TECHNICAL FIELD
[001] The present invention is in the field of chemical sciences and relates to a
method and system for treatment/purification of effluent water.
5 BACKGROUND OF THE INVENTION
[002] The following description includes information that may be useful in
understanding the present invention. It is not an admission that any of the information
provided herein is prior art or relevant to the presently claimed invention, or that any
publication specifically or implicitly referenced is prior art.
10
[003] Effluent is wastewater that is discharged from industrial facilities, sewage
treatment plants, or other sources. The treatment of effluent is crucial to protect the
environment and public health. There are several wastewater treatment methods, and
the choice of method depends on the specific characteristics of the effluent. Effluent
15 water contains various toxic chemical substances such as organic compounds from
various sources, such as food processing, chemical manufacturing, and agricultural
runoff; inorganic substances such as salts, metals, and minerals. If such substances
are released into natural water bodies, they may cause problems such as
eutrophication. Common metals include copper, zinc, lead, iron, and mercury, which
20 can have environmental implications. Long-term exposure to even minute doses of
such substances can cause a significant increase in risk of health-related issues such
as skin cancer, dyspnoea, tachycardia, and unconsciousness.
[004] One of the widely practiced industrial processes include electroplating.
25 Electroplating effluents from industries has been a serious threat to the ecological
systems and human health. Hence, it becomes very important to treat Electroplatingwastewater before it is discharged into the environment. Electroplating
effluent/wastewater has high concentrations of different ions and acids, which go to
the effluent treatment plant (ETP) for removal of solids pollutants and toxicity.
30 However, to reduce load on ETP and to improve the efficiency of the overall
electroplating wastewater treatment, there is a need for initial removal of contaminants
3
from effluent water and improving the effluent water quality before sending to ETP.
The present disclosure addresses the need.
SUMMARY OF THE INVENTION
5 [005] The following presents a simplified summary to provide a basic understanding
of some aspects of the present method for treating effluent water. This summary is not
an extensive overview and is intended to neither identify key or critical elements nor
delineate the scope of such elements. Its purpose is to present some concepts of the
described features in a simplified form as a prelude to the more detailed description
10 that is presented later.
[006] An exemplary aspect of the disclosure relates to a method for treating effluent
water. The method includes adding iron particles to the effluent water comprising
copper sulfate. The iron particles react with the copper sulfate to form ferrous sulfate
15 in the effluent water and remove copper as a by-product precipitate, from the effluent
water. The method further includes converting the ferrous sulfate in the effluent water
to a stable ferric sulfate by an electro-oxidation reaction. The method further includes
neutralizing the stable ferric sulphate in the effluent water to iron-based precipitates,
which may be filtered out from the effluent water.
20
[007] In another exemplary aspect, the present disclosure provides a system to treat
effluent water. The system includes an element to perform galvanic displacement
reaction, wherein said element may be configured to add iron particles to the effluent
water comprising copper sulfate. The iron particles react with the copper sulfate to
25 form ferrous sulfate in the effluent water and remove copper as a by-product
precipitate, from the effluent water. The system further includes a power controller,
wherein the power controller is configured to supply a Direct Current (DC) supply and
facilitate an electro-oxidation reaction and convert the ferrous sulfate in the effluent
water to a stable ferric sulfate. The system further includes a neutralizer element,
30 wherein the neutralizer is configured to neutralize the stable ferric sulphate in the
effluent water to iron-based precipitates, which is filtered out from the effluent water.
4
[008] It is to be understood that the aspects and embodiments of the disclosure
described above may be used in any combination with each other. Several of the
aspects and embodiments may be combined to form a further embodiment of the
disclosure.
5
[009] The above summary is provided merely for the purpose of summarizing some
example embodiments to provide a basic understanding of some aspects of the
disclosure. Accordingly, it will be appreciated that the above-described embodiments
are merely examples and should not be construed to narrow the scope or spirit of the
10 disclosure in any way. It will be appreciated that the scope of the disclosure
encompasses many potential embodiments in addition to those here summarized,
some of which will be further described below.
OBJECTS OF THE INVENTION
15 [010] The main object of the present disclosure is to treat effluent water.
[011] Another objective of the present disclosure is to provide a method to treat
effluent water from electroplating techniques.
20 [012] Yet another objective of the present disclosure is to provide a method to treat
effluent water from electroplating techniques before transferring to the effluent
treatment plant (ETP).
[013] Still another objective of the present disclosure is to selectively remove copper
25 and iron-based precipitates from the effluent water from electroplating.
[014] Still another objective of the present disclosure is to produce a stable form of
iron-based compound during the treatment of the effluent water.
30 [015] Still another objective of the present disclosure is to reduce the load on ETP
for improving the overall efficiency of effluent water treatment.
[016] Still another objective of the present disclosure is to additionally utilize/recycle
the treated effluent water into industrial processes.
5
[017] Another object of the present disclosure is to provide a system to treat effluent
water for removal of contaminants.
5 BRIEF DESCRIPTION OF THE DRAWINGS
[018] The accompanying drawings, which are incorporated in and constitute a part
of this disclosure, illustrate exemplary embodiments and, together with the description,
explain the disclosed principles.
10 [019] FIG. 1 provides schematic illustration of treatment of effluent water (e.g.,
electroplating wastewater), in accordance with an embodiment of the disclosure.
[020] FIG. 2A illustrates the solution appearance of electroplating wastewater (Bath
I) before performing the effluent water treatment method in accordance with an
15 embodiment of the disclosure. FIG. 2B illustrates the solution appearance of
electroplating wastewater (Bath 2) before performing the effluent water treatment
method in accordance with an embodiment of the disclosure.
[021] FIG. 3A illustrates the appearance of Bath 1 before and after performing
20 galvanic displacement reaction, in accordance with an embodiment of the disclosure.
FIG. 3B illustrates the appearance of Bath 2 before and after performing galvanic
displacement reaction, in accordance with an embodiment of the disclosure.
[022] FIG. 4A shows the cemented copper powder recovered after galvanic
25 displacement reaction, in accordance with an embodiment of the disclosure. FIG. 4B
illustrates XRD pattern of the recovered cemented copper powder, in accordance with
an embodiment of the disclosure.
[023] FIG. 5A illustrates the electroplating wastewater solution comprising ferrous
30 sulphate before electrolysis/electro-oxidation, in accordance with an embodiment of
the disclosure. FIG. 5B illustrates the electroplating wastewater solution comprising
ferric sulphate after electrolysis/electro-oxidation, in accordance with an embodiment
of the disclosure.
6
[024] FIG. 6A illustrates neutralization reaction using sodium hydroxide to obtain
treated effluent water (electroplating wastewater) and recovery of iron-based
precipitates as magnetic iron oxide, in accordance with an embodiment of the
5 disclosure. FIG. 6B illustrates XRD pattern of the recovered magnetic iron oxide, in
accordance with an embodiment of the disclosure.
[025] FIG. 7 illustrates neutralization reaction using calcium hydroxide to obtain
treated effluent water (electroplating wastewater) and recovery of iron-based
10 precipitates as calcium ferrite, in accordance with an embodiment of the disclosure.
FIG. 7B illustrates XRD pattern of the recovered calcium ferrite, in accordance with an
embodiment of the disclosure.
DETAILED DESCRIPTION OF THE INVENTION
15 [026] The various features of the present invention are described as embodiments.
While examples and features of disclosed principles are described herein,
modifications, adaptations, and other implementations are possible without departing
from the spirit and scope of the disclosed embodiments. It is intended that the following
detailed description and accompanying drawings be considered as exemplary only,
20 with the true scope and spirit being indicated by the following claims.
[027] As used herein, the term “effluent water” or “wastewater” refers to wastewater
comprising contaminants produced and discharged by different processes including
but limiting to industrial processes such as electroplating operations. In some
25 embodiments, the effluent water may comprise various contaminants including one or
more of iron, copper, heavy metals, acids, and other contaminants (organic, inorganic,
biological, or radiological).
[028] The term “contaminants” as used herein refers to the substances in effluent
30 water that are present in concentrations higher than what is considered acceptable for
the specific discharge standards.
7
[029] The present disclosure relates to a method for treating effluent water. The
present method aims to incorporate a combination of galvanic displacement reaction,
electro-oxidation reaction and neutralization reaction, resulting in treated/purified
effluent water.
5
[030] Accordingly, the present disclosure provides a method for treating effluent
water, the method comprising: adding iron particles to the effluent water comprising
copper sulfate, wherein the iron particles react with the copper sulfate to form ferrous
sulfate in the effluent water and remove copper as a by-product precipitate, from the
10 effluent water. The method further includes converting the ferrous sulfate in the
effluent water to a stable ferric sulfate by an electro-oxidation reaction. The method
further includes neutralizing the stable ferric sulfate in the effluent water to iron-based
precipitates, which is filtered out from the effluent water.
15 [031] In some embodiments, the method for treating effluent water comprises:
- adding iron particles to the effluent water comprising copper sulfate, wherein
the iron particles react with the copper sulfate to form ferrous sulfate in the
effluent water and remove copper as a by-product precipitate, from the effluent
water;
20 - converting the ferrous sulfate in the effluent water to a stable ferric sulfate by
an electro-oxidation reaction; and
- neutralizing the stable ferric sulphate in the effluent water to iron-based
precipitates, which is filtered out from the effluent water.
25 [032] In some embodiments, the removal of copper from the effluent water takes
place by galvanic displacement reaction, wherein the iron particles react with the
copper sulfate to form the ferrous sulfate to remove the copper as the by-product
precipitate. In galvanic displacement reaction, one metal displaces another from a
solution of one of its salts. A metal capable of displacing another from a solution of
30 one of its salts is said to be ‘more active’ than the displaced metal. Accordingly, in the
present galvanic displacement reaction, iron displaces copper sulphate wherein iron
is more active than copper.
8
[033] In some embodiments, the galvanic displacement reaction is carried out at a
temperature of about 20°C to 30°C, including values and ranges therebetween.
5 [034] In some embodiments, the galvanic displacement reaction is carried out at a
temperature of about 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, or 30℃,
including values and ranges therebetween.
[035] In some embodiments, the galvanic displacement reaction is carried out at
10 room temperature.
[036] In some embodiments of the present disclosure, the galvanic displacement
reaction is carried out at the temperature described herein for a duration of about 15
minutes to 180 minutes. In some embodiments, the galvanic displacement reaction is
15 carried out for a duration of about 15 minutes to 2.5 hours, 15 minutes to 2 hours, 15
minutes to 1.5 hours, 15 minutes to 1 hour, 30 minutes to 2.5 hours, 30 minutes to 2
hours, 30 minutes to 1.5 hours, 30 minutes to 1 hour, 45 minutes to 2.5 hours, 45
minutes to 2 hours, 45 minutes to 1.5 hours, 45 minutes to 1 hour, 1 to 3 hours, 1 to
2.5 hours, 1 to 2 hours, 1 to 1.5 hours, 1.5 to 2.5 hours, 1.5 to 2 hours, including values
20 and ranges therebetween.
[037] It is understood that the galvanic displacement reaction is carried out by
employing any combination of the time, and temperature described herein. In some
embodiments, the iron particles react with the copper sulfate via galvanic displacement
25 reaction at about 25℃ for about 1 hour to form ferrous sulfate in the effluent water and
remove copper as the by-product precipitate.
[038] In some embodiments, the electro-oxidation reaction is carried out by applying
a current density of about 0.01 A/cm2
to 0.05 A/cm2
, including values and ranges
30 therebetween.
[039] In some embodiments, the electro-oxidation is carried out by applying a
current density of about 0.01 A/cm2
, 0.02 A/cm2
, 0.03 A/cm2
, 0.04 A/cm2 or 0.05 A/cm2
.
9
[040] In some embodiments, the electro-oxidation is carried out at a temperature of
about 50℃ to 80℃, including values and ranges therebetween.
5 [041] In some embodiments, the electro-oxidation reaction is carried out at a
temperature of about 50-70℃, 50-65℃, 50-60℃, 50-55℃, 55-70℃, 55-65℃, 55-60℃,
70-80℃, 60-80℃, 65-70℃, 65-75℃, or 75-78℃, including values and ranges
therebetween.
10 [042] In some embodiments, the electro-oxidation is carried out at a temperature of
about 50℃ to 60℃, including values and ranges therebetween. In some embodiments,
the electro-oxidation is carried out at a temperature of about 50℃.
[043] In some embodiments, the electro-oxidation is carried out at the temperature
15 described herein for a duration of about 300 minutes to 400 minutes, including values
and ranges therebetween.
[044] In some embodiments, the electro-oxidation is carried out for a duration of
about 340 minutes to 380 minutes, including values and ranges therebetween. In
20 some embodiments, the electro-oxidation is carried out for a duration of about 360
minutes.
[045] It is understood that the electro-oxidation reaction is carried out by employing
any combination of the time and temperature described herein. In some embodiments,
25 the ferrous sulfate in the effluent water is converted to a stable ferric sulfate by electrooxidation reaction at the temperature of 50℃ for 360 minutes.
[046] As described above, the electro-oxidation reaction converts the ferrous sulfate
in the effluent water to a stable ferric sulfate, wherein said stable ferric sulphate
30 remains in a same oxidation state. The same state herein corresponds to an oxidation
state of the stable ferric sulfate that remains constant until the subsequent
neutralization reaction. In some embodiments, the oxidation state of the iron in the
stable ferric sulfate is +3.
10
[047] In some embodiments, stable ferric sulfate also means that said compound is
stable and does not decompose or transform into other compound(s).
5 [048] In some embodiments, the neutralization of the stable ferric sulfate in the
effluent water to iron-based precipitates is carried out at a pH in the range of about 6.0
to 8.0, including values and ranges therebetween.
[049] In some embodiments, the neutralization of the stable ferric sulfate in the
10 effluent water to iron-based precipitates is carried out at a pH of about 6.0, about 6.1,
about 6.2, about 6.3, about 6.4, about 6.5, about 6.6, about 6.7, about 6.8, about 6.9,
about 7.0, about 7.1, about 7.2, about 7.3, about 7.4, about 7.5, about 7.6, about 7.7,
about 7.8, about 7.9, or about 8.0.
15 [050] In some embodiments, the neutralization of the stable ferric sulfate in the
effluent water to iron-based precipitates is carried out at a pH the range of about 6.0
to 8.0, including values and ranges therebetween. In some embodiments, the present
inventors without wishing to be bound by any theory surprisingly found that employing
said pH range of 6.0 to 8.0 for neutralization reaction enables the formation of iron20 based precipitates including soft-metallic ferrites such as calcium ferrite and/or metallic
oxides such as magnetic iron oxide since said iron-based by-products were not
precipitated in acidic phase.
[051] In some embodiments, the iron-based precipitates removed during
25 neutralization are selected from a group comprising: soft-metallic ferrites, metallic
oxides, and combinations thereof.
[052] In some embodiments, the iron-based precipitates removed during
neutralization is a soft-metallic ferrite. In some embodiments, the iron-based
30 precipitates removed during neutralization is a metallic oxide.
[053] In some embodiments, the neutralization of the stable ferric sulfate in the
effluent water to iron-based precipitates is carried out in the presence of the base
11
which is a hydroxide selected from a group comprising: sodium hydroxide, calcium
hydroxide, potassium hydroxide, and combinations thereof.
[054] In some embodiments, the neutralization of the stable ferric sulfate in the
5 effluent water to iron-based precipitates is carried out in the presence of calcium
hydroxide.
[055] In some embodiments, the neutralization of the stable ferric sulphate in the
effluent water to iron-based precipitate is carried out in the presence of calcium
10 hydroxide to filter the iron-based precipitate as calcium ferrite.
[056] In some embodiments, the neutralization of the stable ferric sulfate in the
effluent water to iron-based precipitates is carried out in the presence of sodium
hydroxide.
15
[057] In some embodiments, the neutralization of the stable ferric sulfate in the
effluent water to iron-based precipitate is carried out in the presence of sodium
hydroxide to filter the iron-based precipitate as magnetic iron oxide.
20 [058] In some embodiments, the treated effluent water is transferred to an effluent
treatment plant (ETP).
[059] In some embodiments, the effluent water is electroplating wastewater (or the
spent solution) from the electroplating industry. In some embodiments, the present
25 method treats the electroplating wastewater prior to transferring said effluent water to
an effluent treatment plant (ETP).
[060] In some embodiments, the electroplating wastewater comprises copper
sulfate, iron, acid and tin based compound. Additionally, the electroplating wastewater
30 may also comprise additional constituents based on factors including but not limiting
to type of metal, electroplating techniques/types etc., as understood by a person
skilled in the art.
12
[061] In some embodiments, the electroplating wastewater comprises copper
sulfate, iron, sulphuric acid, and tin sulphate.
[062] In some embodiments, the electroplating wastewater has a chemical
5 composition comprising copper sulfate in an amount of about 5 g/L to 40 g/L, iron in
an amount of about 0.16 g/L to 15 g/L, tin-based compound in an amount of about
0.13 g/L to 0.18 g/L, and acid in an amount of about 30 g/L to 35 g/L, including values
and ranges therebetween.
10 [063] In some embodiments, the electroplating wastewater has a chemical
composition comprising copper sulfate in an amount of about 5 g/L to 40 g/L, iron in
an amount of about 0.16 g/L to 15 g/L, tin sulphate in an amount of about 0.13 g/L to
0.18 g/L, and sulphuric acid in an amount of about 30 g/L to 35 g/L, including values
and ranges therebetween.
15
[064] In some embodiments, the electroplating wastewater comprises copper
sulfate at a concentration of about 5 g/L to 10 g/L, 5 g/L to 20 g/L, 5 g/L to 25 g/L, 5
g/L to 30 g/L, 5 g/L to 35 g/L, 5 g/L to 40 g/L, or 30 g/L to 40 g/L, including values and
ranges therebetween.
20
[065] In some embodiments, the electroplating wastewater comprises iron at a
concentration of about 0.16 g/L to 2 g/L, 0.16 g/L to 5 g/L, 0.16 g/L to 10 g/L, or 10 g/L
to 15 g/L, including values and ranges therebetween.
25 [066] In some embodiments, the electroplating wastewater comprises tin sulfate at
a concentration of about 0.13 g/L to 0.15 g/L, or 0.15 g/L to 0.18 g/L, including values
and ranges therebetween.
[067] In some embodiments, the present method of treating electroplating
30 wastewater includes: adding iron particles to the electroplating wastewater comprising
copper sulfate, wherein the iron particles react with the copper sulfate to form ferrous
sulfate in the electroplating wastewater and remove copper as a by-product
precipitate, from the electroplating wastewater. The method further includes
13
converting the ferrous sulfate in the electroplating wastewater to a stable ferric sulfate
by an electro-oxidation reaction, wherein the stable ferric sulfate comprises iron in the
ferric sulphate remaining in a same oxidation state of +3. The method further includes
neutralizing the stable ferric sulphate in the electroplating wastewater to iron-based
5 precipitates, which is filtered out from the electroplating wastewater.
[068] In some embodiments, the present method of treating electroplating
wastewater includes adding iron particles to the electroplating wastewater comprising
copper sulfate, wherein the iron particles react with the copper sulfate via a galvanic
10 displacement reaction at a temperature of about 20℃ to 30℃ and for a time-period of
about 15 minutes to 180 minutes to form ferrous sulfate in the electroplating
wastewater and remove copper as the by-product precipitate, from the electroplating
wastewater. The method further includes converting the ferrous sulfate in the
electroplating wastewater to a stable ferric sulfate by an electro-oxidation reaction by
applying a current density of about 0.01 A/cm2 to 0.05 A/cm2 15 at a temperature of about
50 ℃ to 80 ℃ and for a time-period of about 300 minutes to 400 minutes, wherein the
stable ferric sulfate comprises iron in the ferric sulphate remaining in a same oxidation
state of +3. The method further includes neutralizing the stable ferric sulphate in the
electroplating wastewater to iron-based precipitates which is filtered out from the
20 electroplating wastewater, wherein said neutralization is carried out at a pH of about
6.0 to 8.0 and in presence of hydroxide base.
[069] In some embodiments, the present method of treating electroplating
wastewater includes adding iron particles to the electroplating wastewater comprising
25 copper sulfate, wherein the iron particles react with the copper sulfate via a galvanic
displacement reaction at a temperature of about 20℃ to 30℃ and for a time-period of
about 15 minutes to 180 minutes to form ferrous sulfate in the electroplating
wastewater and remove copper as a by-product precipitate, from the electroplating
wastewater, wherein the electroplating wastewater may include the copper sulfate,
30 iron, acid and tin based compound. The method further includes converting the ferrous
sulfate in the electroplating wastewater to a stable ferric sulfate by an electro-oxidation
reaction by applying a current density of about 0.01 A/cm2 to 0.05 A/cm2 at a
temperature of about 50 ℃ to 80 ℃ and for a time-period of about 300 minutes to 400
14
minutes, wherein the stable ferric sulfate comprises iron in the ferric sulphate
remaining in a same oxidation state of +3. The method further includes neutralizing
the stable ferric sulphate in the electroplating wastewater to calcium ferrite, which is
filtered out from the electroplating wastewater, wherein said neutralization is carried
5 out at a pH of about 6.0 to 8.0 and in presence of calcium hydroxide.
[070] In some embodiments, the present method of treating electroplating
wastewater includes adding iron particles to the electroplating wastewater comprising
copper sulfate, wherein the iron particles react with the copper sulfate via a galvanic
10 displacement reaction at a temperature of about 20℃ to 30℃ and for a time-period of
about 15 minutes to 180 minutes to form ferrous sulfate in the electroplating
wastewater and remove copper as a by-product precipitate, from the electroplating
wastewater, wherein the electroplating wastewater includes the copper sulfate, iron,
acid and tin based compound. The method further includes converting the ferrous
15 sulfate in the electroplating wastewater to a stable ferric sulfate by an electro-oxidation
reaction by applying a current density of about 0.01 A/cm2 to 0.05 A/cm2 at a
temperature of about 50 ℃ to 80 ℃ and for a time-period of about 300 minutes to 400
minutes, wherein the stable ferric sulfate comprises iron in the ferric sulphate
remaining in a same oxidation state of +3. The method further includes neutralizing
20 the stable ferric sulphate in the electroplating wastewater to magnetic iron oxide, which
is filtered out from the electroplating wastewater, wherein said neutralization is carried
out at a pH of about 6.0 to 7.0 and in presence of sodium hydroxide.
[071] In some embodiments, the method reduces the concentration of copper in the
25 effluent water by about 90% to 100% when compared to the initial concentration of
copper in the effluent water before subjecting to the present method.
[072] In some embodiments, the method reduces the concentration of iron in the
effluent water by about 90% to 100% when compared to the initial concentration of
30 iron in the effluent water before subjecting to the present method.
[073] The present disclosure also relates to a system for treatment of effluent water
including an element to perform galvanic displacement reaction, wherein said element
15
is configured to add iron particles to the effluent water comprising copper sulfate. The
iron particles react with the copper sulfate to form ferrous sulfate in the effluent water
and remove copper as a by-product precipitate, from the effluent water. The system
further includes a power controller, wherein the power controller is configured to supply
5 a Direct Current (DC) supply and facilitate an electro-oxidation reaction and convert
the ferrous sulfate in the effluent water to a stable ferric sulfate. The system further
includes a neutralizer element, wherein the neutralizer is configured to neutralize the
stable ferric sulfate in the presence of base in the effluent water to obtain iron-based
precipitates, which is filtered out from the effluent water.
10
[074] In some embodiments of the system, the stable ferric sulphate comprises iron
in the ferric sulphate to be configured to remain in a same oxidation state wherein said
oxidation state of the iron in the stable ferric sulfate is +3. In some embodiments of the
system, the same state of the stable ferric sulphate corresponds to an oxidation state
15 of the stable ferric sulfate that remains constant until the subsequent neutralization
reaction; and wherein said oxidation state of the iron in the stable ferric sulfate is +3.
[075] In some embodiments of the system, the iron-based precipitates removed in
the neutralizer element during neutralization is selected from a group comprising: soft20 metallic ferrites, metallic oxides, and combinations thereof.
[076] In some embodiments of the system, the neutralization in the neutralizer
element is carried out in presence of calcium hydroxide to filter the iron-based
precipitate as calcium ferrite.
25
[077] In some embodiments of the system, the neutralization in the neutralizer
element is carried out in presence of sodium hydroxide to filter the iron-based
precipitate as magnetic iron oxide.
30 [078] In some embodiments of the present disclosure, the system treats
electroplating wastewater, and includes an element to perform galvanic displacement
reaction, wherein said element is configured to add iron particles to the effluent water
16
comprising copper sulfate, wherein the iron particles react with the copper sulfate at a
temperature of about 20℃ to 30℃ and for a time-period of about 15 minutes to 180
minutes to form ferrous sulfate in the electroplating wastewater and remove copper as
the by-product precipitate, from the electroplating wastewater. The system further
5 includes a power controller, wherein the power controller is configured to supply a
Direct Current (DC) of about 0.01 A/cm2
to 0.05 A/cm2 at a temperature of about 50℃
to 80℃ and for a time-period of about 300 minutes to 400 minutes and facilitate an
electro-oxidation reaction and convert the ferrous sulfate in the effluent water to a
stable ferric sulfate. The system further includes a neutralizer element, wherein the
10 neutralizer is configured to neutralize the stable ferric sulfate in the effluent water at a
pH of about 6.0 to 8.0 in the presence of hydroxide base to remove iron contaminant
in the form of iron-based precipitates, which is filtered out from the electroplating
wastewater.
15 [079] In some embodiments of the present disclosure, the system treats
electroplating wastewater, and includes an element to perform galvanic displacement
reaction, wherein said element is configured to add iron particles to the effluent water
comprising copper sulfate, wherein the iron particles react with the copper sulfate at a
temperature of about 20℃ to 30℃ and for a time-period of about 15 minutes to 180
20 minutes to form ferrous sulfate in the electroplating wastewater and remove copper as
the by-product precipitate, from the electroplating wastewater. The system further
includes a power controller, wherein the power controller is configured to supply a
Direct Current (DC) of about 0.01 A/cm2
to 0.05 A/cm2 at a temperature of about 50℃
to 80℃ and for a time-period of about 300 minutes to 400 minutes and facilitate an
25 electro-oxidation reaction and convert the ferrous sulfate in the effluent water to a
stable ferric sulfate. The system further includes a neutralizer element, wherein the
neutralizer is configured to neutralize the stable ferric sulfate in the effluent water at a
pH of about 6.0 to 7.0 in the presence of calcium hydroxide to remove iron contaminant
in the form of calcium ferrite or in the presence of sodium hydroxide to remove iron
30 contaminant in the form of magnetic iron oxide, which is filtered out from the
electroplating wastewater.
17
[080] It is to be understood that the foregoing descriptive matter is illustrative of the
disclosure and not a limitation. While considerable emphasis has been placed herein
on the features of this disclosure, it will be appreciated that various modifications can
be made and that many changes can be made in the preferred embodiments without
5 departing from the principles of the disclosure. Those skilled in the art will recognize
that the embodiments herein can be practiced with modification within the spirit and
scope of the embodiments as described herein. Similarly, additional embodiments and
features of the present disclosure will be apparent to one of ordinary skill in the art
based upon the description provided herein.
10
[081] Descriptions of well-known/conventional methods/steps and techniques are
omitted to not unnecessarily obscure the embodiments herein. Further, the disclosure
herein provides for examples illustrating the above-described embodiments, and to
illustrate the embodiments of the present disclosure certain aspects have been
15 employed. The examples used herein for such illustration are intended merely to
facilitate an understanding of ways in which the embodiments herein may be practiced
and to further enable those of skill in the art to practice the embodiments herein.
Accordingly, the following examples should not be construed as limiting the scope of
the embodiments herein.
20
EXAMPLES
Example 1: Treatment of Effluent water
[082] Electroplating wastewater/spent solution from the electroplating process was
25 employed for conducting the effluent water treatment experiments. The electroplating
wastewater compositions had the following broad composition were used in the
experiments:
30
18
Table 1: Electroplating wastewater compositions
[083] The treatment of electroplating wastewater was performed by the following
5 method steps and is further schematically illustrated in FIG. 1:
Step 1 (galvanic displacement reaction):
Performing galvanic displacement reaction by adding iron particles to the
electroplating wastewater, wherein said iron particles react with copper sulfate to form
10 ferrous sulfate and remove copper as a by-product precipitate, from the electroplating
wastewater.
Step 2 (electro-oxidation reaction):
Converting the ferrous sulfate in the electroplating wastewater to stable ferric sulfate
15 by electro-oxidation reaction in presence of DC current, wherein the stable ferric
sulfate remains in a same oxidation state (iron in Fe3+ state)
19
Step 3 (neutralization):
Neutralizing the stable ferric sulphate in the electroplating wastewater to iron-based
precipitates including calcium ferrite or magnetic iron oxide powder in presence of a
hydroxide base, and filtering out the iron-based precipitates to obtain treated
5 electroplating wastewater solution.
[084] Bath 1 and Bath 2 were specifically treated as follows:
[085] Treatment of Bath 1:
10 Bath 1 (FIG. 2A) was treated as follows:
1. Galvanic displacement reaction for Bath 1 was carried out based on the
following reaction conditions/parameters to extract copper by addition of iron
powder.
15
Table 2: Parameters employed for galvanic displacement reaction
Parameters Quantity/Temp./Time
Volume of solution taken 500 ml
Amount of copper sulphate
present in solution
10 gm/L
Amount of iron powder added 1.75 gm
Reaction temperature 25℃
Reaction time 60 minutes
After filtration
Volume of clear solution
collected
495 ml
20
Amount of cemented copper
collected
2 gm
[086] The compositions of Bath 1 before and after performing galvanic displacement
reaction (FIG. 3A) are provided in Table 3.
5 Table 3
[087] The above experiment yielded 2 gm of cemented copper and an increase in
ferrous sulphate concentration. The results demonstrate 99% copper removal and the
10 purity of cemented copper obtained was about 90%. Particularly, 10 g/L copper
sulphate concentration was reduced to 500 ppm, and the iron concentration (FeSO4)
increased from 40 g/L to 51 g/L. FIG. 4A shows the removed cemented copper and
FIG. 4B illustrates the XRD pattern of cemented copper powder.
15 [088] The chemical reaction and chemistry of galvanic displacement reaction for
conversion of metal iron to ferrous sulfate and displacing/removing copper is as
follows:
Chemical reaction:
CuSO4
+ Fe FeSO4
20 + Cu
21
Chemistry of the process:
[089] The possible main cathodic reactions in the electrochemical copper/iron
couple system in the presence of sulfate ions are as follows -
2H+ 5 + 2e- H2 EO = O.OO V
Cu2+ + e- Cu+ EO = O.l59 V
Cu2+ + 2e- Cu EO = 0.340 V
O2 + 4H++ 4e- 2H2O EO = 1.229 V
10 2. Next, the electro-oxidation reaction was performed to convert the ferrous sulfate
in the bath solution to stable ferric sulfate.
[090] The spent solution obtained after the galvanic displacement reaction was
adjusted to a pH of 0.6. Sulfuric acid was added at 31 g/L followed by applying a
current density between 0.01A/cm2
to 0.05A/cm2 15 at about 50°C for about 6 hours/360
minutes (FIG. 5A and 5B).
[091] The specific parameters employed in the electro-oxidation reaction are
summarized in the following Table 4:
20
Table 4: Parameters employed for electro-oxidation reaction
Parameters Quantity/temp./time
The volume of solution taken 500 ml
Cathode SS304 sheet
Anode mixed metal oxide (MMO) anode
Electrode dimensions 16 cm * 5.5 cm
Effective area 176 cm2
22
Current density 0.02 A/cm2
Cell voltage 2.0 V
Energy consumption 0.012 kWh/L
Reaction temperature 50℃
Reaction time 360 minutes
[092] The compositions of Bath 1 before and after performing electro-oxidation
reaction are provided in Table 5.
5 Table 5
[093] The results show that a significant amount of ferrous sulfate (51 g/L) was
converted into stable ferric sulfate (41.5 g/L). The presence of Fe2+ (ferrous sulphate)
10 had led to turbidity in clear water. Hence, the criticality of this electro-oxidation reaction
lies in the fact that maximum amount of iron compounds in the bath solution must be
in the stable Fe3+ state which was achieved by the conversion of ferrous sulfate to
stable ferric sulfate with the oxidation state of iron in the stable ferric sulfate being +3
which remained constant until the subsequent neutralization reaction.
15
23
[094] The chemical reaction involved in conversion of ferrous sulfate to stable ferric
sulfate by electro-oxidation reaction is as follows:
2 FeSO4
+ 4H2SO4 Fe2 (SO4)
3
+ H2SO4
+ 3H2
5
3. Finally, to remove iron, the stable ferric sulphate was neutralized to obtain ironbased precipitates as by-product which was filtered out.
[095] After extraction of copper by galvanic displacement reaction, the bath solution
10 contained mixed metals. Iron concentration was enriched in the solution including the
formation of stable ferric sulphate after electro-oxidation reaction. Neutralization of the
stable ferric sulfate and any remaining ferrous sulphate into iron-based precipitates
was carried out by adding hydroxide base - calcium hydroxide. Since iron content was
more in Bath 1, calcium hydroxide was used as a neutralizer. Hydroxide addition
15 effectively removes iron from the solution.
[096] The discharged water obtained from the electro-oxidation reaction comprising
stable ferric sulfate and any remaining ferrous sulphate was subjected to the addition
of calcium hydroxide to prepare the calcium ferrite from electro-oxidized solution at a
20 temperature of about 25ºC, pH between 6 to 8 and for about 30 minutes (FIG 7A). The
solution was filtered to obtain a clear solution (treated electroplating wastewater) and
solid residue. After filtration, the solid residue was calcined at about 600°C - 700°C for
about 2 hours.
25 [097] The specific parameters employed in the neutralization reaction are
summarized in Table 6:
24
Table 6: Parameters employed for neutralization reaction in presence of calcium
hydroxide.
Parameters Quantity/temp./time
Volume of solution taken 200 ml
Amount of calcium hydroxide added 10 gm
Reaction pH 6
Reaction temperature 25℃
Reaction time 30 minutes
After filtration
Volume of clear solution collected 140 ml
Amount of calcium ferrite (iron-based
precipitate) collected
28 gm
[098] Thus, the iron in the spent solution was completely removed/recovered in
5 calcium ferrite form and finally, the effluent wastewater (Bath 1) was effectively treated.
FIG 7B demonstrates the X-ray diffraction pattern of the recovered calcium ferrite
powder.
[099] The chemical reactions involved in the neutralization reaction to obtain iron10 based precipitate (calcium ferrite) is as follows:
Fe2
(SO4
)
3
+ H2
SO4
+ 3Ca(OH)2
Ca {2Fe(OOH)(SO4
)} + 2 CaSO4
+ 2H2
O
Ca {2Fe(OOH)(SO4
)} CaFe2
O4 + H2
O + 2SO2
The above method removed 98% of copper and 99.3% of iron from the effluent water
15 (Bath 1).
25
Treatment of Bath 2:
[0100] Similar to the treatment of Bath 1, Bath 2 solution (FIG. 1A) was treated as
follows:
5 1. Galvanic displacement reaction for Bath 2 was carried out based on the
following reaction conditions/parameters to extract copper by addition of iron
powder –
Table 7: Parameters employed for galvanic displacement reaction
Parameters Quantity/Temp./Time
Volume of solution taken 500 ml
Amount of copper sulphate
present in solution
30 gm/L
Amount of iron powder added 5.25 gm
Reaction temperature 25℃
Reaction time 60 minutes
After filtration
Volume of clear solution
collected
490 ml
Amount of cemented copper
collected
6 gm
10
[0101] The compositions of Bath 2 before and after performing galvanic displacement
reaction (FIG. 3B) is shown in Table 8.
26
Table 8
[0102] The above experiment yielded 6 gm of cemented copper and an increase in
5 ferrous sulphate concentration. The results demonstrate 99% copper removal and the
purity of cemented copper obtained was about 90%. Particularly, 30 g/L copper
sulphate concentration was reduced to 500 ppm, and the iron concentration (FeSO4)
increased from 0.5 g/L to 29 g/L. FIG. 4A shows the removed cemented copper and
FIG. 4B illustrates the XRD pattern of cemented copper powder.
10
2. Next, the electro-oxidation reaction was performed to convert the ferrous sulfate
in the bath solution to stable ferric sulfate.
[0103] The spent solution obtained after the galvanic displacement reaction was
15 adjusted to a pH of 0.6. Sulfuric acid was added at 36 g/L followed by applying a
current density between 0.01A/cm2
to 0.05A/cm2 at about 50°C for about 360 minutes
(FIG 3A and 3B). The specific parameters employed in the electro-oxidation reaction
are summarized in the following Table 9:
20 Table 9: Parameters employed for electro-oxidation reaction
Parameters Quantity/temp./time
The volume of solution taken 500 ml
Cathode SS304 sheet
27
Anode mixed metal oxide (MMO) anode
Electrode dimensions 16 cm * 5.5 cm
Effective area 176 cm2
Current density 0.02 A/cm2
Cell voltage 2.0 V
Energy consumption 0.012 kWh/L
Reaction temperature 50℃
Reaction time 360 minutes
[0104] The compositions of Bath 2 before and after performing electro-oxidation
reaction is shown in Table 10.
5 Table 10
28
[0105] The results show that a significant amount of ferrous sulfate (29 g/L) was
converted into stable ferric sulfate (25.42 g/L). The criticality of the electro-oxidation
reaction lies in the fact that maximum amount of ferrous sulfate was converted to
stable ferric sulfate with the oxidation state of iron in the stable ferric sulfate being +3
5 which remained constant until the subsequent neutralization reaction.
3. Finally, to remove iron, the stable ferric sulphate was neutralized to obtain ironbased precipitates as by-product which was filtered out.
10 [0106] After extraction of copper by galvanic displacement reaction, the bath solution
contained mixed metals. Iron concentration was enriched in the solution including the
formation of stable ferric sulphate after electro-oxidation reaction. Neutralization of the
stable ferric sulfate and any remaining ferrous sulphate into iron-based precipitates
was carried out by adding hydroxide base - sodium hydroxide. Since copper content
15 was more in Bath 2, sodium hydroxide was used as a neutralizer.
[0107] The discharged water obtained from the electro-oxidation reaction comprising
stable ferric sulfate and any remaining ferrous sulphate was subjected to the addition
of sodium hydroxide at a temperature of about 25 ºC for about 30 minutes and between
20 a pH of about 6 to 8 (FIG. 6A). The solution was filtered to obtain a clear solution
(treated electroplating wastewater) and solid residue. The solid residue was vacuum
dried at about 70℃.
[0108] The specific parameters employed in the neutralization reaction are
25 summarized in Table 11:
29
Table 11: Parameters employed for neutralization reaction in presence of sodium
hydroxide.
Parameters Quantity/temp./time
Volume of solution taken 150 ml
Amount of sodium hydroxide added 5 gm
pH 6
Reaction temperature 25℃
Reaction time 30 minutes
After filtration
Volume of clear solution collected 125 ml
Amount of magnetic iron oxide (ironbased precipitate) collected
6.66 gm
[0109] Thus, the iron in the spent solution was completely removed/recovered in the
5 magnetic iron oxide powder form and the effluent wastewater (bath 1) was effectively
treated. FIG. 6B demonstrates the X-ray diffraction (XRD) pattern of the recovered
magnetic iron oxide powder (magnetite).
[0110] The chemical reaction involved in the neutralization reaction to obtain iron10 based precipitate (magnetic iron oxide) is as follows:
FeSO4
+ Fe2 (SO4)
3
+ 8NaOH + H2O Fe3O4+ 4Na2SO4 + 5H2O
[0111] The above method removed 98% of copper and 99.45% of iron from the
15 effluent water (Bath 2).
[0112] Similar to the above experiments, the results of effluent treatment including
electroplating wastewater treatment are expected to yield similar results with respect
30
to % removal of copper and iron when different process parameters as described
herein are employed for galvanic displacement reaction, electro-oxidation reaction and
neutralization reaction, respectively. For instance, similar results effectively removing
copper-based and iron-based contaminants from electroplating wastewater are
5 expected when parameters including neutralization pH between 7 to 8; temperature
between 20℃ to 30℃ and time-period between 15 minutes to 180 minutes for galvanic
displacement reaction; temperature between 50℃ to 80℃, time-period between 300
minutes to 400 minutes and current density between 0.01 A/cm2 to 0.05 A/cm2
for
electro-oxidation reaction, are employed.
10
EFFECTS/ADVANTAGES OF THE PRESENT INVENTION
[0113] One of the advantages of the present method and system for effluent water
treatment is the purification of effluent water and sending the purified/treated effluent
water to the ETP (Effluent Treatment Plant) for further/final treatment. Thus, the
15 present method and system is able to reduce the load/burden on ETP.
[0114] Another advantage of the present method and system is obtaining a stable
ferric sulfate wherein the oxidation state of the iron is +3 and the levels of said ferric
sulfate is stably maintained throughout the process leading to efficient removal of iron20 based precipitates during neutralization.
[0115] Yet another advantage of the present method and system is the generation of
by-products that have several advantages. For example, magnetic iron oxide obtained
after the neutralization step can be used: a) as a catalyst in the Haber process and
25 the water gas shift reaction; b) as black pigment in paint industries due to its has
coloring properties; c) as a contrast agent in MRI scanning; and d) in magnetic
applications such as magnetic storage devices and superparamagnetic relaxometry.
Similarly, the calcium ferrite obtained after the neutralization step has applications: a)
as absorbent in gas absorption system; b) as oxygen evolution catalyst in Water
30 electrolysis (OER); c) as high temperature ceramic material; and d) as electrode
material for solid oxide fuel cell (SOFL).
31
[0116] Yet another advantage of the present disclosure is improving the overall
efficiency and cost-effectiveness of the effluent water treatment process, more
particularly by treating the effluent water such as electroplating wastewater by the
present method/system before sending to ETP.
5
[0117] With respect to the use of any plural and/or singular terms herein, those having
skill in the art can translate from the plural to the singular and/or from the singular to
the plural as is appropriate to the context and/or application. The various
singular/plural permutations may be expressly set forth herein for sake of clarity. The
10 use of the expression “at least” or “at least one” suggests the use of one or more
elements or ingredients or quantities, as the use may be in the embodiment of the
disclosure to achieve one or more of the desired objects or results. Throughout this
specification, the word “comprise”, or variations such as “comprises” or “may include”
or “include” or “comprising” or “containing” or “has” or “having” or “including” wherever
15 used, will be understood to imply the inclusion of a stated element, integer or step, or
group of elements, integers or steps, but not the exclusion of any other element,
integer or step, or group of elements, integers or steps.
[0118] Reference throughout this specification to “some embodiments” or “an
20 embodiment” or “one embodiment” means that a particular feature, structure or
characteristic described in connection with the embodiment may be included in at least
one embodiment of the present disclosure. Thus, the appearances of the phrases “in
some embodiments”, “in one embodiment” or “in an embodiment” in various places
throughout this specification may not necessarily all refer to the same embodiment. It
25 is appreciated that certain features of the disclosure, which are, for clarity, described
in the context of separate embodiments, may also be provided in combination in a
single embodiment. Conversely, various features of the disclosure, which are, for
brevity, described in the context of a single embodiment, may also be provided
separately or in any suitable sub-combination. The illustrated steps are set out to
30 explain the exemplary embodiments shown, and it may be anticipated that ongoing
technological development will change the way particular functions are performed.
These examples are presented herein for purposes of illustration, and not limitation.
32
Further, the boundaries of the functional building blocks have been arbitrarily defined
herein for the convenience of the description. Alternative boundaries can be defined
so long as the specified functions and relationships thereof are appropriately
performed.
5
[0119] The word “exemplary” is used herein to mean “serving as an example,
instance, or illustration.” Any implementation described herein as “exemplary” is not
necessarily to be construed as preferred or advantageous over other implementations.
10 [0120] If the specification states a component or feature “can,” “may,” “could,”
“should,” “would,” “preferably,” “possibly,” “typically,” “optionally,” “for example,”
“often,” or “might” (or other such language) be included or have a characteristic, that
component or feature is not required to be included or to have the characteristic. Such
component or feature may be optionally included in some embodiments, or it may be
15 excluded.
[0121] In some example embodiments, certain ones of the operations herein may be
modified or further amplified as described below. Moreover, in some embodiments
additional optional operations may also be included. It should be appreciated that each
20 of the modifications, optional additions or amplifications described herein may be
included with the operations herein either alone or in combination with any others
among the features described herein.
[0122] Many modifications and other embodiments of the inventions set forth herein
25 will come to mind to one skilled in the art to which these inventions pertain having the
benefit of teachings presented in the foregoing descriptions of the method and system,
and the associated drawings. Therefore, it is to be understood that the inventions are
not to be limited to the specific embodiments disclosed and that modifications and
other embodiments are intended to be included within the scope of the appended
30 claims. Moreover, the steps in the method described above may not be limiting and
additional steps may be involved. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for purposes of limitation.
33
I/WE CLAIM:
1. A method for treating effluent water, comprising:
adding iron particles to the effluent water comprising copper sulfate, wherein
5 the iron particles react with the copper sulfate to form ferrous sulfate in the effluent
water and remove copper as a by-product precipitate, from the effluent water;
converting the ferrous sulfate in the effluent water to a stable ferric sulfate by
an electro-oxidation reaction; and
neutralizing the stable ferric sulphate in the effluent water to iron-based
10 precipitates, which is filtered out from the effluent water.
2. The method as claimed in claim 1, wherein the stable ferric sulphate comprises iron
in the ferric sulphate remaining in a same oxidation state;
and wherein said oxidation state of the iron in the stable ferric sulfate is +3.
15
3. The method as claimed in 1, wherein the iron-based precipitates removed during
neutralization is selected from a group comprising: soft-metallic ferrites, metallic
oxides, and combinations thereof.
20 4. The method as claimed in claim 1, wherein the neutralization is carried out at a pH
of about 6.0 to 8.0.
5. The method as claimed in claim 1, wherein the neutralization is carried out in
presence of a base which is a hydroxide selected from a group comprising: sodium
25 hydroxide, calcium hydroxide, potassium hydroxide, and combinations thereof.
6. The method as claimed in claim 1 or claim 5, wherein the neutralization is carried
out in presence of calcium hydroxide to filter the iron-based precipitate as calcium
ferrite.
30
34
7. The method as claimed in claim 1 or claim 5, wherein the neutralization is carried
out in presence of sodium hydroxide to filter the iron-based precipitate as magnetic
iron oxide.
5 8. The method as claimed in claim 1, wherein, the iron particles react with the copper
sulfate via a galvanic displacement reaction to form the ferrous sulfate in the effluent
water and remove the copper as the by-product precipitate.
9. The method as claimed in claim 8, wherein the galvanic displacement reaction is
10 carried out at a temperature of about 20℃ to 30℃ and for a time-period of about 15
minutes to 180 minutes.
10. The method as claimed in claim 1, wherein the electro-oxidation is carried out by
applying a current density of about 0.01 A/cm2 to 0.05 A/cm2
.
15
11. The method as claimed in claim 1, wherein the electro-oxidation is carried out at a
temperature of about 50℃ to 80℃ and for a time-period of about 300 minutes to 400
minutes.
20 12. The method as claimed in claim 1, wherein the effluent water is electroplating
wastewater, which is treated by said method prior to transferring said effluent water to
an effluent treatment plant (ETP).
13. The method as claimed in claim 12, wherein the electroplating wastewater
25 comprises copper sulfate, iron, acid and tin based compound.
14. The method as claimed in claim 12, wherein the electroplating wastewater
comprises copper sulfate, iron, sulphuric acid and tin sulphate.
30 15. The method as claimed in any of the claims claim 12 to 14, wherein the
electroplating wastewater comprises copper sulphate at a concentration of about 5
gram per litre (g/L) to 40 g/L, iron at a concentration of about 0.16 g/L to 15 g/L, acid
35
at a concentration of about 30 g/L to 35 g/L, and tin based compound at a
concentration of about 0.13 g/L to 0.18 g/L;
or wherein the electroplating wastewater comprises copper sulphate at a
concentration of about 5 gram per litre (g/L) to 40 g/L, iron at a concentration of about
5 0.16 g/L to 15 g/L, sulphuric acid at a concentration of about 30 g/L to 35 g/L, and tin
sulphate at a concentration of about 0.13 g/L to 0.18 g/L.
16. The method as claimed in any of the claims 1 to 15, wherein the method reduces
concentration of copper and iron in the effluent water by about 90% to 100% with
10 respect to the initial concentration of copper and iron in the effluent water before
subjecting to the method.
17. A system to treat effluent water, comprising:
an element to perform galvanic displacement reaction, wherein said element is
15 configured to add iron particles to the effluent water comprising copper sulfate,
wherein the iron particles react with the copper sulfate to form ferrous sulfate in the
effluent water and remove copper as a by-product precipitate, from the effluent water;
a power controller, wherein the power controller is configured to supply a Direct
Current (DC) supply and facilitate an electro-oxidation reaction and convert the ferrous
20 sulfate in the effluent water to a stable ferric sulfate; and
a neutralizer element, wherein the neutralizer is configured to neutralize the
stable ferric sulphate in the effluent water to iron-based precipitates, which is filtered
out from the effluent water.
25 18. The system as claimed in claim 17, wherein the stable ferric sulphate comprises
iron in the ferric sulphate to be configured to remain in a same oxidation state;
and wherein the oxidation state of the iron in the stable ferric sulfate is +3.
19. The system as claimed in claim 17, wherein the iron-based precipitates removed
30 during neutralization is selected from a group comprising: soft-metallic ferrites, metallic
oxides, and combinations thereof.
36
20. The system as claimed in claim 17, wherein the neutralization is carried out in
presence of calcium hydroxide to filter the iron-based precipitate as calcium ferrite;
or the neutralization is carried out in presence of sodium hydroxide to filter the
iron-based precipitate as magnetic iron oxide.