is washed.
- Valve 8 is closed and valve 1 8 is opened so as to allow sending the iron hydroxide suspension (now free from sodium chloride) to the membrane filter press 20 where part of the water is removed to obtain a cake, which is placed inside the freezer 22 at temperatures lower than 0 °C for a time comprised between 24 and 48 hours and operating at atmospheric pressure.
- the product is then left to thaw to reach ambient temperature and appear in form of mechanically stable grains, with a grain size comprised between 0.1 and 3 mm of diameter and with less than 1 0% of the material under the limits in percentage by weight.
- the grains are placed inside a filter 24 and washed with a water flow having different speeds so as to remove only the fine particles (smaller than or equal to 0.2 mm of diameter) of iron hydroxide which are sent to the separator 4 through the pipe 28.
- the presence of particles of oxyhydroxide already formed helps the filtering because they promote the water permeation through the filter cake which is being formed.
- the retrieved fine particles are incorporated in the new granules being formed and thus totally retrieved.
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Analytical Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
A method for producing a filter material containing iron for the treatment of water, characterized in that: - a trivalent iron compound and a base are made to react in a reactor (2), until the trivalent iron is completely neutralized, to obtain an iron hydroxide and a salt constituted by the anion of the trivalent iron compound and the cation of the base, which are sent to a separator (4), - iron hydroxide and the salt are sent into ceramic membranes (14) for cross- flow washing of the iron hydroxide from the salt and the solution is recirculated to the separator (4) until said solution is substantially free from salt, - the iron hydroxide suspension is sent to a membrane filter press (20), in which part of the water is partially removed to obtain a cake, - said cake is positioned for a given period of time inside a freezer (22), - the cake is thawed and the iron hydroxide granules which are obtained are placed in a filtering element (24), in which they are washed with a water flow in order to remove only the fine particles (equal to or smaller than 0.2 mm in diameter) of iron hydroxide, which are sent to the separator (4).
Description
METHOD FOR PRODUCING A FILTER MATERIAL CONTAIN ING IRON FOR THE TREATMENT OF WATER AND PLANT FOR IMPLEMENTING THE METHOD.
The present invention relates to a method for producing a filter material containing iron for the treatment of water and plant for implementing the method.
It is known that iron oxide- or hydroxide- or oxyhydroxide-based filter materials are capable of removing undesired pollutants, such as phosphates, arsenic, vanadium, selenium, antimony and other metals, from water.
A method is currently known for making the filter material which envisages the following steps:
- making a trivalent iron compound and a base react in a reactor, until the trivalent iron is completely neutralized, to obtain an iron hydroxide and a salt constituted by the anion of the trivalent iron compound and the cation of the base,
- sending the iron hydroxide and the salt into ceramic membranes for cross- flow washing the iron hydroxide from the salt,
- sending the iron hydroxide suspension to a membrane filter press, in which part of the water is removed to obtain a cake with a dry percentage higher than 23%,
- inserting the cake into recipients,
- positioning the recipients in a refrigerating chamber operating at atmospheric pressure and at temperatures lower than 0 °C for a time comprised between 24 and 48 hours (freeze thawing) to obtain the granulate.
The material in grains thus obtained is taken to the purification system site and inserted in filters to be crossed by the water to be treated.
The first operation which is performed when the filter is commissioned consists in washing the filtering material. The purpose of the washing is to remove the fine particles which could otherwise reach the treated water, with unfavorable consequences of various nature, from coloring the water red to making it non-drinkable due to the excessive iron content. Furthermore, removing the fine particles is needed because otherwise these particles would be interposed during filtering between those of larger size and would at least partially prevent the water flow, with consequent increase of the load loss through the filter. Finally, the presence of fine particles promotes the packing of the material and may damage it beyond repair for this reason.
On the other hand, the presence of fine particles in the material is inevitable. Indeed, the main production processes employed envisage granulating the material by means of a freeze thawing process, which inevitably forms a fine fraction (granules smaller than 0.2 mm in diameter), which can be estimated in about 10-15% of the total mass.
Currently, in order to eliminate such fine particles, after having loaded the material into the filter, the water is made to cross the material from the bottom upwards and once the water has reached the upper outlet of the filter it is discharged. The washing water flow rate is regulated so that the speed at which it crosses the material bed is generally comprised between 25 and 28 m/h. This is the falling speed in water of particles of size greater than about 0.2 mm in diameter, while those of smaller size sediment at a lower speed. The effect is that particles with sedimentation speed higher than that of the washing water cannot exit from the filter, while those with slower speed are carried away by the water flow. This method is continued until the outlet water is clear, and
this generally takes at least two hours. The water volume containing the fine particles which is generated is at least 50 cubic meters for each square meter of section of the filter.
The disposal of this water is the real problem of the initial washing. Indeed, even if a connection to the sewerage system is present, not all the generated waste may be conveyed into it given the high concentrations of iron, the concentration limit for the discharging into sewers being 4 mg/l.
The situation is even worse if there is no connection to the sewerage system because in this case the iron concentration limit (for discharging into surface water) is even lower and equal to 2 mg/l. For this reason, all the eluate must be transported to a disposal plant.
When possible, a basin obtained in the ground is used, provided with a draining sand layer into which the waste is conveyed. After washing and after the water as percolated into the ground underneath through the sand layer, the layer itself is removed (having retained the fine part removed from the material) and this sand mixed with the oxyhydroxide is taken to a landfill.
In all cases, these operations are slow and costly.
It is the object of the invention to eliminate such drawbacks and to provide a filter material and at the same time to wash it in a filtering device cost- effectively without requiring any consumption of water.
Such object is achieved according to the invention by a method for producing a filter material containing iron for treating water as described in claim 1 .
The present invention is further explained below with reference to the attached drawing showing a diagrammatic view of a plant for implementing the method according to the invention.
As shown in the figures, the method according to the invention envisages the use of a system substantially constituted by:
- a reactor 2,
- a separator 4 connected to the reactor 2,
- a recirculation circuit 6 connected to the separator 4 provided with an on-off valve 8, a recirculation pump 10 and a conductivity meter 12, the meter 12 and the pump 10 being placed respectively downstream and upstream of the ceramic separation membranes 14,
- a pipe 16 exiting from the separator 4 provided with on-off valve 18 and connected to a membrane filter press 20,
- a freezer 22
- a tank 24 provided with a water introduction pipe 26 and with a pipe 28, the outlet of which leads to the separator 4.
The operation of the system is as follows:
The reactor 2 is fed with a compound of trivalent iron, i.e. ferric chloride, and a base, e.g. sodium hydroxide. The reaction product is an iron hydroxide in colloidal form and sodium chloride.
In all cases, all the pairs which can be obtained by choosing the iron compound from ferric chloride, ferric nitrate, ferric sulfate and the base from sodium hydroxide, potassium hydroxide, ammonia, are suitable.
It is also possible to use a bivalent iron compound, e.g. ferrous sulfate, as initial iron compound and to oxidize the bivalent iron to trivalent iron during
the reaction, by using an oxidant, such as air or oxygen blown into the reaction environment.
Successively, the iron hydroxide and the sodium chloride are sent into the separator 4. With valve 18 in closed configuration and valve 8 in open configuration the solution is sent into the ceramic membranes 14 for cross-flow washing. A partial separation of the iron hydroxide from the sodium chloride is obtained since the membranes let the water and the sodium chloride through, but not the iron hydroxide.
The sodium chloride solution is discharged outside, while the iron hydroxide solution still containing sodium chloride is reintroduced into the separator 4 and is recirculated with the addition of water coming from the washing of the water contained in the tank 24 until the conductivity meter 12 detects the near absence of sodium chloride. Indeed, by gradually replacing the water downstream of the membranes (which contains sodium chloride) with water fed upstream of the membranes free from sodium chloride, the suspension progressively loses sodium chloride and is washed.
Valve 8 is closed and valve 1 8 is opened so as to allow sending the iron hydroxide suspension (now free from sodium chloride) to the membrane filter press 20 where part of the water is removed to obtain a cake, which is placed inside the freezer 22 at temperatures lower than 0 °C for a time comprised between 24 and 48 hours and operating at atmospheric pressure.
The product is then left to thaw to reach ambient temperature and appear in form of mechanically stable grains, with a grain size comprised between 0.1 and 3 mm of diameter and with less than 1 0% of the material under the limits in percentage by weight.
The grains are placed inside a filter 24 and washed with a water flow having different speeds so as to remove only the fine particles (smaller than or equal to 0.2 mm of diameter) of iron hydroxide which are sent to the separator 4 through the pipe 28.
During the successive step of processing, constituted by the press filtering of the washed suspension, the presence of particles of oxyhydroxide already formed helps the filtering because they promote the water permeation through the filter cake which is being formed.
Finally, during the step of processing, i.e. that of freeze thawing, the retrieved fine particles are incorporated in the new granules being formed and thus totally retrieved.
From the above, it is apparent that the method according to the invention has many advantages, such as:
- it allows to product granules ready for use without requiring any further washing,
- it uses the fine part to form new granules,
- it eliminates wasting of water to remove the fine part of the material,
- it promotes press filtering by virtue of the presence of the already formed granules.
Claims
1 . A method for producing a filter material containing iron for the treatment of water, characterized in that:
- a trivalent iron compound and a base are made to react in a reactor (2), until the trivalent iron is completely neutralized, to obtain an iron hydroxide and a salt constituted by the anion of the trivalent iron compound and the cation of the base, which are sent to a separator (4),
- iron hydroxide and the salt are sent into ceramic membranes (14) for cross- flow washing of the iron hydroxide from the salt and the solution is recirculated to the separator (4) until said solution is substantially free from salt,
- the iron hydroxide suspension is sent to a membrane filter press (20), in which part of the water is partially removed to obtain a cake,
- said cake is positioned for a given period of time inside a freezer (22),
- the cake is thawed and the iron hydroxide granules which are obtained are placed in a filtering element (24), in which they are washed with a water flow in order to remove only the fine particles (equal to or smaller than 0.2 mm in diameter) of iron hydroxide, which are sent to the separator (4).
2. A method according to claim 1 , characterized in that the trivalent iron compound is chosen from ferric chloride, ferric nitrate, ferric sulfate.
3. A method according to claim 1 , characterized in that the base is chosen from sodium hydroxide, potassium hydroxide, ammonia.
4. A method according to claim 1 , characterized in that the trivalent iron is obtained starting from a bivalent iron compound which is oxidized to trivalent
iron during the reaction, by using an oxidant blown into the reaction environment.
5. A method for implementing the method according to claim 1 , characterized in that it comprises:
- a reactor (2) for a trivalent iron compound and a base to obtain an iron hydroxide and a salt constituted by the anion of the trivalent iron compound and by the cation of the base,
- a separator (4) connected to the reactor (2) of the iron hydroxide from the salt,
- a recirculation circuit (6) of the salt, said circuit being connected to the separator (4) and provided with an on-off valve (8), a recirculation pump (10) and a conductivity meter (12), the meter and the pump being placed respectively downstream and upstream of the ceramic separation membranes (14),
- a pipe (16) for the iron hydroxide exiting from the separator (4), said pipe (16) being provided by an on-off valve (18) and connected to a membrane filter press (20) to obtain a cake,
- a freezer (22) of the formed cake,
- a separating element (24) of the fine particles (smaller than or equal to 0.2 mm of diameter) from the filtering material obtained by freeze thawing the cake in the freezer (22), said element (24) being provided with water introduction pipe (26) and pipe (28), the outlet of which leads to the separator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT102016000106297 | 2016-10-21 | ||
| IT102016000106297A IT201600106297A1 (en) | 2016-10-21 | 2016-10-21 | METHOD TO PRODUCE A FILTERING MATERIAL CONTAINING IRON FOR WATER TREATMENT, A PLANT TO IMPLEMENT THE METHOD AND FILTERING MATERIAL OBTAINED BY METHOD. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2018073723A1 true WO2018073723A1 (en) | 2018-04-26 |
Family
ID=58159405
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/IB2017/056408 WO2018073723A1 (en) | 2016-10-21 | 2017-10-16 | Method for producing a filter material containing iron for the treatment of water and plant for implementing the method. |
Country Status (2)
| Country | Link |
|---|---|
| IT (1) | IT201600106297A1 (en) |
| WO (1) | WO2018073723A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022136736A1 (en) * | 2020-12-21 | 2022-06-30 | Kemira Oyj | Moist iron hydroxide gel and its use |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4320003A1 (en) * | 1993-06-11 | 1994-12-15 | Jekel Martin Prof Dr Ing | Process for removing dissolved arsenic by means of solid iron hydroxide in water purification |
| US20080271600A1 (en) * | 2000-09-26 | 2008-11-06 | Andreas Schlegel | Contact and adsorbent granules |
| WO2016181262A1 (en) * | 2015-05-12 | 2016-11-17 | Gruppo Zilio S.P.A. | Method for producing a filter material containing iron for the treatment of water |
-
2016
- 2016-10-21 IT IT102016000106297A patent/IT201600106297A1/en unknown
-
2017
- 2017-10-16 WO PCT/IB2017/056408 patent/WO2018073723A1/en active Application Filing
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4320003A1 (en) * | 1993-06-11 | 1994-12-15 | Jekel Martin Prof Dr Ing | Process for removing dissolved arsenic by means of solid iron hydroxide in water purification |
| US20080271600A1 (en) * | 2000-09-26 | 2008-11-06 | Andreas Schlegel | Contact and adsorbent granules |
| WO2016181262A1 (en) * | 2015-05-12 | 2016-11-17 | Gruppo Zilio S.P.A. | Method for producing a filter material containing iron for the treatment of water |
Non-Patent Citations (1)
| Title |
|---|
| THIRUNAVUKKARASU O S ET AL: "ARSENIC REMOVAL FROM DRINKING WATER USING GRANULAR FERRIC HYDROXIDE", WATER, PRETORIA, SA, vol. 29, no. 2, April 2003 (2003-04-01), pages 161 - 170, XP008071993, ISSN: 0378-4738 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022136736A1 (en) * | 2020-12-21 | 2022-06-30 | Kemira Oyj | Moist iron hydroxide gel and its use |
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| Publication number | Publication date |
|---|---|
| IT201600106297A1 (en) | 2018-04-21 |
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